岷江上游林草交错带祁连山圆柏群落的物种多样性及乔木种群的分布格局

应用5种多样性指数对祁连山圆柏群落的物种多样性进行了研究，并采用相邻格子样方法测定了乔木种群及其各立木级的分布格局．结果表明，灌木层的物种多样性偏低，而草本层多样性较高，群落总的物种多样性(以丰富度表示)较高．群落总的物种多样性较高是由于较低的灌木层多样性与较高的草本层多样性综合作用的结果，与放牧影响、阳坡的干燥环境有关，可能是林草交错区固有的特点．乔木种群的分布格局呈现出集群分布，但在其发育过程中显示了动态变化的特征，即在幼苗和小树阶段为集群分布，到了大树阶段转变为随机分布或均匀分布．表6参32

SPECIES DIVERSITY AND ARBOR POPULATION DISTRIBUTION PATTERN OF SABINA PRZEWALSKII COMMUNITY IN THE FOREST-GRASSLAND ECOTONE IN THE WATERSHED OF UPPER MINJIANG RIVER

Five indices were applied to analyze the species diversity of Sabina przewalskii community, and contiguous grid quadrats were used to test the distribution pattern of arbor population and its tree classes. Comparing with broad leaved forests in subtropic and temperate zones and with the dark coniferous forests on shady slopes, the results show that the species diversity of fruticose stratum is relatively lower, while herb layer relatively higher. However, the result of integrating the fruticose stratum and herb layers indicates that the total species diversity (indicated by species richness) of Sabina community is still higher than the comparing communities, which has been attributed to the grazing disturbances and natural conditions of sunny slopes, and shows an intrinsic characteristic of ecotone on high altitude region. The distribution pattern of arbor population is clump, but it is dynamic during the process of plant growth, i.e., its pattern changes from clump to Poisson or uniform with the growth of trees from seedlings or young trees stages. Tab 6, Ref 32