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Remote Sensing of Rangeland Biophysical Variables: The Case of Nebraska Sandhills
Rangelands have played a critical role in the conservation of biological diversity, as well in economic development, it is crucial that the research community take advantage of the capabilities afforded by remote sensing to generate reliable data to support management decisions. This research seeks to use satellite data for measuring and mapping rangeland aboveground biomass(AGB) and vegetation fraction (VF) the Nebraska Sandhills. Four distinct objectives that would contribute towards achieving the ultimate goal were addressed. First, characterize the effects of variable compositions and the spatial arrangements of: a. switchgrass and sand, and b. switchgrass, sand, and litter within the instantaneous field of view (IFOV) of a hyperspectral instrument, specifically as those effects relate to estimating VF. It was found that varying the spatial arrangements of components within the IFOV influenced the relationships of the Vegetation Indices (VIs) with percent VF. In addition, the VIs from the doughnut design (DNT) was found to be more accurate than both the checkerboard(CHB) and completely randomized design (CRD). Of the VIs tested, SAVI was superior in predicting VF. The third objective demonstrates that the models developed from objectives 1 and 2 can be applied to compensate for the effects of variable compositions of components within a sensor IFOV. The application of the model improved AGB estimation by about 78%. Finally, AGB spatial distribution was mapped by means of Terra MODIS satellite sensor. AGB production decreased from east to west in the three years studied. Both 2009 and 2010 had comparatively high ABG values than 2011. The changes observed could reflect the general precipitation trends associated with the Sandhills and Nebraska in general. Overall, the findings of this study suggest that using controlled experiments mimicking the conditions on the rangeland may have significant impact on biophysical parameter estimation using remote sensing. The models developed in this study may possibly be applied to other greenness VIs to estimate VF or other biophysical parameters not only in the Sandhills but probably other rangeland ecosystems in mid-latitude locations.
Boateng, Andrews, "Remote Sensing of Rangeland Biophysical Variables: The Case of Nebraska Sandhills" (2018). ETD collection for University of Nebraska - Lincoln. AAI10791963.