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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    Detecting clear-cuts and decreases in forest vitality using MODIS NDVI time series
    Lambert, J. ; Denux, J.P. ; Verbesselt, J. ; Balent, G. ; Cheret, V. - \ 2015
    Remote Sensing 7 (2015)4. - ISSN 2072-4292 - p. 3588 - 3612.
    coarse spatial-resolution - vegetation indexes - climate-change - landsat imagery - boreal forest - cover - trends - avhrr - disturbance - drought
    This paper examines the potential of MODIS-NDVI time series for detecting clear-cuts in a coniferous forest stand in the south of France. The proposed approach forms part of a survey monitoring the status of forest health and evaluating the forest decline phenomena observed over the last few decades. One of the prerequisites for this survey was that a rapid and easily reproducible method had to be developed that differentiates between forest clear-cuts and changes in forest health induced by environmental factors such as summer droughts. The proposed approach is based on analysis of the breakpoints detected within NDVI time series, using the “Break for Additive Seasonal and Trend” (BFAST) algorithm. To overcome difficulties detecting small areas on the study site, we chose a probabilistic approach based on the use of a conditional inference tree. For model calibration, clear-cut reference data were produced at MODIS resolution (250 m). According to the magnitude of the detected breakpoints, probability classes for the presence of clear-cuts were defined, from greater than 90% to less than 3% probability of a clear-cut. One of the advantages of the probabilistic model is that it allows end users to choose an acceptable level of uncertainty depending on the application. In addition, the use of BFAST allows events to be dated, thus making it possible to perform a retrospective analysis of decreases in forest vitality in the study area.
    Diversification and Labor Market Effects of the Mexican Coffee Crisis
    Rodriguez Padron, B. ; Burger, C.P.J. - \ 2015
    World Development 68 (2015). - ISSN 0305-750X - p. 19 - 29.
    determinants - cover
    This paper analyses how coffee-producing households responded to the low coffee prices prevailing around 2003. We provide theory on differential responses in regions dedicated to coffee growing, compared to more diversified or better accessible regions. We show how labor market effects can explain why in the former regions value-adding activities (processing, certification) are undertaken while in the latter regions off-farm activities are adopted. Farm size favors value-adding activities as well as on-farm diversification. These findings call for policy responses to low prices that distinguish between specialized regions and diversified or well-connected regions.
    Rapid assessment of historic, current and future habitat quality for biodiversity around UK Natura 2000 sites
    Vogiatzakis, I.N. ; Stirpe, M.T. ; Rickebusch, S. ; Metzger, M.J. ; Xu, G. ; Rounsevell, M.D.A. ; Bommarco, R. ; Potts, S.G. - \ 2015
    Environmental Conservation 42 (2015)1. - ISSN 0376-8929 - p. 31 - 40.
    use change scenarios - land-use - aerial-photography - conservation - fragmentation - landscapes - dynamics - cover - area - grasslands
    Changes in landscape composition and structure may impact the conservation and management of protected areas. Species that depend on specific habitats are at risk of extinction when these habitats are degraded or lost. Designing robust methods to evaluate landscape composition will assist decision- and policy-making in emerging landscapes. This paper describes a rapid assessment methodology aimed at evaluating land-cover quality for birds, plants, butterflies and bees around seven UK Natura 2000 sites. An expert panel assigned quality values to standard Coordination of Information on the Environment (CORINE) land-cover classes for each taxonomic group. Quality was assessed based on historical (1950, 1990), current (2000) and future (2030) land-cover data, the last projected using three alternative scenarios: a growth-applied strategy (GRAS), a business-as-might-be-usual (BAMBU) scenario, and sustainable European development goal (SEDG) scenario. A quantitative quality index weighted the area of each land-cover parcel with a taxa-specific quality measure. Land parcels with high quality for all taxonomic groups were evaluated for temporal changes in area, size and adjacency. For all sites and taxonomic groups, the rate of deterioration of land-cover quality was greater between 1950 and 1990 than current rates or as modelled using the alternative future scenarios (2000–2030). Model predictions indicated land-cover quality stabilized over time under the GRAS scenario, and was close to stable for the BAMBU scenario. The SEDG scenario suggested an ongoing loss of quality, though this was lower than the historical rate of c. 1% loss per decade. None of the future scenarios showed accelerated fragmentation, but rather increases in the area, adjacency and diversity of high quality land parcels in the landscape.
