Browsing by Subject "ecosystem respiration"

Peat lands are net sinks of carbon (C) and a net source of carbon dioxide (CO2) emissions owing to drainage during the growing season. The surface peat layer can be lost because of aerobic decomposition (oxidation) after drainage resulting in emissions of CO2. One way to reduce these emissions is to keep the water table at a high level as much as possible. The resulting anoxic conditions reduce the decomposition of organic matter and hence CO2 emissions. In the current Finnish agri-environmental scheme, the farmers may receive subsidies for controlled drainage on peatlands, and a raised ground water level through controlled drainage could be used as a greenhouse gas mitigation measure. This study reports the carbon balance of drained peatland under controlled drainage during the growing season in Mouhijärvi, Southwestern Finland. The CO2 fluxes measured with a transparent chamber method were divided into gross primary productivity (GPP) and ecosystem respiration (ER) for modelling based on environmental factors (light and temperature) and canopy reflectance (leaf area index, LAI). The GPP model estimates the effect of light and vegetation status, whereas the ER model captures the share of foliar biomass-dependent respiration and the ground water table. The sum of the study period (June–August 2016) GPP varied from -1301 to -670 g C m-2, ER from 632 to 1029 g C m-2 and net ecosystem exchange (NEE) from -322 to 68.5 g C m-2. NEE indicated a net sink of C in all plots except one with poor crop growth. The net ecosystem carbon balance (as the sum of NEE and carbon export as grains), indicated a net source of carbon in both plots with controlled drainage and a net sink in conventionally drained plots during the cultivation period. The greatest sink reported either as NEE or with the harvest included was the wettest plot, indicating that cereal production is possible in wetter than normal conditions.