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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    Demography of the ecosystem engineer Crassostrea gigas, related to vertical freef accretion and reef persistence
    Walles, B. ; Mann, R.M. ; Ysebaert, T. ; Troost, K. ; Herman, P.M.J. ; Smaal, A.C. - \ 2015
    Estuarine Coastal and Shelf Science 154 (2015). - ISSN 0272-7714 - p. 224 - 233.
    sea-level rise - introduced pacific oysters - wadden sea - chesapeake bay - population-dynamics - shell dissolution - eastern oyster - james river - virginica - habitats
    Marine species characterized as structure building, autogenic ecosystem engineers are recognized worldwide as potential tools for coastal adaptation efforts in the face of sea level rise. Successful employment of ecosystem engineers in coastal protection largely depends on long-term persistence of their structure, which is in turn dependent on the population dynamics of the individual species. Oysters, such as-the Pacific oyster (Crassostrea gigas), are recognized as ecosystem engineers with potential for use in coastal protection. Persistence of oyster reefs is strongly determined by recruitment and shell production (growth), processes facilitated by gregarious settlement on extant shell substrate. Although the Pacific oyster has been introduced world-wide, and has formed dense reefs in the receiving coastal waters, the population biology of live oysters and the quantitative mechanisms maintaining these reefs has rarely been studied, hence the aim of the present work. This study had two objectives: (1) to describe the demographics of extant C. gigas reefs, and (2) to estimate vertical reef accretion rates and carbonate production in these oyster reefs. Three long-living oyster reefs (>30 years old), which have not been exploited since their first occurrence, were examined in the Oosterschelde estuary in the Netherlands. A positive reef accretion rate (7.0-16.9 mm year(-1) shell material) was observed, consistent with self-maintenance and persistent structure. We provide a framework to predict reef accretion and population persistence under varying recruitment, growth and mortality scenarios. (C) 2015 Elsevier Ltd. All rights reserved.
    Spatial heterogeneity of plant–soil feedback affects root interactions and interspecific competition
    Hendriks, M. ; Ravenek, J. ; Smit-Tiekstra, A.E. ; Paauw, J.W.M. van der; Caluwe, H. de; Putten, W.H. van der; Kroon, H. de; Mommer, L. - \ 2015
    New Phytologist 207 (2015)3. - ISSN 0028-646X - p. 830 - 840.
    nutrient heterogeneity - species-diversity - population-dynamics - relative abundance - deciduous woodland - temporal variation - borne pathogens - grassland - community - coexistence
    Plant-soil feedback is receiving increasing interest as a factor influencing plant competition and species coexistence in grasslands. However, we do not know how spatial distribution of plant-soil feedback affects plant below-ground interactions. We investigated the way in which spatial heterogeneity of soil biota affects competitive interactions in grassland plant species. We performed a pairwise competition experiment combined with heterogeneous distribution of soil biota using four grassland plant species and their soil biota. Patches were applied as quadrants of 'own' and 'foreign' soils from all plant species in all pairwise combinations. To evaluate interspecific root responses, species-specific root biomass was quantified using real-time PCR. All plant species suffered negative soil feedback, but strength was species-specific, reflected by a decrease in root growth in own compared with foreign soil. Reduction in root growth in own patches by the superior plant competitor provided opportunities for inferior competitors to increase root biomass in these patches. These patterns did not cascade into above-ground effects during our experiment. We show that root distributions can be determined by spatial heterogeneity of soil biota, affecting plant below-ground competitive interactions. Thus, spatial heterogeneity of soil biota may contribute to plant species coexistence in species-rich grasslands.
    Mobile dune fixation by a fast-growing clonal plant: a full life-cycle analysis
    Werger, M.J.A. ; During, H.J. ; Zuidema, P.A. - \ 2015
    Scientific Reports 5 (2015). - ISSN 2045-2322 - 7 p.
    integral projection models - inner mongolian dune - comparative demography - population-dynamics - psammochloa-villosa - relative importance - hedysarum-laeve - desert cactus - china - growth
    Desertification is a global environmental problem, and arid dunes with sparse vegetation are especially vulnerable to desertification. One way to combat desertification is to increase vegetation cover by planting plant species that can realize fast population expansion, even in harsh environments. To evaluate the success of planted species and provide guidance for selecting proper species to stabilize active dunes, demographic studies in natural habitats are essential. We studied the life history traits and population dynamics of a dominant clonal shrub Hedysarum laeve in Inner-Mongolia, northern China. Vital rates of 19057 ramets were recorded during three annual censuses (2007–2009) and used to parameterize Integral Projection Models to analyse population dynamics. The life history of H. laeve was characterized by high ramet turnover and population recruitment entirely depended on clonal propagation. Stochastic population growth rate was 1.32, suggesting that the populations were experiencing rapid expansion. Elasticity analysis revealed that clonal propagation was the key contributor to population growth. The capacity of high clonal propagation and rapid population expansion in mobile dunes makes H. laeve a suitable species to combat desertification. Species with similar life-history traits to H. laeve are likely to offer good opportunities for stabilizing active dunes in arid inland ecosystems.
