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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    How much Biodiversity is in Natura 2000? : the “Umbrella Effect” of the European Natura 2000 protected area network : technical report
    Sluis, T. van der; Foppen, R. ; Gillings, Simon ; Groen, T.A. ; Henkens, R.J.H.G. ; Hennekens, S.M. ; Huskens, K. ; Noble, David ; Ottburg, F.G.W.A. ; Santini, L. ; Sierdsema, H. ; Kleunen, A. van; Schaminee, J.H.J. ; Swaay, C. van; Toxopeus, Bert ; Wallis de Vries, M.F. ; Jones-Walters, L.M. - \ 2016
    Wageningen : Alterra, Wageningen-UR (Alterra-rapport 2738) - 147
    biodiversity - habitats directive - birds directive - natura 2000 - statistical analysis - geographical information systems - biodiversiteit - habitatrichtlijn - vogelrichtlijn - natura 2000 - statistische analyse - geografische informatiesystemen
    In order to assess the significance of the presumed “umbrella effect” of Natura 2000 areas the European Commission initiated a study, in 2013, to address the following questions: 1) Which are, amongst the species regularly occurring within the European territory of the EU-28 Member States, those that significantly benefit from the site conservation under the EU Birds and Habitats Directive? 2) What is the percentage of all species occurring in the wild in the EU that benefit significantly from Natura 2000? 3) How significant is the contribution of Natura 2000 in relation to the objective of halting and reversing biodiversity loss? The approach used existing data, and covered the terrestrial mammals, birds, reptiles, amphibian, butterfly and plant species. The analysis is mostly based on statistical distribution models and GIS processing of species distribution data in relation to their presence within protected areas of the Natura 2000 network. The main findings for all species groups were: Animal species for which Natura 2000 areas were not specifically designated occur more frequently inside Natura 2000 than outside (in particular breeding birds and butterflies). These species do, therefore, gain benefit from the protected areas network. The species for which Natura 2000 areas were designated generally occur more frequently within the Natura 2000 site boundaries than the nonannex species; this is in particular the case for birds and butterflies, for amphibians and reptiles the difference is negligible. More specific conclusions and findings, as well as discussion of these results and implications for further studies are included in the report.
    Tracing glacial refugia of Triturus newts based on mitochondrial DNA phylogeography and species distribution modeling
    Wielstra, B.M. ; Crnobrnja-Isailovic, J. ; Litvinchuk, S.N. ; Reijnen, B.T. ; Skidmore, A.K. ; Sotiropoulos, K. ; Toxopeus, A.G. ; Tzankov, N. ; Vukov, T. ; Arntzen, J.W. - \ 2013
    Frontiers in Zoology 10 (2013)1. - ISSN 1742-9994 - 14 p.
    crested newt - niche conservatism - climate-change - hybrid zone - gene flow - time - space - introgression - quaternary - evolution
    Introduction The major climatic oscillations during the Quaternary Ice Age heavily influenced the distribution of species and left their mark on intraspecific genetic diversity. Past range shifts can be reconstructed with the aid of species distribution modeling and phylogeographical analyses. We test the responses of the different members of the genus Triturus (i.e. the marbled and crested newts) as the climate shifted from the previous glacial period (the Last Glacial Maximum, ~21 Ka) to the current interglacial. Results We present the results of a dense mitochondrial DNA phylogeography (visualizing genetic diversity within and divergence among populations) and species distribution modeling (using two different climate simulations) for the nine Triturus species on composite maps. Conclusions The combined use of species distribution modeling and mitochondrial phylogeography provides insight in the glacial contraction and postglacial expansion of Triturus. The combined use of the two independent techniques yields a more complete understanding of the historical biogeography of Triturus than both approaches would on their own. Triturus newts generally conform to the ‘southern richness and northern purity’ paradigm, but we also find more intricate patterns, such as the absence of genetic variation and suitable area at the Last Glacial Maximum (T. dobrogicus), an ‘extra-Mediterranean’ refugium in the Carpathian Basin (T. cristatus), and areas where species displaced one another postglacially (e.g. T. macedonicus and western T. karelinii). We provide a biogeographical scenario for Triturus, showing the positions of glacial refugia, the regions that were postglacially colonized and the areas where species displaced one another as they shifted their ranges
    Measuring the Insecurity Index of species in networks of protected areas using species distribution modeling and fuzzy logic: The case of raptors in Andalusia
    Diaz-Gomez, D.L. ; Toxopeus, A.G. ; Groen, T.A. ; Munoz, A.R. ; Skidmore, A.K. ; Real, R. - \ 2013
    Ecological Indicators 26 (2013). - ISSN 1470-160X - p. 174 - 182.
