Species Composition Of Plant Communities And Influencing Factors In Horqin Sandy Land

Horqin Sandy Land,one of important constituent parts of the farming-pastoral ecotone in northern China,is a typical ecologically vulnerable region.Its local plant communities are quite sensitive to human disturbance and climatic changes.In recent years,human activities have played an essential role in regulating plant communities in this region,due to the rapid development of farming and animal husbandry as well as ecological restoration projects.However,much still remains unclear about the current status of the vegetation and its species composition in Horqin Sandy Land under the impact of farming,animal husbandry and ecological restoration projects.A field survey was carried out at 51 sites in Horqin Sandy Land from July to September during 2018-2019 in order to explore the species composition of vegetation types,plant beta diversity patterns and their influencing factors.Hopefully,this study can provide a theoretical basis for the conservation of plant species diversity as well as ecological restoration in Horqin Sandy Land,and offer basic data for further studies on species diversity in this region.The main results are as follows:(1)There were 8 vegetation formations in Horqin Sandy Land,belonging to three vegetation types,including temperate deciduous forest,temperate broadleaf deciduous scrub and temperate needlegrass arid steppe.The species composition and structures of plant communities in Horqin Sandy Land were simple.(2)Herb and shrub beta diversities were mainly derived from species turnover between local plant communities in Horqin Sandy Land.We found that species turnover components contributed almost all variance for herb and shrub beta diversities(93.2% and 91.4%),while nestedness components contributed only a small proportion of variance for herb and shrub beta diversities(6.8% and 8.6%).(3)The dissimilarity index of herb and shrub layer had a significant positive correlation with geographic distance(P < 0.001),while the similarity index of herb and shrub layer had a significant negative correlation with geographic distance(P < 0.001).(4)Grazing disturbance had different effects on the species composition of herb layer and shrub layer.There was a shift in dominant species of herb layer with increasing grazing intensity,while there was no shift in dominant species of shrub layer with increasing grazing intensity.Besides,there was a significant difference in species composition of herb layer among grazing intensities(P < 0.001),while there was no significant difference in species composition of shrub layer among grazing intensities(P >0.05).(5)Herb beta diversity was shaped by environmental factors together with grazing factors andspatial factors,and the synergism between environmental and spatial factors was the major factor regulating herb beta diversity.Shrub beta diversity was shaped by environmental factors together with spatial factors,and the synergism between environmental and spatial factors was the major factor regulating shrub beta diversity.