Abstract: By the method of substituting temporal change with spatial difference, and through the additive partitioning of β-diversity, this paper studied the change patterns of βdiversity and its components (nestedness component and species replacement component) of six plant communities along a succession gradient in the Ziwu Mountain of Loess Plateau, Northwest China. During the process of the community succession, the β-diversity in herb layer presented an obvious hump-shaped pattern, i.e., increased with succession and peaked from shrub to birch stage, the β-diversity in shrub layer decreased gradually, while that in tree layer increased gradually. All the changes in the βdiversity during the process of the community succession were accomplished by the nestedness component and species replacement, and the contributions of them varied with succession stage and species layer. Overall, species replacement had dominant effects on the β-diversity at all succession stages and in different species layers. From the viewpoint of species diversity conservation, it would be necessary to conserve more different communities as possible, rather than the fewer communities with richer species diversity.

Key words: irrigation, nitrogen, paddy field, microbial community, microfauna.