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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Resource gradients and movements across the edge of transfrontier parks
Murwira, A. ; Garine-Wichatitsky, M. de; Zengeya, F. ; Poshiwa, X. ; Matema, S. ; Caron, A. ; Guerbois, C. ; Hellard, E. ; Fritz, H. - \ 2012
In: Transfrontier conservation areas; people living on the edge. / de Garine-Wichatitsky, M., Cumming, D.H.M., Dzingirai, V., Giller, K., Andersson, J.A., New York and Abingdon (Can.) : Routledge (earthscan from Routledge ) - ISBN 9781849712088 - p. 123 - 136.
A common dominant scale emerges from images of diverse satellite platforms using the wavelet transform
Pittiglio, C. ; Skidmore, A.K. ; Bie, C.A.J.M. de; Murwira, A. - \ 2011
International Journal of Remote Sensing 32 (2011)13. - ISSN 0143-1161 - p. 3665 - 3687.
spatial-patterns - ecological data - landscape - decomposition - vegetation - resolution - fusion - heterogeneity - avhrr - zone
In this article we investigate the scale dependence of spatial heterogeneity in multiresolution and multisensor data using the wavelet transform. The landscape analysed with the wavelets retains the same dominant pattern irrespective of the original pixel size of the image. In agricultural areas, typically characterized by a mosaic of cultivated fields, the wavelet transform quantified consistently a median dominant scale of 512 m in the Orthophoto, Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) and Landsat Enhanced Thematic Mapper Plus (ETM+). The dominant scale represented the dominant field size of cultivated areas. The shape of the average wavelet energy curves was also similar among the images. In semi-natural areas the wavelet transform quantified consistently a median dominant scale of 128 m in the Orthophoto and ASTER. The median dominant scale of ETM+ was slightly smaller and located at 64 m. We characterized the spatial heterogeneity of agricultural and semi-natural areas in Andalucia (Spain) using multisensor data not time coincident ranging from 1 m (Orthophoto), to 15 m (ASTER) to 28.5 m (ETM+). The contrast in vegetation cover was measured using Normalized Difference Vegetation Index (NDVI) in ASTER and ETM+ and red band in Orthophoto. We performed a multiresolution analysis using a Haar two-dimension discrete wavelet transform to quantify and compare the intensity (maximum degree of contrast in vegetation cover), the dominant scale (the scale at which the maximum intensity occurs) and the wavelet energy curve (intensity plotted as a function of the scale) of different images at intervals of power of 2 within the scale range from 2 to 4096 m
Comparing direct image and wavelet transform-based approaches to analysing remote sensing imagery for predicting wildlife distribution
Murwira, A. ; Skidmore, A.K. - \ 2010
International Journal of Remote Sensing 31 (2010)24. - ISSN 0143-1161 - p. 6425 - 6440.
spatial heterogeneity - species richness - patterns - vegetation - elephants - landscape - movements - ndvi
In this study we tested the ability to predict the probability of elephant (Loxodonta africana) presence in an agricultural landscape of Zimbabwe based on three methods of measuring the spatial heterogeneity in vegetation cover, where vegetation cover was measured using the Landsat Thematic Mapper (TM)-derived normalized difference vegetation index (NDVI). The three methods of measuring spatial heterogeneity were: one wavelet-derived spatial heterogeneity measure; and two direct image measures. The wavelet-derived spatial heterogeneity measure consists of the intensity, which measures the maximum contrast in the vegetation cover, and the dominant scale, which determines the scale at which this intensity occurs. The two direct image measures use the NDVI average and the NDVI coefficient of variation (NDVIcv). The results show that the wavelet-derived spatial heterogeneity significantly explains 80% of the variance in elephant presence compared with 60% and 48% variance explained by the NDVI average and NDVIcv, respectively. We conclude that the wavelet transform-based approach predicts elephant distribution better than the direct image measures of spatial heterogeneity
Remote sensing of the link between arable field and elephant (Loxodonta africana) distribution change along a tsetse eradication gradient in the Zambezi valley, Zimbabwe
Murwira, A. ; Skidmore, A.K. ; Huizing, H.G.J. ; Prins, H.H.T. - \ 2010
International Journal of applied Earth Observation and Geoinformation 12 (2010)Suppl. 1. - ISSN 0303-2434 - p. S123 - S130.
