Anthropogenic N deposition alters soil organic matter biochemistry and microbial communities on decaying fine roots
Anthropogenic N deposition alters soil organic matter biochemistry and microbial communities on decaying fine roots
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DOI：
10.1111/gcb.14770
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发表时间：
2019-08-14
影响因子：
11.6
通讯作者：
Grandy, A. Stuart
中科院分区：
文献类型：
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作者：
Argiroff, William A.;Zak, Donald R.;Grandy, A. Stuart
细根凋落物是土壤有机质（SOM）的主要来源，土壤有机质是全球重要的碳库，对气候变化具有响应作用。我们之前建立了类似于20年的氮(N)沉积实验，减缓了细根腐烂，增加了广泛的北方阔叶林生态系统中土壤碳的储存（C; +18%）。然而，直接减缓细根腐烂的微生物机制尚不清楚。本研究表明，实验N沉降降低了Agaricales真菌的相对丰度（-31%），增加了部分木质素分解放线菌在腐烂细根上的相对丰度（+24%）。此外，实验N沉降增加了SOM中木质素衍生化合物的相对丰度（+53%），这种生化反应与真菌和细菌群落组成的变化显著相关。具体而言，SOM中木质素衍生化合物的积累与木质素分解菌和Kuehneromyces真菌的相对丰度呈负相关，与microbacteraceae呈正相关。我们的研究结果表明，通过改变腐烂细根上微生物群落的组成，使其降解木质素的能力降低，实验N沉降减缓了细根凋落物的腐烂，增加了细根中木质素衍生化合物对SOM的贡献。我们观察到的微生物反应可能解释了人类氮沉降增加陆地生态系统土壤碳储量的广泛发现。更广泛地说，我们的发现直接将土壤微生物群落的组成与功能联系起来，并暗示了具有全球意义的生物地球化学过程的组成变化。
Fine root litter is a primary source of soil organic matter (SOM), which is a globally important pool of C that is responsive to climate change. We previously established that similar to 20 years of experimental nitrogen (N) deposition has slowed fine root decay and increased the storage of soil carbon (C; +18%) across a widespread northern hardwood forest ecosystem. However, the microbial mechanisms that have directly slowed fine root decay are unknown. Here, we show that experimental N deposition has decreased the relative abundance of Agaricales fungi (-31%) and increased that of partially ligninolytic Actinobacteria (+24%) on decaying fine roots. Moreover, experimental N deposition has increased the relative abundance of lignin-derived compounds residing in SOM (+53%), and this biochemical response is significantly related to shifts in both fungal and bacterial community composition. Specifically, the accumulation of lignin-derived compounds in SOM is negatively related to the relative abundance of ligninolytic Mycena and Kuehneromyces fungi, and positively related to Microbacteriaceae. Our findings suggest that by altering the composition of microbial communities on decaying fine roots such that their capacity for lignin degradation is reduced, experimental N deposition has slowed fine root litter decay, and increased the contribution of lignin-derived compounds from fine roots to SOM. The microbial responses we observed may explain widespread findings that anthropogenic N deposition increases soil C storage in terrestrial ecosystems. More broadly, our findings directly link composition to function in soil microbial communities, and implicate compositional shifts in mediating biogeochemical processes of global significance.