Seasonal Variation in Aboveground Production and Radiation-use Efficiency of Temperate rangelands Estimated through Remote Sensing

摘要: Aboveground net primary production (ANPP) of grasslands varies spatially and temporally. Spectral information provided by remote sensors is a promising new tool that may be able to estimate ANPP in real time at low cost. The objectives this study were (a) evaluate seasonal scale the relationship between normalized difference vegetation index (NDVI), (b) variations coefficient conversion absorbed radiation into aboveground biomass (ea), (c) identify environmental controls on such temporal changes. We used biomass-based field determinations for two grassland sites Flooding Pampa, Argentina, related them with NDVI data derived from NOAA Advanced Very High Resolution Radiometer (AVHRR) satellites using three different models. Results compared obtained Moderate Imaging Spectroradiometer (MODIS) sensor an additional site. first model was based solely NDVI; second amount photosynthetically active green (APARg), which incoming (PAR); third APARg ea, turn estimated climatic variables. explained 63 93% variation, depending site considered. Estimates not improved considering variation PAR. At both sites, ea varied seasonally (from 0.2 1.2 g DM/MJ) significantly associated combinations precipitation temperature. Combining increased our ability account sites. Our results indicate produces good, direct estimates only if NDVI, PAR, are correlated throughout seasons. Thus, most cases, temperature must taken generate acceptable accuracy.