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Drying-rewetting cycles decrease temperature sensitivity of soil organic matter decomposition
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DOI：10.1016/j.agrformet.2025.110442.png)
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Abstract
En 中文
Soil organic carbon (SOC) decomposition is crucial in the global carbon cycle. Its sensitivity to warming significantly impacts climate change. However, the effect of soil drying-rewetting, a consequence of climate change-induced water cycling shifts, on SOC decomposition sensitivity remains poorly understood. This study investigated how drying-rewetting cycles affect the temperature sensitivity (Q(10)) of SOC decomposition and its underlying mechanisms. We collected soils from two farmlands with 23- and 33-year C-3-C-4 vegetation switches The soils were incubated at 20 degrees C or 30 degrees C for 180 days under alternate drying-rewetting cycles (100 %-20 % water holding capacity, WHC) or constant moisture (60 % WHC). Using C-13 natural abundance, we differentiated CO2 sources from recent SOC (C-4, <23 or <33 years) and old SOC (C-3, >23 or >33 years). Results showed that warming and drying-rewetting enhanced total SOC decomposition. Across moisture conditions, the Q(10) of old SOC was 0.25-0.40 units higher than that of recent SOC. Six drying-rewetting cycles decreased the Q(10) of total, recent, and old SOC by 0.30-0.44 units compared to constant moisture, as warming became less dominant during the drying-rewetting process. This indicates that the commonly used Q(10) might be overestimated under constant moisture, suggesting that the feedback of SOC pools to climate warming might be weaker than previously expected under real soil moisture fluctuations.
Keywords:
Soil moisture
Drying-rewetting cycles
Climate change
Temperature sensitivity
delta C-13 isotopic abundance
CO2 trapping system
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