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Estimating Winter Annual Biomass in the Sonoran and Mojave Deserts with Satellite- and Ground-Based Observations
Department of Biology, Whitworth University, Spokane, WA 99251, USA
School of Natural Resources and the Environment, University of Arizona, Tucson, AZ 85721, USA
School of Geography and Development, University of Arizona, Tucson, AZ 85721, USA
Climate and Land Use Change, United States Geological Survey USGS), Reston, VA 20192, USA
* Author to whom correspondence should be addressed.
Received: 22 December 2012; in revised form: 16 February 2013 / Accepted: 16 February 2013 / Published: 22 February 2013
Abstract: Winter annual plants in southwestern North America influence fire regimes, provide forage, and help prevent erosion. Exotic annuals may also threaten native species. Monitoring winter annuals is difficult because of their ephemeral nature, making the development of a satellite monitoring tool valuable. We mapped winter annual aboveground biomass in the Desert Southwest from satellite observations, evaluating 18 algorithms using time-series vegetation indices (VI). Field-based biomass estimates were used to calibrate and evaluate each algorithm. Winter annual biomass was best estimated by calculating a base VI across the period of record and subtracting it from the peak VI for each winter season (R2 = 0.92). The normalized difference vegetation index (NDVI) derived from 8-day reflectance data provided the best estimate of winter annual biomass. It is important to account for the timing of peak vegetation when relating field-based estimates to satellite VI data, since post-peak field estimates may indicate senescent biomass which is inaccurately represented by VI-based estimates. Images generated from the best-performing algorithm show both spatial and temporal variation in winter annual biomass. Efforts to manage this variable resource would be enhanced by a tool that allows the monitoring of changes in winter annual resources over time.
Keywords: invasive species; MODIS; NDVI; monitoring; vegetation index
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MDPI and ACS Style
Casady, G.M.; van Leeuwen, W.J.; Reed, B.C. Estimating Winter Annual Biomass in the Sonoran and Mojave Deserts with Satellite- and Ground-Based Observations. Remote Sens. 2013, 5, 909-926.
Casady GM, van Leeuwen WJ, Reed BC. Estimating Winter Annual Biomass in the Sonoran and Mojave Deserts with Satellite- and Ground-Based Observations. Remote Sensing. 2013; 5(2):909-926.
Casady, Grant M.; van Leeuwen, Willem J.; Reed, Bradley C. 2013. "Estimating Winter Annual Biomass in the Sonoran and Mojave Deserts with Satellite- and Ground-Based Observations." Remote Sens. 5, no. 2: 909-926.