Microbial decomposition of soil organic matter is mediated by quality and quantity of crop residues: mechanisms and thresholds
Microbial decomposition of soil organic matter is mediated by quality and quantity of crop residues: mechanisms and thresholds
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DOI：
10.1007/s00374-016-1174-9
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发表时间：
2017-01
影响因子：
6.5
通讯作者：
M. Shahbaz;Y. Kuzyakov;M. Sanaullah;F. Heitkamp;V. Zelenev;Amit Kumar;E. Blagodatskaya
中科院分区：
文献类型：
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作者：
M. Shahbaz;Y. Kuzyakov;M. Sanaullah;F. Heitkamp;V. Zelenev;Amit Kumar;E. Blagodatskaya
农作物残留物的质量和数量对土壤有机质（SOM）分解具有相反的影响，但解释这种启动效应（PE）的机制仍然难以捉摸。为了揭示残留物质量和数量在 SOM 引发中的作用，我们将两种比例（5.4–10.8 g kg−1）的 13 C 标记小麦残留物（分别：叶、茎、根）施用于土壤并培养 120 天。为了区分PE机制，在CO2流出和微生物生物量中追踪标记的C，并在培养期间测量酶活性（涉及C、N和P循环）。无论残渣类型如何，PE 强度都会随着 C 添加量的增加而下降。根的矿化程度最低，但与叶或茎相比，PE 值高出 60%。在强化残渣矿化期间（前 2-3 周），低 PE 或负 PE 是由池替代造成的。此后（15-60 天），微生物生物量大幅下降，酶活性增加，表明微生物坏死物可作为 SOM 引物。最后，将 SOM 衍生的 C 掺入剩余的微生物生物质中对应于酶活性的增加，这表明 SOM 共代谢。 PE 和酶活性主要与代谢残留物的土壤微生物相关。统一模型表明，PE 是残渣矿化的函数，PE 强烈增加的阈值是根矿化度高达 20%、茎矿化度为 44%、叶矿化度为 51%。因此，根矿化对于 PE 的强劲增加具有最低的阈值。我们的研究强调了以残渣为食的微生物作为 PE 中活跃参与者的作用，这是由作物残渣添加的质量和数量介导的。
Crop residue quality and quantity have contrasting effects on soil organic matter (SOM) decomposition, but the mechanisms explaining such priming effect (PE) are still elusive. To reveal the role of residue quality and quantity in SOM priming, we applied two rates (5.4–10.8 g kg−1) of13C-labeled wheat residues (separately: leaves, stems, roots) to soil and incubated for 120 days. To distinguish PE mechanisms, labeled C was traced in CO2efflux and in microbial biomass and enzyme activities (involved in C, N, and P cycles) were measured during the incubation period. Regardless of residue type, PE intensity declined with increasing C additions. Roots were least mineralized but caused up to 60% higher PE compared to leaves or stems. During intensive residue mineralization (first 2–3 weeks), the low or negative PE resulted from pool substitution. Thereafter (15–60 days), a large decline in microbial biomass along with increased enzyme activity suggested that microbial necromass served as SOM primer. Finally, incorporation of SOM-derived C into remaining microbial biomass corresponded to increased enzyme activity, which is indicative of SOM cometabolism. Both PE and enzyme activities were primarily correlated with residue-metabolizing soil microorganisms. A unifying model demonstrated that PE was a function of residue mineralization, with thresholds for strong PE increase of up to 20% root, 44% stem, and 51% leaf mineralization. Thus, root mineralization has the lowest threshold for a strong PE increase. Our study emphasizes the role of residue-feeding microorganisms as active players in the PE, which are mediated by quality and quantity of crop residue additions.