Staff Publications

Staff Publications

  • external user (warningwarning)
  • Log in as
  • language uk
  • About

    'Staff publications' is the digital repository of Wageningen University & Research

    'Staff publications' contains references to publications authored by Wageningen University staff from 1976 onward.

    Publications authored by the staff of the Research Institutes are available from 1995 onwards.

    Full text documents are added when available. The database is updated daily and currently holds about 240,000 items, of which 72,000 in open access.

    We have a manual that explains all the features 

    Current refinement(s):

    Records 1 - 100 / 196

    • help
    • print

      Print search results

    • export

      Export search results

    Check title to add to marked list
    EUNIS Habitat Classification: Expert system, characteristic species combinations and distribution maps of European habitats
    Chytrý, Milan ; Tichý, Lubomír ; Hennekens, Stephan M. ; Knollová, Ilona ; Janssen, John A.M. ; Rodwell, John S. ; Peterka, Tomáš ; Marcenò, Corrado ; Landucci, Flavia ; Danihelka, Jiří ; Hájek, Michal ; Dengler, Jürgen ; Novák, Pavel ; Zukal, Dominik ; Jiménez-Alfaro, Borja ; Mucina, Ladislav ; Abdulhak, Sylvain ; Aćić, Svetlana ; Agrillo, Emiliano ; Attorre, Fabio ; Bergmeier, Erwin ; Biurrun, Idoia ; Boch, Steffen ; Bölöni, János ; Bonari, Gianmaria ; Braslavskaya, Tatiana ; Bruelheide, Helge ; Campos, Juan Antonio ; Čarni, Andraž ; Casella, Laura ; Ćuk, Mirjana ; Ćušterevska, Renata ; Bie, Els De; Delbosc, Pauline ; Demina, Olga ; Didukh, Yakiv ; Dítě, Daniel ; Dziuba, Tetiana ; Ewald, Jörg ; Gavilán, Rosario G. ; Gégout, Jean Claude ; Giusso del Galdo, Gian Pietro ; Golub, Valentin ; Goncharova, Nadezhda ; Goral, Friedemann ; Graf, Ulrich ; Indreica, Adrian ; Isermann, Maike ; Jandt, Ute ; Jansen, Florian ; Jansen, Jan ; Jašková, Anni ; Jiroušek, Martin ; Kącki, Zygmunt ; Kalníková, Veronika ; Kavgacı, Ali ; Khanina, Larisa ; Yu. Korolyuk, Andrey ; Kozhevnikova, Mariya ; Kuzemko, Anna ; Küzmič, Filip ; Kuznetsov, Oleg L. ; Laiviņš, Māris ; Lavrinenko, Igor ; Lavrinenko, Olga ; Lebedeva, Maria ; Lososová, Zdeňka ; Lysenko, Tatiana ; Maciejewski, Lise ; Mardari, Constantin ; Marinšek, Aleksander ; Napreenko, Maxim G. ; Onyshchenko, Viktor ; Pérez-Haase, Aaron ; Pielech, Remigiusz ; Prokhorov, Vadim ; Rašomavičius, Valerijus ; Rodríguez Rojo, Maria Pilar ; Rūsiņa, Solvita ; Schrautzer, Joachim ; Šibík, Jozef ; Šilc, Urban ; Škvorc, Željko ; Smagin, Viktor A. ; Stančić, Zvjezdana ; Stanisci, Angela ; Tikhonova, Elena ; Tonteri, Tiina ; Uogintas, Domas ; Valachovič, Milan ; Vassilev, Kiril ; Vynokurov, Denys ; Willner, Wolfgang ; Yamalov, Sergey ; Evans, Douglas ; Palitzsch Lund, Mette ; Spyropoulou, Rania ; Tryfon, Eleni ; Schaminée, Joop H.J. - \ 2020
    Applied Vegetation Science (2020). - ISSN 1402-2001
    coastal habitat - diagnostic species - distribution map - dune vegetation - European Nature Information System (EUNIS) - European Vegetation Archive (EVA) - expert system - forest - grassland - habitat classification - man-made habitat - shrubland - vegetation database - vegetation plot - wetland

    Aim: The EUNIS Habitat Classification is a widely used reference framework for European habitat types (habitats), but it lacks formal definitions of individual habitats that would enable their unequivocal identification. Our goal was to develop a tool for assigning vegetation-plot records to the habitats of the EUNIS system, use it to classify a European vegetation-plot database, and compile statistically-derived characteristic species combinations and distribution maps for these habitats. Location: Europe. Methods: We developed the classification expert system EUNIS-ESy, which contains definitions of individual EUNIS habitats based on their species composition and geographic location. Each habitat was formally defined as a formula in a computer language combining algebraic and set-theoretic concepts with formal logical operators. We applied this expert system to classify 1,261,373 vegetation plots from the European Vegetation Archive (EVA) and other databases. Then we determined diagnostic, constant and dominant species for each habitat by calculating species-to-habitat fidelity and constancy (occurrence frequency) in the classified data set. Finally, we mapped the plot locations for each habitat. Results: Formal definitions were developed for 199 habitats at Level 3 of the EUNIS hierarchy, including 25 coastal, 18 wetland, 55 grassland, 43 shrubland, 46 forest and 12 man-made habitats. The expert system classified 1,125,121 vegetation plots to these habitat groups and 73,188 to other habitats, while 63,064 plots remained unclassified or were classified to more than one habitat. Data on each habitat were summarized in factsheets containing habitat description, distribution map, corresponding syntaxa and characteristic species combination. Conclusions: EUNIS habitats were characterized for the first time in terms of their species composition and distribution, based on a classification of a European database of vegetation plots using the newly developed electronic expert system EUNIS-ESy. The data provided and the expert system have considerable potential for future use in European nature conservation planning, monitoring and assessment.

    Field data of "Monitoring forest phenology and leaf area index with the autonomous, low-cost transmittance sensor PASTiS-57"
    Brede, Benjamin ; Gastellu-Etchegorry, Jean Philippe ; Lauret, Nicolas ; Baret, Frederic ; Clevers, Jan ; Verbesselt, Jan ; Herold, Martin - \ 2020
    Wageningen University & Research
    forest - ground-based - Land Surface Phenology - Leaf Area Index - validation
    Land Surface Phenology (LSP) and Leaf Area Index (LAI) are important variables that describe the photosynthetically active phase and capacity of vegetation. Both are derived on the global scale from optical satellite sensors and require robust validation based on in situ sensors at high temporal resolution. This study assesses the PAI Autonomous System from Transmittance Sensors at 57? (PASTiS-57) instrument as a low-cost transmittance sensor for simultaneous monitoring of LSP and LAI in forest ecosystems. In a field experiment, spring leaf flush and autumn senescence in a Dutch beech forest were observed with PASTiS-57 and illumination independent, multi-temporal Terrestrial Laser Scanning (TLS) measurements in five plots. Both time series agreed to less than a day in Start Of Season (SOS) and End Of Season (EOS). LAI magnitude was strongly correlated with a Pearson correlation coefficient of 0.98. PASTiS-57 summer and winter LAI were on average 0.41m2m-2 and 1.43m2m-2 lower than TLS. This can be explained by previously reported overestimation of TLS. Additionally, PASTiS-57 was implemented in the Discrete Anisotropic Radiative Transfer (DART) Radiative Transfer Model (RTM) model for sensitivity analysis. This confirmed the robustness of the retrieval with respect to non-structural canopy properties and illumination conditions. Generally, PASTiS-57 fulfilled the CEOS LPV requirement of 20% accuracy in LAI for a wide range of biochemical and illumination conditions for turbid medium canopies. However, canopy non-randomness in discrete tree models led to strong biases. Overall, PASTiS-57 demonstrated the potential of autonomous devices for monitoring of phenology and LAI at daily temporal resolution as required for validation of satellite products that can be derived from ESA Copernicus’ optical missions, Sentinel-2 and -3.
    Similar factors underlie tree abundance in forests in native and alien ranges
    Sande, Masha T. van der; Bruelheide, Helge ; Dawson, Wayne ; Dengler, Jürgen ; Essl, Franz ; Field, Richard ; Haider, Sylvia ; Kleunen, Mark van; Kreft, Holger ; Pagel, Joern ; Pergl, Jan ; Purschke, Oliver ; Pyšek, Petr ; Weigelt, Patrick ; Winter, Marten ; Attorre, Fabio ; Aubin, Isabelle ; Bergmeier, Erwin ; Chytrý, Milan ; Dainese, Matteo ; Sanctis, Michele De; Fagundez, Jaime ; Golub, Valentin ; Guerin, Greg R. ; Gutiérrez, Alvaro G. ; Jandt, Ute ; Jansen, Florian ; Jiménez-Alfaro, Borja ; Kattge, Jens ; Kearsley, Elizabeth ; Klotz, Stefan ; Kramer, Koen ; Moretti, Marco ; Niinemets, Ülo ; Peet, Robert K. ; Penuelas, Josep ; Petřík, Petr ; Reich, Peter B. ; Sandel, Brody ; Schmidt, Marco ; Sibikova, Maria ; Violle, Cyrille ; Whitfeld, Timothy J.S. ; Wohlgemuth, Thomas ; Knight, Tiffany M. - \ 2020
    Global Ecology and Biogeography 29 (2020)2. - ISSN 1466-822X - p. 281 - 294.
    abundance - dissimilarity - forest - functional traits - global - plant invasion - trees

    Aim: Alien plant species can cause severe ecological and economic problems, and therefore attract a lot of research interest in biogeography and related fields. To identify potential future invasive species, we need to better understand the mechanisms underlying the abundances of invasive tree species in their new ranges, and whether these mechanisms differ between their native and alien ranges. Here, we test two hypotheses: that greater relative abundance is promoted by (a) functional difference from locally co-occurring trees, and (b) higher values than locally co-occurring trees for traits linked to competitive ability. Location: Global. Time period: Recent. Major taxa studied: Trees. Methods: We combined three global plant databases: sPlot vegetation-plot database, TRY plant trait database and Global Naturalized Alien Flora (GloNAF) database. We used a hierarchical Bayesian linear regression model to assess the factors associated with variation in local abundance, and how these relationships vary between native and alien ranges and depend on species’ traits. Results: In both ranges, species reach highest abundance if they are functionally similar to co-occurring species, yet are taller and have higher seed mass and wood density than co-occurring species. Main conclusions: Our results suggest that light limitation leads to strong environmental and biotic filtering, and that it is advantageous to be taller and have denser wood. The striking similarities in abundance between native and alien ranges imply that information from tree species’ native ranges can be used to predict in which habitats introduced species may become dominant.

    Patterns of nitrogen-fixing tree abundance in forests across Asia and America
    Menge, Duncan N.L. ; Chisholm, Ryan A. ; Davies, Stuart J. ; Abu Salim, Kamariah ; Allen, David ; Alvarez, Mauricio ; Bourg, Norm ; Brockelman, Warren Y. ; Bunyavejchewin, Sarayudh ; Butt, Nathalie ; Cao, Min ; Chanthorn, Wirong ; Chao, Wei Chun ; Clay, Keith ; Condit, Richard ; Cordell, Susan ; Silva, João Batista da; Dattaraja, H.S. ; Andrade, Ana Cristina Segalin de; Oliveira, Alexandre A. de; Ouden, Jan den; Drescher, Michael ; Fletcher, Christine ; Giardina, Christian P. ; Savitri Gunatilleke, C.V. ; Gunatilleke, I.A.U.N. ; Hau, Billy C.H. ; He, Fangliang ; Howe, Robert ; Hsieh, Chang Fu ; Hubbell, Stephen P. ; Inman-Narahari, Faith M. ; Jansen, Patrick A. ; Johnson, Daniel J. ; Kong, Lee Sing ; Král, Kamil ; Ku, Chen Chia ; Lai, Jiangshan ; Larson, Andrew J. ; Li, Xiankun ; Li, Yide ; Lin, Luxiang ; Lin, Yi Ching ; Liu, Shirong ; Lum, Shawn K.Y. ; Lutz, James A. ; Ma, Keping ; Malhi, Yadvinder ; McMahon, Sean ; McShea, William ; Mi, Xiangcheng ; Morecroft, Michael ; Myers, Jonathan A. ; Nathalang, Anuttara ; Novotny, Vojtech ; Ong, Perry ; Orwig, David A. ; Ostertag, Rebecca ; Parker, Geoffrey ; Phillips, Richard P. ; Abd. Rahman, Kassim ; Sack, Lawren ; Sang, Weiguo ; Shen, Guochun ; Shringi, Ankur ; Shue, Jessica ; Su, Sheng Hsin ; Sukumar, Raman ; Fang Sun, I. ; Suresh, H.S. ; Tan, Sylvester ; Thomas, Sean C. ; Toko, Pagi S. ; Valencia, Renato ; Vallejo, Martha I. ; Vicentini, Alberto ; Vrška, Tomáš ; Wang, Bin ; Wang, Xihua ; Weiblen, George D. ; Wolf, Amy ; Xu, Han ; Yap, Sandra ; Zhu, Li ; Fung, Tak - \ 2019
    Journal of Ecology 107 (2019)6. - ISSN 0022-0477 - p. 2598 - 2610.
    forest - legume - nitrogen fixation - nutrient limitation - Smithsonian ForestGEO - symbiosis

    Symbiotic nitrogen (N)-fixing trees can provide large quantities of new N to ecosystems, but only if they are sufficiently abundant. The overall abundance and latitudinal abundance distributions of N-fixing trees are well characterised in the Americas, but less well outside the Americas. Here, we characterised the abundance of N-fixing trees in a network of forest plots spanning five continents, ~5,000 tree species and ~4 million trees. The majority of the plots (86%) were in America or Asia. In addition, we examined whether the observed pattern of abundance of N-fixing trees was correlated with mean annual temperature and precipitation. Outside the tropics, N-fixing trees were consistently rare in the forest plots we examined. Within the tropics, N-fixing trees were abundant in American but not Asian forest plots (~7% versus ~1% of basal area and stems). This disparity was not explained by mean annual temperature or precipitation. Our finding of low N-fixing tree abundance in the Asian tropics casts some doubt on recent high estimates of N fixation rates in this region, which do not account for disparities in N-fixing tree abundance between the Asian and American tropics. Synthesis. Inputs of nitrogen to forests depend on symbiotic nitrogen fixation, which is constrained by the abundance of N-fixing trees. By analysing a large dataset of ~4 million trees, we found that N-fixing trees were consistently rare in the Asian tropics as well as across higher latitudes in Asia, America and Europe. The rarity of N-fixing trees in the Asian tropics compared with the American tropics might stem from lower intrinsic N limitation in Asian tropical forests, although direct support for any mechanism is lacking. The paucity of N-fixing trees throughout Asian forests suggests that N inputs to the Asian tropics might be lower than previously thought.

    Resilience of tropical tree cover : The roles of climate, fire, and herbivory
    Staal, Arie ; Nes, Egbert H. van; Hantson, Stijn ; Holmgren, Milena ; Dekker, Stefan C. ; Pueyo, Salvador ; Xu, Chi ; Scheffer, Marten - \ 2018
    Global Change Biology 24 (2018)11. - ISSN 1354-1013 - p. 5096 - 5109.
    alternative stable states - bistability - forest - grasslands - livestock - model - regime shifts - remote sensing - tipping points - wildfire

    Fires and herbivores shape tropical vegetation structure, but their effects on the stability of tree cover in different climates remain elusive. Here, we integrate empirical and theoretical approaches to determine the effects of climate on fire- and herbivore-driven forest-savanna shifts. We analyzed time series of remotely sensed tree cover and fire observations with estimates of herbivore pressure across the tropics to quantify the fire–tree cover and herbivore–tree cover feedbacks along climatic gradients. From these empirical results, we developed a spatially explicit, stochastic fire-vegetation model that accounts for herbivore pressure. We find emergent alternative stable states in tree cover with hysteresis across rainfall conditions. Whereas the herbivore–tree cover feedback can maintain low tree cover below 1,100 mm mean annual rainfall, the fire–tree cover feedback can maintain low tree cover at higher rainfall levels. Interestingly, the rainfall range where fire-driven alternative vegetation states can be found depends strongly on rainfall variability. Both higher seasonal and interannual variability in rainfall increase fire frequency, but only seasonality expands the distribution of fire-maintained savannas into wetter climates. The strength of the fire–tree cover feedback depends on the spatial configuration of tree cover: Landscapes with clustered low tree-cover areas are more susceptible to cross a tipping point of fire-driven forest loss than landscapes with scattered deforested patches. Our study shows how feedbacks involving fire, herbivores, and the spatial structure of tree cover explain the resilience of tree cover across climates.

    On the relationship between fire regime and vegetation structure in the tropics
    Veenendaal, Elmar M. ; Torello-Raventos, Mireia ; Miranda, Heloisa S. ; Sato, Naomi Margarete ; Oliveras, Imma ; Langevelde, Frank van; Asner, Gregory P. ; Lloyd, Jon - \ 2018
    New Phytologist 218 (2018)1. - ISSN 0028-646X - p. 153 - 166.
    alternative stable states - feedbacks - fire ecology - forest - savannah
    We assessed data from 11 experiments examining the effects of the timing and/or frequency of fire on tropical forest and/or savanna vegetation structure over one decade or more. The initial ‘control treatment’ in many such cases consisted of previously cleared land. This is as opposed to natural vegetation subject to some sort of endogenous fire regime before the imposition of fire treatments. Effects of fire on fractional foliar cover are up to 10-fold greater when clearing pre-treatments are imposed. Moreover, because many of the ‘classic’ fire trials were initialised with applied management questions in mind, most have also used burning regimes much more frequent and/or severe than those occurring in the absence of human activity. Once these factors are taken into account, our modelling analysis shows that nonanthropogenic fire regimes serve to reduce canopy vegetative cover to a much lower extent than has previously been argued to be the case. These results call into question the notion that fire effects on tropical vegetation can be of a sufficient magnitude to maintain open-type savanna ecosystems under climatic/soil regimes otherwise sufficient to give rise to a more luxurious forest-type vegetation cover.
    Alien plant invasions in European woodlands
    Wagner, Viktoria ; Chytrý, Milan ; Jiménez-Alfaro, Borja ; Pergl, Jan ; Hennekens, Stephan ; Biurrun, Idoia ; Knollová, Ilona ; Berg, Christian ; Vassilev, Kiril ; Rodwell, John S. ; Škvorc, Željko ; Jandt, Ute ; Ewald, Jörg ; Jansen, Florian ; Tsiripidis, Ioannis ; Botta-Dukát, Zoltán ; Casella, Laura ; Attorre, Fabio ; Rašomavičius, Valerijus ; Ćušterevska, Renata ; Schaminée, Joop H.J. ; Brunet, Jörg ; Lenoir, Jonathan ; Svenning, Jens Christian ; Kącki, Zygmunt ; Petrášová-Šibíková, Mária ; Šilc, Urban ; García-Mijangos, Itziar ; Campos, Juan Antonio ; Fernández-González, Federico ; Wohlgemuth, Thomas ; Onyshchenko, Viktor ; Pyšek, Petr - \ 2017
    Diversity and Distributions 23 (2017)9. - ISSN 1366-9516 - p. 969 - 981.
    EUNIS - exotic - forest - invasive plants - life-form - neophyte - non-native - origin - tree
    Aim: Woodlands make up a third of European territory and carry out important ecosystem functions, yet a comprehensive overview of their invasion by alien plants has never been undertaken across this continent. Location: Europe. Methods: We extracted data from 251,740 vegetation plots stored in the recently compiled European Vegetation Archive. After filtering (resulting in 83,396 plots; 39 regions; 1970–2015 time period), we analysed the species pool and frequency of alien vascular plants with respect to geographic origin and life-forms, and the levels of invasion across the European Nature Information System (EUNIS) woodland habitats. Results: We found a total of 386 alien plant species (comprising 7% of all recorded vascular plants). Aliens originating from outside of and from within Europe were almost equally represented in the species pool (192 vs. 181 species) but relative frequency was skewed towards the former group (77% vs. 22%) due, to some extent, to the frequent occurrence of Impatiens parviflora (21% frequency among alien plants). Phanerophytes were the most species-rich life-form (148 species) and had the highest representation in terms of relative frequency (39%) among aliens in the dataset. Apart from Europe (181 species), North America was the most important source of alien plants (109 species). At the local scale, temperate and boreal softwood riparian woodland (5%) and mire and mountain coniferous woodland (<1%) had the highest and lowest mean relative alien species richness (percentage of alien species per plot), respectively. Main conclusions: Our results indicate that European woodlands are prone to alien plant invasions especially when exposed to disturbance, fragmentation, alien propagule pressure and high soil nutrient levels. Given the persistence of these factors in the landscape, competitive alien plant species with a broad niche, including alien trees and shrubs, are likely to persist and spread further into European woodlands.
    MODIS VCF should not be used to detect discontinuities in tree cover due to binning bias. A comment on Hanan et al. (2014) and Staver and Hansen (2015)
    Gerard, France ; Hooftman, Danny ; Langevelde, Frank van; Veenendaal, Elmar ; White, Steven M. ; Lloyd, Jon - \ 2017
    Global Ecology and Biogeography 26 (2017)7. - ISSN 1466-822X - p. 854 - 859.
    alternative stable states - forest - frequency distribution - MODIS VCF - remote sensing - savanna - tree cover

    In their recent paper, Staver and Hansen (Global Ecology and Biogeography, 2015, 24, 985–987) refute the case made by Hanan et al. (Global Ecology and Biogeography, 2014, 23, 259–263) that the use of classification and regression trees (CARTs) to predict tree cover from remotely sensed imagery (MODIS VCF) inherently introduces biases, thus making the resulting tree cover unsuitable for showing alternative stable states through tree cover frequency distribution analyses. Here we provide a new and equally fundamental argument for why the published frequency distributions should not be used for such purposes. We show that the practice of pre-average binning of tree cover values used to derive cover values to train the CART model will also introduce errors in the frequency distributions of the final product. We demonstrate that the frequency minima found at tree covers of 8–18%, 33–45% and 55–75% can be attributed to numerical biases introduced when training samples are derived from landscapes containing asymmetric tree cover distributions and/or a tree cover gradient. So it is highly likely that the CART, used to produce MODIS VCF, delivers tree cover frequency distributions that do not reflect the real world situation.