    Growth of anaerobic methane oxidizing archaea and sulfate reducing bacteria in a high pressure membrane-capsule bioreactor
    Timmers, P.H.A. ; Gieteling, J. ; Widjaja-Greefkes, H.C.A. ; Plugge, C.M. ; Stams, A.J.M. ; Lens, P.N.L. ; Meulepas, R.J.W. - \ 2015
    Applied and Environmental Microbiology 81 (2015)4. - ISSN 0099-2240 - p. 1286 - 1296.
    cold-seep sediments - 16s ribosomal-rna - gradient gel-electrophoresis - guaymas basin - hydrothermal sediments - microbial diversity - marine-sediments - population-dynamics - community structure - gene database
    Anaerobic methane oxidizing communities of archaea (ANME) and sulfate reducing bacteria (SRB) grow slowly, which limits physiological studies. High methane partial pressure was previously successfully applied to stimulate growth, but it is not clear how different ANME subtypes and associated sulfate reducing bacteria (SRB) are affected by it. Here, we report growth of ANME/SRB in a membrane-capsule bioreactor inoculated with Eckernförde Bay sediment that combines high pressure incubation (10.1 MPa methane) and thorough mixing (100 rpm) with complete cell retention by a 0.2 µm membrane. Results were compared to previously obtained data from an ambient-pressure (0.101 MPa methane) bioreactor inoculated with the same sediment. Labelled-methane oxidation rates were not higher at 10.1 MPa, likely because measurements were done at ambient pressure. The subtype ANME-2a/b was abundant in both reactors, but subtype ANME-2c was only enriched at 10.1 MPa. SRB at 10.1 MPa mainly belonged to the SEEP-SRB2, Eel-1 group and Desulforomonadales and not to the typically found SEEP-SRB1. Increase of ANME-2a/b occurred in parallel with increase of SEEP-SRB2 which was previously only found associated with ANME-2c. Our results imply that the syntrophic association is flexible and that methane pressure and sulfide concentration influence growth of different ANME-SRB consortia. We also studied the effect of elevated methane pressure on methane production and oxidation by a mixture of methanogenic and sulfate-reducing sludge. Here, methane oxidation rates decreased and were not coupled to sulfide production, indicating trace methane oxidation during net methanogenesis and not anaerobic methane oxidation, even at high methane partial pressure.
    Fish abundance, fisheries, fish trade and consumption in sixteenth-century Netherlands as described by Adriaen Coenen
    Bennema, F.P. ; Rijnsdorp, A.D. - \ 2015
    Fisheries Research 161 (2015). - ISSN 0165-7836 - p. 384 - 399.
    pleuronectes-platessa l - atlantic bluefin tuna - southern north-sea - cod gadus-morhua - wadden sea - population-dynamics - medieval europe - resource use - lower rhine - history
    Concern about fisheries impact on marine ecosystems has raised the interest in the reconstruction of the state of marine ecosystems and the nature of the human activities in the past. We present late 16th century information on the occurrence and relative abundance of biota in Dutch coastal and inland waters (50 marine fish, 13 diadromous or freshwater and 4 marine mammal species), as well as a description of the sea fisheries (target species, fishing grounds, gear), fish trade, export, and fish consumption in Holland as documented in the handwritten Fish Book by Adriaen Coenen (1577–1581). The species composition and abundances are compared to published trawl survey data from around 1900 and in the 1990s. Fish species that have disappeared almost completely, were already rare around 1900 and are characterised by a large body size (rays and sharks, sturgeon, ling), whereas currently abundant species were already abundant in the 16th century. Intensive fisheries for herring occurred near Orkney, Fairhill and Shetland. Coastal and freshwater fisheries provided fresh fish for local as well as export markets, but also provided bait for the massive offshore hook and line fishery for the production of salted cod, which remained largely unnoticed. Dried flatfish were exported to Germany. Consumption of fish and marine invertebrates differed between social classes. Coenen distinguished eight consumer categories, a refinement of the categories ‘rich’ and ‘poor’ used in archaeological studies.
