放牧家畜组合对环青海湖高寒草地优势种空间格局的影响

Effects of Grazing Livestock Combination on Spatial Pattern of Dominant Species in Alpine Grassland around Qinghai Lake

研究放牧家畜组合对高寒草地优势种空间格局的影响有助于对草地的管理。依托2014年建成的高寒草地-家畜系统适应性管理技术平台,利用空间点格局分析方法,系统分析了中等放牧强度放牧家畜组合对优势种矮生嵩草(Carex alatauensis)与星毛委陵菜(Potentilla acaulis)空间格局的影响。结果显示,1)基于完全空间随机模型,各处理矮生嵩草与星毛委陵菜均表现为集群分布,且集群程度随尺度增加而降低。不同放牧处理下矮生嵩草与星毛委陵菜的局部邻域密度,较随机分布预期的提升程度低于CK处理。2)基于托马斯模型与异质托马斯模型,不放牧处理(CK)矮生嵩草呈集群分布,牦牛单独放牧(YG)、藏羊单独放牧(SG)、牦牛藏羊个体数量1:6混合放牧(MG1:6)处理表现为嵌套双集群空间格局。CK处理星毛委陵菜表现为嵌套双集群空间分布格局,YG、MG1:6处理在大尺度集群中不存在小尺度集群信号。与CK处理相比,放牧导致矮生嵩草与星毛委陵菜种群空间格局的集群半径降低和集群数量增加,且两个物种的种群空间格局在小尺度上表现出异质性。3)基于环形位移零模型,两个物种种间关联表现为小尺度上的显著负关联,并随着尺度的增加转变为显著无关联。放牧导致两个优势种的种间空间关联在小尺度上呈现负关联的尺度范围增大,其中藏羊对种间关系的影响高于牦牛。结果表明,放牧通过改变矮生嵩草与星毛委陵菜个体的空间分布来调控种内、种间邻体的竞争强度,其中牦牛藏羊1:2混牧能够更好地维持优势种群与放牧压力之间的相对平衡。

The spatial patterns of plant communities are a prominent ecological research area This study utilizes the adaptive management technology platform for the alpine grassland-livestock system established in 2014 to systematically analyze the effects of moderate grazing intensity livestock assemblages on the spatial patterns of the dominant species Carex alatauensis and Potentilla acaulis using spatial point pattern analysis methods.The results indicate the following,1)Based on the complete spatial randomness model,both Carex alatauensis and Potentilla acaulis exhibited clumped distributions across all treatments,with the degree of clustering decreasing with scale.Under different grazing treatments,the local neighborhood density of Carex alatauensis and Potentilla acaulis increased compared to the expected random distribution,but to a lesser extent than that in CK(enclosure).2)According to the Thomas and heterogeneous Thomas models,Carex alatauensis under the CK treatment exhibited a clumped distribution,whereas treatments with yak grazing(YG),sheep grazing(SG),and mixed grazing of yaks and sheep at a ratio of 1:6(MG1:6)demonstrated a nested double-clump spatial pattern.For Potentilla acaulis,the CK treatment showed a nested double-clump spatial distribution pattern,whereas the YG and MG1:6 treatments did not exhibit small-scale signals within large-scale clusters.Compared with the CK treatment,grazing led to a reduction in clump radius and an increase in the number of clumps for the spatial patterns of both species,with heterogeneity observed at small scales.3)Based on the ring displacement null model,the interspecific association between the two species showed a significant negative association at small scales,which transitioned to a significant nonassociation with increasing scales.Grazing increased the range of the negative association between the two dominant species at small scales,with sheep having a greater impact on the interspecific relationship than yaks.These results suggest that grazing regulates the intensity of intraspecific and interspecific neighbor competition by altering the spatial distribution of Carex alatauensis and Potentilla acaulis individuals,with mixed grazing of yaks and sheep at a 1꞉2 ratio to maintain the relative balance between dominant populations and grazing pressure.