南方红壤丘陵区3种森林群落内主要草本植物种群生态位特征

生态位是解释自然群落中种间共存与竞争机制的基本理论,对了解植物群落构建及其与环境因子的耦合关系具有重要意义。本研究以南方红壤丘陵区3种森林群落内主要草本植物为研究对象,在群落调查的基础上,运用Levins生态位宽度、Pianka生态位重叠指数和生态位相似性公式,分析了针叶林、阔叶林和针阔混交林下主要草本物种的生态位宽度以及物种间的生态位重叠与生态位相似性,并从生态位角度探讨了不同森林群落内草本种群的生长状况。结果表明,3种森林群落内草本种群的生态位宽度平均值从大到小依次为针叶林(0.572)>针阔混交林(0.508)>阔叶林(0.424),且针叶林中崖爬藤(Tetrastigma formosanum)、淡竹叶(Lophatherum gracile)、鳞毛蕨(Dryopteris sp.)以及六月雪(Serissa japonica)等草本植物的生态位宽度均大于针阔混交林和阔叶林的;生态位重叠度与生态位宽度之间不是绝对的正相关关系,生态位宽度小的物种与其他种群也可能发生较大的生态位重叠,甚至出现完全重叠的现象;针叶林和阔叶林内主要草本植物的生态位宽度与其重要值呈显著正相关(P<0.01),相关系数分别为0.758和0.918;3种森林群落内草本种群的生态位宽度与其重要值变异系数均呈显著负相关(P<0.01),相关系数分别为-0.996、-0.967和-0.963。在现阶段植被演替过程中,针叶林和针阔混交林下草本种群的重叠程度较高,环境资源存在着高度的空间异质性,群落结构仍处于不稳定状态。

Niche characteristics of herb populations within three forest types in hilly red soil region of southern China

The niche theory has been successfully used to explain competition mechanisms among the coexisting species in natural communities, which is significant for understanding of the coupling between plant community construction and environmental factors. The niche characteristics of herb populations were examined within coniferous forest(CF), broad-leaved forest(BF) and mixed broadleaf conifer forest(MF) in hilly red soil region of southern China, using Levins niche breadth, Pianka index of niche overlap and niche similarity formula, from the perspective of the growth status in different forest communities in herbage species. Results showed, the mean niche breadth of all herbage species in the studied forest communities was in order CF(0.572)>MF(0.508)>BF(0.424). The niche breadth of Tetrastigma formosanum, Lophatherum gracile, Dryopteris sp., Serissa japonica and other herbaceous plants in CF were higher than that in MF and BF. The niche overlap did not always correlate to niche breadth. Larger niche overlap or even completely overlapping might occurr between the species with narrow niche breadth. There was a significant positive correlation between the niche breadth and the important value of the main herbaceous plants in CF and BF(P<0.01),with the correlation coefficients of 0.758 and 0.918, respectively. There was a significant negative correlation between the niche breadth and the important value of the coefficient of variation of herbage species in three forest communities(P<0.01), with the correlation coefficients of -0.996, -0.967 and -0.963, respectively. Our study suggested the CF and MF were still in an instability state at present stage of community succession due to high niche overlap among herb populations and high spatial heterogeneity of environmental resources in study region.