喀斯特常绿落叶阔叶混交林植物与土壤地形因子的耦合关系

基于中国科学院亚热带农业生态研究所在木论国家级自然保护区借鉴CTFS标准建立的2hm2喀斯特常绿落叶阔叶混交林动态监测样地(50个20m×20m样方),选取代表木本植物群落、土壤性质和地形因子的22个指标,对其总体特征及三者之间的相互关系进行了经典统计分析、主成分分析、聚类分析与典型相关分析。结果表明,喀斯特常绿落叶阔叶混交林生态系统的景观异质性强、土壤养分含量高、物种丰富且结构合理,除海拔、Simpson指数、均匀度、pH之外的18个指标均呈中、强变异;综合土壤因子是影响生态系统的主要因子群,其次是综合群落多样性因子和结构性因子,综合地形因子的作用相对较弱;4种不同类型真实而直观地表征了群落类型、土壤肥力和地形的差异,相对优化的第3种类型主要分布在海拔较高、裸石率较大、坡度较高的阴坡中上部;植被、土壤、地形两两之间均存在着较高的相关性,植被与土壤因子之间,有机质、氮、磷起较大的作用,主要影响群落结构,植被和地形之间,坡向和岩石裸露率影响群落结构和物种丰富度,而坡向和坡位直接导致了土壤有机质、全氮、有效磷和pH的变化。

The coupling relationships between vegetation, soil, and topography factors in karst mixed evergreen and deciduous broadleaf forest

A monitoring sample site with 2 hm2 of karst mixed evergreen and deciduous broadleaf forest in Mulun National Nature Reserve was established according to the standard of CTFS (i.e., the Center of Tropical Forest Sciences) by the Institute of Subtropical Agriculture. 22 indexes covering plant community, soil property, and topography were chosen to study the relationships between the three factors through the analysis of traditional statistics, principal component analysis (PCA), cluster analysis and canonical correlation analysis (CCA). The results indicated that the Mulun karst forest had high landscape heterogeneity, high content of soil nutrients, abundant woody species, and rational community structure. Variations were observed based on the indexes except elevation, Simpson index, evenness, and pH. Soil indexes were the primary factor to the ecosystem, plant community diversity and structure indexes were the second, topographical indexes were the last. Based on the differences from the community types, soil fertility and topography, the forest was divided into four groups through the cluster analysis. The third group with best optimized characteristics was mostly distributed in the middle and upper part of shady slope with larger percentage of exposed rock, larger slope degree and greater elevation. High correlation existed between vegetation, soil and topography. Between vegetation and soil factors, organic matter, nitrogen and phosphorus primarily affected plant community structure. Between vegetation and topography factors, slope direction and percentage of exposed rock were the major factors affected plant community structure and diversity. Between soil and topography factors, slope direction and position directly resulted in the variance of soil organic matter, total nitrogen, available phosphorus, and pH.