Osler Graham H R, Sommerkorn Martin
The Macaulay Institute, Craigiebuckler, Aberdeen AB15 8QH, United Kingdom.
Ecology. 2007 Jul;88(7):1611-21. doi: 10.1890/06-1357.1.
Increasing pressures on ecosystems through global climate and other land-use changes require predictive models of their consequences for vital processes such as soil carbon and nitrogen cycling. These environmental changes will undoubtedly affect soil fauna. There is sufficient evidence that soil fauna have significant effects on all of the pools and fluxes in these cycles, and soil fauna mineralize more N than microbes in some habitats. It is therefore essential that their role in the C and N cycle be understood. Here we introduce a new framework that attempts to reconcile our current understanding of the role of soil fauna within the C and N cycle with biogeochemical models and soil food web models. Using a simple stoichiometric approach to integrate our understanding of N mineralization and immobilization with the C:N ratio of substrates and faunal life history characteristics, as used in food web studies, we consider two mechanisms through which soil fauna can directly affect N cycling. First, fauna that are efficient assimilators of C and that have prey with similar C:N ratios as themselves, are likely to contribute directly to the mineral N pool. Second, fauna that are inefficient assimilators of C and that have prey with higher C:N ratios than themselves are likely to contribute most to the dissolved organic matter (DOM) pool. Different groups of fauna are likely to contribute to these two pathways. Protists and bacteria-feeding nematodes are more likely to be important for N mineralization through grazing on microbial biomass, while the effects of enchytraeids and fungal-feeding microarthropods are most likely to be important for DOM production. The model is consistent with experimental evidence and, despite its simplicity, provides a new framework in which the effects of soil fauna on pools and fluxes can be understood. Further, the model highlights our gaps in knowledge, not only for effects of soil fauna on processes, but also for understanding of the soil C and N cycle in general.
全球气候和其他土地利用变化对生态系统造成的压力不断增加，这就需要建立预测模型，来评估这些变化对土壤碳氮循环等关键过程的影响。这些环境变化无疑会影响土壤动物群落。有充分证据表明，土壤动物群落对这些循环中的所有库和通量都有显著影响，并且在某些生境中，土壤动物群落使氮矿化的能力比微生物更强。因此，了解它们在碳氮循环中的作用至关重要。在此，我们引入一个新框架，试图将我们目前对土壤动物群落在碳氮循环中作用的理解与生物地球化学模型和土壤食物网模型协调起来。我们采用一种简单的化学计量方法，将我们对氮矿化和固定的理解与底物的碳氮比以及动物的生活史特征相结合，就像在食物网研究中那样，我们考虑了土壤动物群落直接影响氮循环的两种机制。首先，那些对碳有高效同化能力且猎物的碳氮比与其自身相似的动物，可能会直接对矿质氮库做出贡献。其次，那些对碳同化能力低且猎物的碳氮比高于自身的动物，可能对溶解有机物（DOM）库的贡献最大。不同类群的动物可能对这两条途径都有贡献。原生生物和以细菌为食的线虫通过捕食微生物生物量对氮矿化可能更为重要，而蚯蚓和以真菌为食的微型节肢动物的作用对溶解有机物的产生可能最为重要。该模型与实验证据一致，尽管其简单，但提供了一个新框架，在这个框架中可以理解土壤动物群落对库和通量的影响。此外，该模型凸显了我们在知识上的差距，不仅是关于土壤动物群落对过程的影响，还包括对土壤碳氮循环总体的理解。
