甘南山地草原人工草场的演替

 在同一地点选择了1985年和1979年播种的两块垂穗披碱草(Elymus nutans)人工草地，于1986年和1988年进行两次观测。所得结果如下：(1)人工草场建立后就开始逐渐向天然植被恢复；(2)在初期演替速度大于在后期的演替速度；(3)多样性和均匀性随着演替而增大，而群落优势度则随着演替而减小；(4)草场质量随着演替趋于下降，到天然群落阶段又开始恢复。

SUCCESSION OF THE ARTIFICIAL GRASSLANDS IN THE MOUNTAIN GRASSLAND AREA OF GANNAN DISTRICT GANSU

Two artificial grasslands of Elymus nutans, one seeded in 1985 and one in 1979, were chosen for our study. Two surveys were made in both 1986 and 1988. Results of our analysis show that (1) There is a continuous shift in community composition toward the original vegetation; (2) Succession rate in the early stages of succession is much faster than in the later ones; (3) Simpson's diversity and homogeneity increase with time, but community dominance decreases; (4) Quality of grassland can be quantaititively measured by the index proposed in this paper, and it tends to decrease after succession begins, and then recovers in final stage.