人类活动引起的植物功能群的丧失对生态系统性质和功能的影响是生态学研究的重要问题之一。由于生态系统地上部分与地下部分紧密相关，植物功能群的丧失必然会影响地下群落的特性和功能。但是，植物功能群的丧失如何影响土壤微生物的群落结构和功能往往被忽视。因此，开展相关的研究对生态学理论和人工林经营管理都具有重要的意义。
中科院华南植物园恢复生态学研究团队博士生吴建平和刘占锋博士等在傅声雷研究员的指导下，以2年和24年的桉树人工林为研究对象，采用茎干环割和林下灌草去除的方法研究了植物功能群去除对土壤微生物群落结构及其分解功能的影响。结果表明：林下灌草去除显著降低土壤中真菌的生物量及真菌/细菌比值，但对细菌和微生物生物量总量影响不显著，这主要是土壤微环境的改变所致。同时，林下灌草去除引起的土壤微生物群落结构的改变显著减缓凋落物的分解；相反，茎干环割对土壤微生物的影响不明显，这主要是因为桉树的萌发特性或菌根真菌的相互作用造成的。
该研究表明，作为亚热带人工林的重要组成部分，林下灌草在维持土壤微生物群落结构和功能方面发挥着重要的作用，并且在幼年林和成熟林中扮演不同角色。本研究首次从地下碳输入的角度将乔木树种和林下植被在驱动土壤微生物群落结构与功能方面的相对贡献区分开，相关研究结果已经在生态学研究领域主流期刊Functional Ecology上在线发表。（生物谷Bioon.com）
生物谷推荐原文出处：
Functional Ecology DOI: 10.1111/j.1365-2435.2011.01845.x
Effects of understory removal and tree girdling on soil microbial community composition and litter decomposition in two Eucalyptus plantations in South China
Jianping Wu1,2,?, Zhanfeng Liu1,?, Xiaoling Wang1,2, Yuxin Sun2,3, Lixia Zhou1, Yongbiao Lin1, Shenglei Fu1,*
Keywords:Eucalyptus;forest management;girdling;phospholipid fatty acids;principal response curves;redundancy analysis;understory
Summary
1. Soil micro-organisms play important roles in ecosystems and respond quickly to environmental changes. We examined how understory removal and tree girdling influence the composition of soil microbial community and the litter decomposition in two subtropical plantations.
2. Phospholipid fatty acids (PLFAs) analysis was used to characterize soil microbial community. Redundancy analysis and principal response curves (PRC) were used to investigate the relationships between soil microbial community and environmental factors.
3. Understory removal significantly reduced the amount of fungal PLFAs, the ratio of fungal to bacterial PLFAs, and the litter decomposition but did not affect bacterial PLFAs and total PLFAs. In contrast, tree girdling did not affect the soil microbial characteristics. The changes in soil microbial community caused by understory removal were mainly attributed to the indirect effects such as increased soil temperature and soil NO3?-N availability. In addition, PRC analysis showed that the relative abundance of most PLFAs increased in response to understory removal in the 2-year-old plantation but decreased in the 24-year-old plantation.
4. We propose that understory plants are important components in subtropical forest ecosystems, and play different roles in maintaining soil microbial community and driving litter decomposition processes in young vs. old plantations. The functions of understory plants should be considered in forest management and restoration. The negligible effect of tree girdling on the soil micro-organisms can be attributed to the resprouting trait and mycorrhizal interactions of Eucalyptus.