    To Tree or Not to Tree : Cultural Views from Ancient Romans to Modern Ecologists
    Holmgren, Milena ; Scheffer, Marten - \ 2017
    Ecosystems 20 (2017)1. - ISSN 1432-9840 - p. 62 - 68.
    ecosystem services - forest - grassland - land degradation - savanna - tree encroachment - visions of nature

    Few things are more defining in a landscape compared to the absence or presence of trees, both in aesthetic and in functional terms. At the same time, tree cover has been profoundly affected by humans since ancient times. It is therefore not surprising that opinions about deforestation and colonization of landscapes by trees have always been strong. Although loss of forests is often lamented, there is also profound cultural affection for open landscapes including some that have been deforested in the past. Here we take a historical view on perceptions of changing tree cover, and subsequently argue that the current ecological literature on forest-savanna-grassland transitions is not immune to value-laden perspectives. So far, ecosystem science has not done enough to analyze the effects of tree cover changes on ecosystem services and indicators of human well-being. Until these analyses are done, debates about forested versus open landscapes will be clashes of values rather than scientific evaluations. We discuss how ecosystem science may contribute to developing this field.

    The island rule of body size demonstrated on individual hosts : phytophagous click beetle species grow larger and predators smaller on phylogenetically isolated trees
    Molleman, Freerk ; Depoilly, Alexandre ; Vernon, Philippe ; Müller, Jörg ; Bailey, Richard ; Jarzabek-Müller, Andrea ; Prinzing, Andreas - \ 2016
    Journal of Biogeography 43 (2016)7. - ISSN 0305-0270 - p. 1388 - 1399.
    community ecology - dispersal selection - Elateridae - forest - island biogeography - local adaptation - microevolution - phenotypic plasticity - plant–animal interactions - vegetation diversity

    Aim: Under spatial isolation on oceanic islands, species tend to show extreme body sizes. From the point of view of many colonizers, individual hosts surrounded by phylogenetically distant neighbours are phylogenetically isolated. This study addresses for the first time how phylogenetic isolation of individual hosts affects body size of colonizers, and whether effects on body size reflect selection among colonizers established on host individuals rather than selection among colonizers dispersing toward trees or phenotypic plasticity of colonizers. Location: Rennes National Forest, Western France. Methods: We sampled click beetles (Elateridae) on individual oak trees varying in phylogenetic isolation from their neighbours and in age. We measured body size and fluctuating asymmetry (which we found to correlate to reduced body size) and related both to phylogenetic isolation and age of trees. We compared these relationships among species of different larval trophic position and adult body size, using meta-analytical approaches. Results: Within species, body size changes with phylogenetic isolation of individual host trees: root feeders tend to become larger, predators smaller. Effects were independent of mean body-size, disappeared with tree age, and were inconsistent with patterns of fluctuating asymmetry. Main conclusions: Our results are consistent with body-size selection among colonizers established on individual trees, rather than selection among colonizers dispersing toward trees or phenotypic plasticity. Overall, phenotype patterns of animals across islands in the ocean may resemble those across host individuals in a phylogenetically distant neighbourhood, suggesting micro-evolution of colonizers in response to the macro-evolutionary structure of the host community.

    Forest–climate nexus : linking adaptation and mitigation in Cameroon's climate policy process
    Chia, Eugene Loh ; Somorin, O.A. ; Sonwa, D.J. ; Bele, Y.M. ; Tiani, M.A. - \ 2015
    Climate and Development 7 (2015)1. - ISSN 1756-5529 - p. 85 - 96.
    adaptation - Cameroon - climate change - forest - mitigation - policy actors

    In Cameroon, as in other countries of the Congo basin region, policy processes and activities related to climate change have been hitherto geared mostly towards mitigation and related questions, with limited concern about adaptation issues. However, the increasing vulnerability of Cameroon to climate variability and change makes adaptation significant to its national climate-change policy. Nonetheless, it remains a challenge to make both adaptation and mitigation occupy the same policy space in Cameroon. This paper builds partly on studies carried out in two community forest carbon initiatives in the southern rainforest of Cameroon. It also argues, supported by existing literature on adaptation and mitigation, that mitigation activities have the potential to produce adaptation outcomes; a situation which avoids duplication of efforts and waste of financial and technical resources, if synergetic options are anticipated and planned. However, whether such integrated approaches succeed and are subsequently reflected in national-level climate policy depends on how actors across different sectors and at different levels engage and carry out their roles. The paper discusses these roles and how they can support each other in pursuing integrated initiatives – a context which is vital for Cameroon.

