Influence of selective intensity on bivariate distribution of spatial structure in Cunninghamia lanceolata-broadleaved mixed plantation
To overcome the limitation of parameters univariate distribution or mean in describing stand spatial structure, we take the bivariate distribution of mingling, dominance degree and uniform angle index as an effective method to analyze the influence of selective logging on stand spatial structure of Cunninghamia lanceolata-broadleaved mixed plantation.The stand were harvested by selective cutting of different intensities (medium intensity of 34.4%, high intensity of 47.1% and over-high intensity of 69.5%).In terms of the bivariate distribution of mingling and dominance degree, the results showed that fewer trees were in a state of low mingling and inferior, and no in absolute inferiority or only surrounded by the same species under medium intensity cutting.Over-high intensity cutting showed opposite result.The number of tree of medium and high mingling reduced under high intensity cutting.The results of the bivariate distribution of mingling degree and uniform angle index indicated that most of trees were still in absolute asymmetrical pattern after selective cutting.More trees were in a randomly distributed and surrouded by more then two different species under medium intensity cutting.However, more trees were asymmetrical and low mingling in high intensity cutting stand,and it was worse in over-high cutting stand.In terms of the bivariate distribution of uniform angle index and dominance degree, more trees were in the state of relative superior and random pattern after selective cutting.Over-high intensity cutting resulted in increased numbers of trees under situation of absolute inferiority and reunion distribution.Generally, the stand under medium intensity cutting presented more ideal structure, aud we suggest take medium intensity as an effective method to optimize spatial structure of C.lanceolata-broadleaved mixed plantation.
Cunninghamia lanceolata (Lamb.) Hookselective intensityspatial structurebivariate distribution