    Seasonal differences assist in mapping granite outcrops using Landsat TM imagery across the Southwest Australian Floristic Region
    Alibegovic, G. ; Schut, A.G.T. ; Wardell-Johnson, G.W. ; Robinson, T.P. - \ 2015
    Journal of Spatial Science 60 (2015)1. - ISSN 1449-8596 - p. 37 - 49.
    machine learning algorithms - spaceborne thermal emission - reflection radiometer aster - climate-change - western-australia - band ratios - biodiversity - vegetation - refugia - cover
    Knowledge of the location and extent of granite outcrops (GOs) in the Southwest Australian Floristic Region is important to understand their role as refugia. We present a methodology to map GOs using biannual Landsat TM imagery. An adaptive vegetation cover mask capitalising on seasonal differences, combined with a supervised classification, allowed differentiation of granite from other land covers on five GOs across the rainfall gradient. This methodology provided high classification accuracy (Overall Kappa ranged from 0.83 to 0.91) irrespective of location. Therefore, there is potential to use these methods to compile a more complete GO inventory over the region.
    Mapping and monitoring High Nature Value farmlands: Challenges in European landscapes
    Lomba, A. ; Guerra, C. ; Alonso, J. ; Honrado, J.P. ; Jongman, R.H.G. ; McCracken, D. - \ 2014
    Journal of Environmental Management 143 (2014). - ISSN 0301-4797 - p. 140 - 150.
    common agricultural policy - plant-species richness - land-use - biodiversity conservation - farm-management - intensity - intensification - conflicts - systems - cover
    The importance of low intensity farming for the conservation of biodiversity throughout Europe was acknowledged early in the 1990s when the concept of ‘High Nature Value farmlands’ (HNVf) was devised. HNVf has subsequently been given high priority within the EU Rural Development Programme. This puts a requirement on each EU Member State not only to identify the extent and condition of HNVf within their borders but also to track trends in HNVf over time. However, the diversity of rural landscapes across the EU, the scarcity of (adequate) datasets on biodiversity, land cover and land use, and the lack of a common methodology for HNVf mapping currently represent obstacles to the implementation of the HNVf concept across Europe. This manuscript provides an overview of the characteristics of HNVf across Europe together with a description of the development of the HNVf concept. Current methodological approaches for the identification and mapping of HNVf across EU-27 and Switzerland are then reviewed, the main limitations of these approaches highlighted and recommendations made as to how the identification, mapping and reporting of HNVf state and trends across Europe can potentially be improved and harmonised. In particular, we propose a new framework that is built on the need for strategic HNVf monitoring based on a hierarchical, bottom-up structure of assessment units, coincident with the EU levels of political decision and devised indicators, and which is linked strongly to a collaborative European network that can provide the integration and exchange of data from different sources and scales under common standards. Such an approach is essential if the scale of the issues facing HNVf landscapes are to be identified and monitored properly at the European level. This would then allow relevant agrienvironmental measures to be developed, implemented and evaluated at the scale(s) required to maintain the habitats and species of high nature conservation value that are intimately associated with those landscapes.
    Integrated analysis of land use changes and their impacts on agrarian livelihoods in the western highlands of Kenya
    Mutoko, M.C. ; Hein, L.G. ; Bartholomeus, H. - \ 2014
    Agricultural Systems 128 (2014). - ISSN 0308-521X - p. 1 - 12.
    soil fertility management - proximate causes - cover - deforestation - africa - sustainability - expansion - dynamics - district - growth
    Land degradation is affecting rural livelihoods across sub-Saharan Africa. Promoting sustainable land management requires a thorough understanding of land use change drivers, processes and effects. However, in most African countries reliable data for such investigations are missing. We therefore test an integrated approach to analyse land use dynamics, combining remote sensing images, an in-depth quantitative survey, stakeholder interviews and local statistics. We analyse land dynamics and agricultural production over a 25-year period in Vihiga District, Western Kenya. Specifically, we examine how land use has changed in this period, the main drivers for land use change, and the main effects of these changes on agricultural production. Vihiga District is one of the most densely populated rural areas in Africa. We find that the district has undergone rapid land use change in the past 25 years. In particular, there has been a major conversion of forest and bare land to agricultural land use. Often, it is stated that increasing population pressure triggers agricultural intensification; however, we find little evidence of such a process in Vihiga District. Productivity of tea and, to a lesser extent, vegetables increased but the yields of maize and beans, the most common crops, fluctuated around a ton per hectare. Overall, per capita food crop production dropped by 28% during the past two decades. Our study shows that high and increasing population pressures do not necessarily lead to agricultural intensification, and that there is a need to consider more explicitly off-farm income in development and land management policies and projects.
