From Soils to Streams: Connecting Terrestrial Carbon Transformation, Chemical Weathering, and Solute Export Across Hydrological Regimes
From Soils to Streams: Connecting Terrestrial Carbon Transformation, Chemical Weathering, and Solute Export Across Hydrological Regimes
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DOI：
10.1029/2022wr032314
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发表时间：
2022-06
影响因子：
5.4
通讯作者：
H. Wen;P. Sullivan;S. Billings;H. Ajami;Alejandro Cueva;A. Flores;D. Hirmas;A. Koop;K. Murenbeeld;Xi Zhang;Li Li-Li
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作者：
H. Wen;P. Sullivan;S. Billings;H. Ajami;Alejandro Cueva;A. Flores;D. Hirmas;A. Koop;K. Murenbeeld;Xi Zhang;Li Li-Li
土壤生物群产生的碳垂直向大气输出（CO2），横向向溪流和河流输送（溶解的有机碳和无机碳，DOC和DIC）。这些过程，连同化学风化，随着水文制度的流动路径而变化；然而，对这些相互作用过程的综合理解仍然缺乏。在这里，我们的问题是：地下碳转化、化学风化和溶质出口在水文和地下结构制度下是如何以及在多大程度上不同的？我们利用来自Fitch的土壤CO2和水化学数据校准的山坡反应输运模型来解决这个问题。Fitch是位于美国堪萨斯州东部温带森林和中大陆草原过渡带边界的温带森林。模型结果表明，干旱（0.08 mm/d的流量）促进了更深的流动路径、更长的水传递时间、碳酸盐降水和有机碳（OC）矿化为无机碳（IC）（~ 98%的OC）。在产生的IC中，约86%以CO2气体的形式向上排放，约14%以DIC的形式横向出口到河流中。风暴（8.0 mm/天）导致碳酸盐溶解，但减少了OC矿化（~ 88%的OC），促进了DOC的产生（~ 12%的OC）和IC的侧向通量（~ 53%的产出IC）。浅层和深层渗透率差异导致的差异小于放电引起的差异（<10%），并且在潮湿条件下最为明显。高渗透率对比（低垂直连通性）增强了横向通量。模型结果一般将干燥条件下的山坡描述为活跃的CO2生产者和垂直碳转运体，湿润条件下的山坡是活跃的DOC生产者和横向碳转运体。
Soil biota generates carbon that exports vertically to the atmosphere (CO2) and transports laterally to streams and rivers (dissolved organic and inorganic carbon, DOC and DIC). These processes, together with chemical weathering, vary with flow paths across hydrological regimes; yet an integrated understanding of these interactive processes is still lacking. Here we ask: How and to what extent do subsurface carbon transformation, chemical weathering, and solute export differ across hydrological and subsurface structure regimes? We address this question using a hillslope reactive transport model calibrated using soil CO2 and water chemistry data from Fitch, a temperate forest at the ecotone boundary of the Eastern temperate forest and mid‐continent grasslands in Kansas, USA. Model results show that droughts (discharge at 0.08 mm/day) promoted deeper flow paths, longer water transit time, carbonate precipitation, and mineralization of organic carbon (OC) into inorganic carbon (IC) (∼98% of OC). Of the IC produced, ∼86% was emitted upward as CO2 gas and ∼14% was exported laterally as DIC into the stream. Storms (8.0 mm/day) led to carbonate dissolution but reduced OC mineralization (∼88% of OC) and promoted DOC production (∼12% of OC) and lateral fluxes of IC (∼53% of produced IC). Differences in shallow‐versus‐deep permeability contrasts led to smaller difference (<10%) than discharge‐induced differences and were most pronounced under wet conditions. High permeability contrasts (low vertical connectivity) enhanced lateral fluxes. Model results generally delineate hillslopes as active CO2 producers and vertical carbon transporters under dry conditions, and as active DOC producers and lateral carbon transporter under wet conditions.