Non-spatial structural characteristics and quality evaluation of Malus sieversii stands in the Tacheng region of Xinjiang

To clarify the population structural characteristics and health quality of Malus sieversii forests in Tacheng region, Xinjiang, 26 sample plots were set up within M. sieversii forests in Emin and Toli counties.Non-spatial structure of the forests were measured ,and the stand quality was comprehensively evaluatrd using membership functions and principal component analysis. The assessment results were validated through viability grading. The results indicated: M.sieversii forests in Tacheng area were pure consists of stands, with densities ranging from 420.83 to 795.00 trees per hectare and canopy closure between 0.54 and 0.80; the average tree height, diameter at breast height (D_BH), and crowns widths were 6.85 m, 19.27 cm, and 5.05 m respectively. The conservation management of the stand did not significantly change the non-spatial structure, only the average tree height of M.sieversii increased significantly in Emin Conservation forests. The age-class structure was dominated by the middle-aged (III-V) group, with fewer young (I-II), old (VI-VIII), and extra-large (greater than VIII) groups, which exhibited a declining pattern. The weighted composite index for the health evaluation of M.sieversii forests in Tacheng region ranged from 0.13 to 0.15 (extremely poor), while the weighted sum method index ranged from 0.80 to 0.83 (excellent), indicating moderately healthy; within the vitality verification stand groups, the grade 1～2 healthy plants accounted for 55.58%～68.68%, while the grade 5 dead wood constituted 6.98%～15.35%, and the population exhibited a risk of decline. In summary the M.sieversii forests of the Tacheng area currently exhibite moderate levels of health, and require urgent conservation measures.