24 October 2013 Measuring pasture degradation on the Qinghai-Tibet Plateau using hyperspectral dissimilarities and indices
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Abstract
Despite that relevance of pasture degradation on the Qinghai-Tibet Plateau (QTP) is widely postulated, its extent is still unknown. However, livestock grazing is widely accepted as a major factor. This study investigated spectral differences of vegetation patterns along gradients of grazing intensities using plot-based hyperspectral measurements. The measurements were used to define spectral indicators for pasture degradation, which were applied to map asserted proxies for degradation from satellite images. For this purpose, hyperspectral measurements were taken at 11 sites on the north-eastern QTP using a transect design from heavy grazing and therefore asserted degradation near the settlement to less degradation with increasing distance. Potential spectral indicators for degradation were derived from the spectra by calculating the size of continuum removed absorption features and narrow-band indices (NBI). They were compared between degraded and less degraded plots. Linear regressions between proxies and each of the potential spectral indicators were calculated to assess its predictive power. The findings were transferred to larger scales by applying the indicators on two WorldView-2 (WV-2) scenes. Spectral differences between degraded and less degraded plots were obvious regarding a wide range of tested indicators. Several NBIs were considered as good indicators for vegetation cover and species numbers. WV-2 images could be successfully classified into vegetation cover whilst the estimation of species numbers was afflicted with uncertainties. The results demonstrate the potential to estimate degradation proxies using spectrometer measurements and satellite data. Applying these techniques will contribute to a better estimation of spatial degradation patterns on the QTP.
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Hanna Meyer, Lukas W. Lehnert, Yun Wang, Christoph Reudenbach, Jörg Bendix, "Measuring pasture degradation on the Qinghai-Tibet Plateau using hyperspectral dissimilarities and indices", Proc. SPIE 8893, Earth Resources and Environmental Remote Sensing/GIS Applications IV, 88931F (24 October 2013); doi: 10.1117/12.2028762; https://doi.org/10.1117/12.2028762
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