陕西子午岭生态因素对植物群落的影响

为探讨生境对植被格局分布的影响,对黄土高原马栏林区60块样地进行植被学调查的基础上,采用17个环境指标刻画植物群落的空间位置、地形和土壤特征;利用双向指示种分析(TWINSPAN)划分了该区不同演替阶段的植物群落类型;利用前向选择法(forward selection)及Monte Carlo检验对不同演替阶段植物群落物种组成影响显著(p＜0.05)的环境因子进行筛选;利用去势典范对应分析(DCCA)排序方法分析不同演替阶段植物群落分布格局与环境的关系;利用偏典范对应分析(partial CCA)定量分离环境、空间及其交互作用对植被格局总体变异的影响.结果表明:(1)马栏林区的植物群落可划分为13个类型,分别属于4个不同的演替阶段;(2)对演替初期阶段群落影响显著的环境因子是土壤含盐量和碱解氮,对演替过渡阶段群落影响显著的环境因子是海拔和腐殖质厚度,对演替亚顶级阶段群落影响显著的因子是海拔、坡向、枯落物厚度、腐殖质厚度和pH值,而对演替顶级阶段群落分异影响显著的因子是海拔、坡向、pH值和速效磷;(3)不同演替阶段群落的生态学特性和分布规律与环境空间的生态梯度格局吻合较好;(4)随着演替的进行,环境因子单独对植物群落的影响越来越大,而样地位置单独作用和样地位置与环境因子的交互作用之和越来越小.

Effects of ecological factors on plant communities of Ziwuling Mountain, Shaanxi Province

This paper explores the relationships between environmental factors and vegetation patterns. In 60 plots in the Malan Forest Region of Loess Plateau, 17 variables were used as indicators of spatial position, soil characteristics and topography. Plant community types in different successional stages in this region were analyzed by TWINSPAN. Environmental factors which have significant influence on the composition of plant communities in different successional stages were selected by forward selection and Monte Carlo tests. The relationship between the distribution pattern of plant communities in different succession stages and environmental factors was identified by DCCA. The influence of environmental and spatial variables and their interaction on the variation of community distribution patterns was quantitatively separated by Partial CCA. The results showed that: (1) The plant communities in this region can be divided into 13 types, and include four different successional stages. (2)Salt content and alkali-hydrolyzable nitrogen are the significant factors related to plant community distribution at early stages of succession. Elevation and humus are the significant factors in the transitional stage; elevation, slope aspect, forest floor, humus and pH are the significant factors for the sub-climax stage, while elevation, slope aspect, pH and available phosphorus are the significant factors for the climax stage. (3)The ecological characters and the distribution patterns of plant communities in different successional stages are consistent with environmental gradients. (4)As succession proceeds, the impact of environmental conditions on plant communities increases, while the total influence of spatial location, and the interaction between spatial and environmental factors decreases.