Analysis of Ecological Gradients in Forest Communities in the Malan Forest Region on the Loess Plateau

To identify ecological relationships among different forest community types in the Malan Forest Region on the Loess Plateau,45 forest community plots in the region were evaluated.Twinspan was applied to analyze and classify the forest community types,while CCA and partial DCA were used to study the environmental gradients among these forest community types.The results were as follows:(1) Eight forest types were divided into 45 forest communities;(2) CCA ordination revealed that the litter thickness,aspect,elevation and organic matter content are the most important environmental factors impacting the distribution of forest community types.In addition,partial DCA ordination revealed that disturbance is an important potential environmental factor that affects the distribution of forest community types;(3) Regular distribution of all of the forest community types in the ordination diagraph indicates that the plant species adapt to their environment,and that there is a tendency for planted forests of Pinus tabulaeformis develop gradually in a fashion similar to natural forests;(4) CCA and partial DCA are effective methods of evaluating an ecological gradient in plant communities.