Abstract: In this paper, the features of Picea crassifolia pure forests at regional scale were analyzed by selecting three typical P. crassifolia forests in the Haxi, Xishui and Qifeng forest centers in the eastern, middle and western parts of the Qilian Mountains in China. The community structure characteristics, including the layer structure, DBH, height structure and static distribution of crown diameter structure of P. crassifolia forests in the designed temporary plots, were investigated. The regression correlations among these three indexes(DBH, height and crown diameter) were developed. The results are as follows: (1) Four layers, i.e. the arborous, shrub, herb and moss layers, could be observed. To some extent, the structure characters of arborous layer were negatively correlated with that of shrub and herb layers. Furthermore, moss in the middle part of the Qilian Mountains developed well; (2) The DBH of P. crassifolia in eastern part of the Qilian Mountains was in an “intermittent” type, and it was in a “reverse J” type in the middle part and a “unimodal” type in the western part. Moreover, the analyzed result of structure of the tree height and crown diameter showed that the regeneration of P. crassifolia was unhealthy in the study area; (3) In the different regions and sample plots, DBH, height and crown diameter of P. crassifolia were significantly correlated with each other, the regression model Y=aX^b(P<0.01) could be used to depict their correlations. It is believed that these results can provide the theoretical basis for sustainable management, community regeneration and tending management of P. crassifolia forest in the Qilian Mountains.

Key words: Picea crassifolia, community structure, layer structure, state nature reserve, Qilian Mountains