川西亚高山针叶林土壤动物群落对模拟林下植物丧失的响应

受研究手段的限制,有关森林物种组成对土壤动物群落影响的研究少有报道。采用人工除灌和除草的林地控制实验方法,研究了亚高山人工林灌草层关键物种丧失对土壤动物群落结构的影响。结果表明:(1)灌木层去除后土壤动物密度极显著低于对照(P0.01);线虫纲(Nematoda)优势度持续增加,处理15个月时极显著高于对照(P0.01);土壤动物群落多样性指数极显著低于对照(P0.01);腐食性功能团类群数及个体数百分比有所下降。(2)草本层去除后土壤动物密度显著低于对照(P0.05);线虫纲优势度持续增加,处理15个月时显著高于对照(P0.05);土壤动物群落多样性指数极显著低于对照(P0.01);腐食性功能团类群数略低于对照,个体数百分比无显著差异。综上所述,林下灌草层去除,尤其是灌木层去除,导致土壤动物群落个体数量、多样性指数降低,优势类群格局、腐食性功能团构成发生变化,从而在一定程度上影响到森林生态系统的物质循环功能。

Response of soil faunal community to simulated understory plant loss in the subalpine coniferous plantation of western Sichuan

Although numerous studies have been given to the effects of species composition and biodiversity on soil faunal communities in different ecosystems worldwide, far less information has been available on the relations between soil fauna diversity and plant species diversity in the forest ecosystem due to the limited technique. In order to understand the linkages of forest plant diversity with soil animal diversity, from July 2007 to October 2008, an experiment with herb and shrub layer removals was therefore conducted in the subalpine forest ecosystem of western Sichuan, which is sensitive to biotic and abiotic environment changes. After three months with the experiment of shrub and herb removals beneath the control plots, soil fauna density, group and diversity began to decrease significantly (P <0. 01), and the dominant groups were also changed. Moreover, the effect of plant removal experiment enhanced with the prolonged experiment. The removals of understory plant species made the numbers of Diplopoda, Acarina, Collembola and larvae of Diptera decrease more significantly. The effect of shrub removal on the structure of soil animal community is more significant than that of herb removal. Regardless of the treatments, the dominant groups were Nematoda, Acarina, and Collembola in the study forests. However, the removals of both herb and shrub layers significantly (RS:sig. =0. 002 <0. 01; RH:sig. =0. 039 <0. 05) increased the ratio of Nematoda in the dominant groups and density in the study plots. The ratios of the number of Nematoda to dominant groups changed from 39. 5% to 60. 58% after 15 months with herb layer removal in the study plot, and theshrub layer removal made that ratio account for 78. 91% of the dominant groups. Correspondingly, the removal of understory plant altered the value of A/C, because of the changes of dominance of Acarina and Collembola. Similarly, the removals of herb and shrub with 15 months significantly (RS: sig. =0. 025 <0. 05; RH:sig. =0. 014 <0. 05) decreased the indices of DG in soil animal community. Meanwhile, the herb and shrub removal experiments also altered the composition of soil animal guilds, and both the percentages of Saprozoic guilds and their individual number were decreased after shrub removals with 15 months. The results indicated that the removals of both shrub and herb layers altered the composition of soil animal community and decreased the soil animal biodiversity in the study plots, implying that plant species loss could lead to the loss of belowground biodiversity in the subalpine forest ecosystem. In addition, the present study also implied the plant species removal experiment was a useful method to investigate the interactions between above-and below-ground biodiversity, and the linkages of biodiversity with ecological process in the high-frigid forest ecosystem, owing to the sensitivity of soil biodiversity response to changed biotic environment in the fragile forest ecosystem. However, this study only provided a valuable the results of short-term herb and shrub layer removal experiment, and long-term and systematic experiment needed to carry out in the future.