Nature：菌根真菌是土壤碳存储的关键

波士顿学院的一项研究证实，“外生菌根和杜鹃花类菌根”(EEM)生态系统中的植物与分解者竞争土壤氮，因此增加土壤碳存储。相关文章发表于2014年1月8日的《Nature》杂志上。

不同生态系统在居主导地位的、与植物相关的菌根真菌(与几乎所有陆地植物相关的根共生体)的类型上有所不同。“外生菌根和杜鹃花类菌根”(EEM)真菌产生降解氮的酶，而“丛枝菌根”则不，于是便有了这样的预测：EEM生态系统中的植物将会与分解者竞争土壤氮，因此增加土壤碳存储。

本文作者通过综合一个全球数据集发现，的确是这样的：EEM生态系统中碳存储量要比由“丛枝菌根”主导的生态系统中多70%，而且菌根类型要比土壤碳存储水平的其他决定因素更为重要。

原文摘要：

Mycorrhiza-mediated competition between plants and decomposers drives soil carbon storage

Colin Averill, Benjamin L. Turner & Adrien C. Finzi

Soil contains more carbon than the atmosphere and vegetation combined. Understanding the mechanisms controlling the accumulation and stability of soil carbon is critical to predicting the Earth’s future climate. Recent studies suggest that decomposition of soil organic matter is often limited by nitrogen availability to microbes and that plants, via their fungal symbionts, compete directly with free-living decomposers for nitrogen. Ectomycorrhizal and ericoid mycorrhizal (EEM) fungi produce nitrogen-degrading enzymes, allowing them greater access to organic nitrogen sources than arbuscular mycorrhizal (AM) fungi. This leads to the theoretical prediction that soil carbon storage is greater in ecosystems dominated by EEM fungi than in those dominated by AM fungi. Using global data sets, we show that soil in ecosystems dominated by EEM-associated plants contains 70% more carbon per unit nitrogen than soil in ecosystems dominated by AM-associated plants. The effect of mycorrhizal type on soil carbon is independent of, and of far larger consequence than, the effects of net primary production, temperature, precipitation and soil clay content. Hence the effect of mycorrhizal type on soil carbon content holds at the global scale. This finding links the functional traits of mycorrhizal fungi to carbon storage at ecosystem-to-global scales, suggesting that plant–decomposer competition for nutrients exerts a fundamental control over the terrestrial carbon cycle.