    mainland spain - gap analysis
    Networks of protected areas often fail to include favorable areas for all species, even when they cover a considerable percentage of a territory. To assess the effectiveness of protected areas, harsh thresholds are commonly used (e.g. minimum 20% of the cell must be covered by a protected area to define it as protected). Setting a threshold implies a transformation of continuous data into binary data which frequently results in information loss and in outcomes changing sharply depending on the threshold set. To avoid uncertainty and information loss when evaluating the effectiveness of protected areas, we developed the "Insecurity Index" based on species distribution modeling and fuzzy logic. The Insecurity Index (0-1) of a species represents how much of the fuzzy set of favorable areas for the species is not included in the protected areas. The larger the extent of favorable areas of a species that is not covered by protected areas, the higher the Insecurity Index. We applied this approach to Andalusia, in the south of Spain, which sustains 22 out of the 40 raptor species present in Europe, and has about 30% of its territory covered by regional and Natura 2000 protected areas. By measuring and mapping the Insecurity Index of raptors in Andalusia we assessed the extent to which protected areas exclude favorable sites for forest, cliff and steppe nesting raptors, identified species with a high Insecurity Index and mapped high priority areas for implementing conservation actions. The Insecurity Index was significantly higher for steppe nesting raptors (mean Insecurity Index = 0.81) compared to forest (mean Insecurity Index = 0.62) and cliff nesting raptors (mean Insecurity Index = 0.59). We propose areas of high insecurity for steppe nesting raptors, as potential sites for implementing actions aimed at providing nesting habitat for these species. As demonstrated here for raptors in Andalusia, the Insecurity Index can be used to assess and compare the extent to which species' favorable areas are left unprotected by reserves while avoiding uncertainty and information loss due to the use of thresholds.
    Walk or stride? A question for roaming herds of elephants in Marsabit protected area
    Ngene, S.M. ; Skidmore, A.K. ; Gils, H. van; Prins, H.H.T. ; Toxopeus, A.G. ; Douglas-Hamilton, I. - \ 2012
    In: Elephants: Ecology, Behavior and Conservation / Aranovich, M., Dufresne, O., Hauppauge NY, USA : Nova Science Publishers, Inc. (Animal Science, Issues and Professions ) - ISBN 9781621000662 - p. 173 - 192.
    Intensity of elephant occupancy in Marsabit protected area, Kenya: Effects of Biophysical and Anthropogenic Factors
    Ngene, S.M. ; Skidmore, A.K. ; Gils, H. van; Wieren, S.E. van; Prins, H.H.T. ; Douglas-Hamilton, I. ; Toxopeus, A.G. - \ 2012
    In: Elephants: Ecology, Behavior, and Conservation / Aranovich, M., Dufresne, O., Hauppauge NY, USA : Nova Scientific Publishers, Inc. (Animal Science, Issues and Professions ) - ISBN 9781621000662 - p. 153 - 172.
    The significance of using satellite imagery data only in Ecological Niche Modelling of Iberian herps
    Sillero, N. ; Brito, J.C. ; Martin-Alfageme, S. ; Garcia-Melendez, E. ; Toxopeus, A.G. ; Skidmore, A.K. - \ 2012
    Acta Herpetologica 7 (2012)2. - ISSN 1827-9635 - p. 221 - 237.
    tropical forest regeneration - noaa avhrr data - land-cover - species distributions - vegetation dynamics - climate - biodiversity - prediction - conservation - amphibians
    The environmental data used to calculate ecological niche models (ENM) are obtained mainly from ground-based maps (e.g., climatic interpolated surfaces). These data are often not available for less developed areas, or may be at an inappropriate scale, and thus to obtain this information requires fieldwork. An alternative source of eco-geographical data comes from satellite imagery. Three sets of ENM were calculated exclusively with variables obtained (1) from optical and radar images only and (2) from climatic and altitude maps obtained by ground-based methods. These models were compared to evaluate whether satellite imagery can accurately generate ENM. These comparisons must be made in areas with well-known species distribution and with available satellite imagery and ground-based data. Thus, the study area was the south-western part of Salamanca (Spain), using amphibian and reptiles as species models. Models' discrimination capacity was measured with ROC plots. Models' covariation was measured with a Spatial Spearman correlation. Four modelling techniques were used (Bioclim, Mahalanobis distance, GARP and Maxent). The results of this comparison showed that there were no significant differences between models generated using remotely sensed imagery or ground-based data. However, the models built with satellite imagery data exhibited a larger diversity of values, probably related to the higher spatial resolution of the satellite imagery. Satellite imagery can produce accurate ENM, independently of the modelling technique or the dataset used. Therefore, biogeographical analysis of species distribution in remote areas can be accurately developed only with variables from satellite imagery.