    No evidence of the effect of extreme weather events on annual occurrence of four groups of ectothermic species
    Malinowska, A.H. ; Strien, A.J. van; Verboom, J. ; Wallis de Vries, M.F. ; Opdam, P. - \ 2014
    PLoS ONE 9 (2014)10. - ISSN 1932-6203 - 10 p.
    climate-change - metapopulation dynamics - habitat fragmentation - population-dynamics - occupancy models - european climate - range expansion - dispersal - trends - impact
    Weather extremes may have strong effects on biodiversity, as known from theoretical and modelling studies. Predicted negative effects of increased weather variation are found only for a few species, mostly plants and birds in empirical studies. Therefore, we investigated correlations between weather variability and patterns in occupancy, local colonisations and local extinctions (metapopulation metrics) across four groups of ectotherms: Odonata, Orthoptera, Lepidoptera, and Reptilia. We analysed data of 134 species on a 1×1 km-grid base, collected in the last 20 years from the Netherlands, combining standardised data and opportunistic data. We applied dynamic site-occupancy models and used the results as input for analyses of (i) trends in distribution patterns, (ii) the effect of temperature on colonisation and persistence probability, and (iii) the effect of years with extreme weather on all the three metapopulation metrics. All groups, except butterflies, showed more positive than negative trends in metapopulation metrics. We did not find evidence that the probability of colonisation or persistence increases with temperature nor that extreme weather events are reflected in higher extinction risks. We could not prove that weather extremes have visible and consistent negative effects on ectothermic species in temperate northern hemisphere. These findings do not confirm the general prediction that increased weather variability imperils biodiversity. We conclude that weather extremes might not be ecologically relevant for the majority of species. Populations might be buffered against weather variation (e.g. by habitat heterogeneity), or other factors might be masking the effects (e.g. availability and quality of habitat). Consequently, we postulate that weather extremes have less, or different, impact in real world metapopulations than theory and models suggest.
    A global assembly of adult female mosquito mark-release-recapture data to inform the control of mosquito-borne pathogens
    Guerra, C.A. ; Reiner Jr, R.C. ; Perkins, T.A. ; Lindsay, S.W. ; Midega, J.T. ; Brady, O.J. ; Barker, C.M. ; Reisen, W.K. ; Harrington, L.C. ; Takken, W. ; Kitron, U. ; Lloyd, A.L. ; Hay, S.I. ; Scott, T.W. ; Smith, D.L. - \ 2014
    Parasites & Vectors 7 (2014). - ISSN 1756-3305 - 15 p.
    dominant anopheles vectors - plasmodium-falciparum transmission - distribution maps - bionomic precis - human malaria - sensitivity-analysis - population-dynamics - mathematical-model - aedes-aegypti - culicidae
    Background Pathogen transmission by mosquitos is known to be highly sensitive to mosquito bionomic parameters. Mosquito mark-release-recapture (MMRR) experiments are a standard method for estimating such parameters including dispersal, population size and density, survival, blood feeding frequency and blood meal host preferences. Methods We assembled a comprehensive database describing adult female MMRR experiments. Bibliographic searches were used to build a digital library of MMRR studies and selected data describing the reported outcomes were extracted. Results The resulting database contained 774 unique adult female MMRR experiments involving 58 vector mosquito species from the three main genera of importance to human health: Aedes, Anopheles and Culex. Crude examination of these data revealed patterns associated with geography as well as mosquito genus, consistent with bionomics varying by species-specific life history and ecological context. Recapture success varied considerably and was significantly different amongst genera, with 8, 4 and 1% of adult females recaptured for Aedes, Anopheles and Culex species, respectively. A large proportion of experiments (59%) investigated dispersal and survival and many allowed disaggregation of the release and recapture data. Geographic coverage was limited to just 143 localities around the world. Conclusions This MMRR database is a substantial contribution to the compilation of global data that can be used to better inform basic research and public health interventions, to identify and fill knowledge gaps and to enrich theory and evidence-based ecological and epidemiological studies of mosquito vectors, pathogen transmission and disease prevention. The database revealed limited geographic coverage and a relative scarcity of information for vector species of substantial public health relevance. It represents, however, a wealth of entomological information not previously compiled and of particular interest for mosquito-borne pathogen transmission models.