middle
We investigated whether the proportion of remotely sensed arable fields increased along a tsetse eradication gradient in the Sebungwe region. We also investigated whether and to what extent this increase in arable fields affected the distribution of the African elephant (Loxodonta africana) between the 1980s and 1990s. Results showed a relatively higher increase in the proportion of arable fields in the zone cleared of tsetse by 1986 compared to the zone that was still tsetse infested by the same date. Results also showed contrasting patterns in the relationship between the proportion of the habitat under arable fields and elephant distribution between the two periods. Specifically, in the 1980s, when arable field cover was between 0% and 11%, there was a weak (p > 0.05) positive relationship between elephant presence and the proportion of the habitat under arable fields. In contrast, a significant (p <0.05) negative relationship emerged in the 1990s, when arable field cover ranged between 0% and 88%. Furthermore, the results demonstrated that the change in the probability of elephant presence between the early 1980s and the early 1990s was significantly (p <0.05) related to the change in the proportion arable fields. In conclusion, this study demonstrated that the expansion of arable fields in the Sebungwe was greater in areas where tsetse had been eradicated compared with areas that were still tsetse infested. Overall, the results suggest that using remotely sensed data, we can conclude that tsetse eradication led to the redistribution of elephants in response to arable field expansion.
Land, productivity, and agricultural research: Towards an understanding of the multiple meanings of land
Andersson, J.A. ; Twine, W. ; Murwira, A. ; Giller, K.E. ; Mashingaidze, A.B. ; Slingerland, M.A. - \ 2007
- p. 1 - 23.
Monitoring change in the spatial heterogeneity of vegetation cover in an African savanna
Murwira, A. ; Skidmore, A.K. - \ 2006
International Journal of Remote Sensing 27 (2006)11. - ISSN 0143-1161 - p. 2255 - 2269.
ndvi - ecology - pattern
The extent to which a new intensity-dominant scale approach to characterizing spatial heterogeneity from remote sensing imagery can be used to monitor two-dimensional changes (i.e. variability and patch size) in the spatial heterogeneity of vegetation cover (estimated from a Landsat Thematic Mapper (TM)-derived Normalized Difference Vegetation Index (NDVI)) was tested in the Sebungwe region in north-western Zimbabwe between 1984 and 1992. Intensity of spatial heterogeneity (i.e. the maximum variance obtained when a spatially distributed landscape property is measured with a successively increasing window size) was used to measure variability in vegetation cover. Dominant scale of spatial heterogeneity (i.e. the window size at which the maximum variance in the landscape property is measured) was used to measure the dominant patch dimension of vegetation cover. This approach was validated by testing whether the observed change in the dominant scale and intensity of spatial heterogeneity of vegetation cover between 1984 and 1992 was related to changes in the proportion of arable fields. The results also indicated that there was a significant relationship (p <0.05) between changes in the proportion of agricultural fields and changes in the intensity and the product of intensity and dominant scale of spatial heterogeneity (intensity x dominant scale), suggesting that the new approach captures observable changes in the landscape, and is not an artefact of the data. The results imply that the intensity-dominant scale approach to quantifying spatial heterogeneity in remote sensing imagery can be used for a comprehensive characterization and monitoring of changes in landscape condition.
The response of elephants to the spatial heterogeneity of vegetation in a Southern African agricultural landscape
Murwira, A. ; Skidmore, A.K. - \ 2005
Landscape Ecology 20 (2005)2. - ISSN 0921-2973 - p. 217 - 234.
