不同放牧强度下羊草草原群落斑块植被-土壤特征

Vegetation and soil characteristics of plant community micro-patches under different grazing intensities

植物群落斑块化是天然放牧草地最基本的特征之一,影响着草地生态系统结构和功能。本研究以不同放牧强度下典型羊草草原植物群落斑块为研究对象,对植物群落多样性特征、初级生产力、土壤理化性质、植物养分含量及其相关关系进行研究。结果表明:随着放牧强度的增加,斑块群落内植物种类组成发生改变并趋于简单化,放牧敏感物种消失,物种多样性降低;高放牧强度显著降低了植物群落的地上净初级生产力;初级生产力与土壤氮含量具有显著的正相关关系;随着放牧强度增加,土壤碳、氮、磷含量呈现增加趋势;由于放牧强度及斑块结构的影响,土壤碳、氮、磷含量存在空间分布差异;同时,斑块群落中植被碳、氮、磷含量与土壤碳、氮、磷含量之间没有显著的相关性。研究表明,放牧能够改变草地群落结构和功能,引起植被-土壤养分之间的非同步性发展。

The co-existence of micro-patches in plant community is one of the basic characteris- tics of grazing pasture, which affects ecosystem structure and functioning. In this study, we inves- tigated characteristics of plant communities, primary productivity, soil physical and chemical properties, plant nutrient content, and their correlations in different patches selected from plant communities under different grazing intensities. The results showed that with the increase of graz- ing intensity, species composition of plant community patches tended to be simplified, the spe- cies sensitive to grazing disappeared, and species richness decreased. High grazing intensity sig- nificantly decreased aboveground biomass of plant community. In addition, there was a significant relationship between aboveground biomass and total nitrogen concentration. The concentrations of soil total carbon, total nitrogen and total phosphorus showed increasing trends with the increase of grazing intensity. Influenced by the grazing intensity and patch structure, the spatial distribution of soil total carbon, nitrogen and phosphorus are heterogeneous. There were no significant correla- tions between plant and soil nutrient concentrations. The results suggested that community struc- ture and ecosystem function would be changed by livestock grazing, with asynchronous dynamics between plant and soil nutrients.