Carbon dynamics in topsoil and in subsoil may be controlled by different regulatory mechanisms
Carbon dynamics in topsoil and in subsoil may be controlled by different regulatory mechanisms
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DOI：
10.1111/j.1365-2486.2009.01884.x
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发表时间：
2010-01-01
影响因子：
11.6
通讯作者：
Chenu, Claire
中科院分区：
文献类型：
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作者：
Salome, Clemence;Nunan, Naoise;Chenu, Claire
据估计，超过50%的土壤碳储存在底土（20-30厘米以下）中。尽管如此，很少有研究关注底土。虽然地表和地下层位在土壤学、环境和物理化学特征方面有所不同，这些特征都可能影响所涉及的机制和生物行为体，但碳动力学模型倾向于假设所有层位的基本过程是相同的，但地下层位的总通量较低。这项研究的目的是通过分析表层土（5-10厘米深）和底土（80-100厘米深）有机物分解的制约因素来检验这一假设。为此，我们建立了持续51天的孵化，其中被认为是控制有机质矿化的因素被改变：氧浓度，土壤结构和能量和营养状况。在培养期结束时，测量微生物生物量并建立群落水平的生理概况。矿化每单位有机碳被证明是一样重要的底土，因为它是在表面样品，尽管碳含量较低，不同的分解剖面。处理效果的差异表明，C动力学的控制是不同的表土和底土：破坏底土的结构引起矿化增加75%，而表面样品保持不受影响。另一方面，一个显着的启动效应被发现在表土，但不是在底土样品。在田间尺度上，土壤碳含量、呼吸作用和微生物群落的空间异质性表现为下层土壤大于表层土壤。这些数据表明，如果要充分了解全球碳动态，应更加重视底土。
It is estimated that in excess of 50% of the soil carbon stock is found in the subsoil (below 20-30 cm). Despite this very few studies have paid attention to the subsoil. Although surface and subsurface horizons differ in pedological, environmental and physicochemical features, which are all likely to affect the mechanisms and biological actors involved, models of carbon dynamics tend to assume that the underlying processes are identical in all horizons, but with lower gross fluxes in the subsurface. The aim of this study was to test this assumption by analysing factors governing organic matter decomposition in topsoil (from depths of 5-10 cm) and subsoil (from depths of 80-100 cm). To this end, we established incubations that lasted 51 days, in which factors that were thought to control organic matter mineralization were altered: oxygen concentration, soil structure and the energetic and nutritional status. At the end of the incubation period, the microbial biomass was measured and the community level physiological profiles established. The mineralization per unit organic carbon proved to be as important in the subsoil as it was in surface samples, in spite of lower carbon contents and different catabolic profiles. Differences in the treatment effects indicated that the controls on C dynamics were different in topsoil and subsoil: disrupting the structure of the subsoil caused a 75% increase in mineralization while the surface samples remained unaffected. On the other hand, a significant priming affect was found in the topsoil but not in the subsoil samples. Spatial heterogeneity in carbon content, respiration and microbial communities was greater in subsoil than in topsoil at the field scale. These data suggest greater attention should be paid to the subsoil if global C dynamics is to be fully understood.