    Predicting micro thermal habitat of lizards in a dynamic thermal environment
    Fei, T. ; Skidmore, A.K. ; Venus, V. ; Wang, T. ; Toxopeus, A.G. ; Bian, B.M. ; Liu, Y. - \ 2012
    Ecological Modelling 231 (2012). - ISSN 0304-3800 - p. 126 - 133.
    climate-change - thermoregulatory behavior - vegetation distribution - mechanistic ecology - distribution models - cellular-automata - activity patterns - body-temperature - selection - movement
    Understanding behavioural thermoregulation and its consequences is a central topic in ecology. In this study, a spatial explicit model was developed to simulate the movement and thermal habitat use of lizards in a controlled environment. The model incorporates a lizard's transient body temperatures with a cellular automaton (CA) algorithm and links the physiology knowledge of the animal with the spatial utilization of its microhabitat. The model assumed that a lizard tries to maintain its preferred body temperature in a dynamic thermal environment by continuously selecting positions with different thermal conditions. The sequence of chosen positions formed a chain defining the individual's path, to be later aggregated into a map of thermal habitat use. An experiment was designed to test the model. An ocellated lizard (Timon lepidus) was kept in a terrarium with controlled dynamic thermal environment, and the thermal environment as well as the movement of the lizard were recorded by a variety of sensors. The model was tested to predict the spatial utilization of a lizard's thermal habitat in the terrarium based on three categories: high, moderate and low occupancy. The simulated results were compared with observations from the animal experiment. The predicted overall pattern of the micro-habitat occupancy of the lizard within 4 days matched the observation, at an overall accuracy of 75.7%. The results suggest that thermal habitat use by lizards in a controlled environment may be predicted by the integrated model of the lizard's body temperature and the CA algorithm.
    Corresponding Mitochondrial DNA and Niche Divergence for Crested Newt Candidate Species
    Wielstra, B.M. ; Beukema, W. ; Arntzen, J.W. ; Skidmore, A.K. ; Toxopeus, A.G. ; Raes, N. - \ 2012
    PLoS ONE 7 (2012)9. - ISSN 1932-6203
    absence data - models - phylogeography - delimitation - speciation - ecology - areas
    Genetic divergence of mitochondrial DNA does not necessarily correspond to reproductive isolation. However, if mitochondrial DNA lineages occupy separate segments of environmental space, this supports the notion of their evolutionary independence. We explore niche differentiation among three candidate species of crested newt (characterized by distinct mitochondrial DNA lineages) and interpret the results in the light of differences observed for recognized crested newt species. We quantify niche differences among all crested newt (candidate) species and test hypotheses regarding niche evolution, employing two ordination techniques (PCA-env and ENFA). Niche equivalency is rejected: all (candidate) species are found to occupy significantly different segments of environmental space. Furthermore, niche overlap values for the three candidate species are not significantly higher than those for the recognized species. As the three candidate crested newt species are, not only in terms of mitochondrial DNA genetic divergence, but also ecologically speaking, as diverged as the recognized crested newt species, our findings are in line with the hypothesis that they represent cryptic species. We address potential pitfalls of our methodology.
