Effects of thinning intensity on the growth of interplanting broadleaved trees under Pinus massoniana plantation

  Objective  This paper analyzes the thinning effect of replanting tree species of Pinus massoniana plantation in southwestern Guangxi, southern China in order to provide a better guidance and theoretical basis for scientific and reasonable management.

  Method  Four kinds of artificial replanting tree species were used as the research objects to study the growth of replanting tree species under Pinus massoniana plantation after three thinning intensities (80%, 50%, 30%), and to analyze the influence of stand and habitat factors.

  Result  The thinning intensity had a significant impact on the growth of interplanting broadleaved trees. The thinning intensity significantly affected the growth of broadleaf trees, and the growth of Castanopsis fissa and Manglietia glauca increased with thinning intensity increasing, but the influence of cutting intensity on Erythrophleum fordii was not significant. The DBH growth of Castanopsis fissa was higher than that of other three tree species, and the peak appeared in the third year or so. The effect of thinning intensity on the growth of Erythrophleum fordii was accelerated in 30% thinning intensity after nineth years. Castanopsis fissa and Castanopsis hystrix were suitable to grow under 50% thinning intensity, and the increase of DBH appeared in the fifth year. The main factors affecting the growth of replanted trees were tree density, organic matter and soil thickness, showing significant differences in replanted trees (P < 0.05).

  Conclusion  Different tree species have better growth rate under medium and high intensity thinning. Castanopsis fissa and Castanopsis hystrix can make full use of the space left behind by high-intensity thinning, give full play to the advantages of rapid growth and improvement of forest soil, while Erythrophleum fordii and Castanopsis hystrix can keep the growth rate continuously by the environmental conditions created by Castanopsis fissa and Manglietia glauca. It is suggested that Quercus griffithii and Manglietia glauca are suitable tree species in the thinning intensity (80% or 50%), Castanopsis hystrix and Erythrophleum fordii are suitable tree species under the 30% thinning intensity of Pinus massoniana plantation.