三江源区不同建植年代人工草地群落演替与土壤养分变化

研究了了三源区不同建植期人工修复草地在不同演替阶段毒杂草[主要是甘肃马先蒿(Pedicularis kansuensis)]的入侵规律、数量特征,植物群落物种组成、生物苗和草地质最以及土壤养分、微生物活性的变化规律.结果表明,不同建植期人工修复草地植物群落的种类组成、植物功能群组成和群落数量特征存在显著差异.随着演替时间的推移,人工草地群落盖度、高度、物种数、生物最和多样性指数均表现出"V"字型变化规律,杂类草--甘肃马先蒿的数量特征变化尤为明显,在4 a的人工草地群落中开始局部入侵,在5～6 a的人工草地群落中大面积入侵,其入侵速度、入侵面积达到高峰期.土壤的含水量、容重、土壤中有机质、氮素和磷素在演替过程(7 a、9 a草地)中逐渐降低,到一定时期又逐步增加;随着演替的进行,不同建植期人工草地的土壤微牛物生物量碳和酶活性均呈"V"字型,变化.对于退化生态系统的恢复首先是植被恢复,其次是土壤肥力的恢复.土壤有机质等养分的积累、微生物活性的改善不仅能使土壤-植物复合系统的功能得以恢复,同时也能促进物种多样性的形成,有利于人工草地群落稳定性的提高.在试验区尽管植被恢复演替进行得比较缓慢,但从土壤发展的角度看,仍属进展演替.所以,在退化高寒草甸的恢复过程中,若降低和有效控制外界的干扰(如围栏封育),可为退化草地恢复提供繁殖体与土壤环境,实现人工草地逐步向恢复(正向)演替进行.图3表6参34

Community Succession of Differently Aged Artificial Grasslands and Their Soil Nutrient Changes in Three Rivers' Source Regions in Qinghai, China

Restoration starts at the degraded systems with impaired structure and function due to anthropogenic or natural causes. Ecological restoration means restoring both ecosystem structure, including species composition and trophic interaction, and ecosystem function. Soil is a fundamental component in every terrestrial ecosystem, making restoration a vital process during ecological restoration. This study was conducted to examine the invasion regulation and quantitative characteristics of forbs (mainly Pedicularis kansuensis); species composition, biomass and grassland quality; changes in soil nutrients and soil microbial activities of the differently aged artificial grassland communities in the source regions of the Yangtze, Yellow and Lantsang rivers. The results showed that the species composition, functional group composition, and quantitative characters of the plant communities varied greatly in the artificial grasslands cultivated in different years. The coverage, height, species number, biomass, and diversity index of the communities had a "V" type change, which was consistent with the changing pattern of soil moisture, soil bulk density, soil organic matter, N, P, soil microbial biomass C, and soil enzyme activity with the succession processes of artificial grasslands. There were also changes in plant species composition, community structure, and environmental factors (e.g., soil moisture, soil resources, and soil enzyme activity) at the different succession stages in the artificial grassland ecosystem. The restorations of vegetation and soil fertility are important to restore the deteriorated ecosystem. Understanding how to improve soil microbial activities and accumulate soil organic matter is essential to restore the function of plant-soil interaction, enrich plant species diversity and enhance plant community stability. In the restoration process of the degraded grasslands, if disturbance was effectively controlled, suitable seeds were available and soil nutrients were provided, the vegetation restoration could be achieved in the artificial grasslands. Fig 3, Tab 6, Ref 34