Grazing and mowing were the most common utilization types in the Inner Mongolia steppe,and they had been proved to play different roles on the plant-plant interactions and community succession.In the present study,There was a 3-years of continuous monitoring experiment on the typical steppe community.We compared the two different indices of community small scale patterns with 2 algorithms by the Ecosim 7.72 software.The results were shown as follows:(1) For 3 consecutive years,the plant species interactions in community-level under grazing were competitive,especially in 2014,the results didn't support the stress gradient hypothesis.(2) In 2013 and 2015,the species interactions of community under mowing were competitive,but in 2014,on account of the drought and elevated air temperature,they were facilitative.(3) Different grassland utilization types had distinct effects on plant species interactions,and the effect were also regulated by monthly precipitation and monthly average air temperature in growing season.The present results provided the improvement of stress gradient hypothesis and the theoretical foundation in rational utilization of grassland and the recovery of degraded grassland.%放牧和刈割作为内蒙古草原主要利用方式,对大针茅群落演替以及建群种更替有着重要影响.以内蒙古典型草原大针茅群落为研究对象,2013-2015年连续3年对放牧和刈割两种利用方式下大针茅群落小尺度格局进行定点观测,其中,2014年气候极端干旱且温度较高:运用Ecosim7.72软件计算C-score和V-ratio来反映群落物种间相互作用关系,并分析相互作用关系的年际变化以及影响因素.结果表明:(1) 2013年和2015年温度和降水与该区域年均值比较接近,放牧和刈割两种利用方式下群落植物间相互作用关系均为竞争;(2) 2014年为极端干旱和高温的年份,放牧和刈剖两种利用方式下群落植物间相互作用的值或方向发生了很大变化,其中,放牧利用加剧植物间的竞争,而刈割利用方式下植物间相互作用为促进.(3)所得结果表明气候波动是影响群落物种间相互作用的主要因素,而在极端年份,利用方式会影响群落物种间相互作用的方向和大小,这不仅为胁迫梯度假说的完善提供了实验数据,而且可为该区域草原的合理利用和保护措施的制定提供理论指导.
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