    Modelling the future of Boswellia papyrifera population and its frankincense production
    Lemenih, M. ; Arts, B.J.M. ; Wiersum, K.F. ; Bongers, F. - \ 2014
    Journal of Arid Environments 105 (2014). - ISSN 0140-1963 - p. 33 - 40.
    economic-systems - metema district - dry forest - tree size - land-use - ethiopia - stella - cover
    Sustainable production of the aromatic forest product frankincense is at stake due to rapid decline in its resource base. This affects livelihoods of thousands of citizens and several global industries. A system dynamic model approach is used to predict the future population of Boswellia papyrifera trees and its frankincense yield for three decades (2010e2040) in Metema and Abergelle districts in northern Ethiopia. Data from studies on the ecology, distribution, rate of deforestation and participatory future scenario development were put together and analysed using a model platform developed with STELLA. Four alternative scenarios namely Business As Usual (BAU); Low Intervention Scenario (LS), High Intervention Scenario (HS) and Stabilization Scenario (SS) were used. The model predicts 3%, 8% and 37% of the current stem population to exist in 2040 under BAU, LS, HS scenarios, respectively in Metema. Similarly, 11%, 13% and 46% stem density is predicted under BAU, LS and HS, respectively for Abergelle. Test of model sensitivity shows adult mortality is the most serious problem facing the resource. Immediate management intervention should focus on reducing adult tree mortality followed by reducing deforestation. Medium and long term interventions need to focus on how to improve recruitment and afforestation/reforestation of the species.
    Validating gap-filling of Landsat ETM+ satellite images in the Golestan Province, Iran
    Mohammdy, M. ; Moradi, H.R. ; Zeinivand, H. ; Temme, A.J.A.M. ; Pourghasemi, H.R. ; Alizadeh, H. - \ 2014
    Arabian Journal of Geosciences 7 (2014)9. - ISSN 1866-7511 - p. 3633 - 3638.
    slc-off images - modis - cover
    The Landsat series of satellites provides a valuable data source for land surface mapping and monitoring. Unfortunately, the scan line corrector (SLC) of the Landsat7 Enhanced Thematic Mapper plus (ETM+) sensor failed on May 13, 2003. This problem resulted in about 22 % of the pixels per scene not being scanned and has seriously limited the scientific applications of ETM+ data. A number of methods have been developed to fill the gaps in the incorrect images. Most of these methods have problems in heterogeneous landscapes. We applied and validated a simple and effective gap-fill algorithm developed by the US Geological Survey to a study area in the Golestan Province in the north of Iran. This algorithm operates under the assumption that the same-class neighboring pixels around the unscanned pixels have similar spectral characteristics, and that these neighboring and unscanned pixels share patterns of spectral differences between dates. For validation, unsupervised land use classification was performed on both gap-filled SLC-off data and the original “sound” data set. Classification results and accuracies were very comparable
    Impact of African elephants on baobab (Adansonia digitata L.) population structure in northern Gonarezhou National Park, Zimbabwe
    Kupika, O.L. ; Kativu, S. ; Gandiwa, E. ; Gumbie, A. - \ 2014
    Tropical Ecology 55 (2014)2. - ISSN 0564-3295 - p. 159 - 166.
