大渡河中游干暖河谷区生境对植物群落分布格局和多样性的影响

大渡河中游干暖河谷区滑坡和泥石流灾害频发, 对该区域坡面植物群落的研究有助于揭示植被演替的方向, 为坡面植被生态恢复提供基本依据。本研究沿大渡河中游河谷区每隔约5 km设置典型样地, 调查了植被的物种组成和分布以及样地的地形、土壤等10个生境因子, 探讨河谷区植被的连续性变化, 并通过多元回归树(multivariate regression trees, MRT)、多样性指数和典范对应分析(canonical correspondence analysis, CCA)等方法对植物群落进行分类、比较和排序。结果表明: 大渡河中游干暖河谷植被以土壤碳含量、pH值和C : N等3个因子为节点, 可划分为多花胡枝子(Lespedeza floribunda)-荩草(Arthraxon hispidus)-香薷(Elsholtzia ciliate)(群落A)、地果(Ficus tikoua)-车桑子(Dodonaea viscosa)-川滇薹草(Carex schneideri)(群落B)、云南松(Pinus yunnanensis)-栓皮栎(Quercus variabilis)(群落C)和荩草-扭黄茅(Heteropogon contortus)(群落D)等4种群落。该区域以灌木和草本为主要植被类型(群落A、B、C), 间或有裸地分布, 易成为泥石流灾害产生的物源区; 以多花胡枝子为主的灌草群落A的物种丰富度、优势度与多样性表现一致, 均高于以乔木和草本为主的群落C和D, 但物种多样性优势并不显著, 灌草群落分布广而结构单一, 外来物种占比为8.33%, 是生态系统脆弱和不稳定的表现。多元回归树和典范对应分析结果表明, pH值、C : N、坡向和土壤容重等4个因子对植物群落组成和分布影响最大, 且土壤因子的影响大于地形因子。

Influence of habitat on the distribution pattern and diversity of plant community in dry and warm valleys of the middle reaches of the Dadu River,China

In the dry and warm valleys of the middle reaches of the Dadu River, landslides and debris flows occur frequently. Studying vegetation on these slopes is valuable in understanding vegetation succession in regards to ecological restoration of highly disturbed landscapes. In this study, plots were selected along the Dadu River every 5 km to investigate species composition, distribution, topography, soil characteristics, and vegetation change in the middle reaches of the Dadu River valley. Plant communities were classified, compared and sorted using multiple regression tree (MRT), alpha diversity index and canonical correspondence analysis (CCA). The results showed that the landscape were divided into four communities based on three factors: soil carbon, pH and C : N, i.e. Lespedeza floribunda-Arthraxon hispidus-Elsholtzia ciliate, Ficus tikoua-Dodonaea viscosa-Carex schneideri, Pinus yunnanensis-Quercus variabilis and Arthraxon hispidus-Heteropogon contortus. Shrub and grass dominate this area, with occasional areas of bare ground which is liable to debris flow disasters. The species richness, dominance and diversity of shrub-grass (Lespedeza floribunda) community are consistently higher than arbor and grass communities, although species diversity values are not significant. The shrub and grass community is widely distributed, although fragile and unstable as alien species reached 8.33% within these communities. MRT and CCA analysis showed that pH, C : N, slope direction and soil bulk density are the main factors influencing vegetation distribution pattern as soil influences are more important than topography.