Abstract:

Vertical transects of Picea schrenkiana var. tianschanica forests in five sites of different longitude (Zhaosu，Gongliu，Wusu，Urumqi and Hami) in Tianshan Mountains were investigated to analyze the stand factors of the forests along altitudinal gradient in different longitudinal sites. Each stie was divided into three altitudinal ranges (low，middle and high) and the difference in stand factors within each altitudinal range was analyzed，The variation of main stand factors along the altitudinal gradient at 50 m intervals was also investigated. The results showed that the variation of different stand factors within the three altitudinal ranges in five sites presented different patterns. Mean and maximum DBH showed no significant variation while mean and maximum tree height，stand density，total basal area and stand volume of the forests generally showed hump-shaped curves with increasing of the altitude. The changes along the altitudinal gradient could be described by the quadratic curve equations though there was variation in the altitudinal range of the forests in the different sites.

Key words: Picea schrenkiana var. tianschanica, stand factors, longitude, altitudinal gradient, Tianshan Mountains