Spatial Pattern Heterogeneity of Picea schrenkiana var. tianschanica Natural Forest in the Tianshan Mountains, Northwest China

To understand the law of spatial pattern heterogeneity in a Picea schrenkiana var. tianschanica natural forest,five sample plot positions were selected from west to east in the Tianshan Mountains (Zhaosu,Xinyuan,Hutubi,Tianchi,and Qitai) where elevation ranged from 1700 m to 2900 m.Some structure parameters such as uniform angle index and neighborhood comparison were used to analyze the spatial structure characteristics of the P. schrenkiana natural forest.Results showed that,the mean value of the uniform angle index was 0.545 for the P. schrenkiana natural forest in the five sample plots,which indicated reunion distribution for the P. schrenkiana natural forest.The mean value of neighborhood comparison was 0.490,which means that the growth state of the P. schrenkiana natural forest was between sub-dominant and moderate.Uniform angle index changed with the variation in elevation for the five sample plots,suggesting the distribution of P. schrenkiana natural forest exhibited alternating changes from aggregate to random,to aggregate,to random.The variation of neighborhood comparison indicated that the growth state of the P. schrenkiana natural forest changed from sub-dominant to moderate to sub-dominant to poor.Changes in the mean values of the uniform angle indexwere not significant within five sample plots,which showed reunion growth distribution of P. schrenkiana natural forest.But the variation of the mean value of neighborhood comparison had significant changes from moderate to sub-dominant state to moderate within the five sample plots form west to east in the Tianshan Mountains.