ecology - pattern - habitat - zimbabwe - forest - scale - ndvi - classification - movements - ecosystem
Based on the agricultural landscape of the Sebungwe in Zimbabwe, we investigated whether and how the spatial distribution of the African elephant (Loxodonta africana) responded to spatial heterogeneity of vegetation cover based on data of the early 1980s and early 1990s. We also investigated whether and how elephant distribution responded to changes in spatial heterogeneity between the early 1980s and early 1990s. Vegetation cover was estimated from a normalised difference vegetation index (NDVI). Spatial heterogeneity was estimated from a new approach based on the intensity (i.e., the maximum variance exhibited when a spatially distributed landscape property such as vegetation cover is measured with a successively increasing window size or scale) and dominant scale (i.e., the scale or window size at which the intensity is displayed). We used a variogram to quantify the dominant scale (i.e., range) and intensity (i.e., sill) of NDVI based congruent windows (i.e., 3.84 km × 3.84 km in a 61 km × 61 km landscape). The results indicated that elephants consistently responded to the dominant scale of spatial heterogeneity in a unimodal fashion with the peak elephant presence occurring in environments with dominant scales of spatial heterogeneity of around 457-734 m. Both the intensity and dominant scale of spatial heterogeneity predicted 65 and 68% of the variance in elephant presence in the early 1980s and in the early 1990s respectively. Also, changes in the intensity and dominant scale of spatial heterogeneity predicted 61% of the variance in the change in elephant distribution. The results imply that management decisions must take into consideration the influence of the levels of spatial heterogeneity on elephants in order to ensure elephant persistence in agricultural landscapes
Detecting changes in the spatial heterogeneity of NDVI using a wavelet transform
Murwira, A. ; Skidmore, A.K. - \ 2004
In: Scale matters! : a new approach to quantify spatial heterogeneity for predicting the distribution of wildlife / Murwira, A., Wageningen : ITC Enschede / Wageningen University (ITC Dissertations 106) - ISBN 9789058089519 - p. 33 - 48.
Tsetse eradication, arable fields and the elephant (Loxodonta africana) distribution in Zimbabwe: How strong is the link?
Murwira, A. ; Skidmore, A.K. ; Huizing, H.G.J. ; Prins, H.H.T. - \ 2003
In: Scale matters! : a new approach to quantify spatial heterogeneity for predicting the distribution of wildlife / Murwira, A., Wageningen : ITC Enschede / Wageningen University (ITC Dissertations 106) - ISBN 9789058089519 - p. 49 - 66.
Predicting elephant (Loxodonta africana) presence in a Southern African agricultural lanscape from the spatial heterogeneity of NDVI
Murwira, A. ; Skidmore, A.K. - \ 2003
In: Scale matters! : a new approach to quantify spatial heterogeneity for predicting the distribution of wildlife / Murwira, A., Wageningen : ITC Enschede / Wageningen University (ITC Dissertations 106) - ISBN 9789058089519 - p. 133 - 159.
Evaluation a new approach to predict the spatial distribution of elephants from NDVI
Murwira, A. ; Skidmore, A.K. ; Leeuw, J. de - \ 2003
In: Scale matters! : a new approach to quantify spatial heterogeneity for predicting the distribution of wildlife / Murwira, A., Wageningen : ITC Enschede / Wageningen University (ITC Dissertations 106) - ISBN 9789058089519 - p. 67 - 99.
Characterising the spatial heterogeneity of a landscape
Murwira, A. ; Skidmore, A.K. - \ 2003
In: Scale matters! : a new approach to quantify spatial heterogeneity for predicting the distribution of wildlife / Murwira, A., Wageningen : ITC Enschede / Wageningen University (ITC Dissertation 106) - ISBN 9789058089519 - p. 13 - 31.
Scale matters! : a new approach to quantify spatial heterogeneity for predicting the distribution of wildlife
Murwira, A. - \ 2003
Wageningen University. Promotor(en): Andrew Skidmore; Herbert Prins. - Wageningen/ Enschede : Wageningen Universiteit - ISBN 9789058089519 - 195
wild - dierecologie - ruimtelijke verdeling - remote sensing - loxodonta africana - voorspelling - zimbabwe - elephas maximus - wildlife - animal ecology - spatial distribution - remote sensing - loxodonta africana - prediction - zimbabwe - elephas maximus
The spatial distribution of elephants (Loxodonta africana) in relation to the spatial heterogeneity of vegetation cover in southern African agricultural landscape
Murwira, A. ; Skidmore, A.K. - \ 2003
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