CO2 fluxes in adjacent new and permanent temperate grasslands

Carbon dioxide (CO₂) fluxes and grass production were measured in adjacent new and permanent intensively managed, Lolium perenne grasslands. Cumulative grass production during 2004 was 0.38 and 0.70 kg C m^-2 year^-1 in the new and permanent sites, respectively. Chamber measurements were used to create site-specific statistical response functions of gross primary production (GPP) and total respiration (R_TOT) at the two sites. A 1-year time series of GPP and R_TOT was reconstructed by combining these functions with measurements of leaf area index (LAI) and continuous meteorological data. Net ecosystem exchange (NEE) was estimated by subtracting R_TOT from GPP. Seasonal variation in GPP closely followed the changes in grass production and LAI. R_TOT increased in summertime due to increased soil temperature and optimal soil moisture conditions. Both sites were net CO₂ sinks during the grass growing season. Cumulative values of GPP, R_TOT and NEE in the new grassland were 2.14, -1.98 and 0.15 kg C m^-2 year^-1, respectively. In the permanent grassland cumulative values of GPP, R_TOT and NEE were 2.90, -2.52 and 0.38 kg C m^-2 year^-1, respectively.