As the climate warms, drought events are expected to increase in intensity and frequency, with consequences for the carbon cycle. Soil respiration (R_s) accounts for the largest flux of CO₂ from terrestrial ecosystems to the atmosphere. While the drought responses of R_s have been well studied, it is uncertain how they will be modified in a future world, when higher temperatures will occur in combination with elevated atmospheric CO₂ concentrations. In a global change experiment in a managed temperate grassland, we studied drought and post-drought responses of R_s dynamics under current versus likely future conditions (+3°, +300 ppm CO₂). Furthermore, to understand the soil CO₂ production (P_s) and transport dynamics underlying R_s fluxes we continuously monitored in-situ soil CO₂ concentrations across the soil profile. Our results show that R_s was higher and that drought-induced reductions in R_s were delayed under future compared to current conditions. Peak drought reductions and post-drought pulses of R_s were more pronounced in the future scenario. Annual R_s was reduced by drought only under current but not under future conditions. An in-depth analysis of soil CO₂ gradients and fluxes across the soil profile showed that elevated CO₂ stimulated P_s primarily in the main rooting horizon and that warming affected P_s also in deeper soil layers. We found that both in the current and the future scenario drought led to the strongest reductions of P_s in the most productive soil layers, which also exhibited the largest depletion of soil moisture. We conclude that a future warmer climate under elevated CO₂ amplifies soil CO₂ production and efflux and their peak drought and post-drought responses, but delays the onset of the drought responses and thereby eliminates the overall drought effect on annual soil CO₂ emissions.

随着气候变暖，干旱事件的强度和频率预计会增加，从而对碳循环产生影响。土壤呼吸 (R _s ) 是从陆地生态系统到大气的最大 CO ₂通量。虽然已经对 R_的干旱响应进行了深入研究，但不确定在未来世界中它们将如何改变，届时将出现更高的温度和大气 CO ₂浓度升高。在受管理的温带草原的全球变化实验中，我们研究了 R _s动力学在当前和未来可能的条件下（+3 °，+300 ppm CO ₂）。此外，为了了解R _s通量下的土壤 CO ₂产生 (P _s ) 和传输动力学，我们持续监测整个土壤剖面的原位土壤 CO ₂浓度。我们的结果表明，与当前条件相比，R _s更高，并且在未来干旱引起的 R _s减少被推迟。在未来情景中，干旱峰值减少和 R _s的干旱后脉冲更为明显。年 R _s仅在当前条件下因干旱而减少，而在未来条件下则不会。对整个土壤剖面土壤 CO ₂梯度和通量的深入分析表明，升高的 CO₂主要在主要生根层刺激了 P _s并且变暖也影响了较深土壤层中的P _s。我们发现，在当前和未来的情景中，干旱导致生产力最高的土壤层中 P _s的最强烈减少，这也表现出最大的土壤水分消耗。我们得出的结论是，未来在 CO ₂升高的情况下气候变暖会放大土壤 CO _{2 的}产生和流出以及它们的峰值干旱和干旱后响应，但会延迟干旱响应的开始，从而消除总体干旱对年度土壤 CO ₂排放的影响。