Estimating vegetation fractional coverage for temperate grassland in northern China based on remotely sensed data and rainfall time series

摘要

A linear unmixing model considering NDVI and rainfall is used to estimate vegetation fractional coverage, which wet season precipitation and sensitivity of mean NDVI to wet season precipitation are used as state variables in the model. The fractional coverage for each 8 × 8-km area in this region is classified into three categories: (1) a portion of the land surface that always remains as bare soil, fc{sub}b; (2) a portion of the fractional coverage that is shrubs, fc{sub}S; (3) a remaining portion that consists of bare soil and grasses cover, fc{sub}(g/b). Study results of average fractional coverage from 1982 to 1999 show that, the fractional coverage of bare soil indicates a clear decrease from West to East, and that of shrubs indicates a general increase, which is not similar to variability of the mean precipitation of wet season.