[Growth process of Larix principis-rupprechtii stands with different density on south slope of Liupan Mountains].

By the method of sample trees stem analysis, this paper studied the growth process and diameter structure of 21-year-old Larix principis-rupprechtii plantations with the densities of 1200, 1500, and 2000 stems x hm(-2) in the head-water area on the southern slope of Liupan Mountain in Ningxia Hui Autonomous Region. The results showed that there were no significant differences in the growth status of L. principis-rupprechtii stands among the three densities when the stand age was less than 10 years. However, obvious differences were observed in the diameter and timber volume of individual trees and in the stand volume when the stand age was more than 10 years. The tree growth status in low-density stand was apparently better than that in medium- and high-density stands, but the height growth had no significant difference among the three densities. There was a significant difference in the skewness coefficient (Sk) of diameter distribution among the stands with different density, being higher (Sk = 0.338) in high-density stand than in medium-density stand (Sk = 0.072) and low-density stand (Sk = 0.015). The diameter distribution in high-density stand deviated from normal distribution, with a zenith tending to left, while that in medium- and low-density stands approached a normal distribution, with a more reasonable density structure. The kurtosis coefficient (K = 1.691) of medium-density stand was higher than that of high-density stand (K = 1.532) and low-density stand (K = 0.665), indicating a lower degree of polarization of tree growth in medium-density stand than in other two stands. The reasonable remaining density of 21-year-old L. principis-rupprechtii plantations was suggested to be 1200 stems x hm(-2).