关键词: 祁连圆柏林, 植物群落, 青藏高原, 生态序列, 径级结构

Abstract: TThe Juniperus przewalskii forests are a unique forest community in China, widely distributed in the mountains on the northeastern edge of the Qinghai-Tibet Plateau. They play crucial roles in slope protection, soil conservation, water source preservation, and habitat improvement. A systematic study of their distribution, composition, and characteristics can provide a scientific basis for the healthy development and artificial management of Juniperus przewalskii forests, enabling them to better fulfill their ecological role in cold and arid areas. This study conducted a comprehensive survey of Juniperus przewalskii forests throughout the plant growth season from 2018 to 2022. A total of 52 survey sites were selected and 72 survey plots were established, covering the entire distribution area of Juniperus przewalskii forests. The 72 survey plots were analyzed using community ecological analysis methods such as cluster analysis and quantitative statistics. The main findings are as follows: Juniperus przewalskii forests are primarily distributed on sunny and semi-sunny mountain slopes at altitudes of 2800 to 3800 meters, usually inhabit dry, barren, and steep slopes, where the habitat conditions are relatively harsh. The existing forests are mostly climax communities of secondary successional, The forest stands are relatively sparse, with a canopy density of 0.2 to 0.6 and an average height ranging from 5 to 13 meters. The vertical structure consists of tree layer, shrubby layer, and herbaceous layer. The tree layer is dominated by Juniperus przewalskii, and the diameter class structure shows a right-skewed normal distribution, with the diameter at breast height mainly concentrated between 4 to 8 centimeters. The composition of the shrubby and herbaceous layers vary significantly depending on the specific habitat conditions. A total of 370 species of vascular plants have been recorded, distributed among 48 families and 151 genera. Among these, angiosperms comprise 45 families and 148 genera, gymnosperms consist of 2 families and 2 genera, and ferns are represented by 1 family and 1 genus. The top three dominant families are Asteraceae, Poaceae, and Fabaceae. In the composition of life types, there are obviously more herbaceous species than woody species. Based on the dominant and characteristic species of the community, Juniperus przewalskii forests can be further classified into 11 association groups and 25 associations. The spatial distribution exhibits a clear ecological sequence, arranged by altitude from low to high, the sequence includes the Juniperus przewalskii-Berberis diaphana-Herb Association Group, Juniperus przewalskii-Dasiphora fruticosa-Herb Association Group, Juniperus przewalskii-Dasiphora parvifolia-Herb Association Group, Juniperus przewalskii-Dasiphora glabra-Herb Association Group. In areas subjected to significant human disturbance, the community transitions into the Juniperus przewalskii-Herb Association Group.

Key words: Juniperus przewalskii forests, plant community, Qinghai-Tibet Plateau, ecological sequence, diameter class structure