    Coupling socio-economic factors and eco-hydrological processes using a cascade-modeling approach
    Odongo, V.O. ; Mulatu, D.W. ; Muthoni, F.K. ; Oel, P.R. van; Meins, F.M. ; Tol, C. van der; Skidmore, A.K. ; Groen, T.A. ; Becht, R. ; Onyando, J.O. ; Veen, A. van der - \ 2014
    Journal of Hydrology 518 (2014)Part A. - ISSN 0022-1694 - p. 49 - 59.
    land-use change - murray-darling basin - lake naivasha - population-dynamics - water availability - stream ecosystems - human impact - east-africa - kenya - rainfall
    Most hydrological studies do not account for the socio-economic influences on eco-hydrological processes. However, socio-economic developments often change the water balance substantially and are highly relevant in understanding changes in hydrological responses. In this study a multi-disciplinary approach was used to study the cascading impacts of socio-economic drivers of land use and land cover (LULC) changes on the eco-hydrological regime of the Lake Naivasha Basin. The basin has recently experienced substantial LULC changes exacerbated by socio-economic drivers. The simplified cascade models provided insights for an improved understanding of the socio-ecohydrological system. Results show that the upstream population has transformed LULC such that runoff during the period 1986–2010 was 32% higher than during the period 1961–1985. Cut-flower export volumes and downstream population growth explain 71% of the water abstracted from Lake Naivasha. The influence of upstream population on LULC and upstream hydrological processes explained 59% and 30% of the variance in lake storage volumes and sediment yield respectively. The downstream LULC changes had significant impact on large wild herbivore mammal species on the fringe zone of the lake. This study shows that, in cases where observed socio-economic developments are substantial, the use of a cascade-modeling approach, that couple socio-economic factors to eco-hydrological processes, can greatly improve our understanding of the eco-hydrological processes of a catchment.
    Effect of tillage on earthworms over short- and medium-term in conventional and organic farming
    Crittenden, S. ; Eswaramurthy, T. ; Goede, R.G.M. de; Brussaard, L. ; Pulleman, M.M. - \ 2014
    Applied Soil Ecology 83 (2014). - ISSN 0929-1393 - p. 140 - 148.
    cropping systems - soil-structure - population-dynamics - communities - diversity - abundance - lumbricidae - landscapes - compaction - management
    Earthworms play an important role in many soil functions and are affected by soil tillage in agricultural soils. However, effects of tillage on earthworms are often studied without considering species and their interactions with soil properties. Furthermore, many field studies are based on one-time samplings that do not allow for characterisation of temporal variation. The current study monitored the short (up to 53 days) and medium term (up to 4 years) effects of soil tillage on earthworms in conventional and organic farming. Earthworm abundances decreased one and three weeks after mouldboard ploughing in both conventional and organic farming, suggesting direct and indirect mechanisms. However, the medium-term study revealed that earthworm populations in mouldboard ploughing systems recovered by spring. The endogeic species Aporrectodea caliginosa strongly dominated the earthworm community (76%), whereas anecic species remained
    The impact of large herbivores on woodland–grassland dynamics in fragmented landscapes: The role of spatial configuration and disturbance
    Schippers, P. ; Teeffelen, A.J.A. van; Verboom-Vasiljev, J. ; Vos, C.C. ; Kramer, K. ; Wallis de Vries, M.F. - \ 2014
    Ecological Complexity 17 (2014). - ISSN 1476-945X - p. 20 - 31.
    north temperate forests - red deer - population-dynamics - metapopulation dynamics - habitat fragmentation - distribution patterns - grazing systems - management - regeneration - resilience
    The vegetation structure of natural ecosystems is usually considered independent of their size and their location in the landscape. In this study, we examine the effect of size, spatial configuration and disturbances on the dynamic interactions of large herbivores and vegetation in a patchy environment using a metapopulation model. Simulations indicate that small, isolated or unfenced patches have low herbivore numbers and high tree cover whereas large, well-connected or fenced patches support high herbivore densities and are covered by grassland. Recovery of both herbivore numbers and forest cover in response to disturbance is slow (>100 years). These long recovery times are partly attributable to negative feedbacks between herbivore numbers and tree cover. When the population of large herbivores is disturbed, forest is able to expand, subsequently inhibiting herbivore population recovery. Likewise, forest disturbance allows herbivore population expansion, which inhibits forest recovery. Additionally, infrequent and limited disturbances like hunting and forest removal also affect the vegetation cover in patches of nature. Thus, our work indicates that the location and size of patches, together with disturbances, largely determine the structure of the vegetation in fragmented landscapes
    Infectious disease agents mediate interaction in food webs and ecosystems
    Selaković, S. ; Ruiter, P.C. de; Heesterbeek, J.A.P. - \ 2014
    Proceedings of the Royal Society. B: Biological Sciences 281 (2014)1777. - ISSN 0962-8452 - 11 p.