    Estimation of spruce needle-leaf chlorophyll content based on DART and PARAS canopy reflectance models
    Yanez Rausell, L. ; Malenovsky, Z. ; Rautiainen, M. ; Clevers, J.G.P.W. ; Lukes, P. ; Hanus, J. ; Schaepman, M.E. - \ 2015
    IEEE Journal of Selected Topics in Applied Earth Observations and Remote Sensing 8 (2015)4. - ISSN 1939-1404 - p. 1534 - 1544.
    photon recollision probability - area index - spectral invariants - forest - prospect - stands - simulations - resolution - retrieval - lai-2000
    Needle-leaf chlorophyll content (Cab) of a Norway spruce stand was estimated from CHRIS-PROBA images using the canopy reflectance simulated by the PROSPECT model coupled with two canopy reflectance models: 1) discrete anisotropic radiative transfer model (DART); and 2) PARAS. The DART model uses a detailed description of the forest scene, whereas PARAS is based on the photon recollision probability theory and uses a simplified forest structural description. Subsequently, statistically significant empirical functions between the optical indices ANCB670-720 and ANMB670-720 and the needle-leaf Cab content were established and then applied to CHRIS-PROBA data. The Cab estimating regressions using ANMB670_720 were more robust than using ANCB670-720 since the latter was more sensitive to LAI, especially in case of PARAS. Comparison between Cab estimates showed strong linear correlations between PARAS and DART retrievals, with a nearly perfect one-to-one fit when using ANMB670-720 (slope = 1.1, offset = 11 µg · cm-2). Further comparison with Cab estimated from an AISA Eagle image of the same stand showed better results for PARAS (RMSE = 2.7 µg · cm-2 for ANCB670-720; RMSE = 9.5 µg · cm-2 for ANMB670_720) than for DART (RMSE = 7.5 µg · cm-2 for ANCB670-720; RMSE = 23 µg · cm-2 for ANMB670-720). Although these results show the potential for simpler models like PARAS in estimating needle-leaf Cab from satellite imaging spectroscopy data, further analyses regarding parameterization of radiative transfer models are recommended.
    Wildlife comeback in Flanders: tracing the fault lines and dynamics of public debate
    Herzele, A. Van; Aarts, N. ; Casaer, J. - \ 2015
    European Journal of Wildlife Research 61 (2015)4. - ISSN 1612-4642 - p. 539 - 555.
    biodiversity conservation - scale frames - conflicts - forest - policy - discourse - science - europe - city
    Conflicts and debates on wildlife issues often prove intractable or resistant to resolution. This paper develops a three-layered methodological approach to identify the fault lines and dynamics, which perpetuate social division and conflict. This approach was applied to the analysis of six publicly debated events that followed the comeback of the red fox and wild boar in Flanders, Belgium. The integrated findings demonstrate that conflict was not merely a manifestation of incompatible goals and views, but was highly determined by the conduct of the debate itself. The debates evolved along a few main fault lines, most notably belonging/not belonging, opportunity/threat and control by intervention/nature controls itself. A number of dynamics were identified along these fault lines, including the convergence and alignment of arguments (in particular, dichotomisation), the linking and scaling up of issues and the stigmatisation of outgroups. These processes were largely driven by the parties’ strategies to gain credibility and support with audiences. At the same time, however, they tended to magnify the problems, polarised positions along the fault lines, and thus hampered resolution. Furthermore, part of the debate served to confirm institutional roles and identities, which, in turn, contributed to the perpetuation of conflict. Contrasting views on nature were hardly a topic of discussion. Rather they were locked into dichotomies and classifications expressed by the contending parties. Together, the findings from this paper provide useful clues for transforming the dynamics perpetuating the conflict to different dynamics that allow for more constructive relations between the parties involved.
    Spatial boundary of urban ‘acid islands’ in China
    Du, E. ; Vries, W. de; Liu, X. ; Fang, J. ; Galloway, J.N. ; Jiang, Y. - \ 2015
    Scientific Reports 5 (2015). - ISSN 2045-2322 - 9 p.
    atmospheric deposition - nitrogen deposition - air-pollution - soil acidification - emissions - canopy - forest - rain - ecosystems - cities
    Elevated emissions of sulfur dioxide, nitrogen oxides and ammonia in China have resulted in high levels of sulfur and nitrogen deposition, being contributors to soil acidification, especially in and near large cities. However, knowledge gaps still exist in the way that large cities shape spatial patterns of acid deposition. Here, we assessed the patterns of pH, sulfate, nitrate and ammonium in bulk precipitation and throughfall in southern China’s forests by synthesizing data from published literature. Concentrations and fluxes of sulfate, nitrate and ammonium in bulk precipitation and throughfall exhibited a power-law increase with a closer distance to the nearest large cities, and accordingly pH showed a logarithmic decline. Our findings indicate the occurrence of urban ‘acid islands’ with a critical radius of approximately 70¿km in southern China, receiving potential acid loads of more than 2 keq ha-1 yr-1. These urban acid islands covered an area of 0.70¿million km2, accounting for nearly 30% of the land area in southern China. Despite a significant capacity to neutralize acids in precipitation, our analysis highlights a substantial contribution of ammonium to potential acid load. Our results suggest a joint control on emissions of multiple acid precursors from urban areas in southern China
    Influence of human activities on the activity patterns of Japanese sika deer (Cervus nippon) and wild boar (Sus scrofa) in Central Japan
    Doormaal, N. van; Ohashi, H. ; Koike, S. ; Kaji, K. - \ 2015
    European Journal of Wildlife Research 61 (2015)4. - ISSN 1612-4642 - p. 517 - 527.
    agricultural landscapes - habitat selection - human disturbance - roe deer - land-use - forest - prefecture - behavior - density - damage
    Human ageing and population decline in Japan are causing agricultural field abandonment and providing new habitats for Japanese sika deer and wild boar. These species have expanded their distribution and increased in abundance across Japan and are causing increased agricultural damage. Effective countermeasures must factor in the behavioural flexibility of sika deer and wild boar. The aim of this study was to examine the effects of hunting and indirect human activities on the activity patterns of sika deer in central Japan and compare these with previous findings on wild boar. Camera traps were used to observe activity patterns of both species and that of humans. Sika deer and wild boar were most active at night during the non-hunting season. Hunting activities significantly reduced sika deer and wild boar activity patterns. In the non-hunting season, nocturnal activity of sika deer increased with decreasing distance to settlement. A similar, but weak response was also observed for wild boar. This study suggests that sika deer and wild boar avoid humans and humandominated areas by being nocturnal. The recent introduction of night hunting might help to control wildlife populations, but monitoring will be necessary to confirm this expectation.
    Estimation of Aerodynamic Roughness Length over Oasis in the Heihe River Basin by Utilizing Remote Sensing and Ground Data
    Chen, Q. ; Jia, L. ; Hutjes, R.W.A. ; Menenti, M. - \ 2015
    Remote Sensing 7 (2015)4. - ISSN 2072-4292 - p. 3690 - 3709.
    laser altimeter measurements - time-series analysis - leaf-area index - surface-roughness - vegetation - parameters - canopy - forest - lidar - displacement
    Most land surface models require information on aerodynamic roughness length and its temporal and spatial variability. This research presents a practical approach for determining the aerodynamic roughness length at fine temporal and spatial resolution over the landscape by combining remote sensing and ground measurements. The basic framework of Raupach, with the bulk surface parameters redefined by Jasinski et al., has been applied to optical remote sensing data collected by the HJ-1A/1B satellites. In addition, a method for estimating vegetation height was introduced to derive the aerodynamic roughness length, which is preferred by users over the height-normalized form. Finally, mapping different vegetation classes was validated taking advantage of the data-dense field experiments conducted in the Heihe Watershed Allied Telemetry Experimental Research (HiWATER) project. Overall, the roughness model performed well against the measurements collected at most HiWATER flux tower sites. However, deviations still occurred at some sites, which have been further analyzed.
    Satellite Earth observation data to identify anthropogenic pressures in selected protected areas
    Nagendra, H. ; Mairota, P. ; Marangi, C. ; Lucas, R. ; Dimopoulos, P. ; Honrado, J.P. ; Niphadkara, M. ; Mücher, C.A. ; Tomaselli, V. ; Panitsa, M. ; Tarantino, C. ; Manakos, I. ; Blonda, P. - \ 2015
    International Journal of applied Earth Observation and Geoinformation 37 (2015). - ISSN 0303-2434 - p. 124 - 132.
    ecosystem services - species richness - biodiversity - conservation - forest - lidar - classifications - management - predictor - invasions
    Protected areas are experiencing increased levels of human pressure. To enable appropriate conservation action, it is critical to map and monitor changes in the type and extent of land cover/use and habitat classes, which can be related to human pressures over time. Satellite Earth observation (EO) data and techniques offer the opportunity to detect such changes. Yet association with field information and expert interpretation by ecologists is required to interpret, qualify and link these changes to human pressure. There is thus an urgent need to harmonize the technical background of experts in the field of EO data analysis with the terminology of ecologists, protected area management authorities and policy makers in order to provide meaningful, context-specific value-added EO products. This paper builds on the DPSIR framework, providing a terminology to relate the concepts of state, pressures, and drivers with the application of EO analysis. The type of pressure can be inferred through the detection of changes in state (i.e. changes in land cover and/or habitat type and/or condition). Four broad categories of changes in state are identified, i.e. land cover/habitat conversion, land cover/habitat modification, habitat fragmentation and changes in landscape connectivity, and changes in plant community structure. These categories of change in state can be mapped through EO analyses, with the goal of using expert judgement to relate changes in state to causal direct anthropogenic pressures. Drawing on expert knowledge, a set of protected areas located in diverse socio-ecological contexts and subject to a variety of pressures are analysed to (a) link the four categories of changes in state of land cover/habitats to the drivers (anthropogenic pressure), as relevant to specific target land cover and habitat classes; (b) identify (for pressure mapping) the most appropriate spatial and temporal EO data sources as well as interpretations from ecologists and field data useful in connection with EO data analysis. We provide detailed examples for two protected areas, demonstrating the use of EO data for detection of land cover/habitat change, coupled with expert interpretation to relate such change to specific anthropogenic pressures. We conclude with a discussion of the limitations and feasibility of using EO data and techniques to identify anthropogenic pressures, suggesting additional research efforts required in this direction.
    Evidence for an unidentified non-photochemical ground-level source of formaldehyde in the Po Valley with potential implications for ozone production
    Kaiser, J. ; Wolfe, G.M. ; Bohn, B. ; Ganzeveld, L.N. - \ 2015
    Atmospheric Chemistry and Physics 15 (2015). - ISSN 1680-7316 - p. 1289 - 1298.
    volatile organic-compounds - exchange cafe model - total oh reactivity - tropospheric degradation - chemical mechanism - gas-phase - part - atmosphere - forest - hydrocarbons
    Ozone concentrations in the Po Valley of northern Italy often exceed international regulations. As both a source of radicals and an intermediate in the oxidation of most volatile organic compounds (VOCs), formaldehyde (HCHO) is a useful tracer for the oxidative processing of hydrocarbons that leads to ozone production. We investigate the sources of HCHO in the Po Valley using vertical profile measurements acquired from the airship Zeppelin NT over an agricultural region during the PEGASOS 2012 campaign. Using a 1-D model, the total VOC oxidation rate is examined and discussed in the context of formaldehyde and ozone production in the early morning. While model and measurement discrepancies in OH reactivity are small (on average 3.4 ± 13%), HCHO concentrations are underestimated by as much as 1.5 ppb (45%) in the convective mixed layer. A similar underestimate in HCHO was seen in the 2002–2003 FORMAT Po Valley measurements, though the additional source of HCHO was not identified. Oxidation of unmeasured VOC precursors cannot explain the missing HCHO source, as measured OH reactivity is explained by measured VOCs and their calculated oxidation products. We conclude that local direct emissions from agricultural land are the most likely source of missing HCHO. Model calculations demonstrate that radicals from degradation of this non-photochemical HCHO source increase model ozone production rates by as much as 0.6 ppb h-1 (12%) before noon.
    Tree-ring d18O in African mahogany (Entandrophragma utile) records regional precipitation and can be used for climate reconstructions
    Sleen, J.P. van der; Groenendijk, P. ; Zuidema, P. - \ 2015
    Global and Planetary Change 127 (2015). - ISSN 0921-8181 - p. 58 - 66.
    oxygen-isotope ratios - tropical atlantic - west-africa - monsoon - growth - forest - chronologies - temperature - variability - salinity
    The availability of instrumental climate data in West and Central Africa is very restricted, both in space and time. This limits the understanding of the regional climate system and the monitoring of climate change and causes a need for proxies that allow the reconstruction of paleoclimatic variability. Here we show that oxygen isotope values (d18O) in tree rings of Entandrophragma utile from North-western Cameroon correlate to precipitation on a regional to sub-continental scale (1930–2009). All found correlations were negative, following the proposed recording of the ‘amount effect’ by trees in the tropics. The capacity of E. utile to record the variability of regional precipitation is also confirmed by the significant correlation of tree-ring d18O with river discharge data (1944–1983), outgoing longwave radiation (a proxy for cloud cover; 1974–2011) and sea surface salinity in the Gulf of Guinea (1950–2011). Furthermore, the high values in the d18O chronology from 1970 onwards coincide with the Sahel drought period. Given that E. utile presents clear annual growth rings, has a wide-spread distribution in tropical Africa and is long lived (> 250 years), we argue that the analysis of oxygen isotopes in growth rings of this species is a promising tool for the study of paleoclimatic variability during the last centuries in West and Central Africa.
    Soil surface changes increase runoff and erosion risk after a low–moderate severity fire
    Stoof, C.R. ; Ferreira, A.J.D. ; Mol, W. ; Berg, J. van den; Kort, A. De; Drooger, S. ; Slingerland, E.C. ; Mansholt, A.U. ; Ritsema, C.J. - \ 2015
    Geoderma 239-240 (2015). - ISSN 0016-7061 - p. 58 - 67.
    critical shear-stress - random roughness - overland-flow - mediterranean ecosystem - physical-properties - water repellency - prescribed fire - burn severity - forest - wildfire
    Post-fire land degradation is to a large degree determined by what happens to soil properties and ground cover during and after the fire. To study fire impact in relation to fire intensity and post-fire soil exposure, a 9-ha Portuguese shrubland catchmentwas burned by experimental fire in the 2008/9 winter season. Previous studies reported on the significant increase in erosion after this fire, and discussed the role of reduced canopy interception and changed soil water repellency dynamics. Our objective was to assess whether fire-induced changes in soil physical properties and soil surface characteristics may have played an additional role in the increase in runoff and erosion observed after the fire. We sampled these properties before, immediately after, and up to one year after fire, and monitored soil temperatures during the fire using thermocouples. Despite the locally high fire intensity (N15.000kWm-1 in some places), soil physical changeswere not observed: topsoil bulk density, organic matter, porosity and saturated conductivity did not significantly change, likely because soil temperatures stayedlow with the 0.5 cm depth not exceeding 32.5 °C. Soil surface characteristics did change: Manning's n and randomroughness both decreased, increasing the risk and erosivity of overland flow. Results indicate that soil physical changes unlikely contributed to the increase in post-fire erosion observed in the catchment and that a highintensity winter burn does not necessarily lead to severe soil changes. Nevertheless, soil surface changes during and after fire contribute to an increase runoff and erosion risk in these areas
    Multi-model radiometric slope correction of SAR images of complex terrain using a two-stage semi-empirical approach
    Hoekman, D.H. ; Reiche, J. - \ 2015
    Remote Sensing of Environment 156 (2015). - ISSN 0034-4257 - p. 1 - 10.
    radar imagery - topography - forest - classification - backscatter - validation
    Practical approaches for the implementation of terrain type dependent radiometric slope correction for SAR data are introduced. Radiometric slope effects are modelled as the products of two models. The first is a simple physical model based on the assumption of a uniform opaque layer of isotropic scatterers, which is independent of terrain type, frequency and polarization. It accounts for the slope-induced variation in the number of scatterers per resolution cell. The second is a semi-empirical model, which accounts for the variation in scattering mechanisms, dependent on terrain type, frequency and polarization. PALSAR FBD (L-band, HH- and HV-polarization) data are used at two test sites in Brazil and Fiji. Results for the Brazilian area, which has slopes up to 25°, show that remaining slope effects for the multi-model case are much smaller than 0.1 dB, for all land cover types. This is much better than the best single-model approach where remaining slope effects can be very small for forests but be as large as 1.77 dB for woodland in HH-polarization. Results for the Fiji area, which has different vegetation types, are very similar. The potential large improvement, using this multi-model approach, in the accuracy of biomass estimation for transparent or open canopies is discussed. It is also shown that biomass change on slopes can be systematically under- or overestimated because of associated change in scattering mechanism.
    The fate of populations of Euterpe oleracea harvested for palm heart in Colombia
    Vallejo, M.I. ; Galeano, G. ; Bernal, R. ; Zuidema, P. - \ 2014
    Forest Ecology and Management 318 (2014). - ISSN 0378-1127 - p. 274 - 284.
    understory palm - leaf harvest - forest - extraction - management - demography - dynamics - sustainability - arecaceae - responses
    Palm heart is an important non-timber forest product obtained from various palm species in tropical forests. We studied the effect of four decades of palm heart extraction from the clonal palm Euterpe oleracea at the southern Pacific coast of Colombia. We monitored populations that had been subject to a range of harvest intensities and used measured vital rates (survival, growth, sexual and clonal reproduction) to construct population matrix models. We then used these models to simulate several harvest scenarios and to project the population dynamics for the next 50 years. Our projections suggest that the currently implemented intensive harvest regimes - which involve up to four harvests per year - result in dramatic demographic changes, primarily affecting seedlings and adults. In addition, current harvest regimes affect the future supply of palm heart, which is projected to drop sharply during the first years following harvest and fails to recover unless a number of stems are spared. Our simulations indicate that the most sustainable scenarios involve annual harvest between 50% and 75% of all harvestable stems, without any removal of small shoots from the clumps. Implementation of this regime must be accompanied by other management practices, including planning harvestable areas, marking the stems to be cut during subsequent harvests, assigning harvesters to specific areas, and leaving harvest residues as mulch around clumps. The degradation of populations of E. oleracea directly affects livelihoods of local people, by reducing cash income from palm heart sales and by reducing availability of palm fruits, a locally important food resource. (C) 2014 Elsevier B.V. All rights reserved.
    Does phenology distinguish bitter and sweet African bush mango trees (Irvingia spp., Irvingiaceae)?
    Vihotogbe, R. ; Berg, R.G. van den; Bongers, F. ; Sinsin, B. ; Sosef, M.S.M. - \ 2014
    Trees-Structure and Function 28 (2014)6. - ISSN 0931-1890 - p. 1777 - 1791.
    genetic diversity - dahomey gap - west-africa - phenotypic variation - conservation status - gabonensis - domestication - forest - cameroon - fruits
    Key message This phenological analysis of bitter and sweet bush mango trees is part of their biosystematics. It supports the species distinction hypothesis postulated by Harris (Bull J Bot Nat Belg 65(1-2):143-196, 1996 ) and Lowe et al. (Mol Ecol 9:831-841, 2000 ). African Bush Mango trees are priority food trees in Sub-Saharan Africa. The unclear distinction between bitter and sweet fruited trees is still subject to taxonomic debate. This hinders their effective use and conservation programmes. This study investigates differences in phenological behaviour between bitter and sweet fruited populations and their taxonomic implications. Monthly phenological description data on seven populations of bitter or sweet bush mangos across Benin and Togo were used to assess within and between mango type phenological diversity, to discriminate bitter and sweet trees and to evaluate their responses to environmental factors. The phenological states differentiating bitter and sweet trees were identified and individual trees were classified based on the discriminating phenological characters. Finally, phenological variation was analyzed with time of the year, soil type, type of bush mango tree, and climatic zone. Phenological diversity varies significantly among populations. Bitter and sweet trees have consistently different phenological states. Bitter trees have a lower phenological diversity for all phenological phases throughout the year compared to sweet trees, possibly due to their limited distribution range in the study area. The tree types also differ in their reproductive responses to environmental factors, but did not respond differently to soils. These results support the hypothesis that bitter and sweet trees represent different taxa and we suggest for efficient conservation purpose to consider them as different species.
    Vegetation dynamics prior to wildlife reintroductions in southern umfurudzi park, Zimbabwe
    Muposhi, V. ; Ndlovu, N. ; Gandiwa, E. ; Muvengwi, J. ; Muboko, N. - \ 2014
    The JAPS 24 (2014)6. - ISSN 1018-7081 - p. 1680 - 1690.
    gonarezhou national-park - tree species-diversity - woody vegetation - miombo woodlands - tanzania - forest - size - herbivores - elephants - savannas
    Vegetation assessments are critical in the status and success of reintroduction programs and are an important aspect in ecological restoration. Vegetation structure and composition influences the suitability and availability of unique habitats for different wildlife species. The objectives of this study were to (1) establish the vegetation structure and composition, and (2) determine the soil-vegetation associations in southern Umfurudzi Park, Zimbabwe, prior to the reintroduction of wildlife species. Using a stratified random design, 15 rectangular plots from three strata were assessed in April and May 2012. A total of 23 woody plants from 58 tree and 68 shrub families as well as 30 grass species were recorded. Tree basal area, canopy cover, tree density, tree and grass species diversity, and tree height for the riverine strata were significantly different from the miombo and vlei strata. The influence of soil properties on the occurrence and diversity of woody and grass species was evident across the three strata. Long-term changes in the vegetation dynamics and primary productivity in southern Umfurudzi Park due to the reintroduced mega-herbivores is recommended for the success of the restoration program.
    Evaluating a non-destructive method for calibrating tree biomass equations derived from tree branching architecture
    MacFarlane, D.W. ; Kuyah, S. ; Mulia, R. ; Dietz, J. ; Muthuri, C. ; Noordwijk, M. van - \ 2014
    Trees-Structure and Function 28 (2014)3. - ISSN 0931-1890 - p. 807 - 817.
    aboveground biomass - root architecture - fractal analysis - model - agroforestry - allometry - systems - forest - size
    Functional branch analysis (FBA) is a promising non-destructive alternative to the standard destructive method of tree biomass equation development. In FBA, a theoretical model of tree branching architecture is calibrated with measurements of tree stems and branches to estimate the coefficients of the biomass equation. In this study, species-specific and mixed-species tree biomass equations were derived from destructive sampling of trees in Western Kenya and compared to tree biomass equations derived non-destructively from FBA. The results indicated that the non-destructive FBA method can produce biomass equations that are similar to, but less accurate than, those derived from standard methods. FBA biomass prediction bias was attributed to the fact that real trees diverged from fractal branching architecture due to highly variable length–diameter relationships of stems and branches and inaccurate scaling relationships for the lengths of tree crowns and trunks assumed under the FBA model.
    Global cropland monthly gross primary production in the year 2000
    Chen, T. ; Werf, G.R. van der; Gobron, N. ; Moors, E.J. ; Dolman, A.J. - \ 2014
    Biogeosciences 11 (2014). - ISSN 1726-4170 - p. 3871 - 3880.
    net primary production - light-use efficiency - ecosystem exchange - constant fraction - terrestrial gross - model - forest - modis - respiration - climate
    Croplands cover about 12% of the ice-free terrestrial land surface. Compared with natural ecosystems, croplands have distinct characteristics due to anthropogenic influences. Their global gross primary production (GPP) is not well constrained and estimates vary between 8.2 and 14.2 Pg C yr-1. We quantified global cropland GPP using a light use efficiency (LUE) model, employing satellite observations and survey data of crop types and distribution. A novel step in our analysis was to assign a maximum light use efficiency estimate (¿*GPP) to each of the 26 different crop types, instead of taking a uniform value as done in the past. These ¿*GPP values were calculated based on flux tower CO2 exchange measurements and a literature survey of field studies, and ranged from 1.20 to 2.96 g C MJ-1. Global cropland GPP was estimated to be 11.05 Pg C yr-1 in the year 2000. Maize contributed most to this (1.55 Pg C yr-1), and the continent of Asia contributed most with 38.9% of global cropland GPP. In the continental United States, annual cropland GPP (1.28 Pg C yr-1) was close to values reported previously (1.24 Pg C yr-1) constrained by harvest records, but our estimates of ¿*GPP values were considerably higher. Our results are sensitive to satellite information and survey data on crop type and extent, but provide a consistent and data-driven approach to generate a look-up table of ¿*GPP for the 26 crop types for potential use in other vegetation models.
    Spatio-temporal trends of nitrogen deposition and climate effects on Sphagnum productivity in European peatlands
