MUTISCALE ANALYSIS OF VEGETATION INDEX AND TOPOGRAPHIC VARIABLES IN THE YELLOW RIVER DELTA OF CHINA

Abstract

Aims At larger scales, the elevational gradient interacts with the redistribution of water and soil solutes to determine regional vegetation pattern, especially in regions with small variation in elevation. However, little is known about the processes of water redistribution in coastal ecosystems. Our objective is to test if water redistribution affects vegetation pattern at large scales in a coastal eco-system in the Yellow River Delta using an integrated remote sensing and GIS method. Methods One-way ANOVA was employed to test whether normalized difference vegetation index (NDVI) is significantly different among four major plant communities. Correlations between NDVI and topographic indexes were identified by the Spearman non-parametrical method. Moran's I coefficients were also calculated for all selected variables. Important findings NDVI was highly different among the four communities, as determined by differences in habitat structure of coastal plants. Correlations between NDVI and elevation were highly significant at all scales, which may closely associate with the groundwater depth at smaller scales and with water redistribution at larger scales. At the 750 m grain scale, the correlation coefficients between to-pographic wetness index and slope were highly significant and the Moran's I coefficient increased abruptly, indicating water redistribution at this scale. Topographical factors affect the vegetation pattern via scale-dependent adjustment and control on soil moisture and salinity. At small scales, topographic factors regulate soil water and salinity through evaporation from the soil surface. At large scales, topographic factors redistribute the soil water and salinity through runoff and the groundwater system.