    biological-control - population-dynamics - species-diversity - mustela-nigripes - canine-distemper - african lions - host behavior - coral-reef - parasites - communities
    Infectious agents are part of food webs and ecosystems via the relationship with their host species that, in turn, interact with both hosts and non-hosts. Through these interactions, infectious agents influence food webs in terms of structure, functioning and stability. The present literature shows a broad range of impacts of infectious agents on food webs, and by cataloguing that range, we worked towards defining the various mechanisms and their specific effects. To explore the impact, a direct approach is to study changes in food-web properties with infectious agents as separate species in the web, acting as additional nodes, with links to their host species. An indirect approach concentrates not on adding new nodes and links, but on the ways that infectious agents affect the existing links across host and non-host nodes, by influencing the 'quality' of consumer-resource interaction as it depends on the epidemiological state host involved. Both approaches are natural from an ecological point of view, but the indirect approach may connect more straightforwardly to commonly used tools in infectious disease dynamics.
    Sclerotium rolfsii dynamics in soil as affected by crop sequences
    Leoni, C. ; Braak, C.J.F. ter; Gilsanz, J.C. ; Dogliotti, S. ; Rossing, W.A.H. ; Bruggen, A.H.C. van - \ 2014
    Applied Soil Ecology 75 (2014). - ISSN 0929-1393 - p. 95 - 105.
    southern blight - vegetable farms - soilborne pathogens - population-dynamics - organic amendments - north-carolina - management - rotations - survival - residues
    Crop rotation has been used for the management of soilborne diseases for centuries, but has not often been planned based on scientific knowledge. Our objective was to generate information on Sclerotium rolfsii dynamics under different crop or intercrop activities, and design and test a research approach where simple experiments and the use of models are combined to explore crop sequences that minimize Southern blight incidence. The effect of seventeen green manure (GM) amendments on sclerotia dynamics was analyzed in greenhouse and field plot experiments during two years. The relative densities of viable sclerotia 90 days after winter GM (WGM) incorporation were generally lower than after summer GM (SGM) incorporation, with average recovery values of 60% and 61% for WGM in the field, 66% and 43% for WGM in the greenhouse, and 162% to 91% for SGM in the greenhouse, in 2009 and 2010, respectively. Sclerotia survival on day d after GM amendment was described by the model Sf = Si × exp(-b × d), relating initial (Si) and final (Sf) sclerotia densities. Relative decay rates of the sclerotia (b) in SGM amended soil were largest for alfalfa (0.0077 ± 0.0031 day-1) and sudangrass (0.0072 ± 0.0030 day-1). In WGM amended soil, the largest b values were for oat (0.0096 ± 0.0024 day-1), wheat (0.0090 ± 0.0024 day-1) and alfalfa (0.0087 ± 0.0023 day-1). The effect of three cropping sequences (sweet pepper–fallow, sweet pepper–black oat and sweet pepper–onion) on sclerotia dynamics was analyzed in microplot experiments, and the data were used to calibrate the model Pf = Pi/(a + ßPi), relating initial (Pi) and final (Pf) sclerotia densities. Median values for the relative rate of population increase at low Pi (1/a, dimension less) and the asymptote (1/ß, number of viable sclerotia in 100 g of dry soil) were 8.22 and 4.17 for black oat (BO), 1.13 and 8.64 for onion (O), and 6.26 and 17.93 for sweet pepper (SwP). By concatenating the two models, sclerotia population dynamics under several crop sequences were simulated. At steady state, the sequence SwP–O–Fallow–BO resulted in the lowest long-term sclerotia density (7.09 sclerotia/100 g soil), and SwP–Fallow in the highest (17.89 sclerotia/100 g soil). The developed methodology facilitates the selection of a limited number of rotation options to be tested in farmers’ fields.
    Forage fish, their fisheries and their predators: who drives whom?