    Integration of multi-sensor data to assess grassland dynamics in a Yellow River sub-watershed
    Ouyang, W. ; Hao, F. ; Skidmore, A.K. ; Groen, T.A. ; Toxopeus, A.G. ; Wang, T. - \ 2012
    Ecological Indicators 18 (2012)1. - ISSN 1470-160X - p. 163 - 170.
    qinghai-xizang plateau - time-series - land-cover - west-africa - vegetation - modis - variability - patterns - imagery - china
    Grasslands form the dominant land cover in the upper reaches of the Yellow River and provide a reliable indicator by being strongly correlated with regional terrestrial ecological status. Remote sensing can provide information useful for vegetation quality assessments, but no single sensor can meet the needs for the high temporal-spatial resolution required for such assessments on a watershed scale. To observe long-term grassland dynamics in the Longliu Watershed located in the upper reaches of the Yellow River, Moderate Resolution Imaging Spectroradiometer (MODIS) and Landsat images were integrated to obtain Normalized Difference Vegetation Index (NDVI) data. The MODIS images were used to identify patterns of monthly variation. With the temporal dynamics of NDVI provided by the MODIS images, an exponential regression model was obtained that described the relationship between Julian day and NDVI. Four time-series data sets from multi-spectral sensors were constructed to obtain regional grassland NDVI information from 1977 to 2006 in the Longliu Watershed. Using the daily NDVI correlation coefficient, NDVI values for different days were obtained from Landsat series images, standardised to the same day and integrated into TM format by using NDVI coefficients between the four different sensors. Thus, the NDVI data obtained from multi-sensors on different days were integrated into a comparable format. A regression analysis correlating the NDVI data from two sensors with fresh grass biomass showed that the integration procedure was reliable.
    Vegetation NDVI Linked to Temperature and Precipitation in the Upper Catchments of Yellow River
    Hao, F. ; Zhang, X. ; Ouyang, W. ; Skidmore, A.K. ; Toxopeus, A.G. - \ 2012
    Environmental Modeling and Assessment 17 (2012)4. - ISSN 1420-2026 - p. 389 - 398.
    land-cover changes - qinghai-xizang plateau - net primary production - central new-mexico - tibetan plateau - modis - china - soil - climate - basin
    Vegetation in the upper catchment of Yellow River is critical for the ecological stability of the whole watershed. The dominant vegetation cover types in this region are grassland and forest, which can strongly influence the eco-environmental status of the whole watershed. The normalized difference vegetation index (NDVI) for grassland and forest has been calculated and its daily correlation models were deduced by Moderate Resolution Imaging Spectroradiometer products on 12 dates in 2000, 2003, and 2006. The responses of the NDVI values with the inter-annual grassland and forest to three climatic indices (i.e., yearly precipitation and highest and lowest temperature) were analyzed showing that, except for the lowest temperature, the yearly precipitation and highest temperature had close correlations with the NDVI values of the two vegetation communities. The value of correlation coefficients ranged from 0.815 to 0.951 (p <0.01). Furthermore, the interactions of NDVI values of vegetation with the climatic indicators at monthly interval were analyzed. The NDVI of vegetation and three climatic indices had strong positive correlations (larger than 0.733, p <0.01). The monthly correlations also provided the threshold values for the three climatic indictors, to be used for simulating vegetation growth grassland under different climate features, which is essential for the assessment of the vegetation growth and for regional environmental management.
    A body temperature model for lizards as estimated from the thermal environment
    Fei, T. ; Skidmore, A.K. ; Venus, V. ; Wang, T. ; Schlerf, M. ; Toxopeus, A.G. ; Overjijk, S. van; Bian, B.M. ; Liu, Y. - \ 2012
    Journal of Thermal Biology 37 (2012)1. - ISSN 0306-4565 - p. 56 - 64.
    galapagos marine iguana - blue-tongued lizard - thermoregulatory behavior - physiological control - mechanistic ecology - activity patterns - heat-exchange - reptiles - selection - prediction
    A physically based model was built to predict the transient body temperature of lizards in a thermally heterogeneous environment. Six heat transfer terms were taken into account in this model: solar radiation, convective heat flow, longwave radiation, conductive heat flow, metabolic heat gain and respiratory energy loss. In order to enhance the model predictive power, a Monte Carlo simulation was employed to calibrate the bio-physical parameters of the target animal. Animal experiments were conducted to evaluate the calibrated body temperature model in a terrarium under a controlled thermal environment. To avoid disturbances of the animal, thermal infrared imagers were used to measure the land surface temperature and the body temperature. The results showed that the prediction accuracy of lizard’s transient temperature was substantially increased by the use of Monte Carlo techniques (RMSE=0.59 °C) compared to standard model parameterization (RMSE=1.35 °C). Because the model calibration technique presented here is based on physical principles, it should be also useful in more complex, field situations.