    loxodonta-africana - damage - vegetation - woodland - tanzania - savanna - tree - ethiopia - western - cover
    The impact of African elephant (Loxodonta africana) on population structure of baobab trees (Adansonia digitata L.) was assessed in northern Gonarezhou National Park (GNP), southeast Zimbabwe. Baobabs were sampled in March 2008 and September 2012 using 11 randomly laid belt transects of variable length within 1 km of the eastern and western sections of the Runde River and also away (> 1 km) from the water sources. A total of 223 baobabs, 130 near permanent water sources and 93 away from permanent water sources, were sampled. Baobab density did not significantly differ across the two study sites. Furthermore, there were no significant differences in girth at breast height between the two study sites. Results of the present study suggest that elephants target large baobabs (girth = 5 m). In contrast, significant difference in baobab damage was recorded between the two sites. A single dead baobab tree was encountered at a site away from water sources. A larger proportion of elephant damaged baobabs was located closer to permanent water sources. However, baobab recruitment and regeneration was higher in areas close to permanent water sources than in distant areas. Management should come up with strategies to monitor vegetation changes in order to avoid loss of baobabs and other tree species.
    Reductions in soil surface albedo as a function of biochar application rate: implications for global radiative forcing
    Verheijen, F.G.A. ; Jeffery, S.L. ; Velde, M. te; Penizek, V. ; Beland, M. ; Bastos, A.C. ; Keizer, J.J. - \ 2013
    Environmental Research Letters 8 (2013)4. - ISSN 1748-9326
    climate-change - charcoal - systems - cover
    Biochar can be defined as pyrolysed (charred) biomass produced for application to soils with the aim of mitigating global climate change while improving soil functions. Sustainable biochar application to soils has been estimated to reduce global greenhouse gas emissions by 71-130 Pg CO2-C-e over 100 years, indicating an important potential to mitigate climate change. However, these estimates ignored changes in soil surface reflection by the application of dark-coloured biochar. Through a laboratory experiment we show a strong tendency for soil surface albedo to decrease as a power decay function with increasing biochar application rate, depending on soil moisture content, biochar application method and land use. Surface application of biochar resulted in strong reductions in soil surface albedo even at relatively low application rates. As a first assessment of the implications for climate change mitigation of these biochar-albedo relationships, we applied a first order global energy balance model to compare negative radiative forcings (from avoided CO2 emissions) with positive radiative forcings (from reduced soil surface albedos). For a global-scale biochar application equivalent to 120 t ha(-1), we obtained reductions in negative radiative forcings of 5 and 11% for croplands and 11 and 23% for grasslands, when incorporating biochar into the topsoil or applying it to the soil surface, respectively. For a lower global biochar application rate (equivalent to 10 t ha(-1)), these reductions amounted to 13 and 44% for croplands and 28 and 94% for grasslands. Thus, our findings revealed the importance of including changes in soil surface albedo in studies assessing the net climate change mitigation potential of biochar, and we discuss the urgent need for field studies and more detailed spatiotemporal modelling.
    Fly the coop! Vertical structures influence the distribution and behaviour of laying hens in an outdoor range
    Rault, J.L. ; Wouw, A. van de; Hemsworth, P. - \ 2013
    Australian Veterinary Journal 91 (2013)10. - ISSN 0005-0423 - p. 423 - 426.
    egg-production systems - domestic-fowl - cover - runs
    BackgroundThe number of free-range farms has greatly increased in the Australian egg industry, up by 64% over the past 5 years and representing 34% of the retail egg sales last year. Nonetheless, free-range systems offer particular challenges to farmers. The use of the outdoor range is variable among hens; their distribution is usually not uniform across the range and they tend to stay close to features such as walls or fences, resulting in high stocking density in particular areas, with associated welfare and environmental concerns. MethodsUsing video recordings, we investigated the effect of erecting a series of vertical structures in the range on the hens' numbers, distribution and behaviour. ResultsHens were very attracted to the structures, which altered their distribution and behaviour. Up to 160 hens were seen around each structure, giving a density of 6.4 hens/m(2). The hens spent 40% of their time pecking at the structures and standing in these areas and less time walking, preening or ground pecking. ConclusionElucidating which physical features fulfil hens' biological needs could improve their use of outdoor ranges.
