亚高山草甸弃耕地植物群落演替的数量研究I.群落组成分析

本文采用由植被的空间序列推断时间上演替系列的方法对甘南亚高山草甸弃耕地上的植物群落组成进行了分析。结果表明：(1)弃耕初期，莎草，禾草类在群落中的地位从开始时的71%急剧地下降到弃耕十二年时的6%；以后随着密丛型的莎草，禾草的侵入，它们地位又开始上升而恢复到30%一40%：杂类草的地位在开始时上升较快，而到了后期又有所下降；毒害草在群落中的地位基本稳定，保持在10%左右。 (2)群落的种丰富度、均匀度、Simpson多样性指数随弃耕年限增加而增大，而群落优势度随弃耕年限而减小。 (3)优势度—多样性曲线在弃耕初期为几何分布型，中后期演变为对数正态分布型，而对放牧顶极群落又近似于MacArthur分布型。

A Quantitative Study of the Vegetation Succession on the Abandoned Arable Lands of the Subalpine Meadows in Gannan Prefecture of Gansu Province I. Analysis of Community Composition

The study of the succession of plant communities in the abandoned arable lands in the area of subalpine meadows of Gannan prefecture, is made by inferring from comparing the representative sites of abandoned arable lands of different ages. The analysis of community composition in succession shows (1) Importance of the grasses and sedge plants in the’ early stages of succession they rapidly dropped from 71% to 6% in 12 years, and as a result of the aggregation and spreading of grasses and sedge, plants, they recovered gradually to 30–40% the importance of weeds enhances rapidly in the early stage of succession and reduces in the later ones of succession; but the importance of poisonous herbs remains steady, acounting for about 10% of the community. (2) The species richness, Simpson′s diversity and eveness of the community increase while its dominance decreases with the development of succession. (8) The dominance diversity curve of the initial community is roughly geometric; as species are added, the curve approaches to a lognormal distributions but in the final stage, the curve approaches a MacArthur brocken-stick distribution.