    Granath, G. ; Limpens, J. ; Posch, M. ; Mücher, S. ; Vries, W. de - \ 2014
    Environmental Pollution 187 (2014). - ISSN 0269-7491 - p. 73 - 80.
    carbon accumulation - n deposition - boreal mire - bogs - growth - vegetation - impact - mosses - forest - emissions
    To quantify potential nitrogen (N) deposition impacts on peatland carbon (C) uptake, we explored temporal and spatial trends in N deposition and climate impacts on the production of the key peat forming functional group (Sphagnum mosses) across European peatlands for the period 1900–2050. Using a modelling approach we estimated that between 1900 and 1950 N deposition impacts remained limited irrespective of geographical position. Between 1950 and 2000 N deposition depressed production between 0 and 25% relative to 1900, particularly in temperate regions. Future scenarios indicate this trend will continue and become more pronounced with climate warming. At the European scale, the consequences for Sphagnum net C-uptake remained small relative to 1900 due to the low peatland cover in high-N areas. The predicted impacts of likely changes in N deposition on Sphagnum productivity appeared to be less than those of climate. Nevertheless, current critical loads for peatlands are likely to hold under a future climate.
    Negative density dependence of seed dispersal and seedling recruitment in a Neotropical palm
    Jansen, P.A. ; Visser, M.D. ; Joseph Wright, S. ; Rutten, G. ; Muller-Landau, H.C. - \ 2014
    Ecology Letters 17 (2014)9. - ISSN 1461-023X - p. 1111 - 1120.
    scatter-hoarding rodent - tropical tree - spatial-patterns - plant diversity - forest - competition - removal - consequences - mechanisms - herbivores
    Negative density dependence (NDD) of recruitment is pervasive in tropical tree species. We tested the hypotheses that seed dispersal is NDD, due to intraspecific competition for dispersers, and that this contributes to NDD of recruitment. We compared dispersal in the palm Attalea butyracea across a wide range of population density on Barro Colorado Island in Panama and assessed its consequences for seed distributions. We found that frugivore visitation, seed removal and dispersal distance all declined with population density of A. butyracea, demonstrating NDD of seed dispersal due to competition for dispersers. Furthermore, as population density increased, the distances of seeds from the nearest adult decreased, conspecific seed crowding increased and seedling recruitment success decreased, all patterns expected under poorer dispersal. Unexpectedly, however, our analyses showed that NDD of dispersal did not contribute substantially to these changes in the quality of the seed distribution; patterns with population density were dominated by effects due solely to increasing adult and seed density.
    Why trees and shrubs but rarely trubs?
    Scheffer, M. ; Vergnon, R.O.H. ; Cornelissen, J.H.C. ; Hantson, S. ; Holmgren, M. ; Nes, E.H. van; Xu, C. - \ 2014
    Trends in Ecology and Evolution 29 (2014)8. - ISSN 0169-5347 - p. 433 - 434.
    savanna - forest - transitions - height
    An analysis of the maximum height of woody plant species across the globe reveals that an intermediate size is remarkably rare. We speculate that this may be due to intrinsic suboptimality or to ecosystem bistability with open landscapes favouring shrubs, and closed canopies propelling trees to excessive tallness.
    Traditional land use and reconsideration of environmental zoning in the Hawf Protected Area, south-eastern Yemen
    Slecht, E. ; Zaballos, L.G.H. ; Quiroz Villarreal, D.K. ; Scholte, P. ; Buerkert, A. - \ 2014
    Journal of Arid Environments 109 (2014). - ISSN 0140-1963 - p. 92 - 102.
    monsoonal fog oases - arabian peninsula - mountain pastures - genetic-structure - conservation - goats - populations - forest - kenya
    The Al Hawf area at the Yemen–Oman border hosts a unique fog-derived ecosystem which, due to its high diversity of plant and animal species, merits protection. Given the area's remoteness, poor infrastructure, high population growth and limited exchanges across the Omani border, the local livelihoods strongly rely on the exploitation of natural marine and terrestrial resources. Since quantitative data on the intensity of anthropogenic pressure on the terrestrial ecosystem are lacking, the present study analysed the impact of agricultural and pastoral land use on the vegetation of the designated Hawf Protected Area (HPA). To this end structured interviews, village walks and other rural appraisal tools were combined with vegetation surveys and GPS-based monitoring of pasturing livestock herds. The loss of traditional herding systems that regulated selective management of fragile grazing grounds along the altitude gradient in the HPA, particularly for camels, the overexploitation of woody perennials for construction purposes, and the resettlement of former migrant workers are major constraints for the successful implementation of the government-designed management plan. Implementation could be improved by better taking into account the vegetation composition in the area, current and traditional grazing schemes and local people's needs for off-farm income
    Relative growth rate variation of evergreen and deciduous savanna tree species is driven by different traits
    Tomlinson, K.W. ; Poorter, L. ; Bongers, F. ; Borghetti, F. ; Jacobs, L. ; Langevelde, F. van - \ 2014
    Annals of Botany 114 (2014)2. - ISSN 0305-7364 - p. 315 - 324.
    phylogenetically independent contrasts - adaptive significance - carbohydrate storage - shade tolerance - seedling shade - woody-plants - allocation - biomass - forest - strategies
    Background and Aims Plant relative growth rate (RGR) depends on biomass allocation to leaves (leaf mass fraction, LMF), efficient construction of leaf surface area (specific leaf area, SLA) and biomass growth per unit leaf area (net assimilation rate, NAR). Functional groups of species may differ in any of these traits, potentially resulting in (1) differences in mean RGR of groups, and (2) differences in the traits driving RGR variation within each group. We tested these predictions by comparing deciduous and evergreen savanna trees. Methods RGR, changes to biomass allocation and leaf morphology, and root non-structural carbohydrate reserves were evaluated for juveniles of 51 savanna species (34 deciduous, 17 evergreen) grown in a common garden experiment. It was anticipated that drivers ofRGRwould differ between leaf habit groups because deciduous species have to allocate carbohydrates to storage in roots to be able to flush leaves again, which directly compromises their LMF, whereas evergreen species are not subject to this constraint. Key Results Evergreen species had greaterLMFandRGRthan deciduous species. Amongdeciduous speciesLMF explained 27% of RGR variation (SLA 34% and NAR 29 %), whereas among evergreen species LMF explained between 2 and 17% of RGR variation (SLA 32–35% and NAR 38–62 %). RGR and LMF were (negatively) related to carbohydrate storage only among deciduous species. Conclusions Trade-offs between investment in carbohydrate reserves and growth occurred only among deciduous species, leading to differences in relative contribution made by the underlying components of RGR between the leaf habit groups. The results suggest that differences in drivers ofRGRoccur among savanna species because these have different selected strategies for coping with fire disturbance in savannas. It is expected that variation in the drivers of RGR will be found in other functional types that respond differently to particular disturbances.
    Social Networks of Corruption in the Vietnamese and Lao Cross-Border Timber Trade
    To, P.X. ; Mahanty, S. ; Dressler, W.H. - \ 2014
    Anthropological Forum : a journal of social anthropology and comparative sociology 24 (2014)2. - ISSN 0066-4677 - p. 154 - 174.
    forest - politics
    Although corruption is a core issue in discourses on Southeast Asian states and the region's illegal timber trade, its specific meanings, characteristics, and role are poorly understood. Our ethnographic study of corruption and timber trade in the lower Mekong uncovers the relationships, dealings, and networks that enable illegal timber flows. We follow the disputed case of a shipment of high-value timber that originated in Laos and was seized by Vietnamese seaport customs officials in 2011. By examining the actors involved and their efforts to obtain the release of the timber, we reveal the complex and networked nature of relationships from local to national levels that enable illicit rosewood trade from Laos to Vietnam and onward from Vietnamese ports. At the same time, interactions between timber traders and state officials highlight the recursive relationship between ‘private’ and ‘state’ actors, and the scope for mobility between these categories. Our analysis challenges the current international and national emphasis on law enforcement as a means to tackle illegal logging. Instead, policy would be better founded on a more holistic and nuanced understanding of the socio-political relationships that characterise and perpetuate corruption across these multiple scales.
    Rapid characterisation of vegetation structure to predict refugia and climate change impacts across a global biodiversity hotspot
    Schut, A.G.T. ; Wardell-Johnson, G.W. ; Yates, C.J. ; Keppel, G. ; Baran, I. ; Franklin, S.E. ; Hopper, S.D. ; Niel, K.P. Van; Mucina, L. ; Byrne, M. - \ 2014
    PLoS ONE 9 (2014)1. - ISSN 1932-6203 - 15 p.
    australian floristic region - western-australia - conservation - forest - fire - future - scale - distributions - microrefugia - inselbergs
    Identification of refugia is an increasingly important adaptation strategy in conservation planning under rapid anthropogenic climate change. Granite outcrops (GOs) provide extraordinary diversity, including a wide range of taxa, vegetation types and habitats in the Southwest Australian Floristic Region (SWAFR). However, poor characterization of GOs limits the capacity of conservation planning for refugia under climate change. A novel means for the rapid identification of potential refugia is presented, based on the assessment of local-scale environment and vegetation structure in a wider region. This approach was tested on GOs across the SWAFR. Airborne discrete return Light Detection And Ranging (LiDAR) data and Red Green and Blue (RGB) imagery were acquired. Vertical vegetation profiles were used to derive 54 structural classes. Structural vegetation types were described in three areas for supervised classification of a further 13 GOs across the region. Habitat descriptions based on 494 vegetation plots on and around these GOs were used to quantify relationships between environmental variables, ground cover and canopy height. The vegetation surrounding GOs is strongly related to structural vegetation types (Kappa = 0.8) and to its spatial context. Water gaining sites around GOs are characterized by taller and denser vegetation in all areas. The strong relationship between rainfall, soil-depth, and vegetation structure (R2 of 0.8–0.9) allowed comparisons of vegetation structure between current and future climate. Significant shifts in vegetation structural types were predicted and mapped for future climates. Water gaining areas below granite outcrops were identified as important putative refugia. A reduction in rainfall may be offset by the occurrence of deeper soil elsewhere on the outcrop. However, climate change interactions with fire and water table declines may render our conclusions conservative. The LiDAR-based mapping approach presented enables the integration of site-based biotic assessment with structural vegetation types for the rapid delineation and prioritization of key refugia.
    Tipping points in tropical tree cover: linking theory to data
    Nes, E.H. van; Hirota, M. ; Holmgren, M. ; Scheffer, M. - \ 2014
    Global Change Biology 20 (2014)3. - ISSN 1354-1013 - p. 1016 - 1021.
    critical transitions - global resilience - climate-change - stable states - savanna - fire - forest - ecosystems - amazon - deforestation
    It has recently been found that the frequency distribution of remotely sensed tree cover in the tropics has three distinct modes, which seem to correspond to forest, savanna and treeless states. This pattern has been suggested to imply that these states represent alternative attractors, and that the response of these systems to climate change would be characterized by critical transitions and hysteresis. Here, we show how this inference is contingent upon mechanisms at play. We present a simple dynamical model that can generate three alternative tree cover states (forest, savanna and a treeless state), based on known mechanisms, and use this model to simulate patterns of tree cover under different scenarios. We use these synthetic data to show that the hysteresis inferred from remotely sensed tree cover patterns will be inflated by spatial heterogeneity of environmental conditions. On the other hand, we show that the hysteresis inferred from satellite data may actually underestimate real hysteresis in response to climate change if there exists a positive feedback between regional tree cover and precipitation. Our results also indicate that such positive feedback between vegetation and climate should cause direct shifts between forest and a treeless state (rather than through an intermediate savanna-state) to become more likely. Lastly, we show how directionality of historical change in conditions may bias the observed relationship between tree cover and environmental conditions.
    Diversity and dynamics of management of gum and resin resources in Ethiopia: a trade-off between domestication and degradation
    Lemenih, M. ; Wiersum, K.F. ; Teshale Woldeamanuel Habebo, Teshale ; Bongers, F. - \ 2014
    Land Degradation and Development 25 (2014)2. - ISSN 1085-3278 - p. 130 - 142.
    papyrifera del. hochst - boswellia-papyrifera - biodiversity conservation - northern ethiopia - forest - frankincense - acacia - restoration - environment - landscapes
    Although the human domestication of forest and tree resources is often considered to result in resource degradation, it may also lead to improved resource potentials. This paper assesses the nature and dynamics of gum and resin focused woodland exploitation and management systems in Ethiopia in the context of degradation and domestication processes. In three sites with commercial gum resin producing woodlands and production history, we studied variation in (i) woodland management and gum resin production systems and (ii) socio-economic and biophysical factors that condition the management and production systems. On the basis of their organizational features, we formulated nine production models and related them to different phases of domestication and different degrees of ecosystem degradation. The production systems gradually evolved from the extraction of wild trees to production in an adapted forest system. However, domesticated woodlands with an adapted forest structure and composition and increased provisioning services are still little developed despite decades of production history. Many of these woodlands are undergoing serious degradation because of low quality management practices. This is mainly attributable to existing land use practices and the social arrangements for the production of and trade in the gums and resins. The findings illustrate that domestication involves not only a change in ecological and production systems but also the development of social arrangements for production and trade. We conclude that the status of domestication in a social sense determines whether forests and/or specific forest resources are degraded or aggraded in the sense of resource enrichment
    On the variation of regional CO2 exchange over temperate and boreal North America
    Zhang, X. ; Gurney, K.R. ; Peylin, P. ; Chevallier, F. ; Law, R.M. ; Patra, P.K. ; Rayner, P.J. ; Roedenbeck, C. ; Krol, M.C. - \ 2013
    Global Biogeochemical Cycles 27 (2013)4. - ISSN 0886-6236 - p. 991 - 1000.
    atmospheric carbon-dioxide - terrestrial ecosystems - united-states - interannual variability - climate - forest - trends - drought - fluxes - land
    Inverse-estimated net carbon exchange time series spanning two decades for six North American regions are analyzed to examine long-term trends and relationships to temperature and precipitation variations. Results reveal intensification of carbon uptake in eastern boreal North America (0.1 PgC/decade) and the Midwest United States (0.08 PgC/decade). Seasonal cross-correlation analysis shows a significant relationship between net carbon exchange and temperature/precipitation anomalies during the western United States growing season with warmer, dryer conditions leading reduced carbon uptake. This relationship is consistent with global change-type drought dynamics which drive increased vegetation mortality, increases in dry woody material, and increased wildfire occurrence. This finding supports the contention that future climate change may increase carbon loss in this region. Similarly, higher temperatures and reduced precipitation are accompanied by decreased net carbon uptake in the Midwestern United States toward the end of the growing season. Additionally, intensified net carbon uptake during the eastern boreal North America growing season is led by increased precipitation anomalies in the previous year, suggesting the influence of climate memory carried by regional snowmelt water. The two regions of boreal North America exhibit opposing seasonal carbon-temperature relationships with the eastern half experiencing a net carbon loss with near coincident increases in temperature and the western half showing increased net carbon uptake. The carbon response in the boreal west region lags the temperature anomalies by roughly 6months. This opposing carbon-temperature relationship in boreal North America may be a combination of different dominant vegetation types, the amount and timing of snowfall, and temperature anomaly differences across boreal North America.
    Soil organic matter dynamics in Mediterranean A-horizons-The use of analytical pyrolysis to ascertain land-use history
    Schellekens, J. ; Barbera, G.G. ; Buurman, P. ; Perez-Jorda, G. ; Martinez-Cortizas, A. - \ 2013
    Journal of Analytical and Applied Pyrolysis 104 (2013). - ISSN 0165-2370 - p. 287 - 298.
    chromatography-mass-spectrometry - black carbon - fractionation methods - calcareous soils - nw spain - gc/ms - turnover - biomass - lignin - forest
    In archaeology and nature conservation studies, knowledge about (pre)historical land-use is important. The molecular composition of soil organic matter (SOM) supplies information about its history, as its composition is controlled by input material and decay processes. In this study, the molecular composition of SOM of calcareous A-horizons from SE Spain was studied with pyrolysis gas chromatography/mass spectrometry (pyrolysis-GC/MS). The effect of vegetation type (Pinus halepensis forest and Stipa tenacissima grassland), land-use (cultivation with cereals and olive trees) and wildfire were examined. In addition, former grassland and agricultural soils that had been reforested with P. halepensis (35 yr) were selected. Three locations were sampled for each vegetation type, except for the olive tree (two) and cereal (six) fields, resulting in a total of 26 samples. Each sample was a composite of ten sub-samples taken from a plot of I ha. After removal of weakly or non-decomposed particulate OM, two OM fractions were obtained; (i) sodium hydroxide (NaOH) extractable OM and (ii) the OM that remained after extraction, which was isolated after dissolution of minerals by repeated hydrofluoric acid (HF) treatment. The NaOH-extractable fraction is generally used in soil chemistry (i.e. humic acid), but surprisingly little is known about the SOM that remains in the residue (i.e. humin plus minerals). Comparison of the two SOM fractions (by factor analyses applied to 82 quantified pyrolysis products) provided insight into soil OM dynamics. Polyaromatic pyrolysis products were more prominent in the extractable OM, while a relative enrichment of aliphatic compounds was found in the non-extractable OM. Although some pyrolysis products were associated with one vegetation type in both SOM fractions (C-3-naphthalene, dimethylphenanthrene and 2,3,5-trimethylphenanthrene, retene, and monoterpenes for both burnt and unburnt P. halepensis forest: benzene, naphthalene and C-1-naphthalene for burnt and unburnt S. tenacissima grassland), lignin content and composition highly differed between agricultural soils and soils under native vegetation in both SOM fractions. These differences were mainly decay characteristics, reinforced by cultivation. In reforested soils it was still possible to identify their former land-use, decades after the vegetation change. The probability of the sites to be correctly attributed to its present land-use was P > 0.7 for grassland and pine forest, while most of the cultivated sites had a P > 0.5 to be assigned correctly. The results obtained suggest that the molecular composition of SOM has a large potential for reconstructing land-use history, at least at the scale of decades/centuries. (C) 2013 Elsevier B.V. All rights reserved.
    Are the mangroves in the Galle-Unawatuna area (Sri Lanka) at risk? A social-ecological approach involving local stakeholders for a better conservation policy
    Satyanarayana, B. ; Mulder, S. ; Jayatissa, L.P. ; Dahdouh-Guebas, F. - \ 2013
    Ocean & Coastal Management 71 (2013). - ISSN 0964-5691 - p. 225 - 237.
    indian-ocean tsunami - coastal vegetation - environmental-change - socioeconomic data - natural disasters - human-populations - ecosystems - forest - protection - perceptions
    Despite the known ecological and economic importance of mangrove ecosystems, research is still lacking as to what extent local populations depends on various forest products, or how this might be related to their economic status (i.e. poor, middle and rich), age, or gender (male and female) relations. In the present study, the percentage of people depending on such resources in the Galle-Unawatuna area (Sri Lanka) for their subsistence needs was assessed through a survey. The results indicated that local people rely on mangroves to a greater extent for fishery products, fuelwood, and edible plants, than for house/boat construction material, medicinal and other non-timber forest products. All people under the poor, middle and rich categories use mangrove resources, although greater dependency of the poor is common. In relation to age, the mangrove resources utilization was high among old (>60 years) people. A gendered division of labor indicating the men involved in fishery-related activities and women in edible plant collection was observed. In addition, the use of mangrove resources is not necessarily poverty-driven: preference and tradition also play important roles. However, the physical infrastructure developments (i.e. construction of a cement factory, dam and road) have had several negative impacts ranging from water quality deterioration and dynamic shifts in mangrove vegetation to reduced fish production in the vicinity. Given our results, possible amendments to the existing rules governing forest conservation are recommended in order to provide long-term benefits for local livelihoods as well as ecosystem. (C) 2012 Elsevier Ltd. All rights reserved.
    Comparison of Soil Respiration in Typical Conventional and New Alternative Cereal Cropping Systems on the North China Plain
    Gao, B. ; Ju, X.T. ; Su, F. ; Gao, F.B. ; Cao, Q.S. ; Oenema, O. ; Christie, P. ; Chen, X.P. ; Zhang, F.S. - \ 2013
    PLoS ONE 8 (2013)11. - ISSN 1932-6203
    carbon-dioxide - water-content - temperature - nitrogen - dependence - ecosystem - tillage - forest - management - moisture
    We monitored soil respiration (Rs), soil temperature (T) and volumetric water content (VWC%) over four years in one typical conventional and four alternative cropping systems to understand Rs in different cropping systems with their respective management practices and environmental conditions. The control was conventional double-cropping system (winter wheat and summer maize in one year - Con. W/M). Four alternative cropping systems were designed with optimum water and N management, i.e. optimized winter wheat and summer maize (Opt. W/M), three harvests every two years (first year, winter wheat and summer maize or soybean; second year, fallow then spring maize - W/M-M and W/S-M), and single spring maize per year (M). Our results show that Rs responded mainly to the seasonal variation in T but was also greatly affected by straw return, root growth and soil moisture changes under different cropping systems. The mean seasonal CO2 emissions in Con. W/M were 16.8 and 15.1 Mg CO2 ha(-1) for summer maize and winter wheat, respectively, without straw return. They increased significantly by 26 and 35% in Opt. W/M, respectively, with straw return. Under the new alternative cropping systems with straw return, W/M-M showed similar Rs to Opt. W/M, but total CO2 emissions of W/S-M decreased sharply relative to Opt. W/M when soybean was planted to replace summer maize. Total CO2 emissions expressed as the complete rotation cycles of W/S-M, Con. W/M and M treatments were not significantly different. Seasonal CO2 emissions were significantly correlated with the sum of carbon inputs of straw return from the previous season and the aboveground biomass in the current season, which explained 60% of seasonal CO2 emissions. T and VWC% explained up to 65% of Rs using the exponential-power and double exponential models, and the impacts of tillage and straw return must therefore be considered for accurate modeling of Rs in this geographical region.
    An institutional analysis of deforestation processes in protected areas: The case of the transboundary Mt. Elgon, Uganda and Kenya
    Petursson, J.G. ; Vedeld, P. ; Sassen, M. - \ 2013
    Forest Policy and Economics 26 (2013). - ISSN 1389-9341 - p. 22 - 33.
    mount-elgon - forest - conservation - management - biodiversity - livelihoods - tropics - parks
    Protected areas (PAs) are a country's key strategy to conserve and manage forest resources. In sub-Saharan Africa, the effectiveness and efficiency of PA institutions in delivering sustainable outcomes is debated, however, and deforestation has not been avoided within such formal regimes. This paper analyzes the processes that led to deforestation within the PAs on the transboundary Mt. Elgon, Uganda-Kenya, employing institutional theory. Landsat satellite imagery helped identify and quantify forest loss over time. The study showed how, since 1973, about a third of all forests within the PAs on Elgon have been cleared in successive processes. Within formal protected area regimes, complex political and institutional factors drive forest loss. We argue, therefore, that policies to counter deforestation using a PA model have to be considered and understood against the broader background of these factors, originating both inside and outside the PA regimes. (C) 2012 Elsevier B.V. All rights reserved.
    Fusion of MODIS Images Using Kriging With External Drift
    Ribeiro Sales, M.H. ; Souza, C.M. ; Kyriakidis, P.C. - \ 2013
    IEEE Transactions on Geoscience and Remote Sensing 51 (2013)4. - ISSN 0196-2892 - p. 2250 - 2259.
    spatial-resolution - land-cover - wavelet decomposition - prediction - forest - brazil - ihs
    The Moderate Resolution Imaging Spectroradiometer (MODIS) has been used in several remote sensing studies, including land, ocean, and atmospheric applications. The advantages of this sensor are its high spectral resolution, with 36 spectral bands; its high revisiting frequency; and its public domain availability. The first seven bands of MODIS are in the visible, near-infrared, and mid-infrared spectral regions of the electromagnetic spectrum which are sensitive to spectral changes due to deforestation, burned areas, and vegetation regrowth, among other land-use changes, making near-real-time forest monitoring a suitable application. However, the different spatial resolution of the spectral bands placed in these spectral regions imposes challenges to combine them in forest monitoring applications. In this paper, we present an algorithm based on geostatistics to downscale five 500-m MODIS pixel bands to match two 250-m pixel bands. We also discuss the advantages and limitations of this method in relation to existing downscaling algorithms. Our proposed method merges the data to the best spatial resolution and better retains the spectral information of the original data.
    Hot fire, cool soil
