放牧对小叶锦鸡儿种子产量的影响

Influence of Grazing on Seed Production of Caragana microphylla

锡林河流域草地灌木化表现为小叶锦鸡儿(Caragana microphylla)种群的扩张。为了研究放牧与小叶锦鸡儿种群扩张的关系,从小叶锦鸡儿的种子产量和萌发入手,分析放牧对小叶锦鸡儿生殖的直接影响(即放牧的直接影响)以及不同放牧处理下昆虫种群对小叶锦鸡儿生殖造成的影响(即放牧的间接影响)。通过比较不同处理下小叶锦鸡儿果荚的数量、种子产量以及昆虫对种子的取食,发现放牧产生的直接影响和间接影响性质不同,放牧的直接影响是不利于小叶锦鸡儿的繁殖,而其间接影响却对小叶锦鸡儿的繁殖有利,且这两种影响在很大程度上会互相抵消。根据所得的研究结果可知在停止放牧之后的一段时间内,小叶锦鸡儿种群扩张的可能性会增加,因此在草地生态系统管理中应该注意这个问题。

Encroachment by woody plants in the Xilin River Basin of Inner Mongolia is seen with the distribution of Caragana microphylla. To understand the effects of grazing on the expanded distribution of woody plants, we studied how grazing influences the number of seeds produced by C. microphylla （the direct effect of grazing） and how frugivorous insects influence the reproduction success of C. microphylla with different grazing treatments （the indirect effect of grazing）. We surveyed the number of pods and seeds and seed predation after dispersal under sites with further free grazing or enclosed from grazing. Grazing affected seed production directly and indirectly; the indirect effect of grazing can largely offset the direct effect. The risk of C. microphylla expansion increases in the first few years after grazing stops, which should be a focus in grassland ecosystem management.