    Engelhard, G.H. ; Peck, M.A. ; Rindorf, A. ; Smout, S.C. ; Deurs, M. van; Raab, K.E. ; Andersen, K.H. ; Garthe, S. ; Lauerburg, R.A.M. ; Scott, F. ; Brunel, T.P.A. ; Aarts, G.M. ; Kooten, T. van; Dickey-Collas, M. - \ 2014
    ICES Journal of Marine Science 71 (2014)1. - ISSN 1054-3139 - p. 90 - 104.
    herring clupea-harengus - sprat sprattus-sprattus - sandeel ammodytes-marinus - ecosystem-based management - pout trisopterus-esmarkii - cod gadus-morhua - north-sea fish - population-dynamics - trophic cascades - environmental variability
    The North Sea has a diverse forage fish assemblage, including herring, targeted for human consumption; sandeel, sprat, and Norway pout, exploited by industrial fisheries; and some sardine and anchovy, supporting small-scale fisheries. All show large abundance fluctuations, impacting on fisheries and predators. We review field, laboratory, and modelling studies to investigate the drivers of this complex system of forage fish. Climate clearly influences forage fish productivity; however, any single-species considerations of the influence of climate might fail if strong interactions between forage fish exist, as in the North Sea. Sandeel appears to be the most important prey forage fish. Seabirds are most dependent on forage fish, due to specialized diet and distributional constraints (breeding colonies). Other than fisheries, key predators of forage fish are a few piscivorous fish species including saithe, whiting, mackerel, and horse-mackerel, exploited in turn by fisheries; seabirds and seals have a more modest impact. Size-based foodweb modelling suggests that reducing fishing mortality may not necessarily lead to larger stocks of piscivorous fish, especially if their early life stages compete with forage fish for zooplankton resources. In complex systems, changes in the impact of fisheries on forage fish may have potentially complex (and perhaps unanticipated) consequences on other commercially and/or ecologically important species.
    Fusarium oxysporum f.sp. cepae dynamics: in-plant multiplication and crop sequence simulations
    Leoni, C. ; Vries, M. de; Braak, C.J.F. ter; Bruggen, A.H.C. van; Rossing, W.A.H. - \ 2013
    European Journal of Plant Pathology 137 (2013)3. - ISSN 0929-1873 - p. 545 - 561.
    f-sp melonis - ecological intensification - verticillium-dahliae - disease suppression - population-dynamics - organic amendments - soilborne diseases - farming systems - root diseases - wilt pathogen
    To reduce Fusarium Basal Rot caused by Fusarium oxysporum f.sp. cepae (Foc) through crop rotation, plant species should be selected based on Foc multiplication in their roots. Foc multiplication rates in 13 plant species were tested in a greenhouse. All plant species enabled Foc multiplication. The lowest Foc levels (cfu g-1 dry root) were found for wheat, sunflower, cowpea and millet, the highest for black bean. The highest Foc levels per plant were calculated for sudan grass. These data were used to calibrate the model Pf¿=¿Pi/(a¿+¿ßPi) relating final (Pf) and initial (Pi) Foc levels in the soil. The rate of population increase at low Pi (1/a) was highest for onion and black oat and smallest for sunflower. The pathogen carrying capacity (1/ß) was highest for black oat and black bean, and lowest for wheat, cowpea and foxtail millet. Foc soil population dynamics was simulated for crop sequences by concatenating Pi-Pf values, considering instantaneous or gradual pathogen release after harvest. Different soil Foc populations were attained after reaching steady states. Foc populations in the sequence onion –foxtail millet - wheat – cowpea were 67 % lower than in the sequence onion – sudan grass - black oat - black beans. In this work, by combining detailed greenhouse experiments with modelling, we were able to screen crops for their ability to increase Foc population and to explore potential crop sequences that may limit pathogen build-up
    Understanding the effects of a new grazing policy: the impact of seasonal grazing on shrub demography in the Inner Mongolian steppe
    Li, Shou-Li ; Yu, F.H. ; Werger, M.J.A. ; Dong, M. ; Ramula, S. ; Zuidema, P.A. - \ 2013
    Journal of Applied Ecology 50 (2013)6. - ISSN 0021-8901 - p. 1377 - 1386.