    Stoof, C.R. ; Moore, D. ; Fernandes, P. ; Stoorvogel, J.J. ; Fernandes, R. ; Ferreira, A.J.D. ; Ritsema, C.J. - \ 2013
    Geophysical Research Letters 40 (2013)8. - ISSN 0094-8276 - p. 1534 - 1539.
    south-eastern australia - intensity - behavior - forest - temperatures - variability - erodibility - germination - california - vegetation
    Wildfires greatly increase a landscape's vulnerability to flooding and erosion events by removing vegetation and changing soils. Fire damage to soil increases with increasing soil temperature, and, for fires where smoldering combustion is absent, the current understanding is that soil temperatures increase as fuel load and fire intensity increase. Here, however, we show that this understanding that is based on experiments under homogeneous conditions does not necessarily apply at the more relevant larger scale where soils, vegetation, and fire characteristics are heterogeneous. In a catchment-scale fire experiment, soils were surprisingly cool where fuel load was high and fire was hot and, conversely, soils were hot where expected to be cooler. This indicates that the greatest fire damage to soil can occur where fuel load and fire intensity are low rather than high, and has important implications for management of fire-prone areas prior to, during, and after fire events.
    Assessing the effects of seasonal grazing on holm oak regeneration: implications for the conservation of Mediterranean dehesas
    Carmona, C.P. ; Azcárate, F.M. ; Oteros Rozas, E. ; González, J.A. ; Peco, B. - \ 2013
    Biological Conservation 159 (2013). - ISSN 0006-3207 - p. 240 - 247.
    scattered trees - agricultural landscapes - size structure - land-use - forest - environment - future - cattle - consequences - transhumance
    Scattered trees in agricultural landscapes are globally declining due to the intensification of agricultural practices. Dehesas, highly species-diverse Mediterranean open woodlands, are seriously affected by this decline, because of a generalized regeneration failure of oak, which compromise their long-term stability. Traditionally, dehesas were the wintering areas for transhumant herds, but transhumance is disappearing in the Mediterranean, due to multiple causes. Reductions in grazing intensity or grazing abandonment have been proposed to improve oak regeneration in dehesas, but the effect of the recovery of noncontinuous grazing practices such as transhumance has not been tested to date. We measured different indicators of holm oak regeneration and condition in dehesas under transhumant grazing and in dehesas under permanent grazing in southern Spain. Oak juveniles were remarkably less browsed and their canopies covered a much higher area in transhumant estates. As a consequence, the median density of saplings was more than four times higher in transhumant than in permanently-grazed estates. Although transhumant grazing is necessarily associated with a reduction in the stocking rate across the year, the timing of grazing was always included as a predictor in the best models to explain the condition and density of holm oak. Our results suggest that the lack of oak regeneration in dehesas can be caused not only by the increases in stocking rates, but also by the recent abandonment of traditional grazing practices like transhumance. We propose the recovery of seasonal grazing regimes based on transhumant pastoralism as a measure to improve the conservation status of dehesas.
    Soil organic matter: chemistry and physical characteristics and analytical methods. A review
    Branco de Freitas Maia, C.M. ; Novotny, E.H. ; Francischinelli Rittl, T. ; Bermingham Hayes, M.H. - \ 2013
    Current Organic Chemistry 17 (2013)24. - ISSN 1385-2728 - p. 2985 - 2990.
    nuclear-magnetic-resonance - black carbon - humic substances - reflectance spectroscopy - light fraction - amazon region - sediments - acids - charcoal - forest
    Soil organic matter (SOM) holds a prominent place among the many indicators that are studied in relation to soil function. Different viewpoints are reflected in characterizing SOM, depending on the study procedures used, or the focus of the researchers. There are many possibilities for the isolation and fractionation of SOM and this has led to a plurality of interpretations and conclusions. Transformations to organic materials that lead to the more recalcitrant components of SOM are outlined, and the associations which these materials can have in the soil environment, and aspects of their compositions are referred to. A review is given of the organic matter pools in soils, of their functions, and of the controls which they have in soil systems. A succinct review is given of physical fractionation procedures for SOM. This approach is highly relevant, though rarely used in modern studies of SOM. The merits and demerits of wet oxidation procedures, relative to dry combustion for determining soil organic carbon contents are discussed, and reference is made to the emerging chemometric techniques based on the use of Near (NIR) and Mid (MIR) infrared spectroscopy.
    Growth response of Scots pine with different crown transparency status to drought release
    Eilmann, B. ; Dobbertin, M. ; Rigling, A. - \ 2013
    Annals of Forest Science 70 (2013)7. - ISSN 1286-4560 - p. 685 - 693.
    swiss rhone valley - pinning method - pubescent oak - xylem growth - mortality - sylvestris - forest - populations - dynamics - decline
    Context - One short-term adjustment of trees to drought is the reduction of photosynthetic tissues via leaf shedding. But in conifers, it usually takes several years to fully restore needle mass and assimilation capacity. Aims - This study aims to evaluate whether leaf shedding sustainably damages conifers or if these trees still have the ability to recover from drought with respect to their foliage and wood formation. Methods - An irrigation experiment was established in a mature dry forest to test the growth reactions of Scots pine (Pinus sylvestris L.) differing in crown transparency (low, medium, high) to a drought release by irrigation in comparison with equivalent control trees growing under naturally dry conditions on the same site. Results - Drought and high crown transparency had a combined negative effect on radial tree growth: Control trees with medium to high crown transparencies showed a substantially shorter growth period and a long-lasting growth depression in response to the severe summer drought in 2003. However, all trees benefited from irrigation, irrespective of their crown status, and immediately increased growth in response to irrigation. Conclusion - The progressed drought-induced defoliation seemed to be a weakening factor for trees suffering from drought, but this can be reversed if the water supply is improved.
    Microclimate moderates plant responses to macroclimate warming
    Frenne, P. De; Rodríguez-Sánchez, F. ; Coomes, D. ; Baeten, L. ; Verstraeten, G. ; Hommel, P.W.F.M. - \ 2013
    Proceedings of the National Academy of Sciences of the United States of America 110 (2013)46. - ISSN 0027-8424 - p. 18561 - 18565.
    recent climate-change - forest - vegetation - communities - ecosystem - scale - debt
    Recent global warming is acting across marine, freshwater, and terrestrial ecosystems to favor species adapted to warmer conditions and/or reduce the abundance of cold-adapted organisms (i.e., “thermophilization” of communities). Lack of community responses to increased temperature, however, has also been reported for several taxa and regions, suggesting that “climatic lags” may be frequent. Here we show that microclimatic effects brought about by forest canopy closure can buffer biotic responses to macroclimate warming, thus explaining an apparent climatic lag. Using data from 1,409 vegetation plots in European and North American temperate forests, each surveyed at least twice over an interval of 12–67 y, we document significant thermophilization of ground-layer plant communities. These changes reflect concurrent declines in species adapted to cooler conditions and increases in species adapted to warmer conditions. However, thermophilization, particularly the increase of warm-adapted species, is attenuated in forests whose canopies have become denser, probably reflecting cooler growing-season ground temperatures via increased shading. As standing stocks of trees have increased in many temperate forests in recent decades, local microclimatic effects may commonly be moderating the impacts of macroclimate warming on forest understories. Conversely, increases in harvesting woody biomass—e.g., for bioenergy—may open forest canopies and accelerate thermophilization of temperate forest biodiversity.
    Towards a consistent approach for ecosystem accounting
    Edens, B. ; Hein, L.G. - \ 2013
    Ecological Economics 90 (2013). - ISSN 0921-8009 - p. 41 - 52.
    developing-countries - land-use - services - valuation - framework - forest - biodiversity - environment - resilience - limits
    In spite of an increasing interest in environmental economic accounting, there is still very limited experience with the integration of ecosystem services and ecosystem capital in national accounts. This paper identifies four key methodological challenges in developing ecosystem accounts: the definition of ecosystem services in the context of accounting, their allocation to institutional sectors; the treatment of degradation and rehabilitation, and valuing ecosystem services consistent with SNA principles. We analyze the different perspectives taken on these challenges and present a number of proposals to deal with the challenges in developing ecosystem accounts. These proposals comprise several novel aspects, including (i) presenting an accounting approach that recognizes that most ecosystems are strongly influenced by people and that ecosystem services depend on natural processes as well as human ecosystem management; and, (ii) recording ecosystem services as either contributions of a private land owner or as generated by a sector ’Ecosystems’ depending on the type of ecosystem service. We also present a consistent approach for recording degradation, and for applying monetary valuation approaches in the context of accounting.
    Hyperspectral reflectance of leaves and flowers of an outbreak species discriminates season and successional stage of vegetation
    Almeida De Carvalho, S. ; Schlerf, M. ; Putten, W.H. van der; Skidmore, A. - \ 2013
    International Journal of applied Earth Observation and Geoinformation 24 (2013). - ISSN 0303-2434 - p. 32 - 41.
    absorption features - qinling mountains - leaf biochemistry - senecio-jacobaea - golden takin - plant - soil - chemistry - forest - chronosequence
    Spectral reflectance can be used to assess large-scale performances of plants in the field based on plant nutrient balance as well as composition of defence compounds. However, plant chemical composition is known to vary with season – due to its phenology – and it may even depend on the succession stage of its habitat. Here we investigate (i) how spectral reflectance could be used to discriminate successional and phenological stages of Jacobaea vulgaris in both leaf and flower organs and (ii) if chemical content estimation by reflectance is flower or leaf dependent. We used J. vulgaris, which is a natural outbreak plant species on abandoned arable fields in north-western Europe and studied this species in a chronosequence representing successional development during time since abandonment. The chemical content and reflectance between 400 and 2500 nm wavelengths of flowers and leaves were measured throughout the season in fields of different successional ages. The data were analyzed with multivariate statistics for temporal discrimination and estimation of chemical contents in both leaf and flower organs. Two main effects were revealed by spectral reflectance measurements: (i) both flower and leaf spectra show successional and seasonal changes, but the pattern is complex and organ specific (ii) flower head pyrrolizidine alkaloids, which are involved in plant defence against herbivores, can be detected through hyperspectral reflectance.We conclude that spectral reflectance of both leaves and flowers can provide information on plant performance during season and successional stages. As a result, remote sensing studies of plant performance in complex field situations will benefit from considering hyperspectral reflectance of different plant organs. This approach may enable more detailed studies on the link between spectral information and plant defence dynamics both aboveground and belowground.
    Shrimp pond effluent dominates foliar nitrogen in disturbed mangroves as mapped using hyperspectral imagery
    Fauzi, A. ; Skidmore, A.K. ; Gils, H. ; Schlerf, M. ; Heitkonig, I.M.A. - \ 2013
    Marine Pollution Bulletin 76 (2013)1-2. - ISSN 0025-326X - p. 42 - 51.
    leaf-area index - species discrimination - absorption features - chlorophyll content - squares regression - vegetation indexes - avicennia-marina - canopy nitrogen - reflectance - forest
    Conversion of mangroves to shrimp ponds creates fragmentation and eutrophication. Detection of the spatial variation of foliar nitrogen is essential for understanding the effect of eutrophication on mangroves. We aim (i) to estimate nitrogen variability across mangrove landscapes of the Mahakam delta using airborne hyperspectral remote sensing (HyMap) and (ii) to investigate links between the variation of foliar nitrogen mapped and local environmental variables. In this study, multivariate prediction models achieved a higher level of accuracy than narrow-band vegetation indices, making multivariate modeling the best choice for mapping. The variation of foliar nitrogen concentration in mangroves was significantly influenced by the local environment: (1) position of mangroves (seaward/landward), (2) distance to the shrimp ponds, and (3) predominant mangrove species. The findings suggest that anthropogenic disturbances, in this case shrimp ponds, influence nitrogen variation in mangroves. Mangroves closer to the shrimp ponds had higher foliar nitrogen concentrations.
    When Policy Hits the Ground. An Empirical Study of the Communication Practices of Project Managers of a Water Board in Conversations for Collaborative Governance
    Lems, P. ; Aarts, N. ; Woerkum, C.M.J. van - \ 2013
    Environmental Policy and Governance 23 (2013)4. - ISSN 1756-932X - p. 234 - 246.
    conflict - frames - identity - forest
    Civil servants organize collaborations with private actors with the aim of developing policy outcomes that fit environmental policy frameworks, shaping the course and outcome of collaborations through their communication practices. To investigate these practices and their effect, we conducted a case study, shadowing project managers from a Dutch water board. We identified two distinct communication practices: frame incorporation and frame amplification. These practices respectively expanded or narrowed a process of collaborative governance, either purposefully by building social capital or unintentionally by distancing the conversation partner and his concern. The structural difference between these practices suggests that civil servants lack shared practices that foster collaboration. Interestingly, in neither practice do the civil servants discursively acknowledge their dependence on their conversation partner's support, and thus they deny that they are participating in a negotiation process: they claim that their conversation partner should cooperate. In effect, their conversation partners bypass the incorporation and amplification practices. The research suggests that, of the two practices identified, only incorporation builds the social capital that enables civil servants to switch to another approach in future interactions and start an integrative negotiation on problems and solutions
    Evapotranspiration amplifies European summer drought
    Teuling, A.J. ; Loon, A.F. van; Seneviratne, S.I. ; Lehner, I. ; Aubinet, M. ; Heinesch, B. ; Bernhofer, C. ; Grünwald, T. ; Prasse, H. ; Spank, U. - \ 2013
    Geophysical Research Letters 40 (2013)10. - ISSN 0094-8276 - p. 2071 - 2075.
    forest - simulations - exchange - carbon - scale
    Drought is typically associated with a lack of precipitation, whereas the contribution of evapotranspiration and runoff to drought evolution is not well understood. Here we use unique long-term observations made in four headwater catchments in central and western Europe to reconstruct storage anomalies and study the drivers of storage anomaly evolution during drought. We provide observational evidence for the “drought-paradox” in that region: a consistent and significant increase in evapotranspiration during drought episodes, which acts to amplify the storage anomalies. In contrast, decreases in runoff act to limit storage anomalies. Our findings stress the need for the correct representation of evapotranspiration and runoff processes in drought indices.
    Changes in plant defense chemistry (pyrrolizidine alkaloids) revealed through high-resolution spectroscopy
    Almeida De Carvalho, S. ; Macel, M. ; Schlerf, M. ; Moghaddam, F.E. ; Mulder, P.P.J. ; Skidmore, A.K. ; Putten, W.H. van der - \ 2013
    ISPRS Journal of Photogrammetry and Remote Sensing 80 (2013). - ISSN 0924-2716 - p. 51 - 60.
    near-infrared spectroscopy - senecio-jacobaea - red edge - nitrogen - leaf - reflectance - forest - regression - vegetation - prediction
    Plant toxic biochemicals play an important role in defense against natural enemies and often are toxic to humans and livestock. Hyperspectral reflectance is an established method for primary chemical detection and could be further used to determine plant toxicity in the field. In order to make a first step for pyrrolizidine alkaloids detection (toxic defense compound against mammals and many insects) we studied how such spectral data can estimate plant defense chemistry under controlled conditions. In a greenhouse, we grew three related plant species that defend against generalist herbivores through pyrrolizidine alkaloids: Jacobaea vulgaris, Jacobaea erucifolia and Senecio inaequidens, and analyzed the relation between spectral measurements and chemical concentrations using multivariate statistics. Nutrient addition enhanced tertiary-amine pyrrolizidine alkaloids contents of J. vulgaris and J. erucifolia and decreased N-oxide contents in S. inaequidens and J. vulgaris. Pyrrolizidine alkaloids could be predicted with a moderate accuracy. Pyrrolizidine alkaloid forms tertiary-amines and epoxides were predicted with 63% and 56% of the variation explained, respectively. The most relevant spectral regions selected for prediction were associated with electron transitions and CH, OH, and NH bonds in the 1530 and 2100 nm regions. Given the relatively low concentration in pyrrolizidine alkaloids concentration (in the order of mg g-1) and resultant predictions, it is promising that pyrrolizidine alkaloids interact with incident light. Further studies should be considered to determine if such a non-destructive method may predict changes in PA concentration in relation to plant natural enemies. Spectroscopy may be used to study plant defenses in intact plant tissues, and may provide managers of toxic plants, food industry and multitrophic-interaction researchers with faster and larger monitoring possibilities
    Effects of interannual climate variability on tropical tree cover
    Holmgren, M. ; Hirota, M. ; Nes, E.H. van; Scheffer, M. - \ 2013
    Nature Climate Change 3 (2013). - ISSN 1758-678X - p. 755 - 758.
    el-nino - critical transitions - shrub encroachment - south-america - woody cover - savanna - forest - determinants - ecosystems - africa
    Climatic warming is substantially intensifying the global water cycle1 and is projected to increase rainfall variability2. Using satellite data, we show that higher climatic variability is associated with reduced tree cover in the wet tropics globally. In contrast, interannual variability in rainfall can have neutral or even positive effects on tree cover in the dry tropics. In South America, tree cover in dry lands is higher in areas with high year-to-year variability in rainfall. This is consistent with evidence from case studies suggesting that in these areas rare wet episodes are essential for opening windows of opportunity where massive tree recruitment can overwhelm disturbance effects, allowing the establishment of extensive woodlands. In Australia, wet extremes have similar effects, but the net effect of rainfall variability is overwhelmed by negative effects of extreme dry years. In Africa, effects of rainfall variability are neutral for dry lands. It is most likely that differences in herbivore communities and fire regimes contribute to regulating tree expansion during wet extremes. Our results illustrate that increasing climatic variability may affect ecosystem services in contrasting, and sometimes surprising, ways. Expansion of dry tropical tree cover during extreme wet events may decrease grassland productivity but enhance carbon sequestration, soil nutrient retention and biodiversity.
    Home field advantage of cattle manure decomposition affects the apparent nitrogen recovery in production grasslands
    Rashid, M.I. ; Goede, R.G.M. de; Brussaard, L. ; Lantinga, E.A. - \ 2013
    Soil Biology and Biochemistry 57 (2013). - ISSN 0038-0717 - p. 320 - 326.
    leaf-litter decomposition - on-farm experiments - soil - quality - mineralization - community - forest - plant - fertilizers - management
    Based on evidence from forest ecosystems that litter decomposition is highest in its home habitat, the so-called home field advantage (HFA), we tested whether HFA also occurs in production grasslands, to which solid cattle manure (SCM) was applied. Two dairy farms were selected which differed in type of home-produced SCM (stacked or composted) and soil type (sand or peat). Disappearance patterns of manure dry matter (DM) and nitrogen (N) were monitored from litterbags (4 mm mesh size) during the grass growing season. At the same time, apparent herbage N recovery (ANR) of SCM, applied at two rates (200 and 400 kg N ha-1 yr-1), was measured. On average, manure DM and N disappearances on the home farms were 20 and 14% greater, respectively, than on away farms. Differences in ANR were also very pronounced (on average 14 and 53% higher at home than away for the two respective application rates). The two SCM types were also studied on two neighbouring dairy farms (one on sand and one on peat soil) where no SCM had been applied for many years. Here, manure DM and N disappearances from the litterbags were much lower (P <0.01). This experiment provides strong evidence for a home field advantage in production grasslands differing in fertilization history, showing that site-specific manure management affects the soil–plant interactions regulating plant N-availability. These findings have to be taken into account when changing fertilization regimes in production grasslands. This is the first report to quantify a HFA from an agricultural ecosystem. HFA values we report here have not been established in any ecosystem thus far.
    Origin matters! Difference in drought tolerance and productivity of coastal Douglas-fir (Pseudotsuga menziesii (Mirb.)) provenances
    Eilmann, B. ; Vries, S.M.G. de; Ouden, J. den; Mohren, G.M.J. ; Sauren, P. ; Sass, U.G.W. - \ 2013
    Forest Ecology and Management 302 (2013). - ISSN 0378-1127 - p. 133 - 143.
    climate-change - scots pine - tree-growth - variability - seedlings - forest - photosynthesis - populations - sylvestris - adaptation
    Forests of the future should be resistant to exacerbating climatic conditions, especially to increasing drought, but at the same time provide a sufficient amount and quality of timber. In this context coastal Douglas-fir (Pseudotsuga menziesii (Mirb.)) is a promising species since it remains productive even under chronic drought. By choosing suitable provenances within the range of Douglas-fir (P. menziesii (Mirb.)) for a given site we can further optimise tree fitness under dry conditions or even increase timber yield. Eighteen coastal Douglas-fir (Pseudotsuga menziesii (Mirb.) var. menziesii) provenances were tested for seedling survival, yield, wood quality, and drought tolerance by taking advantage of a Dutch provenance trial, established in 1971 within the framework of the 1966/1967 IUFRO seed collection program. The site of the Dutch trial is representative for many sites in Central Europe and is characterised by a moderate precipitation and temperature regime. Measurements on height and diameter growth were combined with a dendrochronological study on growth response to drought years. We found a clear latitudinal trend indicating that Douglas-fir provenances from the northern part of the species-distribution range are generally more productive than provenances from the south. In contrast, drought tolerance increased towards the south. This suggests that it is impossible to identify provenances combining maximum productivity with lowest susceptibility towards drought. However, based on the results from the trial we can give recommendations on suitable provenances that are expected to perform best under future conditions in Central Europe. On sites where severe drought events are unlikely to occur in future, fast growing provenances from the north, like Nimkish, should be planted. These provenances respond plastically to drought years, but the strong reduction of tree growth in the drought year itself indicates that these provenances will be harmed by an increasing frequency of drought events. However, on sites where water availability is likely to decrease, provenances from the Olympic Peninsula like Forks and Matlock are very promising since they showed still relatively high yield in combination with a high potential to cope with drought. If summer drought increases in frequency and severity as expected, the latewood/earlywood ratio will be drastically reduced with negative consequences for wood quality and cavitation resistance. However, some provenances, like Marblemount or Matlock, might compensate for the negative effect of summer drought on latewood/earlywood ratio by the contribution of photosynthesis in winter to whole-year carbon stock.
    Geometrid outbreak waves travel across Europe
    Tenow, O. ; Nilssen, A. ; Bylund, H. ; Petterson, R. ; Moraal, L.G. - \ 2013
    Journal of Animal Ecology 82 (2013)1. - ISSN 0021-8790 - p. 84 - 95.
    operophtera-brumata outbreaks - spatial synchrony - population-cycles - northern fennoscandia - insect outbreaks - lynx populations - larch budmoth - canadian lynx - winter moth - forest
    1.We show that the population ecology of the 9- to 10-year cyclic, broadleaf-defoliating winter moth (Operophtera brumata) and other early-season geometrids cannot be fully understood on a local scale unless population behaviour is known on a European scale. 2.Qualitative and quantitative data on O. brumata outbreaks were obtained from published sources and previously unpublished material provided by authors of this article. Data cover six decades from the 1950s to the first decade of twenty-first century and most European countries, giving new information fundamental for the understanding of the population ecology of O. brumata. 3.Analyses on epicentral, regional and continental scales show that in each decade, a wave of O. brumata outbreaks travelled across Europe. 4.On average, the waves moved unidirectionally ESE–WNW, that is, toward the Scandes and the Atlantic. When one wave reached the Atlantic coast after 9–10 years, the next one started in East Europe to travel the same c. 3000 km distance. 5.The average wave speed and wavelength was 330 km year-1 and 3135 km, respectively, the high speed being incongruous with sedentary geometrid populations. 6.A mapping of the wave of the 1990s revealed that this wave travelled in a straight E–W direction. It therefore passed the Scandes diagonally first in the north on its way westward. Within the frame of the Scandes, this caused the illusion that the wave moved N–S. In analogy, outbreaks described previously as moving S–N or occurring contemporaneously along the Scandes were probably the result of continental-scale waves meeting the Scandes obliquely from the south or in parallel. 7.In the steppe zone of eastern-most and south-east Europe, outbreaks of the winter moth did not participate in the waves. Here, broadleaved stands are small and widely separated. This makes the zone hostile to short-distance dispersal between O. brumata subpopulations and prevents synchronization within meta-populations. 8.We hypothesize that hostile boundary models, involving reciprocal host–herbivore–enemy reactions at the transition between the steppe and the broadleaved forest zones, offer the best explanation to the origin of outbreak waves. These results have theoretical and practical implications and indicate that multidisciplinary, continentally coordinated studies are essential for an understanding of the spatio-temporal behaviour of cyclic animal populations
