Diversity of Plants on the Alluvial Islands of Lijiang River Basin and the Physicochemical Properties of their Soil

anglais. Alluvial islands are unique river landscapes. The vegetation composition of Alluvial islands and the physicochemical properties of its soil are good indicators for studying plants in its riparian zone. This study explores and determines the relationship between the biological diversity of vegetation and the physicochemical properties of soil in the alluvial islands of Lijiang River basin. A field investigation of different vegetation gradient belts in three alluvial islands and an analysis of their soil samples is conducted. Results show that the composition of vegetation species on the three experimental plots is as follows: 6 families, 8 genera and 8 species on experimental plot (I)

8 families, 12 genera and 12 species on experimental plot (II)

and 17 families, 18 genera and 18 species on experimental plot (III). Values of four plant-diversity indices, namely, Margalef richness index, Shannon-Wiener diversity index, Pielou evenness index and Simpson species dominance index, are substantially influenced by the vegetation gradient zone. Change in the gradient zone from gravel to bushes and trees, leads to decreased sand-grain content and increased silt and clay contents, and gravel content of surface soils significantly declines with change in gradient zones. Six types of chemical indicators of soil (organic matter, total nitrogen, available nitrogen, available phosphorus, total potassium, and available potassium) show significant differences with change in gradient zone. Significant correlations were found between plant diversity and physicochemical properties of the soil.