Decrease of soil organic matter stabilization with increasing inputs : Mechanisms and controls
Decrease of soil organic matter stabilization with increasing inputs : Mechanisms and controls
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DOI：
10.1016/j.geoderma.2016.05.019
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发表时间：
2017-10
期刊：
影响因子：
6.1
通讯作者：
M. Shahbaz;Y. Kuzyakov;F. Heitkamp
中科院分区：
文献类型：
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作者：
M. Shahbaz;Y. Kuzyakov;F. Heitkamp
添加农作物秸秆是提高农田土壤有机质 (SOM) 水平的一种方法。然而，有机质投入和 SOM 库存并不线性相关。因此，添加大量残留物（例如秸秆）可能只会在很小程度上增加 SOM，并且残留物的替代使用可能是合理的。本研究的目的是测试残留物添加的水平和类型（地上或地下）如何影响 SOM 的稳定性。我们假设（1）根部残留物的矿化速度慢于叶和茎残留物，（2）土壤团聚体的形成将随着高添加量而增加，（3）小麦残留物的添加将引起正启动，其幅度取决于残留物水平和类型。将均匀 13 C 标记的小麦残留物（叶、茎、根）以 1.40 和 5.04 g DM kg−1 的水平添加到粉壤土中，并在 20 °C 下测量 64 天的 CO2 释放和 δ13 C 特征。分离水稳定性大团聚体 (> 250 μm)、微团聚体 (53–250 μm) 和淤泥加粘土尺寸部分 (< 53 μm)，并在 64 天后对每个部分中残留物中的 13 C 掺入进行定量。聚集体形成通常随着残留量的添加而增加，但聚集体中残留物的比例随着添加水平的增加而减少。随着添加水平的增加，地上生物量残留物的吸留量比根部的吸留量减少更多。残留物矿化随着添加量的增加而增加，但与茎和叶相比，根部的增加较少。不同残渣类型的引发效应相似，主要取决于添加量：低添加水平和高添加水平时，SOM 矿化分别增加 50% 和 90%。我们得出的结论是，随着 C 输入的增加，聚集体中物理保护的残留物比例减少，启动效应增加，导致通过增加残留物添加量，SOM 内的长期 C 稳定率降低。
Crop residue addition is a way to increase soil organic matter (SOM) level in croplands. However, organic matter input and SOM stocks are not linearly related. Consequently, adding high amounts of residues, such as straw, may increase SOM to only a small extent, and an alternative use of the residues may be justified. The objective of this study was to test how the level and type (above- or belowground) of residue addition affect SOM stabilization. We hypothesise that (1) root residues will be mineralised slower than leaf and stalk residues, (2) soil aggregate formation will increase with high additions, and (3) wheat residue addition will induce positive priming, with the magnitude depending on the residue level and type. Homogeneously13C-labelled wheat residues (leaves, stalks, roots) were added to a silt-loam soil at levels of 1.40 and 5.04 g DM kg− 1and CO2release and δ13C signature were measured over 64 days at 20 °C. Water-stable macroaggregates (> 250 μm), microaggregates (53–250 μm) and silt plus clay size fractions (< 53 μm) were separated and13C incorporation from residue was quantified in each fraction after 64 days. Aggregate formation generally increased with added residue amount, but the proportion of residues occluded within aggregates decreased with increasing addition level. The occlusion of residues from aboveground biomass was more reduced with addition level than that of roots. Residue mineralisation increased with the addition level, but this increase was less for roots compared to stalks and leaves. Priming effects were similar between residue types and mainly depended on the added amount: SOM mineralisation increased by 50% and 90% at low and high addition levels, respectively. We conclude that the proportion of residues physically protected within aggregates decreases and priming effects increase with increasing C input leading to decreasing rate of long-term C stabilization within SOM by increasing residue addition.