    Distribution of Barnacle Geese Branta leucopsis in relation to food resources, distance to roosts, and the location of refuges
    Si, Y. ; Skidmore, A.K. ; Wang, T. ; Boer, W.F. de; Toxopeus, A.G. ; Schlerf, M. ; Oudshoorn, M. ; Zwerver, S. ; Jeugd, H. van der; Exo, K.M. ; Prins, H.H.T. - \ 2011
    Ardea 99 (2011)2. - ISSN 0373-2266 - p. 217 - 226.
    bellied brent geese - white-fronted geese - foraging behavior - selection - bernicla - quality - britain - herbivores - digestion - quantity
    We used GPS satellite tracking data and field measurements of vegetation to investigate the effect of food resources, distance to roosts, and the location of refuges on the distribution of Barnacle Geese Branta leucopsis in the northern part of The Netherlands. To deal with spatial dependence among the data, a spatial lag model was used. A significant quadratic effect was found between sward height and goose distribution, indicating that geese prefer patches with intermediate sward heights. The manipulation of sward height can therefore be used to attract geese to refuges and thus reduce goose grazing in agricultural land. No relationship was found between grass nitrogen content and grazing intensity, indicating that geese do not distinguish between areas based on nitrogen content. A higher grazing intensity was observed in areas located within 2 km from roosts. The eight tracked geese spent 80% of their foraging time in refuges, demonstrating the importance of the refuge system
    Finessing atlas data for species distribution models
    Niamir, A. ; Skidmore, A.K. ; Toxopeus, A.G. ; Munoz, A.R. ; Real, R. - \ 2011
    Diversity and Distributions 17 (2011)6. - ISSN 1366-9516 - p. 1173 - 1185.
    eagle hieraaetus-fasciatus - large-scale distribution - bonellis eagle - expert-system - spatial autocorrelation - breeding performance - statistical-models - aquila-fasciata - sample-size - conservation
    Aim The spatial resolution of species atlases and therefore resulting model predictions are often too coarse for local applications. Collecting distribution data at a finer resolution for large numbers of species requires a comprehensive sampling effort, making it impractical and expensive. This study outlines the incorporation of existing knowledge into a conventional approach to predict the distribution of Bonelli's eagle (Aquila fasciata) at a resolution 100 times finer than available atlas data. Location Malaga province, Andalusia, southern Spain. Methods A Bayesian expert system was proposed to utilize the knowledge from distribution models to yield the probability of a species being recorded at a finer resolution (1×1km) than the original atlas data (10×10km). The recorded probability was then used as a weight vector to generate a sampling scheme from the species atlas to enhance the accuracy of the modelling procedure. The maximum entropy for species distribution modelling (MaxEnt) was used as the species distribution model. A comparison was made between the results of the MaxEnt using the enhanced and, the random sampling scheme, based on four groups of environmental variables: topographic, climatic, biological and anthropogenic. Results The models with the sampling scheme enhanced by an expert system had a higher discriminative capacity than the baseline models. The downscaled (i.e. finer scale) species distribution maps using a hybrid MaxEnt/expert system approach were more specific to the nest locations and were more contrasted than those of the baseline model. Main conclusions The proposed method is a feasible substitute for comprehensive field work. The approach developed in this study is applicable for predicting the distribution of Bonelli's eagle at a local scale from a national-level occurrence data set; however, the usefulness of this approach may be limited to well-known species
    Identifying habitat patches and potential ecological corridors for remnant Asiatic black bear (Ursus thibetanus japonicus) populations in Japan
    Doko, T. ; Fukui, H. ; Kooiman, A. ; Toxopeus, A.G. ; Ichinose, T. ; Chen, W. ; Skidmore, A.K. - \ 2011
    Ecological Modelling 222 (2011)3. - ISSN 0304-3800 - p. 748 - 761.
