北京西部小型沙地不同演替阶段植物群落结构特征

对北京西部黄羊滩流动沙地、半固定沙地和固定沙地3个演替阶段的植物群落进行取样分析,结果表明,物种丰富度随演替的进展呈增加的趋势,每一阶段对应着不同的优势种群.藜科植物是流动沙地的先锋植物,在植被演替早期具有不可替代的作用,且在各阶段种类数量比较稳定;菊科植物属于演替的过渡类群,只是在半固定沙地阶段表现出较高的优势度;禾本科和豆科植物呈不断增加的趋势,成为固定沙地生态功能的主要维持者.随演替的进展,初期占绝对优势的1年生植物逐渐被多年生植物替代,沙地植被向杂草类草原方向发展,生态系统趋于稳定.各阶段群落间的生态距离较远,在人工植被建设时应根据沙地环境条件选择最佳植物种和配置.

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.