极端干旱对内蒙古荒漠草原植物群落物种多样性和土壤性质的影响

在内蒙古希拉穆仁荒漠草原利用人工设置野外减雨措施(生长季5~8月减雨66%、6~7月减雨100%和自然降雨)探讨荒漠草原植物群落物种多样性和土壤理化性质对极端干旱的响应特征。结果表明:(1)极端干旱改变了荒漠草原植物群落结构组成,促使多年生根茎型及一二年生草本植物成为主要优势种。(2)减雨66%和减雨100%两种极端干旱处理显著降低了Margalef丰富度指数和Shannon-Wiener多样性指数(P<0.05),Simpson优势度指数只在减雨100%处理下显著降低(P<0.05),但对Pielou均匀度指数的影响均不显著。(3)除表层土壤含水量在减雨66%条件下显著降低(P<0.05)外,两种极端干旱处理对土壤容重、土壤有机碳含量、土壤全氮含量及土壤碳氮比(C/N)的影响较小。以上结果表明在植物生长季,极端干旱对荒漠草原群落的物种组成和多样性水平影响较大,但对土壤性质的影响较小。

Effects of Extreme Drought on Plant Diversity and Soil Properties of Inner Mongolian Desert Steppe

The response of plant community species diversity,and soil physical and chemical properties to extreme drought in Xilamuren desert steppe of Inner Mongolia were studied by using artificial field precipitation reduction measures(precipitation reduced by 66%from May to August,100%from June to July and natural precipitation).The results showed that the structure and composition of the plant community in the desert steppe were changed under extreme drought condition,and the perennial rhizome grasses,and annuals and biennials gradually became the dominant plants.Furthermore,the Margalef richness index and Shannon-Wiener diversity index were significantly decreased under 66%and 100%precipitation reduction treatments(P<0.05).While the Simpson dominance index was significantly decreased only under 100%precipitation reduction treatment,but the two extreme drought treatments had no significant effect on Pielou evenness index.Finally,the surficial soil water content decreased significantly under the condition of 66%rain reduction(P<0.05).The two extreme drought treatments had no effect on soil bulk density,soil organic carbon content,soil total nitrogen content and soil carbon nitrogen ratio(C/N).It can be concluded that the extreme drought had a greater impact on species composition and diversity of desert steppe community in the growing season,but had less influence on soil properties.