Annual CO2 fluxes from a cultivated fen with perennial grasses during two initial years of rewetting

Abstract

Rewetting combined with biomass crop cultivation (paludiculture) has been proposed as a method for reducing carbon dioxide (CO2) emissions from drained peatlands. This field experiment compared CO2 fluxes from drained (control) and rewetted experimental plots in a temperate fen under reed canary grass cultivation over two successive years. The annual weighted mean water table depth from soil surface (WTD) during the study period was 9, 3 and 1 cm in control, semi-flooded and flooded plots, respectively. There were no significant effects of WTD treatment on biomass yields. The choice of response model for CO2 fluxes influenced annual estimates of ecosystem respiration (ER) and gross primary production (GPP), but all models showed that ER and GPP decreased in response to rewetting. The resulting net ecosystem exchange (NEE) of CO2, derived by combining eight ER and eight GPP models, varied widely. For example, NEE (expressed as CO2-C) ranged from 935 to -208 g m 2 yr-1 for the flooded plots. One set of ER and GPP models was selected on the basis of statistical criteria and showed insignificant differences in NEE between the three water table treatments ( 537 to -341 g CO2-C m-2 yr 1). Treatment effects on CO2 emission factors, calculated as the sum of NEE and C export in harvested biomass (58–242 g CO2-C m-2 yr-1), were similarly insignificant. Thus, the results indicated that varying WTD within this narrow range could influence both ER and GPP without altering the net emissions of CO2.

Keywords

• ecosystem respiration
• gross primary production
• paludiculture
• reed canary grass