环境因子和干扰强度对高寒草甸植物多样性空间分异的影响

采用样带与样地结合的方法在三江源自然保护区的核心区沿海拔梯度在阴坡、阳坡分别进行草本植被调查，通过因子分析和偏相关分析研究丰富度指数、多样性指数与环境梯度（包括海拔梯度、裸斑面积、坡度、土壤总碳、总氮含量、土壤pH值、土壤总可溶性盐含量）和干扰强度（鼠类干扰强度、放牧强度）之间的关系。研究结果表明：杂类草丰富度指数（DMa杂）与总物种丰富度指数（DMa总）极显著相关（P<0.01）；阳坡DMa杂和DMa总均呈现“中海拔膨胀”现象，阴坡DMa杂和DMa总与海拔梯度呈正相关，莎草科和禾本科的丰富度指数（DMa莎和DMa禾）随海拔升高并无明显规律；通过主成分分析，及偏相关分析，第一主成分（裸斑面积、鼠类干扰和放牧强度）与除莎草科Margalef丰富度指数、禾本科Simpson指数和禾本科Pielou均匀度指数外的其他草地多样性指数均显著相关，是影响阳坡草地植物多样性的主要因子，土壤总碳、总氮含量对阳坡禾本科类群的多样性指数和均匀度指数有极显著影响，土壤pH值、TDS含量和坡度对阳坡莎草科类群的丰富度有显著影响；海拔梯度、土壤总碳、总氮以及pH值对阴坡草本植物群落的多样性影响较大。研究结论认为，植物群落生物多样性的空间分异特征是地理环境、土壤环境以及干扰强度等因素综合作用的结果。无干扰或干扰较弱时，物种多样性主要受土壤环境状况所影响；而在强干扰存在条件下，干扰强度对物种丰富度和多样性的影响比环境因子更显著；遏制高寒草甸植物多样性降低应首先控制放牧及鼠类等强干扰活动。

The effect of natural factors and disturbance intensity on spacial heterogeneity of plant diversity in alpine meadow

Structure and biodiversity of herbages were examined using the both transects and quadrats along topographical gradients on both shade and sunny slopes at the core zone of Three Rivers Sources Nature Protection Area. The relationships among richness index, diversity index and environmental factors (altitude, bare patch, slope, soil total carbon, soil total nitrogen, soil pH, soil total dissolved salt), disturbance intensity (rodent destroying and livestock grazing) were analyzed by factor analysis and partial correlation analysis. The results showed that the Margalef richness index of forbs had significant (P<0.01) correlation with the Margalef richness index of all species; the Margalef richness index for this two functional groups presented a peak with higher species diversity index in the communities of middle elevation on the sunny side; there was a positive correlation between the Margalef richness index of forbs and all species and altitude gradient on the shade slope. With the increase of altitude, there was not distinct change on Margalef richness index of grasses and sedges. According to the results of Factor Analysis (FA) and Partial Correlation, the First principal component, including soil patch, rodent disturbance and grazing intensity, significantly affected most of the biodiversity index of total species, except Margalef richness index of Cyperaceae, Simpson index of Gramineae and Pielou evenness index of Gramineae. So, the main factors influenced the diversity of all herbages on the sunny slope were soil patch, rodent disturbance and grazing intensity. Soil total carbon and nitrogen had significant effect on the diversity index and evenness index of grassed on the sunny slope. soil pH, total dissolves salt gathered with slope greatly influenced the richness index of sedges on the sunny slope. Altitude, soil total carbon and nitrogen, soil pH all had major effect on species diversity on the shade slope. The conclusions are that the spatial heterogeneity of species diversity resulted from the interaction of geographical environment (altitude, bare patch, slope), soil condition (soil total carbon, soil total nitrogen, soil pH, soil total dissolved salt) and disturbance intensity (rodent destroying and livestock grazing). At the small scale along the altitude gradient, the effect of the environment factor does not have significant effect on species diversity. Soil circumstance was the main Influencing factor for altering species diversity under no-disturbance or slight disturbance. Under heavy disturbance, intensity of disturbance had more significant influence on species richness and diversity than environmental factors. Reducing the heavy disturb such as grazing and rodent destroy was the first choice for preventing the degradation of alpine grassland and loss of herbage diversity in the alpine region.