    integral projection models - herb lathyrus-vernus - population-dynamics - environmental stochasticity - semiarid savanna - elasticities - performance - plants - restoration - variability
    1.Grazing by livestock is a common land use in arid and semi-arid areas. Developing sustainable grazing regimes that conserve vegetation and maintain productivity is therefore important in these ecosystems. To solve environmental problems induced by overgrazing in Chinese semi-arid regions, the Chinese government has recently implemented a new policy of seasonal grazing, with no grazing from April to July. While this policy has been implemented in huge areas, its consequences for grazed plant populations have not been assessed so far. 2.We evaluated the demographic consequences of seasonal grazing for Caragana intermedia, a long-lived dominant shrub serving as a main food source for livestock in Inner Mongolia, China. Controlled seasonally grazed and ungrazed populations were monitored during 2007–2009, and their vital rates were compared. We then constructed integral projection models (IPMs) to analyse the effects of seasonal grazing on population dynamics. 3.Seasonal grazing negatively affected two vital rates: seedling survival and seedling recruitment were 25–71% and 69–91% lower in the seasonally grazed treatment than in the ungrazed situation, respectively. Seasonal grazing had a minimal effect on adult survival and growth, but improved juvenile survival by 8–31%. 4.Despite its effects on several vital rates, seasonal grazing did not significantly affect long-term population growth rates (¿), which remained close to unity in both grazed and ungrazed areas based on deterministic and stochastic analyses. An elasticity analysis showed that population growth rate was mainly governed by the high survival of large adults. Results of Life Table Response Experiments (LTREs) revealed that variation in population growth rates across treatments and years was more strongly governed by temporal differences than by grazing. 5.Synthesis and applications. Our study showed that the relatively large changes in vital rates induced by seasonal grazing did not affect population growth rates. Caragana intermedia populations can be sustained under the seasonal grazing regime probably because the grazing intensity is moderate and because this species has a high probability of adult survival under grazing. Plant species with similar life-history traits to C. intermedia are likely to offer good opportunities for sustainable seasonal grazing regimes in arid and semi-arid inland ecosystems
    Can fisheries-induced evolution shift reference points for fisheries management?
    Heino, M. ; Baulier, L. ; Boukal, D.S. ; Mollet, F.M. ; Rijnsdorp, A.D. - \ 2013
    ICES Journal of Marine Science 70 (2013)4. - ISSN 1054-3139 - p. 707 - 721.
    cod gadus-morhua - north-sea plaice - life-history evolution - exploited fish stocks - pleuronectes-platessa l - eco-genetic model - atlantic cod - population-dynamics - reproductive investment - natural mortality
    Biological reference points are important tools for fisheries management. Reference points are not static, but may change when a population's environment or the population itself changes. Fisheries-induced evolution is one mechanism that can alter population characteristics, leading to “shifting” reference points by modifying the underlying biological processes or by changing the perception of a fishery system. The former causes changes in “true” reference points, whereas the latter is caused by changes in the yardsticks used to quantify a system's status. Unaccounted shifts of either kind imply that reference points gradually lose their intended meaning. This can lead to increased precaution, which is safe, but potentially costly. Shifts can also occur in more perilous directions, such that actual risks are greater than anticipated. Our qualitative analysis suggests that all commonly used reference points are susceptible to shifting through fisheries-induced evolution, including the limit and “precautionary” reference points for spawning-stock biomass, Blim and Bpa, and the target reference point for fishing mortality, F0.1. Our findings call for increased awareness of fisheries-induced changes and highlight the value of always basing reference points on adequately updated information, to capture all changes in the biological processes that drive fish population dynamics.
    Frankincense tree recruitment failed over the past half century
    Tolera Feyissa, M. ; Sass, U.G.W. ; Eshete, A. ; Bongers, F. ; Sterck, F.J. - \ 2013
    Forest Ecology and Management 304 (2013). - ISSN 0378-1127 - p. 65 - 72.
    annual growth rings - long-term growth - dry-forest trees - boswellia-papyrifera - pterocarpus-angolensis - population-dynamics - age-determination - acacia-erioloba - seed predation - tropical trees
    Boswellia papyrifera (Burseraceae) trees grow in dry woodlands south of the Sahara and produce frankincense, the economically important olio-gum resin used for cultural and religious ceremonies throughout the world and as raw material in several industries. Across its distribution area, this species is threatened by farmland expansion, fire, improper tapping and overgrazing. Most of its populations lack saplings and small-sized trees (e.g.
    European Perspectives on the Adoption of Nonchemical Weed Management in Reduced-Tillage Systems for Arable Crops
    Melander, B. ; Munier-Jolain, N.M. ; Charles, R. ; Wirth, J. ; Schwarz, J. ; Weide, R.Y. van der; Bonin, L. ; Jensen, P.K. ; Kudsk, P.K. - \ 2013
    Weed Technology 27 (2013)1. - ISSN 0890-037X - p. 231 - 240.
