Bottom–up or top–down control in forest soil microcosms? Effects of soil fauna on fungal biomass and C/N mineralisation
Bottom–up or top–down control in forest soil microcosms? Effects of soil fauna on fungal biomass and C/N mineralisation
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DOI：
10.1007/s00374-006-0103-8
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发表时间：
2006-04
影响因子：
6.5
通讯作者：
L. Lenoir;T. Persson;Janne Bengtsson;H. Wallander;A. Wirén
中科院分区：
文献类型：
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作者：
L. Lenoir;T. Persson;Janne Bengtsson;H. Wallander;A. Wirén
土壤生态学中的一个主要问题是土壤食物网是由资源还是由捕食者调节的，即自下而上（供体）或自上而下控制。我们测试的假设，中型和大型土壤捕食者可以调节食真菌动物种群，从而导致自上而下的级联效应，真菌生物量和分解/矿化过程中的北方森林土壤。这项研究是作为一个缩影实验，两个对比的土壤（腐殖质层），一个穷人和一个丰富的N，并与不同的组合的食真菌和捕食性土壤动物添加到“defaunated”土壤。与缺乏中型动物（但有线虫和原生动物）的对照缩影相比，多样化弹尾目和甲螨目食菌群落的存在显着减少了FDA活性真菌生物量，或倾向于减少真菌生物量中的麦角固醇部分贫氮腐质，但在富氮腐质中没有检测到明显的影响。食真菌动物以及食真菌动物加捕食者（捕食者社区组成的革螨，蜘蛛和甲虫或其子集）减少C矿化和增加净N矿化在这两种土壤中。捕食者（特别是革螨）的存在减少了弹尾虫的数量，减轻了在氮素缺乏的土壤中真菌生物量的食真菌动物的负面影响。在富含N的土壤中，捕食者的存在增加了真菌生物量（麦角固醇）的“defaunated”土壤。因此，一个自上而下的营养级联可以检测到氮贫腐殖质，但不是在富氮腐殖质。我们的研究结果表明，在土壤动物群落的自上而下的控制程度取决于资源质量和土壤肥力。
A major question in soil ecology is whether soil food webs are regulated by resources or by predators, i.e. bottom–up (donor) or top–down controlled. We tested the hypothesis that meso- and macrofaunal soil predators can regulate fungivore populations and, thereby cause a top–down cascade effect on fungal biomass and decomposition/mineralisation processes in boreal forest soils. The study was performed as a microcosm experiment with two contrasting soils (humus layers), one poor and one rich in N, and with different combinations of fungivore and predator soil fauna added to “defaunated” soil. In comparison with control microcosms lacking mesofauna (but with nematodes and protozoans), the presence of a diverse Collembola and Oribatida fungivore community significantly reduced the FDA-active fungal biomass or tended to reduce the ergosterol fraction of the fungal biomass in the N-poor humus, but no clear effect could be detected in the N-rich humus. Fungivores as well as fungivores plus predators (a predator community consisting of gamasids, spiders and beetles or a subset thereof) reduced C mineralisation and increased net N mineralisation in both soils. The presence of predators (particularly gamasid mites) reduced collembolan numbers and alleviated the negative effect of fungivores on fungal biomass in the N-poor soil. In the N-rich soil, the presence of predators increased fungal biomass (ergosterol) in relation to the “defaunated” soil. Therefore, a top–down trophic cascade could be detected in the N-poor humus but not in the N-rich humus. Our results suggest that the degree of top–down control in soil fauna communities depends on resource quality and soil fertility.