Abstract:

The population and community characteristics of Malus sieversii were investigated in its three typical distribution areas (Damohe valley, Xiaomohe valley, and Jiaowutuohai valley ) in the western part of Tianshan Mountains in Xinjiang. The result showed that most of the M. sieversii trees grew on the shade or semi-shade slopes and formed pure stands, with some mixed with other woody species such as Armeniaca vulgaris and Picea schrenkianavar. tianschanica. The stem diameter classes of the three populations all exhibited a unimodal pattern, with more stems belonged to the Ⅱ-Ⅵ diameter classes. The diameter class pattern of the Damohe valley population was more close to normal distribution than those of the Xiaomohe and the Jiaowutuohai valleys populations. The tree height class distribution of the populations in the three locations all exhibited a unimodal pattern too. There were significant differences in mean tree height in each diameter class among the three populations. In the main distribution elevation of 1 200-1 700 m, the tree height and crown width of the Xiaomohe valley population showed parabolic profile with increasing altitude, while the parameters of the Damohe valley and the Jiaowutuohai valley populations decreased with the increasing elevation, However, their ground diameter and height below the first branch all decreased with the increasing elevation. The mean canopy density of the stands dominated by M. sieversii was 0.48±0.03. The canopy density in the Damohe valley (0.38±0.04) was lower than those in the Xiaomohe valley (0.55±0.09) and the Jiaowutuohai valley (0.51±0.08). The mean stand density in the Damohe valley (319.2±44.1) tree·hm^-2 was lower than those in the Xiaomohe valley (502.3±151.1) tree·hm^-2 and the Jiaowutuohai valley (325.0±91.1) tree·hm^-2. With an increase in elevation, the change of stand canopy density and stand density in the Xiaomohe valley and the Jiaowutuohai valley all revealed a unimodal pattern, while that in the Damohe valley was opposite. There were limited regeneration seedlings in the stands due to farmland development, overgrazing, grass cutting, and insect damage in the wild fruit forest stands.

Key words: Malus sieversii, population, diameter class, tree height class, stand factors