放牧对希拉穆仁草原植物群落及种间联结的影响

Effects of grazing on plant community characteristics and interspecificassociation in Xilamuren grassland

植物群落是维持草原稳定和提供生态系统服务的关键要素。为探究放牧对希拉穆仁草原植物群落及种间联结的影响,文中以禁牧草场、轻度放牧草场、中度放牧草场、重度放牧草场为研究样地,系统调查分析了植物群落组成、物种多样性、物种生态位及种间联结性,并进一步探究其相互关系及土壤肥力的影响。结果表明:除重度放牧草场外,其余放牧强度草场的植物群落均以糙隐子草(Cleistogenes squarrosa)、阿尔泰狗娃花(Heteropappus altaicus)、克氏针茅(Stipa krylovii)为优势种,但放牧改变了物种的相对重要值。重度放牧草场以糙隐子草、羊草(Leymus chinensis)、银灰旋花(Convolvulus Ammannii)、冰草(Agropyron cristatum)为优势种。重度放牧显著增加了群落物种的多样性,但增加的物种重要值普遍较小,且地上生物量显著降低。放牧强度的增强降低了原始优势种的生态位宽度,禁牧草场和重度放牧草场种间联结总体呈显著负联结,轻度放牧草场和中度放牧草场呈显著正联结。随放牧强度的增强种间联结指数逐渐升高,群落内物种间联系紧密,重度放牧草场存在较多种间竞争。土壤C:P比值与Pielou均匀度指数显著正相关,土壤磷含量影响希拉穆仁草原植物群落分布。

The characteristics of plant community are the key factors for maintaining grassland stability and providing ecosystem services.To explore the impact of grazing on the plant community and interspecific association in Xilamuren grassland,taking the fenced grazing grassland,light grazing grassland,medium grazing grassland,and heavy grazing grassland as the case study,we systematically investigated and analyzed the composition of the plant community,species diversity,niche,and species connectivity,and further explored their relationships and the factors influencing the soil fertility.The results showed that Cleistogenes squarrosa,Heteropappus altaicus,and Stipa krylovii are the dominant species in fenced,light and medium grazing grasslands,but grazing changes the relative importance of those species.While C.squarrosa,Leymus chinensis,Convolvulus Ammannii and Agropyron cristatum are the dominant species in heavy grazing grassland.Although heavy grazing significantly increases the species diversity,but the aboveground biomass decreases significantly,and the increased species importance value is generally small.The increase of grazing intensity reduces the niche breadth of the original dominant species.The interspecific association between fenced grazing grassland and heavily grazing grassland shows a negative connection,and that of the light grazing grassland and medium grazing grassland shows a positive connection.With the increase in grazing intensity,the interspecific connection index gradually increases,making the species in the community closely connected,but there is more competition among heavy grazing species.C:P in soil is significantly positively correlated with the Pielou evenness index.Soil phosphorus content affects the distribution of plant communities in Xilamuren grassland.