02443naa a2200241 a 450000100080000000500110000800800410001902400300006010000200009024501220011026000090023252017220024165000210196365000270198465000130201165000090202465000170203370000170205070000170206770000140208470000250209877300780212314071272022-11-23       2008    bl uuuu     u00u1 u    #d7 a10.1029/2007JG0006222DOI1 aDAVIDSON, E. A.  aObjective indicators of pasture degradation from spectral mixture analysis of landsat imagery.h[electronic resource]  c2008  aDegradation of cattle pastures is a management concern that influences future land use in Amazonia. However, ?degradation? is poorly defined and has different meanings for ranchers, ecologists, and policy makers. Here we analyze pasture degradation using objective scalars of photosynthetic vegetation (PV), nonphotosynthetic vegetation (NPV), and exposed soil (S) derived from Landsat imagery. A general, probabilistic spectral mixture model decomposed satellite spectral reflectance measurements into subpixel estimates of PV, NPV, and S covers at ranches in western and eastern Amazonia. Most pasture management units at all ranches fell along a single line of decreasing PV with increasing NPV and S, which could be considered a degradation continuum. The ranch with the highest stocking densities and most intensive management had greater NPV and S than a less intensively managed ranch. The number of liming, herbiciding, and disking treatments applied to each pasture management unit was positively correlated with NPV and negatively correlated with PV. Although these objective scalars revealed signs of degradation, intensive management kept exposed soil to &lt40% cover and maintained economically viable cattle production over several decades. In ranches with few management inputs, the high PV cover in young pastures declined with increasing pasture age, while NPV and S increased, even where grazing intensity was low. Both highly productive pastures and vigorous regrowth of native vegetation cause high PV values. Analysis of spectral properties holds promise for identifying areas where grazing intensity has exceeded management inputs, thus increasing coverage of senescent foliage and exposed soil.  aAnálise do Solo  aDeterioração do Solo  aPastagem  aSolo  aUso da Terra1 aASNER, G. P.1 aSTONE, T. A.1 aNEILL, C.1 aFIGUEIREDO, R. de O.  tJournal of Geophysical Research: Biogeosciencesgv.113, n. G1, Mar. 2008.