我国南方4种常见人工林林下植物多样性特征及影响因素

Understory Plant Diversity Characteristics and Influencing Factors of Four Common Plantations in South China

摘要:

为了解长期植被恢复的成熟人工林林下植物组成与多样性特征及其影响因素，基于广东鹤山生态系统国家野外科学观测研究站的南亚热带人工林生态系统，对环境相似（坡度、坡向、海拔）、30 a生4种类型人工林（桉树混交林、马占相思纯林、乡土混交林、针叶混交林）进行调查研究，分析林下植物组成和物种多样性（Shannon-Wiener指数、Simpson指数、Pielou指数）特征。结果表明，人工林林下植物类型丰富，均可形成乔-灌-草垂直结构；4种林型林下植物组成既有相似性，也有差异性，桉树混交林与针叶混交林、马占相思纯林与乡土混交林的灌木层组成相似；桉树混交林与马占相思纯林、乡土混交林与针叶混交林的草本层组成相似，而桉树混交林与针叶混交林的草本层组成极不相似。林分类型影响林下植物多样性，马占相思纯林林下灌草多样性显著低于其他3种混交林（P<0.05），灌木物种数、个体数最少；针叶混交林林下物种丰富度最高。林分郁闭度与林下植物多样性呈正相关（P<0.001），林下植物分布与土壤养分含量相关，桉树混交林、马占相思纯林林下植物多样性与不同形态氮含量相关，有效磷、全磷影响乡土混交林林下物种的分布，针叶混交林受土壤酸碱度、全钾的影响较为明显。在4种人工林林下植物群落中，乡土混交林多样性，均匀度最高，优势度最低，具有更佳的保育和维持林下生物多样性功能。因此，乡土树种混交林更适用于生态公益林构建或对一些针叶林及外来树种纯林进行林分改造。

Abstract:

In order to understand understory plant composition and diversity characteristics and their influencing factors in mature plantations with long-term vegetation restoration, four types of plantations (30 years old) with similar environmental conditions (slope, direction and altitude) in the Heshan National Field Research Station of Forest Ecosystem were investigated, including mixed Eucalyptus plantation (EE), Acacia mangium plantation (AM), mixed native species plantation (NS), and mixed coniferous plantation (MC), the compositions and diversities (Shannon-Wiener index, Simpson index and Pielou index) of understory vegetation were analyzed. The results showed that the types of understory plants are abundant in the plantation with vertical structure of tree-shrub-herb layers. At the shrub layer, the community composition in EE was similar to MC, so did in AM and NS. At the herb layer, the community composition was similar between EE and AM, and between NS and MC, while the community composition was significantly different between EE and MC. Stand type affected understory plant diversity. The diversity of shrub and herb in AM plantation was significantly lower than that in other three mixed forests (P<0.05), and the number of shrub species and individuals in AM plantation were the lowest. The MC plantation had the highest understory species richness. There was a positive relationship between canopy coverage and understory diversity (P<0.001). The distribution of understory vegetation was related to contents of soil nutrients, contents of different forms of nitrogen were related to the understory vegetation in EE and AM. Available phosphorus and total phosphorus contents correlated to species distribution in NS, while species distribution in MC was related to pH and total potassium. The NS plantation had the highest diversity and evenness, also the lowest dominance, performed best in maintaining the understory diversity. Therefore, the mixed forest of native tree species was more suitable for the construction of ecological public welfare forest or the stand transformation of some coniferous forest and monocultural forest of exotic tree species.