八大公山亚热带森林木质残体中大型无脊椎动物群落特征

木质残体可为大型无脊椎动物提供重要栖息地、食物等资源, 并影响其生物多样性。目前针对不同树种、径级及分解阶段的木质残体如何调控土壤大型无脊椎动物群落结构尚不清楚, 相关研究在亚热带森林地区尤为稀缺。为此, 本文选取湖南省八大公山国家级自然保护区柳杉(Cryptomeria fortunei)、亮叶水青冈(Fagus lucida)及檫木(Sassafras tzumu) 3种树种为研究对象, 每种树种分别选取两类径级(直径分别为10 ± 2 cm、4 ± 2 cm)不同分解阶段的木质残体, 对其中的大型无脊椎动物进行调查。调查于2020年10-11月完成。结果显示: 共捕获大型无脊椎动物2,558只, 隶属4门10纲23目, 不同树种的优势类群、常见类群及稀有类群均存在差异。亮叶水青冈木质残体中大型无脊椎动物个体密度显著高于柳杉和檫木。亮叶水青冈和檫木大径级木质残体中大型无脊椎动物Shannon-Wiener多样性指数显著高于小径级, 3个树种大径级木质残体中大型无脊椎动物的类群数、特有类群数均大于小径级。木质残体中大型无脊椎动物的Shannon-Wiener多样性指数、Simpson优势度指数及Pielou均匀度指数与木材密度显著负相关, 表明随着分解的进行木质残体中大型无脊椎动物群落呈明显变化趋势。木质残体的理化性质(相对含水率、全氮、全碳及碳氮比)和土壤温度、湿度与木质残体中大型无脊椎动物群落特征具有相关性。研究初步表明, 大型无脊椎动物群落特征在所选树种、径级及分解阶段木质残体中具有差异, 在亚热带森林中同时保留不同树种、不同大小径级的木质残体或有利于增加大型无脊椎动物多样性。

Community characteristics of macroinvertebrates in woody debris in a subtropical forest in Badagongshan,China

Aims: Woody debris provides essential habitat and food resources for macroinvertebrate communities and greatly impacts soil macrofauna biodiversity. Little is known about how features of woody debris are associated with soil macroinvertebrate communities, especially for subtropical forests. This study aims to investigate the effects of tree species, diameter classes, and decomposition stages of woody debris on the composition and structure of macroinvertebrate communities.Methods: We sampled the woody debris of three tree species (Sassafras tzumu, Fagus lucida, and Cryptomeria fortunei), crossed with two size classes (10 ± 2 cm and 4 ± 2 cm in diameter) at different decomposition stages in the subtropical forests of the Badagongshan National Nature Reserve, Hunan, China, from October to November 2020. Then, macroinvertebrates in the sampled woody debris (i.e., taxonomical groups and number of individual) were inventoried for community composition.Results: (1) A total number of 2,558 individuals belonging to 4 phyla, 10 classes, and 23 orders were found throughout the study. The dominant groups, common groups, and rare groups of macroinvertebrates differed in preferred tree species. (2) The individual density of macroinvertebrates in the woody debris of Fagus lucida was significantly higher than that in Cryptomeria fortunei and Sassafras tzumu. For Fagus lucida and Sassafras tzumu, the Shannon-Wiener diversity index of macroinvertebrates was significantly higher in large-diameter woody debris than that in small-diameter debris. The number of total groups and specialist groups of invertebrates in large-diameter wood debris were more than those in small-diameter woody debris. The Shannon-Wiener diversity index, Simpson dominance index, and Pielou evenness index of macroinvertebrates in woody debris were significantly and negatively correlated with wood density, indicating shifted macroinvertebrates communities in woody debris with the progress of decomposition. (3) The physical and chemical properties of woody debris (e.g., relative moisture content, total nitrogen, total carbon, and carbon nitrogen ratio), soil temperature and soil humidity were significantly correlated with the characteristics of macroinvertebrate communities in woody debris. Conclusion: Our results highlight that the characteristics of macroinvertebrate community are different depending on the effect of tree species, diameter classes, and decomposition stages of woody debris. Preserving woody debris of both large and small diameter classes and those of different tree species in the subtropical forest can increase the biodiversity of macroinvertebrates.