    A large-eddy simulation of the phase transition of ammonium nitrate in a convective boundary layer
    Brugh, J.M.J. Aan de; Ouwersloot, H.G. ; Vilà-Guerau de Arellano, J. ; Krol, M.C. - \ 2013
    Journal of Geophysical Research: Atmospheres 118 (2013). - ISSN 2169-897X - p. 826 - 836.
    gas-particle interactions - thermodynamic-equilibrium model - heterogeneous land surfaces - exchange fluxes - dutch heathland - turbulent-diffusion - chemical-reactions - relative-humidity - inorganic aerosol - forest
    Under warm and dry conditions, ammonium nitrate aerosol outgasses to form ammonia and nitric acid in the lower atmospheric boundary layer. In the upper boundary layer, where the temperature is lower and the relative humidity is higher, nitric acid and ammonia condense back to the aerosol phase. Measurements show that aerosol nitrate mixing ratios increase with altitude, confirming this phase transition. Since phase equilibrium is not reached instantaneously, updrafts transport aerosol-poor air from the surface to high altitudes and aerosol-rich air subsides from high altitudes to the surface under turbulent conditions. As a result, the partitioning deviates from equilibrium, so the horizontal and temporal variabilities of the aerosol nitrate mixing ratio are enhanced and a continuous downward aerosol nitrate flux emerges. We postulate that observations of this variability and flux should not be interpreted as instrument noise and deposition of nitrate. In an idealized large-eddy simulation (LES) experiment of a convective boundary layer, we find that the larger variability and flux occurred at about one third of the boundary layer height. Both are largest when the gas-aerosol partitioning time scale is assumed to be about half the time scale of turbulence. Our LES result shows negatively skewed nitrate mixing ratios. Under colder conditions, a smaller fraction of ammonium nitrate aerosol outgasses at the surface, so the absolute effect of nitrate repartitioning becomes smaller. However, dimensionless statistical properties do not change as long as the turbulent properties of the boundary layer remain similar. This indicates that the identified processes are also present under colder conditions.
    Linking community-based and national REDD+ monitoring: a review of the potential
    Pratihast, A.K. ; Herold, M. ; Sy, V. de; Murdiyarso, D. ; Skutsch, M. - \ 2013
    Carbon Management 4 (2013)1. - ISSN 1758-3004 - p. 91 - 104.
    forest - lidar - management - deforestation - countries
    Countries participating in REDD+ schemes are required to establish a national monitoring system that keeps track of forest carbon changes over time. Community-based monitoring (CBM) can be useful for tracking locally driven forest change activities and their impacts. In this paper, we review some of the key issues regarding CBM and options to link CBM and national forest monitoring systems. More specifically, we highlight the importance of local drivers of deforestation and degradation and, thus, the relevance of community involvement in REDD+ implementation and monitoring; we review the scientific literature to better define the role and technical conditions under which CBM can contribute to national level monitoring; we develop a conceptual framework for linking local and national monitoring; and we analyze and synthesize 28 REDD+ country approaches to CBM. Finally, we provide recommendations for integrating CBM data into national monitoring systems.
    A proposal for including humus forms in the World Reference Base for soil resources (WRB-FAO)
    Jabiol, B. ; Zanella, A. ; Ponge, J.F. ; Sarton, G. ; Englisch, M. ; Delft, S.P.J. van; Waal, R.W. de; Claire-Le Bayon, R. - \ 2013
    Geoderma 192 (2013). - ISSN 0016-7061 - p. 286 - 294.
    earthworm invasion - organic-matter - forest - classification - vegetation - france
    The morpho-functional classification of humus forms proposed in a previous issue by Zanella and collaborators for Europe has been extended and modified, without any change in diagnostic horizons, in order to embrace a wide array of humus forms at worldwide level and to complete and make more effective the World Reference Base for Soil Resources. For that purpose 31 Humus Form Reference Groups (HFRGs) and a set of prefix and suffix qualifiers are proposed, following the rules erected for the WRB. An exhaustive classification key, respecting the principles of WRB, is suggested and examples of classification are given for some already well known humus forms.
    Leaf litter quality drives litter mixing effects through complementary resource use among detritivores
    Vos, V.C.A. ; Ruijven, J. van; Berg, M.P. ; Peeters, E.T.H.M. ; Berendse, F. - \ 2013
    Oecologia 173 (2013)1. - ISSN 0029-8549 - p. 269 - 280.
    species-diversity - ecosystem function - soil processes - decomposition - biodiversity - mixtures - forest - respiration - millipedes - richness
    To comprehend the potential consequences of biodiversity loss on the leaf litter decomposition process, a better understanding of its underlying mechanisms is necessary. Here, we hypothesize that positive litter mixture effects occur via complementary resource use, when litter species complement each other in terms of resource quality for detritivores. To investigate this, monocultures and mixtures of two leaf litter species varying in quality were allowed to decompose with and without a single macro-detritivore species (the terrestrial woodlice Oniscus asellus). Resource quality of the mixture was assessed by the mean concentration, the dissimilarity in absolute and relative concentrations, and the covariance between nitrogen (N), phosphorus (P) and calcium (Ca) supply. Our results clearly show that litter mixing effects were driven by differences in their resource quality for detritivores. In particular, complementary supply of N and P was a major driver of litter mixing effects. Interestingly, litter mixing effects caused by the addition of woodlice were predominantly driven by N dissimilarity, whereas in their absence, increased P concentration was the main driver of litter mixing effects. These results show that ultimately, litter diversity effects on decomposition may be driven by complementary resource use of the whole decomposer community (i.e., microbes and macro-detritivores).
    Mobile devices for community-based REDD+ monitoring: A case study for Central Vietnam
    Pratihast, A.K. ; Herold, M. ; Avitabile, V. ; Bruin, S. de; Bartholomeus, H. ; Souza Jr., C.M. ; Ribbe, L. - \ 2013
    Sensors 13 (2013)1. - ISSN 1424-8220 - p. 21 - 38.
    data-collection - forest - governance - plus
    Monitoring tropical deforestation and forest degradation is one of the central elements for the Reduced Emissions from Deforestation and Forest Degradation in developing countries (REDD+) scheme. Current arrangements for monitoring are based on remote sensing and field measurements. Since monitoring is the periodic process of assessing forest stands properties with respect to reference data, adopting the current REDD+ requirements for implementing monitoring at national levels is a challenging task. Recently, the advancement in Information and Communications Technologies (ICT) and mobile devices has enabled local communities to monitor their forest in a basic resource setting such as no or slow internet connection link, limited power supply, etc. Despite the potential, the use of mobile device system for community based monitoring (CBM) is still exceptional and faces implementation challenges. This paper presents an integrated data collection system based on mobile devices that streamlines the community-based forest monitoring data collection, transmission and visualization process. This paper also assesses the accuracy and reliability of CBM data and proposes a way to fit them into national REDD+ Monitoring, Reporting and Verification (MRV) scheme. The system performance is evaluated at Tra Bui commune, Quang Nam province, Central Vietnam, where forest carbon and change activities were tracked. The results show that the local community is able to provide data with accuracy comparable to expert measurements (index of agreement greater than 0.88), but against lower costs. Furthermore, the results confirm that communities are more effective to monitor small scale forest degradation due to subsistence fuel wood collection and selective logging, than high resolution remote sensing SPOT imagery.
    Hydrological response of a small catchment burned by experimental fire
    Stoof, C.R. ; Vervoort, R.W. ; Iwema, J. ; Elsen, H.G.M. van den; Ferreira, A.J.D. ; Ritsema, C.J. - \ 2012
    Hydrology and Earth System Sciences 16 (2012)2. - ISSN 1027-5606 - p. 267 - 285.
    soil-water repellency - postfire runoff - overland-flow - portuguese shrubland - mediterranean basin - mountain catchments - interception loss - debris flows - stand age - forest
    Fire can considerably change hydrological processes, increasing the risk of extreme flooding and erosion events. Although hydrological processes are largely affected by scale, catchment-scale studies on the hydrological impact of fire in Europe are scarce, and nested approaches are rarely used. We performed a catchment-scale experimental fire to improve insight into the drivers of fire impact on hydrology. In north-central Portugal, rainfall, canopy interception, streamflow and soil moisture were monitored in small shrub-covered paired catchments pre- and post-fire. The shrub cover was medium dense to dense (44 to 84 %) and pre-fire canopy interception was on average 48.7% of total rainfall. Fire increased streamflow volumes 1.6 times more than predicted, resulting in increased runoff coefficients and changed rainfall-streamflow relationships - although the increase in streamflow per unit rainfall was only significant at the subcatchment-scale. Fire also fastened the response of topsoil moisture to rainfall from 2.7 to 2.1 h (p = 0.058), and caused more rapid drying of topsoils after rain events. Since soil physical changes due to fire were not apparent, we suggest that changes resulting from vegetation removal played an important role in increasing streamflow after fire. Results stress that fire impact on hydrology is largely affected by scale, highlight the hydrological impact of fire on small scales, and emphasize the risk of overestimating fire impact when upscaling plot-scale studies to the catchment-scale. Finally, they increase understanding of the processes contributing to post-fire flooding and erosion events.
    Calibration and validation of models for short-term decomposition and N mineralization of plant residues in the tropics
    Nascimento, A.F. do; Mendona, E.D. ; Leite, L.F.C. ; Scholberg, J.M.S. ; Neves, J.C.L. - \ 2012
    Scientia agricola 69 (2012)6. - ISSN 0103-9016 - p. 393 - 401.
    soil organic-matter - nitrogen mineralization - nutrient release - simulation - lignin - litter - polyphenol - quality - systems - forest
    Insight of nutrient release patterns associated with the decomposition of plant residues is important for their effective use as a green manure in food production systems. Thus, this study aimed to evaluate the ability of the Century, APSIM and NDICEA simulation models for predicting the decomposition and N mineralization of crop residues in the tropical Atlantic forest biome, Brazil. The simulation models were calibrated based on actual decomposition and N mineralization rates of three types of crop residues with different chemical and biochemical composition. The models were also validated for different pedo-climatic conditions and crop residues conditions. In general, the accuracy of decomposition and N mineralization improved after calibration. Overall RMSE values for the decomposition and N mineralization of the crop materials varied from 7.4 to 64.6 % before models calibration compared to 3.7 to 16.3 % after calibration. Therefore, adequate calibration of the models is indispensable for use them under humid tropical conditions. The NDICEA model generally outperformed the other models. However, the decomposition and N mineralization was not very accurate during the first 30 days of incubation, especially for easily decomposable crop residues. An additional model variable may be required to capture initial microbiological growth as affected by the moisture dynamics of the residues, as is the case in surface residues decomposition models.
    A land-use systems approach to represent land-use dynamics at continental and global scales
    Letourneau, A.P. ; Verburg, P.H. ; Stehfest, E. - \ 2012
    Environmental Modelling & Software 33 (2012). - ISSN 1364-8152 - p. 61 - 79.
    remotely-sensed data - cover change - agricultural land - costa-rica - model - validation - science - forest - sustainability - biodiversity
    Most of the current global land cover datasets and global scale land-use models use a classification of land cover based on the dominant land cover type within a distinct region or pixel. Such a classification disregards the diversity and intensity of human influence on land systems. In this paper we propose a novel way of classification and modeling land-use using a classification based on land-use systems (LUSs) that represent specific combinations of human-environment interactions. A cluster analysis was used to identify and map these LUSs. The analysis accounted for population density, accessibility to market places, land-use/cover types and livestock densities. A conceptual framework was developed to model dynamics in LUSs accounting for both land cover and land management changes. LUSs changes were simulated based on changes in both local socio-economic and biophysical conditions and regional-scale changes in demand for agricultural products. The new land-use systems change model was used in the context of the integrated assessment model IMAGE.
    Systematic errors in ground heat flux estimation and their correction
    Gentine, P. ; Entekhabi, D. ; Heusinkveld, B.G. - \ 2012
    Water Resources Research 48 (2012)9. - ISSN 0043-1397 - 15 p.
    large-aperture scintillometer - apparent thermal-diffusivity - energy-balance closure - soil-temperature - net-radiation - land-surface - exchanges - forest
    Incoming radiation forcing at the land surface is partitioned among the components of the surface energy balance in varying proportions depending on the time scale of the forcing. Based on a land-atmosphere analytic continuum model, a numerical land-surface model and field observations we show that high-frequency fluctuations in incoming radiation (with period less than 6 hours, for example due to intermittent clouds) are preferentially partitioned towards ground heat flux. These higher frequencies are concentrated in the 0-1 centimeter surface soil layer. Subsequently, measurements even at a few centimeters deep in the soil profile miss part of the surface soil heat flux signal. The attenuation of the high-frequency soil heat flux spectrum throughout the soil profile leads to systematic errors in both measurements and modeling, which require a very fine sampling near the soil surface (0-1 centimeter). Calorimetric measurement techniques introduce a systematic error in the form of artificial band-pass filter if the temperature probes are not placed at appropriate depths. In addition the temporal calculation of the change in the heat storage term of the calorimetric method can further distort the reconstruction of the surface soil heat flux signal. A correction methodology is introduced which provides practical application as well as insights into the estimation of surface soil heat flux and the closure of surface energy balance based on field measurements.
    Attributing the impacts of land-cover changes in temperate regions on surface temperature and heat fluxes to specific causes: Results from the first LUCID set of simulations
    Boisier, J.P. ; Noblet-Ducoudré, N. de; Pitman, A.J. ; Cruz, F.T. ; Delire, C. ; Hurk, B.J.J.M. van den; Molen, M.K. van der; Müller, C. ; Voldoire, A. - \ 2012
    Journal of Geophysical Research: Atmospheres 117 (2012)D12. - ISSN 2169-897X
    climate system model - soil-moisture - sensitivity - feedbacks - forcings - exchange - forest - energy - biomes - albedo
    Surface cooling in temperate regions is a common biogeophysical response to historical Land-Use induced Land Cover Change (LULCC). The climate models involved in LUCID show, however, significant differences in the magnitude and the seasonal partitioning of the temperature change. The LULCC-induced cooling is directed by decreases in absorbed solar radiation, but its amplitude is 30 to 50% smaller than the one that would be expected from the sole radiative changes. This results from direct impacts on the total turbulent energy flux (related to changes in land-cover properties other than albedo, such as evapotranspiration efficiency or surface roughness) that decreases at all seasons, and thereby induces a relative warming in all models. The magnitude of those processes varies significantly from model to model, resulting on different climate responses to LULCC. To address this uncertainty, we analyzed the LULCC impacts on surface albedo, latent heat and total turbulent energy flux, using a multivariate statistical analysis to mimic the models' responses. The differences are explained by two major ‘features’ varying from one model to another: the land-cover distribution and the simulated sensitivity to LULCC. The latter explains more than half of the inter-model spread and resides in how the land-surface functioning is parameterized, in particular regarding the evapotranspiration partitioning within the different land-cover types, as well as the role of leaf area index in the flux calculations. This uncertainty has to be narrowed through a more rigorous evaluation of our land-surface models.
    Carbon stocks and dynamics under improved tropical pasture and silvopastoral
    Mosquera Vidal, O. ; Buurman, P. ; Ramirez, B.L. ; Amezquita, M.C. - \ 2012
    Geoderma 189-190 (2012). - ISSN 0016-7061 - p. 81 - 86.
    northeastern costa-rica - soil organic-matter - brazilian amazonia - eastern amazonia - forest - conversion - delta-c-13 - rondonia
    To evaluate the effect of land use change on soil organic carbon, the carbon contents and stocks of primary forest, degraded pasture, and four improved pasture systems in Colombian Amazonia were compared in a flat and a sloping landscape. The improved pastures were Brachiaria humidicola, and Brachiaria decumbens, either in monoculture or in combination with native legumes. The age of the treatments was 30 years for degraded pasture and 10 or 15 years for each of the improved pastures. Carbon fractions were Total C, Oxidizable C, and Non-Oxidizable (stable) C. Stocks were compared using a fixed soil mass base. The degraded pasture in the flat landscape was abandoned and dominated by weeds, while that in the sloping area was overgrazed. The latter had much lower C stocks than the former. B. humidicola monoculture had the highest stocks both in flat and sloping areas, while the effect of the other three treatments varied. C replacement based on d13C indicated that after 30 years, the degraded pasture still contained more than 50% forest-derived C in its topsoil. The fraction in the topsoil that is not replaced roughly coincides with the Stable C fraction. d13C values suggest that the changes in carbon stocks ascribed to differences in land use may be – at least partially – inherited from the previous land use, thus confusing the interpretation of land use effects. Nevertheless, the introduction of improved pastures on degraded grassland is a feasible alternative of land use both for carbon sequestration and as an attractive economic alternative to farmers.
    Effects of resin tapping and tree size on the purity, germination and storage behavior of Boswellia papyrifera (Del.) Hochst. seeds from Metema District, northwestern Ethiopia.
    Eshete, A. ; Teketay, D. ; Lemenih, M. ; Bongers, F. - \ 2012
    Forest Ecology and Management 269 (2012). - ISSN 0378-1127 - p. 31 - 36.
    frankincense - forest - fire
    Boswellia papyrifera (Del.) Hochst. is one of the tree species in dry woodlands of Ethiopia that provides several goods and services. Despite its wide economic and ecological importance, its area coverage is dwindling from time to time, and its natural regeneration is hampered. Hence, long-term prospect for a sustained supply of the goods and services from the species is becoming questionable. The objectives of this study were to investigate: (i) the effect of resin tapping and tree size (DBH) on seed susceptibility to insect attack and the production of viable seeds; and (ii) seed longevity and germination ecology of the seeds of B. papyrifera. We collected seeds from tapped and untapped B. papyrifera stands at Lemlem Terara in Metema District, northwestern Ethiopia. The result showed that both tapped and untapped stands produced comparable insect attacked seeds (tapped stands = 16.6%; untapped stands = 15.8%). Untapped trees yielded significantly (P <0.0001) higher viable seeds (59%) than continuously tapped trees (49.3%), and trees with medium size (20 cm DBH) provided more viable seeds than bigger (30 cm DBH) and younger trees (10 cm DBH). Longevity of B. papyrifera seeds indicated significant difference in viability under three different temperature regimes (5, 15 and 21 °C), three storage periods (6, 9 and 12 months) and two tapping regimes (tapped and untapped populations). Fire that produced temperatures above 100 °C was lethal to the seeds as it caused complete loss of germinability regardless of exposure time. However, heat with temperatures less than 100 °C did not cause loss of germinability even after an hour of exposure. We also found that light conditions had no significant impact on the germination percentage. In general, viability of the seeds was affected by tapping and tree size but not by storage conditions and period, modest temperature and light conditions.
    Application of satellite remote sensing for mapping wind erosion risk and dusk emission-deposition in Inner Mongolia grassland, China
    Reiche, M. ; Funk, R. ; Zhang, Z. ; Hoffmann, C. ; Reiche, J. ; Wehrhan, M. ; Li, Y. ; Sommer, M. - \ 2012
    Grassland Science 58 (2012)1. - ISSN 1744-6961 - p. 8 - 19.
    vegetation indexes - northern china - landsat tm - degradation - variability - topography - forest - cover - hills - aster
    Intensive grazing leads to land degradation and desertification of grassland ecosystems followed by serious environmental and social problems. The Xilingol steppe grassland in Inner Mongolia, China, which has been a sink area for dust for centuries, is strongly affected by the negative effects of overgrazing and wind erosion. The aim of this study is the provision of a wind erosion risk map with a spatial high resolution of 25 m to identify actual source and sink areas. In an integrative approach, field measurements of vegetation features and surface roughness length z0 were combined with Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) image data for a land use classification. To determine the characteristics of the different land use classes, a field observation (ground truth) was performed in April 2009. The correlation of vegetation height and z0 (R2 = 0.8, n = 55) provided the basis for a separation of three main classes, “grassland”, “non-vegetation” and “other”. The integration of the soil-adjusted vegetation index (SAVI) and the spectral information from the atmospheric corrected ASTER bands 1, 2 and 3 (visible to near-infrared) led to a classification of the overall accuracy (OA) of 0.79 with a kappa () statistic of 0.74, respectively. Additionally, a digital elevation model (DEM) was used to identify topographical effects in relation to the main wind direction, which enabled a qualitative estimation of potential dust deposition areas. The generated maps result in a significantly higher description of the spatial variability in the Xilingol steppe grassland reflecting the different land use intensities on the current state of the grassland – less, moderately and highly degraded. The wind erosion risk map enables the identification of characteristic mineral dust sources, sinks and transition zones.
    Soil biotic impact on plant species shoot chemistry and hyperspectral reflectance patterns
    Carvalho, S. de; Macel, M. ; Schlerf, M. ; Skidmore, A.K. ; Putten, W.H. van der - \ 2012
    New Phytologist 196 (2012)4. - ISSN 0028-646X - p. 1133 - 1144.
    borne pathogens - spectroscopy - community - leaf - accumulation - herbivores - prediction - invader - quality - forest
    Recent studies revealed that plant-soil biotic interactions may cause changes in above-ground plant chemistry. It would be a new step in below-ground-above-ground interaction research if such above-ground chemistry changes could be efficiently detected. Here we test how hyperspectral reflectance may be used to study such plant-soil biotic interactions in a nondestructive and rapid way. The native plant species Jacobaea vulgaris and Jacobaea erucifolius, and the exotic invader Senecio inaequidens were grown in different soil biotic conditions. Biomass, chemical content and shoot reflectance between 400 and 2500 nm wavelengths were determined. The data were analysed with multivariate statistics. Exposing the plants to soil biota enhanced the content of defence compounds. The highest increase (400%) was observed for the exotic invader S. inaequidens. Chemical and spectral data enabled plant species to be classified with an accuracy > 85%. Plants grown in different soil conditions were classified with 50-60% correctness. Our data suggest that soil microorganisms can affect plant chemistry and spectral reflectance. Further studies should test the potential to study plant-soil biotic interactions in the field. Such techniques could help to monitor, among other things, where invasive exotic plant species develop biotic resistance or the development of hotspots of crop soil diseases.
    Productive leaf functional traits of Chinese savanna species.
    Zhang, J.L. ; Poorter, L. ; Cao, K.F. - \ 2012
    Plant Ecology 213 (2012)9. - ISSN 1385-0237 - p. 1449 - 1460.
    nitrogen-use efficiency - valley-savanna - gas-exchange - dry mass - evergreen - forest - plants - trees - photosynthesis - generality
    The river valleys in Southwest China are characterized by a dry–hot climate and relatively rich soils, and host valley-type savannas that are dominated by deciduous species. However, little is known about the ecological adaptations of Chinese savanna plants to the local environments. We hypothesize that Chinese savanna species mainly possess a drought-avoiding strategy by having a deciduous leaf habit and have productive leaf traits. To test this hypothesis, we measured 26 anatomical, morphological, physiological, and chemical traits for 33 woody species from a valley savanna in Southwest China and compared them with the literature data of other dry and wet tropical tree species and a global dataset. We found that Chinese savanna species showed drought avoidance adaptations and exhibited productive leaf traits, such as thin and dense leaves with high ratio of palisade to spongy mesophyll, leaf nutrient concentrations and photosynthetic capacity. Correlations of photosynthetic capacity with N, P, and stomatal conductance across Chinese savanna species were consistent with global patterns reported for seed plants. However, the Chinese savanna species had consistently greater carbon gain at a given specific leaf area, N, P, and stomatal conductance, suggesting higher nutrient- and intrinsic water use efficiencies. These results suggest that paradoxically, Chinese savanna species are adapted to the stressful dry–hot valley habitat by having productive leaves.
    Characterization of a boreal convective boundary layer and its impact on atmospheric chemistry during HUMPPA-COPEC-2010
    Ouwersloot, H.G. ; Vilà-Guerau de Arellano, J. ; Nölscher, A.C. ; Krol, M.C. ; Ganzeveld, L.N. ; Breitenberger, C. ; Mammarella, I. ; Williams, J. ; Lelieveld, J. - \ 2012
    Atmospheric Chemistry and Physics 12 (2012). - ISSN 1680-7316 - p. 9335 - 9353.
    large-eddy simulation - aerosol formation - forest - model - entrainment - turbulence - evolution - inversion - emissions - exchanges