    geographic distributions - models
    The Japanese National Biodiversity Strategy 2010 calls for the creation of ecological networks as a biodiversity conservation policy. However, there is an obvious lack of information on the spatial distribution of many species and a lack of scientific methods for examining habitat requirements to establish the need for constructing these networks for target species. This study presents a quantitative method for assessing the need for ecological networks through modeling the potential geographic distributions of species based on a case study of local populations of Asiatic black bear (Ursus thibetanus japonicus) in Fuji and Tanzawa, Japan. A total of 1541 point records of occurrences of Asiatic black bears and 11 potential predictors were analyzed in a GIS environment. After a predictive distributional map was obtained using the Maximum Entropy (MaxEnt) algorithm, a gap analysis was carried out and population size was estimated. Approximately 24% of the bear's predicted habitat area fell within a wildlife protection area, 2% within a nature reserve, and 37% within natural parks. Conservation forest comprised 54% of the total area of predicted habitat; of this, national forest comprised 2%, and private and communal forest comprised 37%. The total estimated Asiatic black bear population in this region was 242, with 179 individuals in the Fuji local population, 26 in the Tanzawa local population, and 37 in the corridor patch between the two local populations. Our study also found a potential corridor connecting the Fuji and Tanzawa local populations, as well as potential habitat corridors in the Fuji region containing subpopulations on Mt. Fuji (119 individuals) and Mt. Kenashi (53 individuals). An additional subpopulation on Mt. Ashitaka (7 individuals) is isolated and not fully protected by a zoning plan. Mt. Furo's subpopulation is considered to be almost extinct, although black bears were observed here until 2002 based on the report by Mochizuki et al. (2005). The total black bear population of the Fuji-Tanzawa region is considered to be "endangered" ; thus, an adequate population size might be difficult to maintain even if this region were to be internally connected by means of an ecological network.
    Soil erosion and sediment yield and their relationships with vegetation cover in upper stream of the Yellow River
    Ouyang, W. ; Hao, F. ; Skidmore, A.K. ; Toxopeus, A.G. - \ 2010
    Science of the Total Environment 409 (2010)2. - ISSN 0048-9697 - p. 396 - 403.
    rainfall simulation - slope gradient - model - conservation - plateau - systems - events - runoff - impact - spain
    Soil erosion is a significant concern when considering regional environmental protection, especially in the Yellow River Basin in China. This study evaluated the temporal-spatial interaction of land cover status with soil erosion characteristics in the Longliu Catchment of China, using the Soil and Water Assessment Tool (SWAT) model. SWAT is a physical hydrological model which uses the RUSLE equation as a sediment algorithm. Considering the spatial and temporal scale of the relationship between soil erosion and sediment yield, simulations were undertaken at monthly and annual temporal scales and basin and sub-basin spatial scales. The corresponding temporal and spatial Normalized Difference Vegetation Index (NDVI) information was summarized from MODIS data, which can integrate regional land cover and climatic features. The SWAT simulation revealed that the annual soil erosion and sediment yield showed similar spatial distribution patterns, but the monthly variation fluctuated significantly. The monthly basin soil erosion varied from almost no erosion load to 3.92 t/ha and the maximum monthly sediment yield was 47,540 tones. The inter-annual simulation focused on the spatial difference and relationship with the corresponding vegetation NDVI value for every sub-basin. It is concluded that, for this continental monsoon climate basin, the higher NDVI vegetation zones prevented sediment transport, but at the same time they also contributed considerable soil erosion. The monthly basin soil erosion and sediment yield both correlated with NDVI, and the determination coefficients of their exponential correlation model were 0.446 and 0.426, respectively. The relationships between soil erosion and sediment yield with vegetation NDVI indicated that the vegetation status has a significant impact on sediment formation and transport. The findings can be used to develop soil erosion conservation programs for the study area.
    Long-term vegetation landscape pattern with non-point source nutrient pollution in upper stream of Yellow River basin
    Ouyang, W. ; Skidmore, A.K. ; Toxopeus, A.G. ; Hao, F. - \ 2010
    Journal of Hydrology 389 (2010)3-4. - ISSN 0022-1694 - p. 373 - 380.
