Density structure and growth dynamics of a Larix principis-rupprechtii stand for water conservation in the Wutai Mountain Region of Shanxi Province, North China

Abstract

To discover the site adaptability and density suitability of Larix principis-rupprechtii as a water conservation forest in Wutai Mountain, Shanxi Province, the growth process and diameter distribution characteristics of 10-year-old artificial L. principis-rupprechtii forests with density structures of 2600 trees/hm2 and 3500 trees/hm2 were studied using trunk analysis of a sample tree. The results showed that: 1) The tree height increment of the two kinds of forests were the same, and it was almost not affected by density. However, the growth process of the diameter and timber volume showed a great distinction. The growth status and density structure of the low density forest were superior to the high density forest. 2) The skewness (S k) of diameter distribution had great distinction. The S k (0.01) of the low density forest approached a normal distribution, which showed that the density structure was reasonable, while the S k (0.45) of the high density forest was partial to a normal distribution, which showed that the density structure was on the high side. The kurtosis (K) of the two forests (one was −0.64, the other was −0.74) had little distinction and the density factor had limited function to forest polarization. 3) The increment of diameter at breast height, timber volume and trunk stock of the low density forest increased yearly without the effect of density. However, the increment of high density forests had declined from the sixth year, which was restricted by high density. 4) The reasonable density of the 10-year-old L. principis-rupprechtii artificial forest was about 2600 trees/hm2, which is also the reasonable planting density if the utilization of double cutting is not considered.