三江源区“黑土滩”型退化草地人工恢复植物群落的演替动态

选取青藏高原三江源区"黑土滩"型退化草地上建植的人工草地为研究对象,对不同建植年限人工草地植物群落及其各功能群的物种组成、平均高度、盖度和地上生物量及植物多样性等进行实地调查和对比分析,探讨"黑土滩型"退化草地在人工恢复过程中植物群落组成和多样性变化,以期回答人工恢复的草地植物群落何时才能接近天然草地、人工恢复的时间阈值应为多长等问题,从而为三江源区"黑土滩"型退化草地的恢复重建提供科学的理论指导。研究结果表明:草地恢复前5年内,禾本科植物的数量大量增加,植物群落的高度增加了847.6%,植物群落盖度增加了134.5%;不同恢复年限的草地植物群落的多样性指数都有相似的变化趋势,恢复8年后植物群落组成达到阶段性的稳定状态,在恢复时间达16—18年后,逐渐向更稳定的状态转化;恢复18年的草地与天然草地植物群落的Jaccard及Sorensen相似度指数分别为0.596、0.747,Cody差异度指数为9.5。由此可见,建植人工草地的方式恢复退化草地,可在建植8年后达较好的恢复效果;恢复时间达16年以上的人工草地采取适度的调控措施,有利于其向天然草地恢复演替;建植18年的人工草地物种组成情况与天然草地最接近,但仍有差异。因此,"黑土滩"型退化草地的人工促进恢复,到未退化的状态至少需要18年以上。

Succession dynamics of a plant community of degraded alpine meadow during the human-induced restoration process in the Three Rivers Source region

In this study, the grasslands sown with a single cultivar for the restoration of the "Black Beach", the severely degraded alpine meadow in the headwater areas of the Qinghai-Tibetan Plateau, were investigated. To determine when the plant community structure, composition, and diversity are close to those of the natural grassland and the threshold of the recovery time in terms of plant restoration succession, plant species composition, height, coverage, aboveground biomass, and diversity of both the plant community and functional groups of the cultivated grassland in different planting years were investigated. The objectives of this study were to establish a scientific basis for regulating restored grasslands through cultivation and provide theoretical guidance for the restoration of the degraded grassland in the Three Rivers Source region. The results showed that the number of gramineous plants increased significantly during the first five years after the establishment of the cultivated grassland, the height of plant communities increased by 847.6%, and the coverage plant communities increased by 134.5%. The diversity index of the grassland plant communities across the restoration years showed a growing trend, and plant community composition reached a steady state after eight years of grassland cultivation. After 16 to 18 years of grassland cultivation, the plant community reached a more stable state in terms of species composition and diversity. The Jaccard, Sorensen similarity, and Cody difference indices of the plant community between the cultivated grassland and the non-degraded natural grassland in 18 years of grassland cultivation were 0.596, 0.747, and 9.5, respectively. Consequently, the restoration of the "Black Beach" degraded grassland with grassland cultivation may generate a better recovery effect after 8 years of grass plantation, with appropriate regulation strategies to promote the progress of the cultivated grasslands towards natural conditions. The species composition of the cultivated grassland in 18 years was similar to that of the natural grassland, but with some differences. In the headwater areas, 18 years may be the minimum time needed to fully restore the "Black Beach" degraded grasslands into healthy natural grasslands through grassland cultivation.