    land-use change - water-quality - model - phosphorus - nitrogen - management - erosion - system - region - areas
    Grassland, forest, and farmland are the dominant land covers in upper catchments of the Yellow River and their landscape status has direct connection with dynamics of non-point source (NPS) pollution. Understanding the correlations between landscape variables and different formats of NPS nutrients pollutants is a priority in order to assess pollutants loading and predicting the impact on surface water quality. The regional vegetative cover in 1977, 1996, 2000 and 2006 was determined by classifying historical multi-temporal Landsat imagery and clipping data from the National Landcover Database. The landscape pattern is expressed means of metrics such as patch density, edge density, fractal distribution index, all of which were calculated by FRAGSTATS. The soil and water assessment tool (SWAT) was used to analyze and visualize the fate of NPS nitrogen and phosphorus loads in diverse formats from different land cover types in different years. Statistical analysis indicated that the grassland landscapes played a major role in NPS nutrient pollution dynamics and grassland patch edges benefited pollution control. However, the presence of more forest and farmland lead to more NPS nitrogen emissions. It was found that grassland areas reduced nitrogen loss and had a multi-function role in the nutrient pollution process. Farmland was the direct source of organic nutrients, but did not have great impacts on sediment P and soluble N loadings. Forest areas contributed NPS nutrients pollution loading. The statistical models derived in this study can be used to estimate watershed NPS nutrient pollution losses. These equations can help identify pollution sources and suggest appropriate and effective solutions for planing basin management practices
    Characterizing the spatial distribution of giant pandas (Ailuropoda melanoleuca) in fragmented forest landscapes
    Wang, T. ; Ye, X.P. ; Skidmore, A.K. ; Toxopeus, A.G. - \ 2010
    Journal of Biogeography 37 (2010)5. - ISSN 0305-0270 - p. 865 - 878.
    presence-only data - land-cover classification - habitat-suitability - vegetation indexes - presence-absence - time-series - models - prediction - resolution - accuracy
    Aim. To examine the effects of forest fragmentation on the distribution of the entire wild giant panda (Ailuropoda melanoleuca) population, and to propose a modelling approach for monitoring the spatial distribution and habitat of pandas at the landscape scale using Moderate Resolution Imaging Spectro-radiometer (MODIS) enhanced vegetation index (EVI) time-series data. Location. Five mountain ranges in south-western China (Qinling, Minshan, Qionglai, Xiangling and Liangshan). Methods. Giant panda pseudo-absence data were generated from data on panda occurrences obtained from the third national giant panda survey. To quantify the fragmentation of forests, 26 fragmentation metrics were derived from 16-day composite MODIS 250-m EVI multi-temporal data and eight of these metrics were selected following factor analysis. The differences between panda presence and panda absence were examined by applying significance testing. A forward stepwise logistic regression was then applied to explore the relationship between panda distribution and forest fragmentation. Results. Forest patch size, edge density and patch aggregation were found to have significant roles in determining the distribution of pandas. Patches of dense forest occupied by giant pandas were significantly larger, closer together and more contiguous than patches where giant pandas were not recorded. Forest fragmentation is least in the Qinling Mountains, while the Xiangling and Liangshan regions have most fragmentation. Using the selected landscape metrics, the logistic regression model predicted the distribution of giant pandas with an overall accuracy of 72.5% (kappa = 0.45). However, when a knowledge-based control for elevation and slope was applied to the regression, the overall accuracy of the model improved to 77.6% (kappa = 0.55). Main conclusions. Giant pandas appear sensitive to patch size and isolation effects associated with fragmentation of dense forest, implying that the design of effective conservation areas for wild giant pandas must include large and dense forest patches that are adjacent to other similar patches. The approach developed here is applicable for analysing the spatial distribution of the giant panda from multi-temporal MODIS 250-m EVI data and landscape metrics at the landscape scale
    The ranging patterns of elephants in Marsabit protected area, Kenya: the use of satellite-linked GPS collars
    Ngene, S.M. ; Gils, H. ; Wieren, S.E. van; Rasmussen, H. ; Skidmore, A.K. ; Prins, H.H.T. ; Toxopeus, A.G. ; Omondi, P. ; Douglas-Hamilton, I. - \ 2010
    African Journal of Ecology 48 (2010)2. - ISSN 0141-6707 - p. 386 - 400.
