Species diversity and stability of natural secondary communities in different layers with different cutting intensities 10 years later were investigated by calculating Marglef Richness index（R）,Shannon-Wiener diversity index（H）,Simpson diversity index（P）,and Pielou Evenness index（J）.Results show that the values of R,H and P among different layers are listed in a decreasing order：the shrub layer the arbor layer the herb layer,all the three indices values reach the maximum under medium selective cutting intensity after 10 years.The J value of the shrub layer shows a concave parabolic change with the increase in cutting intensity;it shows a linear increase for the arbor layer,whereas the J value of the herb layer shows an opposite change pattern.The values of R at different cutting intensities had high significant difference,but other indices had not significant difference.The stability of communities at different cutting intensities after 10 years is non-cutting low selective cutting intensity medium selective cutting intensity high selective cutting intensity extra-high intensity clear cutting.The stability of communities at different cutting intensities after 10 years shows that the greater cutting intensities,the worse the stability is.
WU Zhi-long ZHOU Xin-nian ZHENG Li-feng HU Xi-sheng ZHOU Cheng-jun
Diameter frequency distribution in a specific stand provides basic information for forest resources management. In this study, four probability models were applied to analyze diameter distribution of natural forests after selective cutting with different intensities （low intensity of 13.0% in volume, medium intensity of 29.1%, high intensity of 45.8%, and extra-high intensity of 67.1%） The results show that the skewness and kurtosis of the four models are positive except that of low intensity selective cutting, which suggest that the number of small-size trees dominate the stand. The more intensity of selective cutting, the wider range of diameter distributions. The diameter structure of selective cutting with low intensity met Weibull and Beta distributions; that of medium intensity met Weibull, negative exponential as well as Gamma distributions; that of high intensity cutting met Weibull and negative exponential distributions, but that of extra-high intensity could not meet any above model. Weibull distribution model fits better than others regarding the structure of diameter distribution in natural forests managed on polycyclic cutting system. The results will provide basic information for sustainable management for mixed natural stands managed on a polycyclic cutting system.
