Abstract:

Quercus mongolica forest is the most typical secondary mixed forests in north of Xiaolong Mountains.Modern ecological approaches to forest structured management theory were applied to our study where four sample plots of 900m² were selected.Based on structural parameters including mixing(M),uniform angle index (W),neighborhood comparison(U),crowding (C)and diameter distribution,the community structure was analysed,and then the community stability was evaluated by π value method for stand optimal state,all of which aimed to understand this succession and structural characteristics of community,and further to provide scientific basis for natural forest cultivation and conservation.The results showed that the diameter class structure proved not to be a sheer inverted J shape,in which medium and small diameter of trees covering 6cm≤DBH≤12cm maintained stability of diameter class structure.The mingling of community was well,with mingling in highest intensity level accounting for 58.42% and that in higher intensity level accounting for 36.19%.65.46% of trees were in randomly distributed level,but they had not reached threshold value yet.Trees in weaker level for neighborhood comparison accounted for 25.13%,of which tree crown overlaped heavily and 45.17% of trees were in dense level for crowding.The community wasn't in optimal state because of maximum value in 0.66,thus the community was in stage of progressive succession.To maintain the development and stability of forest community,it needs to regulate the spatial structure,improve forest quality,and alleviate competition,so as to promote natural regeneration and recovery of mixed forest community.

Key words: Xiaolong Mountains, community, trees, distribution, structure, stability