Microbial acclimation triggered loss of soil carbon fractions in subtropical wetlands subjected to experimental warming in a laboratory study.

Aims: Wetlands store a substantial amount of soil organic carbon (SOC), and their response to climate warming is critical for predicating global carbon (C) cycling in future climate change. Methods: To understand whether warming causes substantial C loss in wetland soils, a 6-year microcosm experiment was carried out to examine the impact of rising temperature (3-5 °C) on SOC and its two fractions (labile versus recalcitrant) in six types of wetland soils with varied nutrient status. Results: Warming decreased SOC contents in nutrient-enriched soils by invoking a large loss in recalcitrant organic C fractions, while in nutrient-poor soils SOC loss was limited by substrate limitation. With low temperature ranges in the winter (1-10 °C), warming increased the microbial capacity for recalcitrant organic C acquisition greater than that for labile organic C fractions. A relatively higher cross-site contribution of fungi in warmed soils as one strategy of microbial acclimation to rising temperature implies an adjustment of microbial C utilization patterns, leading to substantial C loss in wetland soils. Conclusions: In order to maintain the functional roles of wetlands for C sequestration, our results further suggested that more attention should be paid to nutrient-enriched wetlands in future climate warming scenarios. [ABSTRACT FROM AUTHOR]