    We studied the atmospheric boundary layer (ABL) dynamics and the impact on atmospheric chemistry during the HUMPPA-COPEC-2010 campaign. We used vertical profiles of potential temperature and specific moisture, obtained from 132 radio soundings, to determine the main boundary layer characteristics during the campaign. We propose a classification according to several main ABL prototypes. Further, we performed a case study of a single day, focusing on the convective boundary layer, to analyse the influence of the dynamics on the chemical evolution of the ABL. We used a mixed layer model, initialized and constrained by observations. In particular, we investigated the role of large scale atmospheric dynamics (subsidence and advection) on the ABL development and the evolution of chemical species concentrations. We find that, if the large scale forcings are taken into account, the ABL dynamics are represented satisfactorily. Subsequently, we studied the impact of mixing with a residual layer aloft during the morning transition on atmospheric chemistry. The time evolution of NOx and O3 concentrations, including morning peaks, can be explained and accurately simulated by incorporating the transition of the ABL dynamics from night to day. We demonstrate the importance of the ABL height evolution for the representation of atmospheric chemistry. Our findings underscore the need to couple the dynamics and chemistry at different spatial scales (from turbulence to mesoscale) in chemistry-transport models and in the interpretation of observational data.
    Making conservation research more relevant for conservation practitioners
    Laurance, W.F. ; Koster, H. ; Grooten, M. ; Anderson, A.B. ; Zuidema, P.A. ; Zwick, S. ; Zagt, R.J. ; Lynam, A.J. ; Linkie, M. ; Anten, N.P.R. - \ 2012
    Biological Conservation 153 (2012). - ISSN 0006-3207 - p. 164 - 168.
    wicked problems - amazon - biology - forest - oil - biodiversity - conversion - future - tigers - brazil
    Conservation scientists and practitioners share many of the same goals. Yet in a majority of cases, we argue, research conducted by academic conservation scientists actually makes surprisingly few direct contributions to environmental conservation. We illustrate how researchers can increase the utility and impact of their scientific findings for real-world conservation, using examples of pressing environmental challenges. These examples demonstrate some practices and principles that scientists can adopt to better assist conservation practitioners and advance specific conservation outcomes. These include (1) producing time-critical research rapidly enough to affect political outcomes; (2) attacking ‘wicked’ problems that transcend traditional scientific approaches; (3) using multidisciplinary approaches that link science with fields such as economics, sociology, and politics; and (4) communicating in a bolder, more direct manner in the public arena to advance environmental conservation. We conclude with a plea for more proactive dialogue between conservation scientists and practitioners when devising research priorities.
    Mapping vegetation density in a heterogeneous river floodplain ecosystem using pointable CHRIS/PROBA data
    Verrelst, J. ; Romijn, J.E. ; Kooistra, L. - \ 2012
    Remote Sensing 4 (2012)9. - ISSN 2072-4292 - p. 2866 - 2889.
    leaf-area index - radiative-transfer model - hyperspectral brdf data - chris-proba data - flow resistance - climate-change - rhine basin - sugar-beet - forest - cover
    River floodplains in the Netherlands serve as water storage areas, while they also have the function of nature rehabilitation areas. Floodplain vegetation is therefore subject to natural processes of vegetation succession. At the same time, vegetation encroachment obstructs the water flow into the floodplains and increases the flood risk for the hinterland. Spaceborne pointable imaging spectroscopy has the potential to quantify vegetation density on the basis of leaf area index (LAI) from a desired view zenith angle. In this respect, hyperspectral pointable CHRIS data were linked to the ray tracing canopy reflectance model FLIGHT to retrieve vegetation density estimates over a heterogeneous river floodplain. FLIGHT enables simulating top-of-canopy reflectance of vegetated surfaces either in turbid (e.g., grasslands) or in 3D (e.g., forests) mode. By inverting FLIGHT against CHRIS data, LAI was computed for three main classified vegetation types, ‘herbaceous’, ‘shrubs’ and ‘forest’, and for the CHRIS view zenith angles in nadir, backward (-36°) and forward (+36°) scatter direction. The -36° direction showed most LAI variability within the vegetation types and was best validated, closely followed by the nadir direction. The +36° direction led to poorest LAI retrievals. The class-based inversion process has been implemented into a GUI toolbox which would enable the river manager to generate LAI maps in a semiautomatic way.
    Analyzing transient closed chamber effects on canopy gas exchange for optimizing flux calculation timing
    Langensiepen, M. ; Kupisch, M. ; Wijk, M.T. van; Ewert, F. - \ 2012
    Agricultural and Forest Meteorology 164 (2012). - ISSN 0168-1923 - p. 61 - 70.
    portable chamber - h2o fluxes - sap flow - co2 - evapotranspiration - transpiration - trees - crop - temperature - forest
    Transient type canopy chambers are still the only currently available practical solution for rapid screening of gas-exchange in agricultural fields. The technique has been criticized for its effect on canopy microclimate during measurement which affects the transport regime and regulation of plant gas-exchange. Field studies in which the technique has been compared against independent methods are still fragmentary. The aims of this study were to quantify the changes of the physical environment during chamber placement, to determine optimum flux measuring windows, to compare three flux-calculation procedures, and to test the performance of the method against independent measurements of sap-flow. Two wheat experiments were conducted for these purposes under German temperate climate conditions. Leaf transpiration and sap-flow remained relatively constant during the first 120 s after chamber deployment, but changed considerably afterwards. Canopy H2O fluxes could thus be inferred from concentration measurement series during this interval. A saturation function, previously not mentioned in the literature, was compared against the commonly used constant and quadratic regression methods and identified as the most suitable method for calculating vapor fluxes. The study reconfirmed that small proportional changes of CO2 concentrations during the calculation interval facilitate the application of the frequently applied quadratic regression method for calculating CO2 fluxes. Sap-flow, leaf and canopy gas-exchange were severely perturbed after chamber removal. Revisiting times of same sample locations need to be planned accordingly. The study confirms that the transient chamber technique can be applied for determining canopy gas-exchange, provided that characteristic time intervals within concentration measuring series are determined and their non-linearity tested to establish appropriate flux calculation procedures.
    Do Anthropogenic Dark Earths Occur in the Interior of Borneo? Some Initial Observations from East Kalimantan
    Sheil, D. ; Basuki, I. ; German, L. ; Kuyper, T.W. ; Limberg, G. ; Puri, R.K. ; Sellato, B. ; Noordwijk, M. van - \ 2012
    Forests 3 (2012)2. - ISSN 1999-4907 - p. 207 - 229.
    soil organic-matter - terra-preta - carbon sequestration - brazilian amazon - sustainable agriculture - phosphorus availability - black earth - land-use - forest - indonesia
    Anthropogenic soils of the Amazon Basin (Terra Preta, Terra Mulata) reveal that pre-Colombian peoples made lasting improvements in the agricultural potential of nutrient-poor soils. Some have argued that applying similar techniques could improve agriculture over much of the humid tropics, enhancing local livelihoods and food security, while also sequestering large quantities of carbon to mitigate climate change. Here, we present preliminary evidence for Anthropogenic Dark Earths (ADEs) in tropical Asia. Our surveys in East Kalimantan (Indonesian Borneo) identified several sites where soils possess an anthropogenic development and context similar in several respects to the Amazon’s ADEs. Similarities include riverside locations, presence of useful fruit trees, spatial extent as well as soil characteristics such as dark color, high carbon content (in some cases), high phosphorus levels, and improved apparent fertility in comparison to neighboring soils. Local people value these soils for cultivation but are unaware of their origins. We discuss these soils in the context of local history and land-use and identify numerous unknowns. Incomplete biomass burning appears key to these modified soils. More study is required to clarify soil transformations in Borneo and to determine under what circumstances such soil improvements might remain ongoing.
    Soil macroinvertebrates' abundance and diversity in home gardens in Tabasco, Mexico, vary with soil texture, organic matter and vegetation cover
    Huerta, E. ; Wal, J.C. van der - \ 2012
    European Journal of Soil Biology 50 (2012)May-June. - ISSN 1164-5563 - p. 68 - 75.
    terrestrial ecosystems - generalist predators - food-web - biodiversity - conservation - homegardens - patterns - forest - plant - agroecosystems
    We studied the composition of soil invertebrate communities and vegetation in 50 home gardens in the humid tropical lowlands of Tabasco, Mexico, located in five geomorphological regions. Five monoliths were made in each home garden and soil invertebrates were hand sorted, weighed and classified to morhospecies, functional groups and orders. We determined pH, organic matter, available phosphorus and texture in composed soil samples from each home garden. We determined the botanical name of trees, their diameter at breast height, height, and crown diameter, calculated tree density, tree cover, and biomass per hectare. We found 45 soil invertebrate morphospecies, which belonged to 12 Orders or taxonomical groups. Endogeic macroinvertebrates were significantly more abundant in the fluvial plains, hills, and mountains than in the coastal plains (F = 9.64 p <0.05). Path analysis produced a significant model, wherein soil organic matter influenced earthworm abundance (T = 3.28, p <0.05), while tree cover significantly influenced abundance of litter fragmenters (T = 3.16, p <0.05). Morphospecies richness was not related with tree species diversity. Canonical correspondence analysis with 67% of inertia on principal axes, showed how contents of soil organic matter, clay and silt were associated with earthworms abundance, while abundance of hymenoptera was associated with silt content. Interactions between plants and soil macroinvertebrates varied among regions. The coastal region showed a strong correlation between the abundance of palm trees (Coco nucifera), arachnida and isoptera morphospecies. The abundance of Gliricidia sepium in different regions showed a strong correlation with the abundance of earthworms
    Linking stochasticity to determinism of woody plant recruitment in a mosaic landscape: A spatially explicit approach
    Quero, J.L. ; Herrero, A. ; Zamora, R. - \ 2011
    Basic and Applied Ecology 12 (2011)2. - ISSN 1439-1791 - p. 161 - 171.
    seedling establishment - spatiotemporal dynamics - regeneration niche - heterogeneity - ecology - forest - association - environment - ecosystem - patterns
    Here, we investigate small-scale spatial variation of environmental factors potentially influencing woody-plant establishment for 3 years (2004, 2005 and 2006) along a heterogeneous landscape. Environmental variables of over 2883 potential microsites were sampled in different landscape units with a spatially explicit design, and seeds of four tree species were sown at the different microsites.We used spatial-analysis techniques to quantify spatial heterogeneity of the environment surrounding the seeds, and to relate seedling and sapling survival to the spatial structure of environmental factors studied. Most environmental variables showed aggregated spatial patterns among landscape units. However, survival showed random spatial patterns in most of the cases, although it may depend on year-to-year variation of precipitation. Thus, spatial patterns of survival were random under both wet and dry conditions, while aggregated patterns emerged under intermediate conditions. Aggregated survival, if detected, was better explained by the environmental variables studied as plant age increased. In addition, the spatial consistency found across demographic stages, represents hotspots of recruitment, for which direct identification would be critical for restoration activities. Our results showed a balance between stochasticity at early stages and environmental determinism at later stages, showing, behind the idiosyncratic character of plant recruitment, stronger general rules at sapling stages
    Mature trees as keystone structures in Holarctic ecosystems - a quantitative species comparison in a northern English park
    Hall, S.J.G. ; Bunce, R.G.H. - \ 2011
    Plant Ecology & Diversity 4 (2011)2-3. - ISSN 1755-0874 - p. 243 - 250.
    oak quercus-robur - alnus-glutinosa - conservation - woodland - britain - forest - cattle
    Background: Mature trees often provide ecological niches of value to specialised flora and fauna, signalled by such attributes as epiphytes, trunk rot and dead branches. In Britain, they are often found in parklands and wood pastures, which are rare habitats in Europe. Aims: As species differences in veteran attributes of such trees have not been studied, we surveyed eight Holarctic tree species in Chillingham Park, in north-east England, where the stems are of broadly similar age (200-250 years). Methods: The following variables were scored for 779 trees: presence or absence of veteran attributes, community status (alone, in a group, or in a linear feature), stem diameter, altitude at which growing, and the ground vegetation. Results: Trees were generally of only moderate mean diameter. Alder (Alnus glutinosa) and ash (Fraxinus excelsior) had the most veteran attributes (4.30 and 4.16, respectively), followed by oak (Quercus sp.) (3.65), then by birch (Betula agg.) (3.49), beech (Fagus sylvatica) (3.12), sycamore (Acer pseudoplatanus) (2.77), larch (Larix sp.) (2.47) and Scots pine (Pinus sylvestris) (1.92). Trees growing at middle altitudes and alone, or in linear features (rather than in groups), had most veteran attributes; 32% of trees exhibited three or more. Conclusions: To capture the veteran tree interest of a site, a survey protocol must consider the history of a site as well as the numbers of veteran attributes exhibited by individual trees, which may differ among species. Finally, alder has not attracted particular attention in these habitats, and we suggest that its fast-growing and rot-prone nature may make it of particular interest for conservation of saproxylic biodiversity.
    Optimizing global CO emission estimates using a four-dimensional variational data assimilation system and surface network observations
    Hooghiemstra, P.B. ; Krol, M.C. ; Meirink, J.F. ; Bergamaschi, P. ; Werf, G.R. van der; Novelli, P.C. ; Aben, I. ; Röckmann, T. - \ 2011
    Atmospheric Chemistry and Physics 11 (2011)10. - ISSN 1680-7316 - p. 4705 - 4723.
    carbon-monoxide - tropospheric chemistry - fire emissions - model tm5 - inversion - mopitt - adjoint - forest - asia - algorithm
    We apply a four-dimensional variational (4D-VAR) data assimilation system to optimize carbon monoxide (CO) emissions for 2003 and 2004 and to reduce the uncertainty of emission estimates from individual sources using the chemistry transport model TM5. The system is designed to assimilate large (satellite) datasets, but in the current study only a limited amount of surface network observations from the National Oceanic and Atmospheric Administration Earth System Research Laboratory (NOAA/ESRL) Global Monitoring Division (GMD) is used to test the 4D-VAR system. By design, the system is capable to adjust the emissions in such a way that the posterior simulation reproduces background CO mixing ratios and large-scale pollution events at background stations. Uncertainty reduction up to 60 % in yearly emissions is observed over well-constrained regions and the inferred emissions compare well with recent studies for 2004. However, with the limited amount of data from the surface network, the system becomes data sparse resulting in a large solution space. Sensitivity studies have shown that model uncertainties (e.g., vertical distribution of biomass burning emissions and the OH field) and the prior inventories used, influence the inferred emission estimates. Also, since the observations only constrain total CO emissions, the 4D-VAR system has difficulties in separating anthropogenic and biogenic sources in particular. The inferred emissions are validated with NOAA aircraft data over North America and the agreement is significantly improved from the prior to posterior simulation. Validation with the Measurements Of Pollution In The Troposphere (MOPITT) instrument version 4 (V4) shows a slight improved agreement over the well-constrained Northern Hemisphere and in the tropics (except for the African continent). However, the model simulation with posterior emissions underestimates MOPITT CO total columns on the remote Southern Hemisphere (SH) by about 10 %. This is caused by a reduction in SH CO sources mainly due to surface stations on the high southern latitudes.
    Environmental significance of mineral weathering and pedogenesis of loess on the southernmost Loess Plateau, China
    Huang, C. ; Zhao, W. ; Liu, F. ; Tan, W.F. ; Koopal, L.K. - \ 2011
    Geoderma 163 (2011)3-4. - ISSN 0016-7061 - p. 219 - 226.
    clay-minerals - soils - climate - kaolinite - dynamics - taiwan - forest - quartz - rates - alps
    Soils derived from the Loess Plateau of China are regionally important and expression of the soil properties along the soil profile may be directly related to climate changes. The objective of this research was to analyze the clay mineral transformation of loess from the southernmost Loess Plateau, in relation to the pedogenesis and the regional climate changes. The mineralogy of the soil profile at the site was studied by using X-ray diffraction. The results showed that 2:1 layer type minerals dominated with the illite in the majority throughout the profile. The changes of the soil minerals were consistent with the soil genetic horizons and with the variable CaCO3 content, particle size distribution, and variations of magnetic susceptibility. A relatively high vermiculite content and the presence of hydroxyl-interlayered mineral (HIM) occurred in the most weathered horizon (50–150 cm) corresponding to the buried palaeosol (S0) formed during the ‘optimum’ Holocene (8400–3100 B.P. yr) which indicated the acidic conditions with low organic matter in this period. During the formation of palaeosol, the expected transformation of illite and chlorite into vermiculite through the formation of mixed layers has occurred. The distribution of kaolinite was uniform with depth in the palaeosol suggesting inheritance from the original eolian deposition materials. Generally, the depotassication of illite and the degradation of chlorite were the major mineral transformation processes that occurred with soil-formation. Calculation of the total amount of carbonate leaching of the palaeosol suggested that the annual precipitation during the ‘optimum’ Holocene was probably approximately to 880 mm. The regional climate during the ‘optimum’ Holocene on the southernmost Loess Plateau was analogous with the modern climate conditions in the northern subtropical zone (the southern slope of Qingling Mountains) for the formation of Udic Luvisols (Brown Soil). However, as a result of its specific pedogenic pattern, the pedogenic strength of the palaeosol did not reached the level of Udic Luvisols (Brown Soil). The hydroxyl-interlayered mineral presence in the 50–150 cm horizon only, also illuminated that the palaeosol was buried rapidly by post depositional loess during the abrupt cold-dry climate in the late Holocene. The contradiction between the type clay minerals present and the measured alkaline soil pH values in the palaeosol could be understood by the recalcification caused by the post-pedogenic leaching from the overlying loess.
    The response of Arctic vegetation to the summer climate: relation between shrub cover, NDVI, surface albedo and temperature
    Blok, D. ; Schaepman-Strub, G. ; Bartholomeus, H. ; Heijmans, M.M.P.D. ; Maximov, T.C. ; Berendse, F. - \ 2011
    Environmental Research Letters 6 (2011)3. - ISSN 1748-9326 - 9 p.
    northern alaska - tundra vegetation - siberian tundra - feedbacks - ecosystems - expansion - exchange - trends - forest - map
    Recently observed Arctic greening trends from normalized difference vegetation index (NDVI) data suggest that shrub growth is increasing in response to increasing summer temperature. An increase in shrub cover is expected to decrease summer albedo and thus positively feed back to climate warming. However, it is unknown how albedo and NDVI are affected by shrub cover and inter-annual variations in the summer climate. Here, we examine the relationship between deciduous shrub fractional cover, NDVI and albedo using field data collected at a tundra site in NE Siberia. Field data showed that NDVI increased and albedo decreased with increasing deciduous shrub cover. We then selected four Arctic tundra study areas and compiled annual growing season maximum NDVI and minimum albedo maps from MODIS satellite data (2000–10) and related these satellite products to tundra vegetation types (shrub, graminoid, barren and wetland tundra) and regional summer temperature. We observed that maximum NDVI was greatest in shrub tundra and that inter-annual variation was negatively related to summer minimum albedo but showed no consistent relationship with summer temperature. Shrub tundra showed higher albedo than wetland and barren tundra in all four study areas. These results suggest that a northwards shift of shrub tundra might not lead to a decrease in summer minimum albedo during the snow-free season when replacing wetland tundra. A fully integrative study is however needed to link results from satellite data with in situ observations across the Arctic to test the effect of increasing shrub cover on summer albedo in different tundra vegetation types.
    Leaf area index estimation with MODIS reflectance time series and model inversion during full rotations of Eucalyptus plantations
    Maire, G. Le; Marsden, C. ; Verhoef, W. ; Ponzoni, F.J. ; Seen, D. Lo; Bégué, A. ; Stape, J.L. ; Nouvellon, Y. - \ 2011
    Remote Sensing of Environment 115 (2011)2. - ISSN 0034-4257 - p. 586 - 599.
    optical-properties - vegetation index - bidirectional reflectance - use efficiency - canopy - imagery - forest - chlorophyll - resolution - globulus
    The leaf area index (LAI) of fast-growing Eucalyptus plantations is highly dynamic both seasonally and inter-annually, and is spatially variable depending on pedo-climatic conditions. LAI is very important in determining the carbon and water balance of a stand, but is difficult to measure during a complete stand rotation and at large scales. Remote-sensing methods allowing the retrieval of LAI time series with accuracy and precision are therefore necessary. Here, we tested two methods for LAI estimation from MODIS 250m resolution red and near-infrared (NIR) reflectance time series. The first method involved the inversion of a coupled model of leaf reflectance and transmittance (PROSPECT4), soil reflectance (SOILSPECT) and canopy radiative transfer (4SAIL2). Model parameters other than the LAI were either fixed to measured constant values, or allowed to vary seasonally and/or with stand age according to trends observed in field measurements. The LAI was assumed to vary throughout the rotation following a series of alternately increasing and decreasing sigmoid curves. The parameters of each sigmoid curve that allowed the best fit of simulated canopy reflectance to MODIS red and NIR reflectance data were obtained by minimization techniques. The second method was based on a linear relationship between the LAI and values of the GEneralized Soil Adjusted Vegetation Index (GESAVI), which was calibrated using destructive LAI measurements made at two seasons, on Eucalyptus stands of different ages and productivity levels. The ability of each approach to reproduce field-measured LAI values was assessed, and uncertainty on results and parameter sensitivities were examined. Both methods offered a good fit between measured and estimated LAI (R2 = 0.80 and R2 = 0.62 for model inversion and GESAVI-based methods, respectively), but the GESAVI-based method overestimated the LAI at young ages.
    Macro-detritivore identity drives leaf litter diversity effects
    Vos, V.C.A. ; Ruijven, J. van; Berg, M.P. ; Peeters, E.T.H.M. ; Berendse, F. - \ 2011
    Oikos 120 (2011)7. - ISSN 0030-1299 - p. 1092 - 1098.
    species richness - productivity relationships - current knowledge - woodlice isopoda - plant diversity - soil processes - decomposition - biodiversity - forest - complementarity
    The importance of leaf litter diversity for decomposition, an important process in terrestrial ecosystems, is much debated. Previous leaf litter-mixing studies have shown that non-additive leaf litter diversity effects can occur, but it is not clear why they occurred in only half of the studies and which underlying mechanisms can explain these conflicting results. We hypothesized that incorporating the role of macro-detritivores could be important. Although often ignored, macro-detritivores are known to strongly influence decomposition. To better understand the importance of macro-detritivores for leaf litter mixing effects during decomposition, four common leaf litter species were added separately and in two and four species combinations to monocultures of three different macro-detritivores and a control without fauna. Our results clearly show that leaf litter-mixing effects occurred only in the presence of two macro-detritivores (earthworms and woodlice). Application of the additive partitioning method revealed that in the specific combination of woodlice and the presence of a slow-decomposing leaf litter species in the mixture, leaf litter mixing effects were strongly driven by a selection effect. This was caused by food preference of the isopod: the animals avoided the slow decomposing species when given the choice. However, most leaf litter mixing effects were caused by complementarity effects. The potential mechanisms underlying the complementarity effects are discussed. Our results clearly show that that both leaf litter and macro-detritivore identity can affect litter diversity. This may help to explain the conflicting results obtained in previous experiments
    A system identification approach for developing and parameterising an agroforestry system model under constrained availability of data
    Keesman, K.J. ; Graves, A. ; Werf, W. van der; Burgess, P.J. ; Palma, J. ; Dupraz, C. ; Keulen, H. van - \ 2011
    Environmental Modelling & Software (2011). - ISSN 1364-8152
    land equivalent ratio - light interception - silvoarable agroforestry - production ecology - plant-growth - yield-safe - trees - europe - canopy - forest
    This paper introduces a system identification approach to overcome the problem of insufficient data when developing and parameterising an agroforestry system model. Typically, for these complex systems the number of available data points from actual systems is less than the number of parameters in a (process-based) model. In this paper, we follow a constrained parameter optimization approach, in which the constraints are found from literature or are given by experts. Given the limited a priori systems knowledge and very limited data sets, after decomposition of the parameter estimation problem and after model adaptation, we were able to produce an acceptable correspondence with validation data from a real-world agroforestry experiment
    The effect of feeding time on dispersal of Virola seeds by toucans determined from GPS tracking and accelerometers
    Kays, R.W. ; Jansen, P.A. ; Knecht, E. ; Vohwinkel, R. ; Wikelski, M. - \ 2011
    Acta Oecologica-International Journal of Ecology 37 (2011)6. - ISSN 1146-609X - p. 625 - 631.
    spatial-patterns - animal movement - forest - ecology - models - panama - birds - wild - frugivore - behavior
