PNNL

Abstract

Peatlands are an important carbon (C) reservoir storing one-third of global soil organic carbon (SOC), but little is known about the fate of these vast C stocks under climate change. Here, we examine the impact of warming and elevated atmospheric CO2 concentration (eCO2) on the molecular composition of SOC to infer SOC sources (microbe-, plant- and fire-derived) and stability in a boreal peatland. We show that while warming alone decreased plant- and microbe-derived SOC compounds due to enhanced decomposition, warming combined with eCO2 significantly increased plant-derived SOC compounds. By further characterizing biopolymers specific to either leaf/needle (cutin) or root (suberin) compartments, we observed increasing root-derived inputs and declining leaf-derived inputs into SOC under warming and eCO2. The observed decline in SOC with warming and gains from new root-derived C sources under eCO2, suggest that warming and eCO2 have shifted the C budget towards younger pools with faster turnover. Together, our results indicate that climate change drivers may increase inputs and enhance the decomposition of SOC potentially destabilising C storage in peatlands.