Spatial patterns and correlations of trees in a natural secondary forest of white birch with under-planting of qinghai spruce in a high-cold region of Western China

We investigated the feasibility of artificially promoting forest succession by planting qinghai spruce (picea crassifolia kom.) trees in secondary natural white birch forests (betula platyphylla suk.). survey data in a 100 × 100 m sample plot were analyzed using wiegand-moloney’s o-ring function to determine the spatial point patterns and correlations (intraspecific and interspecific) between two dbh (diameter at breast height) classes of white birch and qinghai spruce. results showed that both the white birch and the qinghai spruce populations were growing,and that the spatial point patterns of all of the dbh classes fit a random distribution. however,the fitted curves of the qinghai spruce trees in dbh classes 2 and 3 were waved and indicated clustered and regular distributions alternately at different scales. the intraspecific correlations changed from negative to positive,and qinghai spruce showed greater negative correlations than white birch. the interspecific correlations also primarily changed from negative to positive,and strong interspecific competition dominated the two species,with the smaller trees suffering serious stress from the larger trees of the other species. the biological characteristics of the white birch were fast-growing,photophilic,and shade-intolerant,while the qinghai spruce were slow-growing and shade-tolerant. these characteristics can be considered as key factors behind the current spatial patterns. in addition,impractical planting methods of the qinghai spruce might be another important cause of the interspecific competition; therefore,ecological thinning of the current forest is advised. © 2017,pakistan botanical society. all rights reserved.