Vegetation fraction inversion and influence analysis of annual ephemeral plants on sandy land evaluation

摘要

Vegetation fraction is an important index for sandy land evaluation, but it changes with time and precipitation obviously, especially the annual ephemeral plants. How to choose the best time for vegetation coverage to evaluate the sandy land degree is an imperative question. In this paper, soil adjusted vegetation index (SAVI), pixel dichotomy model and pixel unmixed model for multi-endmumber were applied to estimate the vegetation fraction based on GF-1 multispectral image, taking Zhenglan Banner in Inner Mongolia as a study area. By validated from filed data, the pixel unmixed model for multi-endmumber was superior to the others, with the lowest RMSE. The vegetation fraction change was analyzed in growing seasons from May to October, taking the precipitation into consideration. It was shown that vegetation in sandy land grown steadily by the middle of July, but it appeared to grow much rapidly after this period due to the effect of precipitation on annual ephemeral plants. In the later period, the plants began to be restrained and became placid until August because of temperature reduction and lack of water. In order to reduce the unsteady effect of annual ephemeral plant, early-middle August was thought as the most reasonable time for vegetation coverage to evaluate the sandy land degree.