The influence of forest-to-cropland conversion on temperature sensitivity of soil microbial respiration across tropical to temperate zones

As one of the most important drivers of global climate change, land use change (LUC) has markedly altered the regional and global carbon (C) cycles. However, the geographic variations and the key drivers in the effects of LUC on temperature sensitivity (Q₁₀) of soil microbial respiration (R_s) are still not fully elucidated, hence impeding the spatially explicit predictions of soil C cycling under climate change. Here, we used a paired-plot approach with data for 19 locations distributed from the tropical to temperate zones in eastern China, and compared the temperature responses of R_s between forest and cropland soil. Results showed that the latitudinal patterns of Q₁₀ in forest soils were better explained by climatic variables; whereas in cropland, soil Q₁₀ trended higher with increasing latitude, with climatic factors, pH, clay, and soil organic C (SOC) jointly modulating the spatial variations in Q₁₀. Overall, the values of Q₁₀ tended to converge with latitude between forests and croplands, with change in Q₁₀ from forest to cropland, ΔQ₁₀, significantly decreasing from the tropical region (9.23 ± 3.58 %) to the subtropical (0.58 ± 1.93 %) and temperate (−0.97 ± 1.11 %) regions. Moreover, the spatial variations of ΔQ₁₀ were significantly affected by climatic factors, ΔpH, Δmicrobial biomass C (ΔMBC), and their interactions. Our findings highlight the potential impacts of LUC-related biogeographic variations in the temperature response of R_s, and emphasize the importance of incorporating the land-use effects on the temperature sensitivity of soil microbial respiration into terrestrial C cycle models to improve predictions of carbon-climate feedbacks in the future.