    From space and from the ground: determining forest dynamics in settlement projects in the Brazilian Amazon
    Diniz, F.H. ; Kok, K. ; Hott, H.C. ; Hoogstra-Klein, M.A. ; Arts, B.J.M. - \ 2013
    International Forestry Review 15 (2013)3. - ISSN 1465-5489 - p. 442 - 455.
    land-use change - secondary forests - ecuadorian amazon - transition theory - deforestation - cover - reforestation - colonization - biodiversity - expansion
    Deforestation in the Brazilian Amazon has been partially attributed to the establishment of settlement projects. Acknowledging the difficulties in quantifying the rate and patterns of deforestation, the objective of this paper is to determine forest dynamics (deforestation and reforestation) in areas where settlement projects have been established, at multiple levels and using different methods. Using satellite images from 1985 to 2010, a study was conducted in five settlement projects in Pará State, aiming to determine forest dynamics at municipal and settlement levels. At property level, participatory maps were constructed to understand settlers’ perception of forest/non-forest areas. The results show that reforestation is the current process in the municipality and in some settlements. Settlers, however, perceive areas with secondary regrowth as potentially fertile cropland and might deforest again in the future. More research is needed to elucidate whether the observed reforestation will lead to a forest transition or is merely a temporary trend.
    Exploring different forest definitions and their impact on developing REDD+ reference emission levels: A case study for Indonesia
    Romijn, J.E. ; Ainembabazi, J.H. ; Wijaya, A. ; Herold, M. ; Angelsen, A. ; Verchot, L. ; Murdiyarso, D. - \ 2013
    Environmental Science & Policy 33 (2013). - ISSN 1462-9011 - p. 246 - 259.
    greenhouse-gas emissions - tropical forests - carbon emissions - oil palm - deforestation - degradation - land - opportunities - conversion - cover
    Developing countries participating in the mitigation mechanism of reducing emissions from deforestation and forest degradation and the role of conservation, sustainable management of forests and enhancement of forest carbon stocks (REDD+), need to determine a national forest reference emission level (REL) as part of their national monitoring system, which serves as a benchmark to measure the impact of their REDD+ actions. Using data from Indonesia, we show that the choice of a forest definition can have a large impact on estimates of deforestation and forest degradation areas, on assessment of drivers of deforestation and on the development of a REL. The total area of deforestation between 2000 and 2009 was 4.9 million ha when using the FAO definition, 18% higher when using a ‘natural forest definition’ and 27% higher when using the national definition. Using the national and natural forest definitions, large areas (>50%) were classified as shrubland after deforestation. We used regression models to predict future deforestation. Deforestation was much better predicted than degradation (R2 of 0.81 vs. 0.52), with the natural forest definition giving the best prediction. Apart from historical deforestation and initial forest cover, gross domestic product and human population were important predictors of future deforestation in Indonesia. Degradation processes were less well modeled and predictions relied on estimates of historical degradation and forest cover.
    The significance of habitats as indicators of biodiversity and their links to species
    Bunce, R.G.H. ; Bogers, M.M.B. ; Evans, D. ; Halada, L. ; Jongman, R.H.G. ; Mücher, C.A. - \ 2013
    Ecological Indicators 33 (2013). - ISSN 1470-160X - p. 19 - 25.
    agricultural landscapes - ecosystem services - europe - stratification - cover
    The first section of the paper discusses the background to the use of habitats as indicators for biodiversity including a discussion of the range of definitions that have been used. Habitats can now be recorded consistently across Europe at different time intervals in order to estimate stock and change as an indicator of biodiversity that is efficient and relatively easy to record. Habitats are considered to be the third level in a hierarchy with biomes and landscapes as higher categories and vegetation, species and genetic diversity as lower levels. An advantage of using habitats is that many other taxa are associated with them and examples are given from the literature. Examples are also given of the association between habitats and species in European Environmental Zones using expert judgement. Statistical analysis using a range of procedures can also be used to assess the association between species and habitats. Reliable data on the extent, status and changes in European habitats is essential for policy makers across the European Union and would also be important for promoting species conservation.
