| Summary: | Root decomposition plays an essential role in the terrestrial carbon cycle, but the responses of roots of different diameters to varying drought periods are unclear. Therefore, artificial drought experiments were conducted to investigate the effects of different drought periods on the decomposition rates of roots with different diameters. In this study, <2 mm, 2–5 mm and 5–10 mm root decomposition experiments were conducted in control (CK), short-term drought (STD, drought during one rainy season), and long-term drought (LTD, two-year drought) treatments. The drought treatments significantly reduced the soil water content by 52.5% and 83.6%, respectively, but had little effect on the soil temperature. According to the decomposition coefficient (k value), the root decomposition rate decreased significantly with increasing diameter, and STD and LTD significantly reduced root decomposition of different diameters by 30.4–41.7% and 47.8–70.8%, respectively. The analysis of covariance (ANCOVA) revealed that diameter, treatments and their interaction had significant effects on the k values. The linear regression showed that the dependence of the stage root decomposition rate (SRDR) and k value of fine roots on the soil water content were higher than that of coarse roots. Therefore, fine roots were more sensitive to the soil water content and drought, thereby affecting the nutrient cycle and health of forest ecosystems under drought. This study provides new insight into the impact of climate change on root decomposition and the carbon cycle.
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