短期封育对滇西北亚高山草甸土壤呼吸速率的影响

目的研究滇西北大狼毒种群扩散蔓延所引起的亚高山草甸群落结构和物种多样性的变化特征。方法以滇西北香格里拉县小中甸镇大狼毒型退化亚高山草甸典型样地为研究对象，采用传统的野外生态学调查和数据统计分析相结合的方法，开展不同大狼毒覆盖度退化亚高山草甸群落结构特征、大狼毒种群数量特征及物种多样性比较研究。结果随着群落中大狼毒覆盖度的增大，滇西北亚高山草甸的优势物种由华扁穗草+三穗苔草+草地早熟禾+西南委陵菜逐渐演变成大狼毒+西南委陵菜+绶草；群落的植株密度、优良牧草比例、Margalef指数、Shannon-Wiener指数和Pielou指数显著下降，毒害草比例以及大狼毒种群的株高、冠幅、分枝数和地上生物量显著增加。结论随着大狼毒覆盖度的增加，滇西北亚高山草甸优良牧草产量下降，物种多样性降低，草地逐渐失去其生产价值。

Chronosequence analysis of two enclosure management strategies in degraded rangeland of semi-arid Kenya

PurposeTo explore the variation characteristics of community structure and species diversity (which was caused by the spread of Euphorbia jolkinii) in subalpine meadow in northwest Yunnan.MethodThe traditional field ecology survey method and the data statistical analysis method were adopted in this research, and the community structure characteristics, the quantitative characteristics of E. jolkinii population and the species diversity were measured in this study.ResultThe dominant species of subalpine meadow in northwest Yunnan changed from Blysmus sinocompressus + Carex tristachya + Poa pratensis + Potentilla fulgens to E. jolkinii + Potentilla fulgens + Spiranthes sinensis. And the plant density, the proportion of excellent forage, the Margalef index, Shannon Wiener index and Pielou index of the community decreased significantly; the proportion of poisonous species, the height, crown width, branch number and aboveground biomass of E. jolkinii increased significantly with the coverage of E. jolkinii increased from less than 10% to over 60%.ConclusionThrough our study we can include that in the subalpine meadow in Northwest Yunnan, the yield of excellent forage and species diversity decreased and lost its production value gradually with the coverage of E. jolkinii increased from less than 10% to over 60%.