    An evaluation of the global potential of bioenergy production on degraded lands
    Nijsen, M. ; Smeets, E.M.W. ; Stehfest, E. ; Vuuren, D.P. van - \ 2012
    Global change biology Bioenergy 4 (2012)2. - ISSN 1757-1693 - p. 130 - 147.
    miscanthus x giganteus - energy crop - carbon sequestration - biomass production - soil-erosion - switchgrass - biofuels - cover - management - yields
    In this article the global potential of energy crop production on degraded lands was estimated using detailed, spatially explicit data about the area, type and extent of degradation derived from the Global Assessment of Land Degradation Dataset, and by combining this dataset with various spatially explicit data sets. Next, an estimate was made of the possible yield of perennial energy crops on the degraded areas as a function of the type and degree of degradation. Lightly degraded areas were not included, as these areas might be suitable for conventional food production. The total global potential energy production on degraded lands was assessed to be slightly above 150 and 190EJyr-1, for grassy and woody energy crops, respectively. Most of this potential, however, is on areas currently classified as forest, cropland or pastoral land, leaving a potential of around 25 and 32EJyr-1 on other land cover categories. Most of the potential energy crop production on degraded land is located in developing regions. China has a total potential of 30EJyr-1, of which 4EJyr-1 from areas classified as other land. Also USA, Brazil, West Africa, East Africa, Russia and India have substantial potentials of 1218EJyr-1, with up to 30% of the potential from areas classified as other land.
    Application of satellite remote sensing for mapping wind erosion risk and dusk emission-deposition in Inner Mongolia grassland, China
    Reiche, M. ; Funk, R. ; Zhang, Z. ; Hoffmann, C. ; Reiche, J. ; Wehrhan, M. ; Li, Y. ; Sommer, M. - \ 2012
    Grassland Science 58 (2012)1. - ISSN 1744-6961 - p. 8 - 19.
    vegetation indexes - northern china - landsat tm - degradation - variability - topography - forest - cover - hills - aster
    Intensive grazing leads to land degradation and desertification of grassland ecosystems followed by serious environmental and social problems. The Xilingol steppe grassland in Inner Mongolia, China, which has been a sink area for dust for centuries, is strongly affected by the negative effects of overgrazing and wind erosion. The aim of this study is the provision of a wind erosion risk map with a spatial high resolution of 25 m to identify actual source and sink areas. In an integrative approach, field measurements of vegetation features and surface roughness length z0 were combined with Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) image data for a land use classification. To determine the characteristics of the different land use classes, a field observation (ground truth) was performed in April 2009. The correlation of vegetation height and z0 (R2 = 0.8, n = 55) provided the basis for a separation of three main classes, “grassland”, “non-vegetation” and “other”. The integration of the soil-adjusted vegetation index (SAVI) and the spectral information from the atmospheric corrected ASTER bands 1, 2 and 3 (visible to near-infrared) led to a classification of the overall accuracy (OA) of 0.79 with a kappa () statistic of 0.74, respectively. Additionally, a digital elevation model (DEM) was used to identify topographical effects in relation to the main wind direction, which enabled a qualitative estimation of potential dust deposition areas. The generated maps result in a significantly higher description of the spatial variability in the Xilingol steppe grassland reflecting the different land use intensities on the current state of the grassland – less, moderately and highly degraded. The wind erosion risk map enables the identification of characteristic mineral dust sources, sinks and transition zones.
    Mapping vegetation density in a heterogeneous river floodplain ecosystem using pointable CHRIS/PROBA data
    Verrelst, J. ; Romijn, J.E. ; Kooistra, L. - \ 2012
    Remote Sensing 4 (2012)9. - ISSN 2072-4292 - p. 2866 - 2889.
    leaf-area index - radiative-transfer model - hyperspectral brdf data - chris-proba data - flow resistance - climate-change - rhine basin - sugar-beet - forest - cover
    River floodplains in the Netherlands serve as water storage areas, while they also have the function of nature rehabilitation areas. Floodplain vegetation is therefore subject to natural processes of vegetation succession. At the same time, vegetation encroachment obstructs the water flow into the floodplains and increases the flood risk for the hinterland. Spaceborne pointable imaging spectroscopy has the potential to quantify vegetation density on the basis of leaf area index (LAI) from a desired view zenith angle. In this respect, hyperspectral pointable CHRIS data were linked to the ray tracing canopy reflectance model FLIGHT to retrieve vegetation density estimates over a heterogeneous river floodplain. FLIGHT enables simulating top-of-canopy reflectance of vegetated surfaces either in turbid (e.g., grasslands) or in 3D (e.g., forests) mode. By inverting FLIGHT against CHRIS data, LAI was computed for three main classified vegetation types, ‘herbaceous’, ‘shrubs’ and ‘forest’, and for the CHRIS view zenith angles in nadir, backward (-36°) and forward (+36°) scatter direction. The -36° direction showed most LAI variability within the vegetation types and was best validated, closely followed by the nadir direction. The +36° direction led to poorest LAI retrievals. The class-based inversion process has been implemented into a GUI toolbox which would enable the river manager to generate LAI maps in a semiautomatic way.
