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 O₂ 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 δ¹³C values of soil CO₂ (>6‰ 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.

中文翻译：

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方解石溶解和形成对土壤呼吸定量的模糊效应

旱地占据了近40％的陆地表面，并拥有全球重要的碳库。旱地-大气碳交换可能调节大气CO _2的年际变化。碳酸钙的存在常常使在这些环境中量化土壤呼吸速率变得复杂，碳酸钙是旱地土壤的常见特征。我们在实验室盆栽土壤实验中通过高精度O ₂测量显示，浇水后的呼吸速率在对照土壤和碳酸盐处理土壤中相似。然而，由于在方解石溶解过程中最初消耗了CO _2，因此在碳酸盐处理土壤中的CO ₂浓度降低了多达72％。随后，CO ₂在碳酸盐处理过的土壤中，由于呼吸作用减缓和方解石沉淀，其浓度增加了166％以上，从而释放出CO ₂。升高的δ ^13个土壤CO的C值₂（> 6‰治疗高于对照）确认观察到的差异是由于方解石溶解。这些发现表明，方解石的溶解和沉淀可以迅速发生，从而影响土壤气体的组成，并且土壤CO _2的变化并不总是与土壤呼吸速率的变化直接相关。对当地土壤呼吸速率和碳交换的研究可能受到碳酸钙在土壤中的溶解和沉淀的影响。我们估计，全球土壤呼吸的五分之一发生在含有一定数量碳酸盐的土壤中，这突显了在试图在区域或全球范围内量化土壤呼吸和净生态系统交换时需要考虑其掩盖效应的必要性。