The Obscuring Effects of Calcite Dissolution and Formation on Quantifying Soil Respiration
The Obscuring Effects of Calcite Dissolution and Formation on Quantifying Soil Respiration
复制标题
DOI：
10.1029/2020gb006584
复制
发表时间：
2020-12-01
影响因子：
5.2
通讯作者：
Breecker, Daniel O.
中科院分区：
文献类型：
--
作者：
Gallagher, Timothy M.;Breecker, Daniel O.
旱地占陆地面积的近40%，是全球重要的碳库。旱地-大气碳交换可调节大气CO2的年际变化。量化这些环境中的土壤呼吸率往往因碳酸钙的存在而变得复杂，而碳酸钙是旱地土壤的共同特征。我们表明，高精度的O-2测量在实验室盆栽土壤实验中，浇水后的呼吸速率在控制和碳酸盐处理土壤相似。然而，CO2浓度高达72%，在碳酸盐处理土壤，因为CO2最初消耗在方解石溶解。随后，CO2浓度超过166%以上的碳酸盐处理土壤呼吸减慢和方解石沉淀，释放CO2。土壤CO2的δ C-13值升高（处理组比对照组高出千分之6）证实了观察到的差异是由于方解石溶解造成的。这些研究结果表明，方解石溶解和沉淀可以迅速发生足以影响土壤气体成分和土壤CO2的变化并不总是直接相关的土壤呼吸速率的变化。对当地土壤呼吸速率和碳交换的研究可能受到土壤中碳酸钙溶解和沉淀的影响。我们估计，五分之一的全球土壤呼吸发生在土壤中含有一定量的土壤碳酸盐，强调需要考虑其模糊的影响时，试图量化土壤呼吸和净生态系统交换在区域或全球范围内。
Drylands occupy nearly 40% of the land surface and comprise a globally significant carbon reservoir. Dryland-atmosphere carbon exchange may regulate interannual variability in atmospheric CO2. Quantifying soil respiration rates in these environments is often complicated by the presence of calcium carbonates, which are a common feature of dryland soils. We show with high-precision O-2 measurements in a laboratory potted soil experiment that respiration rates after watering were similar in control and carbonate treatment soils. However, CO2 concentrations were up to 72% lower in the carbonate treatment soil because CO2 was initially consumed during calcite dissolution. Subsequently, CO2 concentrations were over 166% greater in the carbonate treatment soil as respiration slowed and calcite precipitated, releasing CO2. Elevated delta C-13 values of soil CO2 (>6 parts per thousand higher in the treatment than control) confirm that observed differences were due to calcite dissolution. These findings demonstrate that calcite dissolution and precipitation can occur rapidly enough to affect soil gas compositions and that changes in soil CO2 are not always directly related to changes in soil respiration rates. Studies of local soil respiration rates and carbon exchange are likely to be influenced by dissolution and precipitation of calcium carbonates in soils. We estimate that one fifth of global soil respiration occurs in soils that contain some amount of soil carbonate, underscoring the need to account for its obscuring effects when trying to quantify soil respiration and net ecosystem exchange on a regional or global scale.