    national-park - loxodonta-africana - home-range - northwestern namibia - northern kenya - movements - forest - woodland - tracking - tanzania
    We investigated the ranging patterns of elephants in the Marsabit protected area, north eastern Kenya, to ascertain the range of bachelor and female family herds in different seasons, and to identify corridor and noncorridor areas. Data were acquired for five bachelor and four female family herds equipped with satellite-linked geographical positioning system collars, and monitored from December 2005 to December 2007. Distinct dry (about 260 km2) and wet seasons (about 910 km2) ranges were observed, with connecting corridors (north-eastern corridor: about 90 km long, about 2-7 km wide; southern corridors: about 10-20 km long, about 2-3 km wide). The dry season range corresponded with Marsabit evergreen forest, while the wet season range matched with dry deciduous lowland shrubs. The ranging elephants moved at speed of about 0.2-20 kmh-1. Bachelor herds moved faster than female family herds. Elephants moved fast during the intermediate and wet seasons than during the dry season. The speed of ranging elephants was over 1 kmh-1 in the corridor areas and about 0.2 to less than 1 kmh-1 in the non-corridor areas. Expansion of settlements towards corridor areas needs to be controlled to avoid future blocking of connectivity between wet and dry season elephant ranges
    Accumulated effects on landscape pattern by hydroelectric cascade exploitation in the Yellow River basin from 1977 to 2006
    Ouyang, W. ; Skidmore, A.K. ; Hao, F.H. ; Toxopeus, A.G. ; Abkar, A. - \ 2009
    Landscape and Urban Planning 93 (2009)3-4. - ISSN 0169-2046 - p. 163 - 171.
    environmental-impact - metrics - hydropower - region - forest - indicator - projects - indexes - quality - models
    The accumulated impacts of hydroelectric cascade exploitation (HCE) on the landscape are greater than the simple sum of the impacts from a single dam. The spatial–temporal landscape characteristics resulting from the accumulated impacts of HCE from 1977 to 2006 in Longliu Watershed, a part of the Yellow River basin, were investigated. In this innovative approach, the FRAGSTATS model was employed to calculate landscape indices, which characterized landscape in term of its fragmentation, shape and diversity. Three fragmentation indicators and four shape indicators were analyzed at patch scale for each land use type in period of 1977–2006. The diversity simulators were calculated also at landscape scale. Furthermore, two hydroelectric cascade exploitation indicators, summed dam heights and hydroelectric generator capacities, were used to explore the correlated impact with landscape pattern. The analysis revealed that landscape fragmentation variations are strongly dependent on the magnitude of exploitation. The correlation coefficients ranged from 0.65 to 0.95. Except for PAFRAC value of water area, all other shape metric variations were closely linked to the level of HCE and the correlation coefficients ranged from 0.5267 to 0.9514. This study also demonstrated that landscape diversity changes were exponentially related to hydro-exploitation parameters, with correlation coefficients arranging from 0.7487 to 0.9856. The correlation analysis also demonstrated that HCE a critical factor determining regional landscape variation. It is concluded that these correlation analysis assist in predicting landscape variation about future HCE. The findings will also be helpful for regional environmental management and for the understanding expected landscape transformations.
    Spatio-temporal dynamics of global H5N1 outbreaks match bird migration patterns
    Si, Y. ; Skidmore, A.K. ; Wang, T. ; Boer, W.F. de; Debba, P. ; Toxopeus, A.G. ; Li, L. ; Prins, H.H.T. - \ 2009
    Geospatial Health 4 (2009)1. - ISSN 1827-1987 - p. 65 - 78.
    pathogenic avian influenza - virus h5n1 - genetic-characterization - southern china - a viruses - evolution - spread - thailand - africa - ducks
    The global spread of highly pathogenic avian influenza H5N1 in poultry, wild birds and humans, poses a significant pandemic threat and a serious public health risk. An efficient surveillance and disease control system relies on the understanding of the dispersion patterns and spreading mechanisms of the virus. A space-time cluster analysis of H5N1 outbreaks was used to identify spatio-temporal patterns at a global scale and over an extended period of time. Potential mechanisms explaining the spread of the H5N1 virus, and the role of wild birds, were analyzed. Between December 2003 and December 2006, three global epidemic phases of H5N1 influenza were identified. These H5N1 outbreaks showed a clear seasonal pattern, with a high density of outbreaks in winter and early spring (i.e., October to March). In phase I and II only the East Asia Australian flyway was affected. During phase III, the H5N1 viruses started to appear in four other flyways: the Central Asian flyway, the Black Sea Mediterranean flyway, the East Atlantic flyway and the East Africa West Asian flyway. Six disease cluster patterns along these flyways were found to be associated with the seasonal migration of wild birds. The spread of the H5N1 virus, as demonstrated by the space-time clusters, was associated with the patterns of migration of wild birds. Wild birds may therefore play an important role in the spread of H5N1 over long distances. Disease clusters were also detected at sites where wild birds are known to overwinter and at times when migratory birds were present. This leads to the suggestion that wild birds may also be involved in spreading the H5N1 virus over short distances
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