不同生態系統在居主導地位的、與植物相關的菌根真菌(與幾乎所有陸地植物相關的根共生體)的類型上有所不同。
「外生菌根和杜鵑花類菌根」(EEM)真菌產生降解氮的酶,而「叢枝菌根」則不,於是便有了這樣的預測:EEM生態系統中的植物將會與分解者競爭土壤氮,因此增加土壤碳存儲。
本文作者通過綜合一個全球數據集發現,的確是這樣的:EEM生態系統中碳存儲量要比由「叢枝菌根」主導的生態系統中多70%,而且菌根類型要比土壤碳存儲水平的其他決定因素更為重要。(生物谷Bioon.com)
生物谷推薦的英文摘要:
Nature doi:10.1038/nature12901
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 combined1. Understanding the mechanisms controlling the accumulation and stability of soil carbon is critical to predicting the Earth’s future climate2, 3. Recent studies suggest that decomposition of soil organic matter is often limited by nitrogen availability to microbes4, 5, 6 and that plants, via their fungal symbionts, compete directly with free-living decomposers for nitrogen6, 7. Ectomycorrhizal and ericoid mycorrhizal (EEM) fungi produce nitrogen-degrading enzymes, allowing them greater access to organic nitrogen sources than arbuscular mycorrhizal (AM) fungi8, 9, 10. This leads to the theoretical prediction that soil carbon storage is greater in ecosystems dominated by EEM fungi than in those dominated by AM fungi11. 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.