Priming effects induced by glucose and decaying plant residues on SOM decomposition: A three-source 13C/14C partitioning study
Priming effects induced by glucose and decaying plant residues on SOM decomposition: A three-source 13C/14C partitioning study
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DOI：
10.1016/j.soilbio.2018.03.004
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发表时间：
2018-06
影响因子：
9.7
通讯作者：
M. Shahbaz;Amit Kumar;Y. Kuzyakov;G. Börjesson;E. Blagodatskaya
中科院分区：
文献类型：
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作者：
M. Shahbaz;Amit Kumar;Y. Kuzyakov;G. Börjesson;E. Blagodatskaya
土壤有机质(SOM)分解在新鲜有机输入后可能增加，也可能减少，这种现象被称为“启动效应”。作物残留物和不稳定的C添加可以启动土壤有机质的分解，但不稳定的C输入如何在腐烂的植物残留物质量不同的情况下影响SOM尚不清楚(例如，来自以前的作物，这在耕地土壤中是常见的情况)。我们使用13C/14C双重同位素标记来划分土壤CO2排放和微生物生物量三个碳源：不稳定C(葡萄糖)、部分分解的小麦残留物(叶和根)和SOM。13C标记的残留物与13C标记的残留物(单独的叶或根)预培养30天后，向土壤中添加14C标记的葡萄糖。添加葡萄糖后，叶片残渣的分解率下降了65%，而根系没有受到影响。尽管残留物分解速率不同，但添加葡萄糖后，叶残留物和根残留物处理的底物有机质的量保持不变。在90天内，葡萄糖单独引起193 μg C g−1土壤有机质的累积正启动，相当于没有添加的土壤有机质分解的60%。在土壤中添加葡萄糖和部分分解的植物残体，引发土壤有机质的效果比单一残留物高45%(∼250 μg C g−1)。值得注意的是，这种由葡萄糖和残留物诱导的启动效应只是由于前18天SOM的强烈分解所致。在接下来的阶段(葡萄糖18天后)，SOM启动的下降和残渣分解的增加表明微生物的活性发生了变化。从活跃的微生物到生长缓慢的微生物。葡萄糖的添加显著增加了SOM微生物生物量的比例，但降低了残留物C的比例，这表明在葡萄糖耗竭后，SOM优先于植物残留物。这些结果与不稳定的C输入诱导SOM启动的观点一致，并首次表明，不稳定的C控制着SOM和腐烂植物残体的强度和分解速度。结论是，无论部分分解残留物的质量如何，输入活性碳(如通过根际沉积)总体上在增加有机质分解方面具有相加效应。只有应用创新的13C/14C双标记方法，才能对池之间的相互作用进行研究，并确定三个碳源。
Decomposition of soil organic matter (SOM) may either increase or decrease after fresh organic inputs, the phenomena which are termed as "priming effect". Crop residues and labile C additions can prime SOM decomposition, but it is not known how labile C inputs affect SOM in the presence of decaying plant residues varying in quality (e.g.from previous crops, a common situation in arable soils). We used a dual13C/14C isotopic labelling to partition soil CO2efflux and microbial biomass for three C sources: labile C (glucose), partly decomposed wheat residues (leaves and roots) and SOM.14C-labelled glucose was added to the soil after 30 days of pre-incubation with13C-labelled residues (separately leaves or roots). After glucose addition, the leaf residue decomposition rate declined by up to 65%, while roots remained unaffected. Despite the differences between residue decomposition rates, the quantity of primed SOM remained similar between leaf and root residue treatments after the addition of glucose. Glucose alone caused cumulative positive SOM priming of 193 μg C g−1soil over 90 days, corresponding to 60% of SOM decomposition without addition. Addition of glucose to soil together with partly decomposed plant residues induced up to 45% higher SOM priming than single residues priming effect (∼250 μg C g−1). Remarkably, this priming effect induced by glucose and residues was only due to intensive SOM decomposition during the first 18 days. On the subsequent period (after 18 days of glucose), decline in SOM priming and increase in residue decomposition indicate a shift in microbial activityi.e. from active-to slow-growing microbes. Glucose addition strongly increased the proportion of microbial biomass from SOM but decreased the proportion from residue C, suggesting a preferential use of SOM over plant residues following glucose exhaustion. These results are consistent with the view that labile C inputs induce SOM priming and suggest for the first time, that labile C controls the intensity and decomposition rate of both SOM and decaying plant residues. Concluding, irrespective of the quality of partly decomposed residues, input of labile C (e.g.through rhizodeposition) has overall an additive effect in increasing decomposition of SOM. Such studies of interactions between pools and identification of three C sources were only possible by the application of an innovative dual13C/14C labelling approach.