Influence of Pore Characteristics on the Fate and Distribution of Newly Added Carbon
Influence of Pore Characteristics on the Fate and Distribution of Newly Added Carbon
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DOI：
10.3389/fenvs.2018.00051
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发表时间：
2018-06
影响因子：
4.6
通讯作者：
M. Quigley;W. Negassa;A. Guber;M. Rivers;A. Kravchenko
中科院分区：
文献类型：
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作者：
M. Quigley;W. Negassa;A. Guber;M. Rivers;A. Kravchenko
孔隙在土壤基质中形成了一个运输网络，控制着空气、水的流动和微生物的运动。空气、水的流动和微生物的运动反过来又控制着土壤的碳动态。计算机微断层扫描（μCT）允许在微米尺度上的孔隙结构的可视化，但孔隙的贡献，土壤碳的命运和保护，建模所必需的定量信息，仍然缺乏。本研究利用C3和C4植物碳同位素之间的自然差异，以确定不同大小的孔隙的存在如何影响植物终止后立即增加的碳的空间分布模式，然后经过一个月的培养。我们考虑了两种截然不同的土壤结构方案：土壤结构保持完整，土壤结构被破坏，通过筛分。对于该实验，从20年连续种植的玉米（Zea mays L.，C4植物）实验，将黑麦（Secale cereale L.，C3植物）种植。黑麦在温室中生长3个月后获得完整的土壤碎片（5-6 mm）。通过μCT成像确定碎片的孔隙特征。将每个碎片切片并测量总碳、总氮、δ 13 C和δ 15 N。结果表明，在孵育之前，更大的40-90 μm孔的存在与更高水平的C3碳相关，指出这些孔在运输新的C输入中的积极作用。然而，孵育后，协会成为负的，表明更大的损失，新加入的C在这样的孔。这些趋势在结构破坏的土壤中具有统计学意义，在结构完整的土壤中具有数值意义。在结构完整的土壤中，培养后，较高的总碳水平与6.5-15和15-40 μm孔隙的丰度相关，表明与这些孔隙相关的碳损失较低。结果表明，在所研究的土壤中，40-90 μm的孔隙与新碳的快速流入和快速分解有关，而小于40 μm的孔隙则与碳的保护作用有关。
Pores create a transportation network within a soil matrix, which controls the flow of air, water, and movement of microorganisms .The flow of air, water, and movement of microbes, in turn, control soil carbon dynamics. Computed microtomography (μCT) allows for the visualization of pore structure at micron scale, but quantitative information on contribution of pores to fate and protection of soil carbon, essential for modeling, is still lacking. This study uses the natural difference between carbon isotopes of C3 and C4 plants to determine how the presence of pores of different sizes affects spatial distribution patterns of newly added carbon immediately after plant termination and then after one-month incubation. We considered two contrasting soil structure scenarios: soil with the structure kept intact and soil for which the structure was destroyed via sieving. For the experiment, soil was collected from 0-15 cm depth from a 20-year continuous maize (Zea mays L., C4 plant) experiment into which cereal rye (Secale cereale L., C3 plant) was planted. Intact soil fragments (5-6 mm) were procured after 3 months rye growth in a greenhouse. Pore characteristics of the fragments were determined through μCT imaging. Each fragment was sectioned and total carbon, total nitrogen, δ13C, and δ15N were measured. The results indicate that, prior to incubation, greater presence of 40-90 μm pores was associated with higher levels of C3 carbon, pointing to the positive role of these pores in transport of new C inputs. Nevertheless, after incubation, the association became negative, indicating greater losses of newly added C in such pores. These trends were statistically significant in destroyed-structure soil and numerical in intact-structure soil. In soils of intact-structures, after incubation, higher levels of total carbon were associated with greater abundance of 6.5-15 and 15-40 μm pores, indicating a lower carbon loss associated with these pores. The results indicate that, in the studied soil, pores of 40-90 μm size range are associated with the fast influx of new C followed by its quick decomposition, while pores <40 μm tend to be associated with C protection.