C:N stoichiometry of stable and labile organic compounds determine priming patterns
C:N stoichiometry of stable and labile organic compounds determine priming patterns
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稳定和不稳定有机化合物的 C:N 化学计量决定启动模式
DOI：
10.1016/j.geoderma.2019.114122
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发表时间：
2020-03
期刊：
影响因子：
6.1
通讯作者：
Kuzyakov Y.
中科院分区：
文献类型：
--
作者：
Liu M.;Qiao N.;Xu X.;Fang H.;Wang H.;Kuzyakov Y.
启动效应(PE)可以通过加速有机质(OM)的分解，极大地影响全球土壤碳(C)储量，并导致气候反馈。尽管氮(N)的有效性可以改变启动的大小和方向(化学计量约束)，但添加NO3-−(硝酸盐)和NH4+(铵)是否对各种OM的分解有不同的影响尚不清楚。因此，本研究的目的是研究OM沿衰变连续体的分解(即分解程度递减)对不稳定的C和N输入的响应，并确定这两种N形式引起的PE。在典型的亚热带森林中，沿着腐烂的连续体采集了4种有机质形态，即叶凋落物、木材凋落物、有机土层和矿物土壤，它们的C/N比范围很大，并在添加活性C(13C标记葡萄糖)和N(NO3−)的情况下培养了38天。基于土壤有机质中C/N比的很大范围和活性C、N的输入，我们论证了有机质在衰变连续体中的分解以及PE强度和PE方向转换的阈值。与NH_4~+添加相反，NO_3~(3+)−一般加速了有机质的分解。植物凋落物的启动依赖于不稳定输入的C：N比。而凋落物的分解更多地受到氮素添加的控制，而不是木材凋落物。葡萄糖的添加大大增加了土壤有机质分解的启动，显示了微生物的能量限制。在NO_3、−和NH_4+添加之间观察到了不同的启动模式，无论是对于单独的OM类型还是对于所有四种OM类型都是如此。在碳平衡的基础上，不稳定的C和N输入诱导的PE可以增加或减少C的固存，这取决于不稳定输入的C：N化学计量比。我们的发现为了解NO3、−或NH4+与不稳定的C输入(例如来自根分泌物)的具体作用提供了重要的见解，因此，沉积N的组成的变化(大气沉积和施肥)可能会诱导不同的气候反馈。
Priming effects (PE) can greatly influence global carbon (C) storage in soil and lead to climate feedbacks by accelerating the decomposition of organic matter (OM). Although nitrogen (N) availability can alter the magnitude and direction of priming (stoichiometric constrains), it remains unclear whether additions of NO3−(nitrate) and NH4+(ammonium) have distinct effects on the decomposition of various OM. Thus, the aims of this study were to investigate the responses of OM decomposition along a decay continuum (i.e. decreasing decomposition degree) to labile C and N inputs and determine the PE induced by the two N forms. Four OM forms, namely leaf litter, wood litter, organic soil horizon, and mineral soil, with a broad range of C:N ratios were collected along a decay continuum in a typical subtropical forest and incubated for 38 days with labile C (13C labeled glucose) and N (NO3−) additions. Based on the very broad range of C:N ratios in OM in soil and inputs of labile C and N, we demonstrated the OM decomposition within a decay continuum as well as PE intensities and the thresholds for the switch of PE directions. In contrast to NH4+additions, NO3−generally accelerated the decomposition of all OM. Priming of plant litter was dependent on the C:N ratios of the labile inputs. However, leaf litter decomposition was more controlled by N addition than wood litter. Glucose addition greatly increased the priming of OM decomposition in soils, demonstrating energy limitation for microorganisms. Distinct priming patterns were observed between NO3−and NH4+additions, both for the individual OM types and for all four types of OM. On a basis of C balance between primed C and the remaining added C, PE induced by labile C and N inputs can increase or reduce C sequestration depending on C:N stoichiometric ratios of labile inputs. Our findings provide important insights into the specific role of NO3−or NH4+together with labile C inputs (e.g. from root exudation), and thus changes in the composition of deposited N (atmospheric deposition and fertilization) may induce distinct climate feedbacks.
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