Staff Publications

Staff Publications

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    '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.

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    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
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