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

This paper explores the relationships between environmental factors and community patterns. In 60 plots in the Malan Forest Region of the Loess Plateau, 17 variables were used as indicators of spatial position, soil and topography characteristics. Plant community types were analyzed by TWINSPAN (Two-way Indicator Species Analysis). Significant environmental factors were selected by forward selection and Monte Carlo tests. The relationship between communities and environmental factors was identified by DCCA (Detrended Canonical Correspondence Analysis). Partial CCA (Canonical Correspondence Analysis) partitioned observed compositional variation into components explained by environment, locality and covariation between them. The results showed that: (1) the plant communities can be divided into 13 types including 4 different successional stages. (2) Salt and alkali-hydrolyzable nitrogen are the significant factors related to plant community distribution at early stage. Elevation and humus thickness are the significant factors in the transitional stage. Elevation, slope, aspect, thickness of forest floor, humus thickness and pH are the significant factors for the sub-climax stage. 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 the spatial location and environmental factors decrease