Drought-induced peatland carbon loss exacerbated by elevated CO 2 and warming

Extreme drought events are predicted to increase with climate change, yet their impacts on ecosystem carbon dynamics under warming and elevated carbon dioxide (eCO₂) remain unclear. In a peatland experiment with five warming treatments each under ambient carbon dioxide (aCO₂) and eCO₂ (+500 parts per million), a 2-month extreme drought in 2021 reduced net ecosystem productivity by 444.0 ± 65.8 and 736.6 ± 57.8 grams of carbon per square meter at +9°C under aCO₂ and eCO₂, respectively-228.6 ± 56.8% and 381.9 ± 83.4% of the reduction at +0°C under aCO₂. This exacerbation was driven by warming-induced water table decline, prolonged low water tables, and CO₂-enhanced substrate availability through increased plant carbon inputs. Findings indicate that future climate will greatly amplify carbon loss during extreme drought, reinforcing positive carbon-climate feedbacks.