川西北窄叶鲜卑花灌丛的类型和生物量及其与环境因子的关系

THE COMMUNITY TYPES AND BIOMASS OF SIBIRAEA ANGUSTATA SCRUB AND THEIR RELATIONSHIP WITH ENVIRONMENTAL FACTORS IN NORTHWESTERN SICHUAN 

窄叶鲜卑花（Ｓｉｂｉｒａｅａａｎｇｕｓｔａｔａ（Ｒｅｈｄ．）Ｈａｎｄ．Ｍａｚ．）灌丛是青藏高原东缘高山灌丛中特有的、具代表性的类型。选择该群落的典型分布区域，运用数值分类法，将窄叶鲜卑花群系分为４个群丛组、１０个群丛类型。用ＰＣＡ排序技术定量分析了各类型在空间地理上的分布格局，以及与环境因子之间的关系。结果表明：各类型的分布主要取决于环境中土壤条件（主要是土壤水分和土壤有机质含量）和热量条件的垂直梯度变化，而群落的分类等级越低，对环境因子的变化越敏感。生物量的研究表明，窄叶鲜卑花灌丛的群落生物量在３８．９９～４７．７２ｔ·ｈｍ－２之间，其中灌木层和草本层的生物量分别在２５．８７～３２．１６ｔ·ｈｍ－２和１２．０５～１３．７３ｔ·ｈｍ－２之间，而地下部分的生物量通常高于地上部分。

Sibiraea angustata (Rehd.) Hand. Mazz. scrub is a kind of typical and representative community on the eastern Qinghai Tibetan Plateau, and is distributed on the subalpine and alpine belts in northwestern Sichuan with the latitude between 31° and 34°. 47 quadrats were surveyed in the representative distribution area of Sibiraea angustata scrub in order to probe into its types, characteristics, relationship with environmental factors and biomass structure. Combined with the quantitative classification, the result showed that Sibiraea angustata formation in the northwestern Sichuan could be divided into 4 association groups and 10 association types. Furthermore, the analysis of PCA (principal component analysis) ordination determined that the distribution of the plant communities was closely related to the moisture and organic matter content in the soil and the vertical change of heat. Meanwhile, the lowest classification unit of the community association was most susceptible to the variation of environmental factors. The research of biomass expressed that the total biomass of the Sibiraea angustata community fluctuated between 38.99 t·hm -2 and 47.72 t·hm -2 , among which the biomass of the shrub layer and herb layer were 25.87～32.16 t·hm -2 and 12.05 ～13.73 t·hm -2 respectively. Generally speaking, it could be concluded that on the high altitude area the biomass of the aboveground was more than that of the underground, such as the underground biomass of Sibiraea angustata community was 19.04%～42.72% more than that of the aboveground.