Structure Character istics of Plant Commun ity in Sma ll-sized Sandof Be ijingWestern a t D ifferent Successiona l Stages

Structure characteristics of p lant community at 3 successional stages, namely shifting sandy land, semifixed sandy land and fixed sandy land were investigated in Huangyangtan ofBeijingwestern. The results showed thatspecies abundance increased with community succession, and there were different dominant populations at everystage. Chenopodiaceae p lants were p ioneer ones at shifting sand land, p laying an irrep laceable role at early stage,and their species and number were relatively stable at each stage; Compositae belonged to transitional group insuccessional p rocess, which exhibited a relatively high dominance only at semi2fixed sandy land; Gramineae andLegume p lants p resented a increasing trend, becoming main sustainer of ecological function at fixed sandy land.Along with succession, annual p lants, being absolutely p redominant at early stage, were rep laced gradually byperennial species, sandy vegetation develop ing to weeds grassland, ecological system tending to be stable.Ecological distances among communitieswere far at different stages, so the best species and their allocations shouldbe selected according to sandy environmental condition when artificial vegetation was constructed.