How climate warming and plant diversity affect carbon greenhouse gas emissions from boreal peatlands: Evidence from a mesocosm study

Abstract

Understanding synchronous vegetation changes are crucial to assess the impact of carbon cycle on climate warming in peatlands. We established a mesocosm system to monitor ecosystem respiration (Re) and methane (CH4) fluxes in the growing season from 2020 to 2021 under different scenarios, including warming and manipulations of species diversity. Overall, the mean Re and CH4 fluxes varied in the ranges of 1.38 ± 0.18 to 46.25 ± 6.62 mg CO2–C m−2 h−1 and 2.72 ± 2.36 to 319.55 ± 96.22 μg CH4–C m−2 h−1, respectively, with the highest values appearing in the middle of growing season. The Re and CH4 fluxes in L-III and L-IV mesocosms showed significant increases of 38.86% and 54.28%, and 56.38% and 107.54%, respectively, compared to the monoculture treatment. The primary controls for this phenomenon were the plant biomass and the concentrations of dissolved organic carbon and phenolics. Warming significantly increased the emissions of CO2 by ∼40% during the study period, but it reduced the fluxes of CH4 in 2021. Sustained warming and soil water loss may destroy the original anaerobic environment, which plays a role in inhibiting the generation and emission of CH4 in the long term. Interestingly, although warming has reduced CH4 emissions, a mixture of three and four species seems to buffer more than 50% of this impact, further demonstrating the positive contribution of species diversity. Our results indicate that an increase in species diversity, specifically manifested in the expansion of vascular plants as a community process adapting to warming, can strongly affect carbon fluxes in peatlands and create potential feedback on future climate environments.