Population Structure and Spatial Point Patterns of Individuals in Natural Secondary Poplar-birch Forest in Guandi Mountain

A typical natural secondary poplar-birch forest in Guandi Mountain was selected as a plot.In this plot,population structure was analyzed,and all arbor species at least 1 cm diameter at breast height(DBH,1.3 m above ground) were mapped and identified to species,and their geographic coordinates were recorded following a standard field protocol.The pair correlation function,univariate O-ring statistic of the point pattern analysis,was used to analyze spatial distribution of tree species in the secondary poplar-birch forest,while bivariate O-ring statistic was used to analyze spatial associations of different species in this community.We found that:The statistics of species abundance showed that pioneer species Betula platyphylla,B.albo-sinensis and Populus davidiana are obviously dominant species in present stand.However,the regeneration of the three species is very poor by the analysis of size-class distributions.On the contrary,the regeneration of Picea meyeri,P.wilsonii and Larix principis-rupprechtii seedlings is fine,they will replace the pioneer species and dominate the over story layer with the succession of the community;Spatial distribution pattern analysis showed that B.albo-sinensis,B.platyphylla were obviously but L.principis-rupprechtii,Salix wallichiana were significantly clumped at small scales.Spatial patterns of species are affected by spatial size,community structure and tree age;Spatial associations analysis showed that there are positive associations between B.albo-sinensis and L.principis-rupprechtii,B.albo-sinensis and S.wallichiana,S.wallichiana and L.principis-rupprechtii at small scales,but there is no obvious association between other species.