祁连圆柏(Juniperus przewalskii)林广泛分布于青藏高原东北部山地, 是中国特有的森林植被类型, 是高山林线以及林草交错带的代表性群落, 发挥着不可替代的固土保水、生物多样性保护等生态屏障功能与作用。系统研究祁连圆柏林的空间分布、群落结构与物种组成及其特征, 可为当前祁连圆柏林保护、利用及其持续管理提供科学依据。该研究于2018-2022年在植物生长季对祁连圆柏林进行详细的样方调查, 设置样地53个, 并通过历史资料收集得到20个调查样地, 最终, 共获取完整调查样地资料73个, 基本遍及祁连圆柏林全部分布区。通过群落数量统计及聚类分析发现: (1)祁连圆柏林主要分布于海拔2 800-3 800 m的山地阳坡、半阳坡, 通常占据同地段生境条件相对严酷的干燥、瘠薄、陡峭的山坡, 现存林多为次生演替后的顶极群落, 林分相对稀疏, 郁闭度0.2-0.6, 平均高度5-13 m, 由乔木层、灌木层和草本层组成, 乔木层以祁连圆柏为绝对优势, 径级结构呈右偏正态分布, 胸径集中于4-8 cm, 灌木层和草本层随生境条件变化差异较大。(2)林内共记录到维管植物370种, 隶属于48科151属, 其中被子植物45科148属, 裸子植物2科2属, 蕨类植物1科1属, 前三大科分别为菊科、禾本科和豆科, 生活型组成中, 草本植物种类明显多于木本植物。(3)根据群落优势种和特征种, 祁连圆柏林可进一步划分出11个群丛组、25个群丛, 空间上表现出明显的生态序列, 海拔从低到高依次为祁连圆柏-鲜黄小檗(Berberis diaphana)-草本群丛组、祁连圆柏-金露梅(Dasiphora fruticosa)-草本群丛组、祁连圆柏-小叶金露梅(Dasiphora parvifolia)-草本群丛组、祁连圆柏-银露梅(Dasiphora glabra)-草本群丛组, 在人为扰动严重的区域, 群落中灌木层发育较差, 逐渐向祁连圆柏-草本群丛组发展。

The Juniperus przewalskii forests is a unique vegetation type that only appear in China. They are widely distributed in the mountains of the northeastern edge of the Qingzang Plateau, which became a representative community of the alpine timberline and the forest-grass ecotone. Such forests play crucial roles in slope protection, soil conservation, water source preservation, and habitat improvement. A systematic study on their distribution, composition, and characteristics can provide a scientific basis for the current protection, utilization, and sustainable management of J. przewalskii forests. We conducted a comprehensive survey of J. przewalskii forests throughout the growing seasons from 2018 to 2022. We set up 53 new survey plots and compiled data from 20 historical survey plots; the results covered the entire distribution area of J. przewalskii forests. Through community quantitative statistics and cluster analysis, the main results are as follows. (1) J. przewalskii forests are primarily distributed on sunny and semi-sunny mountain slopes from 2 800 to 3 800 m. They usually occupy harsh environment that is dry, barren, and steep slopes. The existing forests are mostly climax communities after secondary successions. Such forest stands are relatively sparse, with a canopy coverage of 0.2 to 0.6 and an average height from 5 to 13 m. The vertical structure consists of the tree layer, shrub layer, and herb layer. The tree layer is dominated by J. przewalskii, and the diameter class structure shows a right-skewed normal distribution, with the diameter at breast height mainly distributed in the 4-8 cm range. The shrub layer and herb layer vary greatly with changes in habitat conditions. (2) A total of 370 species of vascular plants have been recorded, which belong to 48 families and 151 genera. Among them, there are 45 families, 148 genera of angiosperms, 2 families and 2 genera of gymnosperms, and 1 family and 1 genus of pteridophytes. The top three dominant families are Asteraceae, Poaceae, and Fabaceae. There are obviously more herbaceous species than woody species in terms of the composition of vegetation forms. (3) Juniperus przewalskii forests can be further classified into 11 association groups and 25 associations based on the dominant and characteristic species of the community. The spatial distribution exhibits a clear ecological sequence, including (from low to high altitude) J. przewalskii - Berberis diaphana - Herb Association Group, J. przewalskii - Dasiphora fruticosa - Herb Association Group, J. przewalskii - Dasiphora parvifolia - Herb Association Group, and J. przewalskii - Dasiphora glabra - Herb Association Group. In areas with significant human disturbance, the shrub layer in the community is poorly developed and gradually develops into Juniperus przewalskii - Herb Association group.