Root distributions, precipitation, and soil structure converge to govern soil organic carbon depth distributions
Root distributions, precipitation, and soil structure converge to govern soil organic carbon depth distributions
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DOI：
10.1016/j.geoderma.2023.116569
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发表时间：
2023-09
期刊：
影响因子：
6.1
通讯作者：
Ligia F. T. de Souza;D. Hirmas;P. Sullivan;D. Reuman;M. Kirk;Li Li-Li;H. Ajami;H. Wen;M. V. Sarto;T. Loecke;Aoesta K. Rudick;C. Rice;S. Billings
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文献类型：
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作者：
Ligia F. T. de Souza;D. Hirmas;P. Sullivan;D. Reuman;M. Kirk;Li Li-Li;H. Ajami;H. Wen;M. V. Sarto;T. Loecke;Aoesta K. Rudick;C. Rice;S. Billings
土壤有机碳（SOC）的深度分布受到许多生态系统特征相互作用的控制，包括浅层和深层土壤中不同的碳输入以及通过剖面的水流对碳的重新分配。特别是在富含碳的软土中，我们需要更好地了解原生草原转变为耕地在多大程度上改变了碳的损失和保留。我们使用两种方法探讨了驱动这些过程的多种机制：一种利用源自自然资源保护局（USDA-NRCS）国家合作土壤调查（NCSS）特征数据库的区域规模数据集；另一种利用来自自然资源保护局（USDA-NRCS）国家合作土壤调查（NCSS）特征数据库的区域规模数据集。第二个重点是本地规模的、更详细的数据集，代表较大数据库中调用的气候和土地利用梯度。第一种方法侧重于参数化美国中西部气候梯度上软土的 SOC 深度分布，以研究土地利用和有效降水如何影响 SOC 的垂直梯度。第二种方法通过量化美国堪萨斯州多个土壤剖面的生物、物理和化学特性，进一步研究了 SOC 深度分布驱动因素。随着原生草原土壤中可用水量的增加，SOC 随着深度的增加而逐渐下降，这促使人们提出这样的假设：通过剖面的水流量增加会将 C 带到深层，特别是在高根丰度促进土壤孔隙度的地方。对多个土壤剖面的分析表明，由土地转化驱动的地表变化将其影响传播到深层土壤层，其方式对于跨深度的碳循环耦合具有重要意义。我们的研究结果支持了这一假设，并特别提出了农业条件下根系丰度下降与可溶性碳向下流动增加之间的联系，以及影响 SOC 形成聚集体倾向的土壤结构的相关变化。因此，不同土地利用中根深丰度和可用水量之间的相互作用似乎会影响土壤颗粒和空隙的排列，这对垂直水流和碳传输很重要。我们的工作阐明了驱动 SOC 深度分布形状变化的多种重要机制的融合，其时间尺度比通常假设的要短，这对预测人类世土壤碳循环和储存产生了影响。
The depth distribution of soil organic carbon (SOC) is governed by the interaction of many ecosystem features, including differential C inputs in shallow and deep soils and the redistribution of C via water flow through the profile. In C-rich Mollisols in particular, we need to better understand the degree to which the conversion of native prairie to cultivated lands is changing C loss and retention. We probed multiple mechanisms driving these processes using two approaches: one leverages a regional-scale dataset derived from the Natural Resources Conservation Service (USDA-NRCS) National Cooperative Soil Survey (NCSS) Characterization Database; and a second focusses on a local-scale, more detailed dataset representative of the climatic and land-use gradients invoked in the larger database. The first approach focused on parameterizing SOC depth distributions of Mollisols across a climatic gradient in the US Midwest to investigate how land use and effective precipitation affects vertical gradients of SOC. The second approach furthered the investigation of SOC depth distribution drivers by quantifying biological, physical, and chemical properties of multiple soil profiles across Kansas, US. SOC declined more gradually with depth as water availability increased in native prairie soils, prompting the hypothesis that increased water flow through the profile carries C to deep layers, particularly where high root abundances promote soil porosity. Analyses of multiple soil profiles indicate that surficial changes driven by land conversion propagate their influence to deep soil horizons in ways significant for the coupling of C cycling across depths. Our findings support the hypothesis, and specifically suggest linkages between decreased root abundances and increased flows of soluble C downward under agriculture, and associated changes in soil structure that affect the propensity of SOC to form aggregates. The interplay between rooting depth abundances and water availability in different land uses thus appears to influence the arrangement of soils particles and voids in ways important for vertical water flow and C transport. Our work illuminates the convergence of multiple important mechanisms driving changes in the shape of SOC depth distributions across timescales shorter than typically assumed, with consequences for projecting soil C cycling and storage in the Anthropocene.