    The effect of vegetation on wind-blown mass transport at the regional scale: A wind tunnel experiment
    Youssef, I.F. ; Visser, S.M. ; Karssenberg, D. ; Erpul, G. ; Cornelis, W.M. ; Gabriels, D. ; Poortinga, A. - \ 2012
    Geomorphology 159-160 (2012). - ISSN 0169-555X - p. 178 - 188.
    northern chihuahuan desert - sand transport - erosion control - forest edge - flow - area - turbulence - threshold - cover - speed
    Wind erosion is a global environmental problem. Re-vegetating land is a commonly used method to reduce the negative effects of wind erosion. However, there is limited knowledge on the effect of vegetation pattern on wind-blown mass transport. The objective of this study was to investigate the effect of vegetation pattern on this phenomenon within a land unit and at the border between land units. Wind tunnel experiments were conducted with artificial shrubs representing Atriplex halimus. Wind runs at a speed of 11 m s– 1 were conducted and sand translocation was measured after 200–230 s using a graph paper prepared for this purpose.This research showed that: 1) the transport within a land unit is affected by the neighboring land units and by the vegetation pattern within both the unit itself and the neighboring land units; 2) re-vegetation plans for degraded land can take into account the 'streets' effect (zones of erosion areas similar to streets); 3) the effect of neighboring land units includes sheltering effect and the regulation of sediment passing from one land unit to the neighboring land units and 4) in addition to investigation of the general effect of vegetation pattern on erosion and deposition within the region, it is important to investigate the redistribution of sediment at smaller scales depending on the scope of the project.
    Structure and composition of woody vegetation around permanent-artificial and ephemeral-natural water points in northern Gonarezhou National Park, Zimbabwe
    Gandiwa, E. ; Tupulu, N. ; Zisadza-Gandiwa, P. ; Muvengwi, J. - \ 2012
    Tropical Ecology 53 (2012)2. - ISSN 0564-3295 - p. 169 - 175.
    herbaceous vegetation - african savanna - elephants - impact - provision - botswana - cover - piosphere - landscape - gradients
    The main objective of this study was to compare woody vegetation structure and composition along a distance gradient from permanent-artificial and ephemeral-natural water points in northern Gonarezhou National Park (GNP), Zimbabwe. Woody plants were sampled in May 2010 using a stratified systematic design with plots systematically placed at 100, 500, 1000 and 2000 m from four selected water points. A total of 912 woody plants were assessed in 32 sampling plots and 63 woody plant species were recorded. There were no significant differences in mean height, number of stems per plant, density and diversity with distance from water points. Significant differences in basal areas were only recorded at 2000 m. Only one ephemeral-natural water pan showed a decrease in plant density with increase in distance from the water pan. Our results suggest that there has been some slight degradation of woody vegetation around water points in northern GNP.
    The potential for integration of environmental data from regional stratifications into a European monitoring framework
    Ortega, M. ; Metzger, M.J. ; Bunce, R.G.H. ; Wrbka, T. ; Allard, A. ; Jongman, R.H.G. ; Rosselló, R.E. - \ 2012
    Journal of Environmental Planning and Management 55 (2012)1. - ISSN 0964-0568 - p. 39 - 57.
    strategic ecological survey - land classification - great-britain - climate-change - biodiversity - kappa - agreement - habitats - trends - cover
    The development of a co-ordinated system for monitoring European biodiversity that can provide policy makers with information to underpin the management of ecological resources requires an appropriate environmental stratification to facilitate sampling and data analysis. This paper quantifies the similarities between the European Environmental Stratification (EnS) and four regional stratifications to test whether the EnS is able to distinguish locally important environmental gradients. The results show that in general the EnS is comparable with regional stratifications, and resolves border effects where divergent environmental conditions are combined into dominant strata. However, some regional gradients are not discerned, illustrating the value of national stratifications to provide local detail within continental monitoring strata.
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