Diversity Characteristics Of Understory Plant Species In Juniperus Przewalskii Community,Qinghai Province

As one of the main forest communities in Qinghai Province,the Juniperus przewalskii community plays an important role in maintaining the ecological security,conserving biodiversity and conserving water resources of the Qinghai-Tibet Plateau.Due to its high altitude and inconvenient transportation,there are few studies on the plant species diversity.In order to understand the plant species diversity and its influencing factors of J.przewalskii community in Qinghai province,this study selected the J.przewalskii community as the research object.Based on field investigation and lab analysis,the species composition,faunal characteristics,vertical distribution pattern and dominant factors affecting species diversity of J.przewalskii community in Qinghai province were discussed,in order to provide data support for resource plants exploitation and ecological benefit evaluation of J.przewalskii community.The results were as follows:(1)There were 127 species belonging to 33 families and 87 genera in the community of J.przewalskii in Qinghai province.There were 117 species of resource plants,which can be divided into three types according to their uses: medicinal plants,forage plants and ornamental plants.(2)Species richness of J.przewalskii community decreased gradually along the longitude gradient.The species richness of shrub layer was lower than herb layer and reached the highest at the altitude of 2900 m～3100m.The species richness of herb layer showed double peak curve,and the peak value near the altitude of 2700m was higher than that 3600m.(3)Besides Pielou index,the α diversity index of shrub layer showed single peak curve:Shannon-Wiener index and Simpson index reached the highest at the altitude of 3100m.In the α diversity index of herb layer,Shannon-Wiener index,Simpson index and Pielou index showed wave curve.Among β-diversity index,Whittaker index and Cody index reached the highest values in the range of 2600-3000m above altitude.Sorenson index and Bray-Curtis index had obvious different variation trends at the altitude of 2400m,but had similar variation trends in the rest of the altitude,and reached the maximum value at the altitude of 2600m.(4)The floristic areal types of the plants are mainly Widespread,North Temperate and Old World Temperate.(5)Soil water content of J.przewalskii community decreased with increasing depth,and the influence of habitat difference on soil nutrient content was great.Soil physical and chemical properties had different effects on the diversity of shrub and herb species.The temperate climate was more suitable for the survival of plants in the community of J.przewalskii in Qinghai province.The area of 2900-3100m was more suitable for shrub survival,and the area near the altitude of 2700m was more suitable for herb growth.The species replacement rate of J.community at the altitude of 2300-2600m was slow,and increased at the altitude of 2600-3000m,and to be stable when the altitude rised above 3000m.The resource plant species was rich,which can be cultivated artificially to enlarge the population,in order to enhance the income of local residents.