    thistle cirsium-arvense - population-dynamics - oilseed rape - no-till - alopecurus-myosuroides - herbicide performance - conservation tillage - cropping systems - stubble tillage - spring barley
    Noninversion tillage with tine- or disc-based cultivations prior to crop establishment is the most common way of reducing tillage for arable cropping systems with small grain cereals, oilseed rape, and maize in Europe. However, new regulations on pesticide use might hinder further expansion of reduced-tillage systems. European agriculture is asked to become less dependent on pesticides and promote crop protection programs based on integrated pest management (IPM) principles. Conventional noninversion tillage systems rely entirely on the availability of glyphosate products, and herbicide consumption is mostly higher compared to plow-based cropping systems. Annual grass weeds and catchweed bedstraw often constitute the principal weed problems in noninversion tillage systems, and crop rotations concurrently have very high proportions of winter cereals. There is a need to redesign cropping systems to allow for more diversification of the crop rotations to combat these weed problems with less herbicide input. Cover crops, stubble management strategies, and tactics that strengthen crop growth relative to weed growth are also seen as important components in future IPM systems, but their impact in noninversion tillage systems needs validation. Direct mechanical weed control methods based on rotating weeding devices such as rotary hoes could become useful in reduced-tillage systems where more crop residues and less workable soils are more prevalent, but further development is needed for effective application. Owing to the frequent use of glyphosate in reduced-tillage systems, perennial weeds are not particularly problematic. However, results from organic cropping systems clearly reveal that desisting from glyphosate use inevitably leads to more problems with perennials, which need to be addressed in future research.
    Within-patch habitat quality determines the resilience of specialist species in fragmented landscapes
    Ye, X. ; Skidmore, A.K. ; Wang, T. - \ 2013
    Landscape Ecology 28 (2013)1. - ISSN 0921-2973 - p. 135 - 147.
    metapopulation dynamics - population-dynamics - environmental variation - relative importance - isolation paradigm - extinction risk - effect size - long-term - heterogeneity - persistence
    Patch geometry and habitat quality among patches are widely recognized as important factors affecting population dynamics in fragmented landscapes. Little is known, however, about the influence of within-patch habitat quality on population dynamics. In this paper, we investigate the relative importance of patch geometry and within-patch habitat quality in determining population dynamics using a spatially explicit, agent-based model. We simulate two mobile species that differ in their species traits: one resembles a habitat specialist and the other a habitat generalist. Habitat quality varies continuously within habitat patches in space (and time). The results show that spatial variation in within-patch quality, together with patch area, controls population abundance of the habitat specialist. In contrast, the population size of the generalist species depends on patch area and isolation. Temporal variation in within-patch quality is, however, less influential in driving the population resilience of both species. We conclude that specialist species are more sensitive than generalist species to within-patch variation in habitat quality. The patch area-isolation paradigm, developed in metapopulation theory, should incorporate variation in within-patch habitat quality, particularly for habitat specialists.
    Beyond the Plankton Ecology Group (PEG) Model: Mechanisms Driving Plankton Succession
    Sommer, U. ; Adrian, R. ; Domis, L.D. ; Elser, J.J. ; Gaedke, U. ; Ibelings, B. ; Jeppesen, E. ; Lürling, M.F.L.L.W. ; Molinero, J.C. ; Mooij, W.M. ; Donk, E. van; Winder, M. - \ 2012
    Annual Review of Ecology, Evolution, and Systematics 43 (2012)7. - ISSN 1543-592X - p. 429 - 448.
    phytoplankton spring bloom - fresh-water phytoplankton - critical depth hypothesis - clear-water - long-term - lake constance - climate-change - population-dynamics - food quality - deep lake
    UV/H2O2 treatment can be part of the process converting surface water to drinking water, but would pose a potential problem when resulting in genotoxicity. This study investigates the genotoxicity of samples collected from the water treatment plant Andijk, applying UV/H2O2 treatment with an electrical energy dose of 0.54 kWh/m(3) and a H2O2 dose of 6 mg/l. Genotoxicity was tested in vitro using the Ames and Comet assay. All samples showed negative results. Samples were also tested in in vivo genotoxicity tests in Eastern mudminnow fish (Umbra pygmaea) by a sister chromatid exchange (SCE) and a Comet assay. No significant increases in SCEs were observed, but gill cells isolated from fish exposed to water obtained immediately after UV/H2O2 treatment and to Lake IJsselmeer water showed significantly increased DNA damage in the Comet assay. All other samples tested negative in this Comet assay. This indicates that DNA damaging compounds may result from the UV/H2O2 treatment, but also that these can be efficiently eliminated upon granular activated carbon (GAC) treatment of the water. It is concluded that when combined with this subsequent GAC treatment, UV/H2O2 treatment for the production of drinking water from surface water is not of concern with respect to genotoxicity.
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