Contrasting responses of soil exoenzymatic interactions and the dissociated carbon transformation to short- and long-term drainage in a minerotrophic peatland

Abstract

Lowering of water table owing to climate warming and drainage has threatened the large reservoir of the preserved carbon (C) in peatlands. However, the consequent effects on northern nutrient-deficient peatlands are still under-investigated. Here, we compared a short- (42 days) with a long-term (30 years) drainage experiment, and quantified the activities of the decomposition-related extracellular enzymes as well as C, nitrogen (N) and phosphorus (P) stoichiometries in a minerotrophic peatland in northeastern China. The results showed that the key hydrolytic enzymatic activities increased by 2–145% and 25–465% under short- and long-term drainage respectively, but the preserved nutrients and C in the peat did not vary considerably. The minerotrophic peatland seems to be a complex adaptive system with great resilience to tackle the short- and long-term drainage with two disparate mechanisms. Specifically, the intrinsic nature of severe nutrient-deficiency may weaken enzymatic constraints on decomposition (the ‘enzymatic latch’ mechanism) during the short-term drainage. In contrast, the increases in phenolics input and litter quality due to the shift in vegetation composition may alleviate the threat to C stores during the long-term drainage. These distinct regulatory mechanisms over the course of progressive lowering of water table may potentially provide new insights to assess the risk and benefit of drainage in peatlands.