Ecological Effect Of Selection Cutting Intensity On Cunninghamia Lanceolata-broadleaved Mixed Plantation

With comprehensive implementation of natural forest, the main cutting object was given priority to plantation. Traditional clear cutting resulted in simplification and conifer problem, deterioration of soil quality and poor stability of structure, and as sustainable forest management, selective cutting attracts more and more attention. To analyze the ecological effect of selective logging on plantation, we took 18 year-old Cunninghamia lanceolata-broadleaved mixed plantation as research object. The experimental 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%). We analyzed the changes of growth, diameter structure, spatial structure, species diversity, soil and litter, in order to revealing the relationship between selective cutting intensity and forest ecological effect, and to provide a scientific basis for ecological service function of plantation.We made an assay of the stand growth, species diversity and diameter structure of stand before, after and 3 year after selective cutting, meanwhile we fitted and evaluated cumulative diameter distribution using the four distribution functions including Weibull, Korf, Log-normal function and Logistic. The results indicated that selective cutting was beneficial to promoting growth of trees and improving the undergrowth dominance, medium and over-high intensity selective cutting were able to maintain high richness and diversity of the shrub layer. Furthermore, results revealed that four distribution functions had good imitative effect, but Log-normal function showed better in accurately describing diameter structure of the Chinese fir broadly mixed plantation.To analyze the changes of stand spatial structure after selective cutting of Cunninghamia lanceolata-broadleaved mixed plantation, four structure parameters were used, including mingling degree, uniform angle index, spatial and species advantage degree based on the neighborhood comparison. In addition, we take the bivariate distribution of mingling, dominance degree and uniform angle index as an effective method to overcome the limitation of parameters univariate distribution or mean in describing stand spatial structure. The results showed that medium intensity cutting had advantage to improve the spatial structure. Comprehensively, we suggest take medium intensity of selective cutting as an effective optimization method for Cunninghamia lanceolata-broadleaved mixed plantation.We investigated the ecological effects of selective cutting on litter, soil physical and chemical properties of Cunninghamia lanceolata-broadleaved mixed plantation. The result showed the situation of soil density, porosity and moisture of stand had improved in stand harvested by high intensity. In terms of soil nutrients, three intensities cutting showed different influences while medium selective cutting showed a good tendency. After different intensity of selective cutting, forest litter nutrients declined faster than uncut sample.In the end, we comprehensively evaluate the selective cutting stand by using principal component analysis with the selection of 39 indicators such as stand growth, spatial structure, species diversity, physical and chemical properties and litter. Compared with uncut stand, medium and high intensity selective cutting stand got higher score in evaluation, the later one ranked first, while over-high intensity selective cutting ranked last. So, high intensity selective cutting stand was benefit for improving ecological environment.Considering all these factors, we suggest take medium and high intensity selective cutting as sustainable measure to manage Cunninghamia lanceolata-broadleaved mixed plantation.