Regulation Mechanisms of CO2 Fluxes in Subtropical Mountain Peatlands Based on Long-Term In Situ Observations at the Dajiuhu Peatland

Abstract

The Dajiuhu peatland in Shennongjia, China, is a highly representative subalpine peatland, emblematic of subtropical mountainous peatlands. Due to the lack of long-term in situ continuous observations and in-depth studies on CO₂ absorption and emission patterns, the regulation mechanisms of CO₂ flux in subtropical peatlands remain unclear. Since July 2015, we have conducted over five years of continuous in situ observations of CO₂ fluxes and major environmental factors in the Dajiuhu peatland ecosystem. We calculated the annual average net ecosystem carbon exchange (NEE) of CO₂ and decomposed NEE into gross primary productivity (GPP) and ecosystem respiration (Reco), thus examining the peatland ecosystem's absorption and emission of CO₂ separately. The results indicate that the annual average NEE from 2016 to 2020 was −283.6 g C m⁻² yr⁻¹, reflecting a strong CO₂ sink. Our study indicates the regulation mechanisms of CO₂ flux in the peatland. Temperature is the most direct factor affecting CO₂ absorption and emission, serving as the most important driver of CO₂ flux on short time scales. Precipitation only affects CO₂ absorption but has a significant impact on NEE, being a key factor in maintaining the peatland's CO₂ sink function. Variations in annual precipitation also led to differences in net CO₂ absorption between years. Our results illustrate an important role of sub-tropical mountain peatlands in mitigating the greenhouse effect and maintaining moisture conditions is crucial for protecting its ecological functions.