    Seed dispersal is critical to understanding forest dynamics but is hard to study because tracking seeds is difficult. Even for the best-studied dispersal system of the Neotropics, Virola nobilis, the dispersal kernel remains unknown. We combined high-resolution GPS/3D-acceleration bird tracking, seed-retention experiments, and field observations to quantify dispersal of V. nobilis by their principal dispersers, Ramphastos toucans. We inferred feeding events from movement data, and then estimated spatio-temporally explicit seed-dispersal kernels. Wild toucans moved an average of 1.8 km d-1 with two distinct activity peaks. Seed retention time in captive toucans averaged 25.5 min (range 4–98 min). Estimated seed dispersal distance averaged 144 ± 147 m, with a 56% likelihood of dispersal >100 m, two times further than the behaviour-naive estimate from the same data. Dispersal was furthest for seeds ingested in the morning, and increased with seed retention time, but only up to 60 min after feeding. Our study supports the long-standing hypothesis that toucans are excellent dispersers of Virola seeds. To maximize seed dispersal distances trees should ripen fruit in the morning when birds move the most, and produce fruits with gut-processing times around 60 min. Our study demonstrates how new tracking technology can yield nuanced seed dispersal kernels for animals that cannot be directly observed.
    Agricultural management affects earthworm and termite diversity across humid to semi-arid tropical zones
    Ayuke, F.O. ; Pulleman, M.M. ; Vanlauwe, B. ; Goede, R.G.M. de; Six, J. ; Csuzdi, C. ; Brussaard, L. - \ 2011
    Agriculture, Ecosystems and Environment 140 (2011)1-2. - ISSN 0167-8809 - p. 148 - 154.
    organic-matter dynamics - southern cameroon - soil macrofauna - west-africa - tillage - populations - system - forest - agroecosystems - communities
    Earthworm and termite diversity were studied in 12 long-term agricultural field trials across the sub-humid to semi-arid tropical zones of Eastern and Western Africa. In each trial, treatments with high and low soil organic C were chosen to represent contrasts in long-term soil management effects, including tillage intensity, organic matter and nutrient management and crop rotations. For each trial, a fallow representing a relatively undisturbed reference was also sampled. Earthworm taxonomic richness decreased in the direction fallow > high-C soil > low-C soil and earthworm abundance was higher in fallow than under continuous crop production. Termite abundance was not significantly different between fallow and high and low-C treatments and termite taxonomic richness was higher in fallow soil than in the two cropping systems. We concluded that fewer species of earthworms and termites were favored under agricultural management that led to lower soil C. Results indicated that the soil disturbance induced by continuous crop production was more detrimental to earthworms than to termites, when compared to the fallow.
    Potential solar radiation pattern in relation to the monthly distribution of giant pandas in Foping Nature Reserve, China
    Liu, X. ; Cheng, X. ; Skidmore, A.K. - \ 2011
    Ecological Modelling 222 (2011)3. - ISSN 0304-3800 - p. 645 - 652.
    expert-system - crop growth - forest - vegetation - conservation - simulation
    Solar radiation is an important parameter in ecological process modeling, hydrological modeling and bio-physical modeling. However, models focusing on solar radiation in relation to giant panda habitat and seasonal distribution are limited. The research aims to form spatial models of 12 month solar radiation patterns and to investigate the relation between the solar radiation patterns and the monthly distribution patterns of giant pandas. The solar radiation model of Kumar et al. was adopted for this study in Foping Nature Reserve (NR), China. By comparing twelve monthly solar radiation patterns and calculating statistics such as maximum, minimum, mean and standard deviation of the solar radiation, diversified solar radiation patterns over different months were obtained. Maximum solar radiation occurred in June and July, while minimum solar radiation occurred in December and January. The annual sum of solar radiation was 6954 MJ/m2 in Foping NR. The range in solar radiation was smaller in hot months and larger in cold months. Radio tracking data of giant pandas were collected for twelve months and the ensuing maps were overlaid with the twelve-month solar radiation map to analyze the relation between the giant panda's monthly distribution and solar radiation. Our results showed that giant pandas prefer areas with lower solar radiation in warm months and select areas with higher solar radiation in cold months, which illustrates that the distribution of giant pandas is indeed affected by solar radiation. To a certain degree, it also explains the behavior of seasonal movement by giant pandas in Foping NR.
    Examining the assumptions of integrated coastal management: Stakeholder agendas and elite cooption in Babuyan Islands, Philippines
    Larsen, R.K. ; Acebes, J.M. ; Belen, A. - \ 2011
    Ocean & Coastal Management 54 (2011)1. - ISSN 0964-5691 - p. 10 - 18.
    marine protected areas - resource-management - sustainable management - conservation - policy - science - forest - water
    In the Philippines, Integrated Coastal Management (ICM) represents the dominant response to narratives of ecosystem decline. However, there are persistent challenges to implementation, manifested in continued resource degradation, questioning of the exercise of stakeholder involvement and rising resource conflicts. This paper examines the implementation process and how the assumptions embodied in the ICM regime meet the local reality in one group of islands in the Philippine archipelago. The evidence shows how the transformation towards a supposed equilibrium state of coastal ecosystems is undermined in the face of diverging stakeholder agendas. Expected actors are disempowered by the incoherence between the policy owners’ worldview and reality, paving the way for unethical influence from elite alliances. This is coupled with a deepening of the dominance of state, international development banks, foreign aid agencies, and NGOs in promoting their respective interests. In localities such as the Babuyan Islands, when assumptions of ICM collapse it has destructive consequences for fisherfolk and the coastal environment. We conclude that if ICM is to foster an effective and equitable correction of current unsustainable exploitation patterns, then there is a need to institute improved accountability mechanisms in the devolved governance system as well as taking seriously the espoused commitment to stakeholder involvement in determining the goals and assumptions of ICM
    Crossdating Juniperus procera from North Gondar, Ethiopia
    Wils, T. ; Robertson, I. ; Eshetu, Z. ; Touchan, R. ; Sass-Klaassen, U. ; Koprowski, M. - \ 2011
    Trees-Structure and Function 25 (2011)1. - ISSN 0931-1890 - p. 71 - 82.
    climate-growth relationships - tree-rings - pterocarpus-angolensis - precipitation - africa - dendrochronology - forest - c-14 - reconstruction - dynamics
    The application of dendrochronology in (sub)tropical regions has been limited by the difficulty in finding trees with distinct annual rings that can be crossdated. Here, we report successful crossdating of Juniperus procera trees from North Gondar, Ethiopia. The trees form annual rings in response to a unimodal rainfall regime. The selection of mesic locations ensured that the trees did not respond to intra-seasonal weather anomalies. Crossdating was achieved by comparison of the wood anatomy directly on the surface of the core samples and purpose-adapted skeleton plotting. Wood-anatomical anomalies, such as false and indistinct rings, were regarded as potentially replicated features and used in crossdating. COFECHA yielded site-specific mean series inter-correlations between 0.52 and 0.59. AMS radiocarbon dating during the bomb era indicated that dating uncertainty is ±1 year.
    Water balance in afforestation chronosequences of common oak and Norway spruce on former arable land in Denmark and southern Sweden
    Rosenqvist, L. ; Hansen, K. ; Vesterdal, L. ; Salm, C. van der - \ 2010
    Agricultural and Forest Meteorology 150 (2010)2. - ISSN 0168-1923 - p. 196 - 207.
    forest - soil - transpiration - interception - evaporation - stands - beech - model - conductance - catchment
    Precipitation, throughfall and soil moisture were measured, and interception, transpiration and water recharge were estimated in four afforestation chronosequences on former arable land at two Danish locations (Vestskoven and Gejlvang) and at one southern Swedish location (Tonnersjoheden). Afforestation was performed using Norway spruce (Picea abies (Karst.) L) and common oak (Quercus robur L.) at Vestskoven and only Norway spruce at Gejlvang and Tonnersjoheden. Four to five stands of different ages (5-92 years) were studied in each of these chronosequences. Hydrological fluxes were calculated using the soil hydrological model SWAP. Throughfall flux and soil water content were used for calibration of the model. The simulated water recharge decreased with increased stand age within 30-40 years of afforestation. This was mainly due to increased interception evaporation with age. The annual water recharge was higher below oak stands (149-192 mm yr(-1)) than below spruce stands (107-191 mm yr(-1)) of similar age. The relative water recharge was also considerably higher from the sandy glaciofluvial soils at Gejlvang and Tonnersjoheden than from the sandy loamy till soils at Vestskoven.
    A tool for rapid assessment of erosion risk to support decision-making and policy development at the Ngenge watershed in Uganda
    Mutekanga, F.P. ; Visser, S.M. ; Stroosnijder, L. - \ 2010
    Geoderma 160 (2010)2. - ISSN 0016-7061 - p. 165 - 174.
    soil-erosion - land-cover - evapotranspiration - catchment - australia - highlands - ethiopia - forest - stream - basin
    This study tests a rapid, user-friendly method for assessing changes in erosion risk, which yields information to aid policy development and decision-making for sustainable natural resources management. There is currently a lack of timely, up-to-date and current information to support policy development on sustainable natural resources management in Uganda. The study was carried out in the Ngenge watershed, a typical catchment in the Ugandan Highlands, characterised by deforestation in favour of subsistence agriculture without adequate soil and water conservation measures. The watershed is experiencing soil erosion, sedimentation and flooding problems which are threatening agricultural productivity and food security. Sustainable management of environmental resources is needed to ensure a livelihood for the rural population which is dependent on the land. Historical erosion risk was evaluated in three steps using multi-temporal satellite data. First, current erosion risk was assessed by combining slope and vegetation cover during periods of high intensity rainfall. The data used for the assessment was obtained from public (free) satellite images. Erosion risk was then linked to land use and finally to the change in vegetation cover over the years 1980-2000. The analysis of erosion risk using rainfall, slope and NDVI (Normalised Difference Vegetative Index) as a proxy for vegetation cover gives an indication of the current erosion risk in the area. The results of historical vegetation cover change analysis indicate an overall increase in areas under erosion risk in the study area from 1980 to 2000. This method of erosion risk mapping provides a quick and straightforward means for identifying priority areas for interventions for soil and water resource management. Considering that resources are limited, the interventions to be appropriate have to be focused mainly on areas affected by degradation.
    Mapping water-table depths in space and time to assess desiccation of groundwater-dependent ecosystems in the Netherlands
    Hoogland, T. ; Heuvelink, G.B.M. ; Knotters, M. - \ 2010
    Wetlands 30 (2010). - ISSN 0277-5212 - p. 137 - 147.
    models - series - space - fluctuation - vegetation - forest - maps
    During the past decades, groundwater-dependent ecosystems in the Netherlands have been threatened by a decline in the water-table level. However, information on water-table depths and changes in water-table depths is insufficient and outdated. For policy evaluation, spatially explicit and detailed information on water-table depths is required, especially in areas with groundwater-dependent ecosystems including wetlands. Some 35,000 observations of seasonal fluctuation characteristics of water-table depths in nature conservation areas were made since 1980 during soil surveys. These observations were derived from characteristics of the soil profile or from measurements in boreholes. These observations were used in a space-time geostatistical analysis to map the seasonal fluctuation of water-table depths between 1980 and 2007. First, systematic differences between different estimation modes used through the years were corrected. Next, observations were correlated with area-wide available ancillary data using multiple linear regression. Simple kriging was used to interpolate the resulting space-time residuals. Maps of the predicted mean spring water-table depths and the accuracy of these predictions were used to identify areas where the water-table is deeper than favorable. Changes of water-table depths on the national scale over the past 25 years were assessed, and recommendations were made to increase the accuracy of future predictions.
    Oak Persistence in Mediterranean Landscapes: The Combined Role of Management, Topography, and Wildfires
    Acácio, V.C. ; Holmgren, M. ; Moreira, F. ; Mohren, G.M.J. - \ 2010
    Ecology and Society 15 (2010)4. - ISSN 1708-3087
    eastern iberian peninsula - quercus-suber - ne spain - regeneration - forest - mechanisms - systems - future - ecosystems - challenges
    Mediterranean ecosystems have been shaped by a history of human and ecological disturbances. Understanding the dynamics of these social-ecological systems requires an understanding of how human and ecological factors interact. In this study, we assess the combined role of management practices and biophysical variables, i.e., wildfire and topography, to explain patterns of tree persistence in a cork oak (Quercus suber L.) landscape of southern Portugal. We used face-to-face interviews with landowners to identify the management practices and the incentives that motivated them. We used aerial photographs and a Geographic Information System (GIS) to classify vegetation patch-type transitions over a period of 45 years (1958-2002) and logistic regression to explain such changes based on management and biophysical factors. The best model explaining vegetation transitions leading to cork oak persistence in the landscape included both biophysical and management variables. Tree persistence was more likely to occur on steeper slopes, in the absence of wildfires, and in the absence of understory management. We identified ecological, ideological, and economical barriers that preclude oak persistence and that are important to consider in implementing efficient environmental policies for adequate conservation and reforestation programs of Mediterranean cork oak landscapes
    Ecology and Syntaxonomy of Gymnocarpium dryopteris L. in the Netherlands
    Bremer, P. - \ 2010
    American Fern Journal 100 (2010)2. - ISSN 0002-8444 - p. 110 - 125.
    forest
    Ecology, syntaxonomy and population size of Gymnocarpium dryopteris have been studied, especially during the period 1979–1991 by collecting data on 419 colonies in the Kuinderbos (a planted woodland in the Noordoostpolder, a polder reclaimed from the former Zuiderzee in 1942) and 74 colonies elsewhere in the Netherlands. In this paper the Kuinderbos population is compared with other Dutch populations (pleistocene area) in order to provide more insights in the ecology of the species and circumstances facilitating high density. Populations in Germany were studied as reference. In the period 1979–1991 the species was recorded in the Netherlands with at least 670 colonies, of which 89% are in the Kuinderbos. Gymnocarpium dryopteris prefers shadowed ditches and drainage trenches, but can grow at various other habitats as well. Especially at the western and southern part of the Netherlands, the species grows on canal walls. Sites with Gymnocarpium dryopteris belong to different communities. In the Kuinderbos stands of Picea sitchensis are preferred, while elsewhere in the Netherlands the species prefers the Quercion roboris-petreae (Fago-Quercetum) or Pseudotsuga mensiezii-stands. Gymnocarpium dryopteris is accompanied by 14 fern species, at the Kuinderbos by 12 fern species, with Athyrium filix-femina as characteristic species, often indicating potential sites. Rhizomes are shallow creeping, at average 2.6 cm below the surface (0.5–8 cm). It grows in the ecto-organic layer or just below this layer. At trench sides it often grows in the mineral layer. Most colonies are within the influence of the watertable. The Dutch colonies are small and colonies with more than 1000 fronds are rare. This probably indicates that most colonies are less than 20 years old. Colonies with more than 100 fronds are often fertile, with less than 20% of the fronds bearing sori. At the wall habitat small-sized individuals may be fertile as well. The high density in the Kuinderbos can be attributed to an optimal water supply from a peat subsoil, the composition of the ecto-organic layer consisting of Picea needles and an optimal light climate. The high density in Picea sitchensis within the Kuinderbos is unprecedented in Europe and makes these stands resemble the natural habitat of Picea sitchensis at the west coast of N. America.
    A review of the characteristics of black alder (Alnus glutinosa (L.) Gaertn.) and their implications for silvicultural practices
    Claessens, H. ; Oosterbaan, A. ; Savill, P. ; Rondeux, J. - \ 2010
    Forestry 83 (2010)2. - ISSN 0015-752X - p. 163 - 175.
    soil - populations - growth - forest - frankia - stands
    Black alder is a scattered, widespread and short-lived species that thrives in low-lying damp and riparian places. It has a use in flood control, stabilization of riverbanks and in functioning of the river ecosystems. To thrive, precipitation must exceed 1500 mm if access to groundwater is not possible. Alders are unusual among European trees in that they fix nitrogen. To regenerate naturally, alder requires high levels of both light and moisture, usually achievable only on disturbed sites. Growth rates up to ages 7–10 are very fast but then slow rapidly. Sixty to seventy years is the maximum rotation for growing timber if heart rot is to be avoided. Maximum mean annual increments range from 4 to 14 m3 ha–1 year–1. Alder wood is used for energy, as fibre for paper and particle board and, most profitably, in joinery as solid wood or veneer. Logs must be at least 3 m long and ideally 50–60 cm diameter. Aspects of plantation silviculture are discussed with emphasis on thinning, which needs to be started early and to be heavy and frequent around selected final crop trees to achieve marketable timber before heart rot sets in.
    Seed predation and defleshing in the agouti-dispersed palm Astrocaryum standleyanum
    Jansen, P.A. ; Elschot, K. ; Verkerk, P.J. ; Wright, S.J. - \ 2010
    Journal of Tropical Ecology 26 (2010)5. - ISSN 0266-4674 - p. 473 - 480.
    bruchid beetle - forest - patterns - rodents - fruits - recruitment - germination - survival - poachers - peru
    The agouti (Dasyprocta punctata) meticulously defleshes Astrocaryum standleyanum palm seeds before scatter hoarding. On Barro Colorado Island, Panama, we experimentally tested three hypotheses on how this behaviour could reduce seed predation to the mutual benefit of the tree and the rodent. The first and established hypothesis – that defleshing reduces seed predation by bruchid beetles by intercepting larvae – was rejected. Experiments in which manually defleshed seeds or entire fruits were incubated at different times showed that defleshing reduced bruchid infestation before fruit fall but not after fruit fall. The second hypothesis – that defleshing reduces cache pilferage by making seeds less conspicuous – was supported. An experiment in which intact fruits and manually defleshed seeds were placed in mimicked agouti caches and followed showed that seeds with flesh were pilfered at higher rates than defleshed seeds. The third hypothesis – that defleshing reduces post-dispersal infestation of cached seeds – was rejected. An experiment in which intact fruits and manually defleshed seeds were placed in mammal exclosures and later collected to assess infestation showed that burial reduced seed infestation but defleshing did not. Thus, seed defleshing reduced palm seed predation, but in a different way than previously believed. We also found that (1) bruchid beetles can be pre-dispersal rather than post-dispersal seed predators, (2) seed infestation by scolytid beetles may control bruchid larvae, and (3) scolytids rather than bruchids are the main invertebrate seed predators of this palm
    Inventory analysis of the timber industry in Ghana
    Eshun, J.F. ; Potting, J. ; Leemans, R. - \ 2010
    The International Journal of Life Cycle Assessment 15 (2010)7. - ISSN 0948-3349 - p. 715 - 725.
    life-cycle inventory - renewable resources - lumber production - policy - wood - lca - thinking - forest - needs
    Background, aim, and scope The timber sector, i.e., forestry and timber industry, plays an important role in the socioeconomic development of Ghana through timber products export. Timber production in this sector is associated with increasing environmental burdens in terms of use of materials and energy, production of emissions and waste, and land use changes. The purpose of this study was to compile a comprehensive life cycle inventory (LCI) to identify the most dominant environmental pressures for five major production lines in the timber industry, and to evaluate the influence of the choice of the functional unit on the results (1 m3, 1 kg, and 1 euro). LCA’s of wood typically base their functional unit on volume, but mass or money may be more appropriate for the rather different products considered in this study. Materials and methods The LCI covers five timber production lines, namely, air-dried lumber, kiln-dried lumber, plywood, veneer, and furniture parts. Three functional units were used for this study to identify the most appropriate basis for a fair comparison of the different timber products (functional units were 1 m3, 1 kg and 1 euro). Questionnaires were administered to thirty selected companies in Ghana. These companies provided data about their material uses, energy requirements, and waste production for their operations from 2000 to 2007. The collected data were first converted into total annual average values, and next extrapolated to reflect the national average data for all 104 active companies. Finally, these data were expressed per functional unit for each of the five product lines on the basis of their production outputs (in volume, mass or money according to functional unit applied). Forest land used changes data was taken from the Ghana Timber Industry Development Division. Emissions for the several activities were taken from literature. Results and discussion Land use change for timber production in Ghana between the estimated periods turned out to be 34.0¿×¿103 ha per year, which will lead to complete deforestation in the year 2023 if continued. The total energy consumed by the timber sector per year was estimated at 1.9¿×¿109 MJ per year. The results showed that CO2 emissions by the timber sector activities per year accounted for 745k tons per year and dominate overall greenhouse gases emissions in the timber sector (changes in carbons storage related to land use changes not included). Wood waste by the timber sector accounted for 0.8 million m3 per year. The enormous wastage of wood contributes enormously to the rapid depletion of the country’s timber resources. The choice of the functional unit influences inventory results. The money-based functional unit, which also seems more appropriate for the different products considered, favors the value-added. Value-added products with strict sustainable forest management policy hold a promising future in terms of sustainability for the timber industry in Ghana. Conclusions This study has yielded good quality primary data unique for LCA research in Africa. This will enhance LCA approaches in Ghana, and allows here identification of the main environmental pressures and their dominantly contributing processes in the timber sector. Land use changes due to forestry form a critical issue and require urgent attention. The chosen functional units’ plays a crucial role in the environmental comparison of production line in the timber sector in Ghana. Recommendations and perspectives A comprehensive and transparent inventory for the timber industry provides the industry with an overview of areas in which material and thus economic savings can be made for the good of both environment and the industry finances. Good data keeping in the Ghanaian timber industry will help to build the required research capacity to develop local familiarity and competence in LCA techniques and applying these techniques will help to further certify tropical timber international markets.
    The ranging patterns of elephants in Marsabit protected area, Kenya: the use of satellite-linked GPS collars
    Ngene, S.M. ; Gils, H. ; Wieren, S.E. van; Rasmussen, H. ; Skidmore, A.K. ; Prins, H.H.T. ; Toxopeus, A.G. ; Omondi, P. ; Douglas-Hamilton, I. - \ 2010
    African Journal of Ecology 48 (2010)2. - ISSN 0141-6707 - p. 386 - 400.
    national-park - loxodonta-africana - home-range - northwestern namibia - northern kenya - movements - forest - woodland - tracking - tanzania
    We investigated the ranging patterns of elephants in the Marsabit protected area, north eastern Kenya, to ascertain the range of bachelor and female family herds in different seasons, and to identify corridor and noncorridor areas. Data were acquired for five bachelor and four female family herds equipped with satellite-linked geographical positioning system collars, and monitored from December 2005 to December 2007. Distinct dry (about 260 km2) and wet seasons (about 910 km2) ranges were observed, with connecting corridors (north-eastern corridor: about 90 km long, about 2-7 km wide; southern corridors: about 10-20 km long, about 2-3 km wide). The dry season range corresponded with Marsabit evergreen forest, while the wet season range matched with dry deciduous lowland shrubs. The ranging elephants moved at speed of about 0.2-20 kmh-1. Bachelor herds moved faster than female family herds. Elephants moved fast during the intermediate and wet seasons than during the dry season. The speed of ranging elephants was over 1 kmh-1 in the corridor areas and about 0.2 to less than 1 kmh-1 in the non-corridor areas. Expansion of settlements towards corridor areas needs to be controlled to avoid future blocking of connectivity between wet and dry season elephant ranges
    Biodiversity and agricultural sustainagility: from assessment to adaptive management
    Jackson, L. ; Noordwijk, M. van; Bengtsson, J. ; Foster, W. ; Lipper, L. ; Pulleman, M.M. ; Said, M. ; Snaddon, J. ; Vodouhe, R. - \ 2010
    Current Opinion in Environmental Sustainability 2 (2010)1-2. - ISSN 1877-3435 - p. 80 - 87.
    palm elaeis-guineensis - oil palm - conservation - forest - kenya - intensification - pollination - population - resilience - landscapes
    Rapid changes in land use, food systems, and livelihoods require social–ecological systems that keep multiple options open and prepare for future unpredictability. Sustainagility refers to the properties and assets of a system that sustain the ability (agility) of agents to adapt and meet their needs in new ways. In contrast, sustainability tends to invoke persistence along current trajectories, and the resilience to return to current baselines. With three examples, the use and conservation of agrobiodiversity is explored along temporal, spatial, and human institutional scales for its role in sustainagility: first, farmers’ seed systems; second, complex pollination systems; and third, wildlife conservation in agricultural areas with high poverty. Incentives are necessary if agrobiodiversity is to provide benefits to future generations
    Check title to add to marked list
    << previous | next >>

    Show 20 50 100 records per page

     
    Please log in to use this service. Login as Wageningen University & Research user or guest user in upper right hand corner of this page.