载畜率和氮素添加对短花针茅荒漠草原植物多样性的影响

Effects of Stocking Rate and Nitrogen Addition on Plant Diversity of Stipa breviflora Desert Steppe

在短花针茅荒漠草原进行放牧和模拟氮沉降试验,探讨氮沉降背景下放牧对荒漠草原植物多样性的影响。放牧设置不放牧对照、低载畜率、中载畜率和高载畜率4个处理(载畜率分别为0、0.91、1.82、2.71羊/hm^(2)·半年),施氮设置了N0、N10、N20、N40共4个氮素添加水平(添加量分别为0、10、20、40 kg/hm^(2)·年),5个重复,在施氮处理当年用样方法对植物群落进行调查。结果表明:载畜率对物种丰富度、香农威纳指数、优势度指数和均匀度指数有极显著影响(P<0.001),氮素添加对优势度指数和均匀度指数有显著影响(P<0.05),短期内氮素添加和载畜率对植物多样性没有显著的交互作用。在相同载畜率处理下,3种氮素添加处理的香农威纳指数、均匀度指数以及物种丰富度与不添加氮素处理相比均没有显著差异。在不放牧对照、低载畜率处理、中载畜率处理下,3种氮素添加处理的辛普森指数与不添加氮素处理差异不显著;但是高载畜处理下,N10处理的辛普森指数显著低于不添加氮素处理(P<0.05),而N20、N40处理的辛普森指数与不添加氮素处理相比没有显著差异。

In order to explore the effect of grazing on plant diversity in Stipa breviflora desert steppe under the background of nitrogen deposition,grazing and simulated nitrogen deposition experiments were carried out in Stipa breviflora desert steppe.Four grazing treatments were no grazing,light stocking rate,moderate stocking rate,and high stocking rate(stocking rates of 0,0.91,1.82,2.71 sheep/hm^(2)·half a year).Four nitrogen addition levels(0,10,20,40 kg/hm^(2)·year)were added in the grazing plot,with five replicates.The plant community was investigated using sample method in the same year of nitrogen addition.The results showed that stocking rate had a very significant impact on species richness,Shannon-Wiener index,Simpson index and Pielou index(P<0.001).There was a significant effect of nitrogen addition on Simpson and Pielou index(P<0.05).There was no significant interaction between nitrogen addition and stocking rate on plant diversity in the short term.Under the same stocking rate treatment,there were no significant differences in Shannon-Wiener index,Pielou index,and species richness among the three nitrogen addition treatments compared to the no nitrogen addition treatment.However,under the no grazing treatment,light stocking rate treatment and moderate stocking rate treatment,there were no significant differences in Simpson index among the three nitrogen addition treatments compared to the no nitrogen addition treatment.In contrast,under the high stocking rate treatment,the Simpson index of N10 treatment was significantly lower than that of the no nitrogen addition treatment(P<0.05),while the Simpson index of the N20 and N40 treatments showed no significant difference compared to the no nitrogen addition treatment.