Drivers of long-term variability in CO2 net ecosystem exchange in a temperate peatland

[摘要] Land–atmosphere exchange of carbon dioxide (CO₂) in peatlands exhibitsmarked seasonal and inter-annual variability, which subsequently affects thecarbon (C) sink strength of catchments across multiple temporal scales.Long-term studies are needed to fully capture the natural variability andtherefore identify the key hydrometeorological drivers in the net ecosystemexchange (NEE) of CO₂. Since 2002, NEE has been measured continuouslyby eddy-covariance at Auchencorth Moss, a temperate lowland peatland incentral Scotland. Hence this is one of the longest peatland NEE studies todate. For 11 years, the site was a consistent, yet variable, atmosphericCO₂ sink ranging from −5.2 to −135.9 g CO₂-C m⁻² yr⁻¹(mean of −64.1 ± 33.6 g CO₂-C m⁻² yr⁻¹). Inter-annualvariability in NEE was positively correlated to the length of the growingseason. Mean winter air temperature explained 87% of the inter-annualvariability in the sink strength of the following summer, indicating aneffect of winter climate on local phenology. Ecosystem respiration(R_eco) was enhanced by drought, which also depressed gross primaryproductivity (GPP). The CO₂ uptake rate during the growing season wascomparable to three other sites with long-term NEE records; however, the emissionrate during the dormant season was significantly higher. To summarise, theNEE of the peatland studied is modulated by two dominant factors:

- phenology of the plant community, which is driven by winter air temperature and impacts photosynthetic potential and net CO₂ uptake during the growing season (colder winters are linked to lower summerNEE),

- water table level, which enhanced soil respiration and decreased GPP during dry spells.

Although summer dry spells were sporadic during the study period, thepositive effects of the current climatic trend towards milder winters on thesite's CO₂ sink strength could be offset by changes in precipitationpatterns especially during the growing season.

[学科分类] 地球化学与岩石