土地利用变化对高寒草甸植物群落结构及物种多样性的影响

以原生高寒嵩草草甸封育系统为对照,研究了不同土地利用对植物群落结构和物种多样性的影响,检验了不同人工重建措施对植被的相对影响程度.研究结果表明:高寒嵩草草甸草地退化导致植被稀疏、覆盖度下降、群落物种组成减少、群落中各功能群的比例发生变化、物种多样性降低.退化草地封育自然恢复7年后,恢复最快的是一年生杂草,其次是禾草类;重度退化草地改建成人工草地7年后,禾本科植物仍然是群落中的优势类群,但原生植被中的优势功能群--莎草类在任何人工草地中没有出现;经相关分析表明,物种多样性指数与均匀度指数呈极显著正相关(P＜0.01),与物种丰富度呈显著正相关(P＜0.05).不同土地利用条件下,各群落之间种相似性系数的变化表明,退化草地经过多年的封育,或经松耙补播后逐步向原生植被方向演替;人工草地逐步向退化演替方向发展.

Effects of changes in land use on plant community structure and species diversity in alpine meadows

In this paper, the effect of land degradation on species composition and species diversity has been studied and the relative influence of various rehabilitation practices (three seeding treatment and a non-seeded natural recovery treatment) on vegetation in early secondary succession examined. The results showed that grassland degradation on alpine meadow led to a drop in vegetation cover, change of plant species composition, loss of species diversity and decrease in the type of functional group (for example sedges and grasses almost disappeared in severely degraded land). Many annual forbs and a few grasses have invaded and established themselves during the seven years of natural recovery. After 7 years, grasses are still the dominant group in all seeding treatments. But sedges that are the dominant group on primary vegetation have not appeared in any seeding treatment. Correlation analysis showed that species diversity index was of significantly positive correlation with evenness index (P < 0.01), and was of positive correlation with species richness (P < 0.05). Similarity index among the treatments showed that natural recovery and harrowing + seeding treatment accelerated succession to primary vegetation while plowing + seeding treatment secured succession to degraded grassland.