CO2 exchange and carbon balance in two grassland sites on eutrophic drained peat soils
- 1Nature Conservation and Plant Ecology Group, Wageningen University, Droevendaalse Steeg 3a, 6708 PD Wageningen, The Netherlands
- 2Max Planck institute for Biogeochemistry, Hans Knöll Straße 10D, 07745 Jena, Germany
- 3Department of Plant Production Systems, Wageningen University, P.O. Box 430, 6700 AK Wageningen, The Netherlands
- 4Free University, Department of Hydrology and Geo-Environmental Sciences, Faculty of Earth and Life Sciences, Boelelaan 1085, 1081 HV Amsterdam, The Netherlands
Abstract. In this study we investigated the role of intensive and extensive dairy farm practices on CO2 exchange and the carbon balance of peatlands by means of eddy covariance (EC) measurements. Year long EC measurements were made in two adjacent farm sites on peat soil in the western part of the Netherlands. One site (Stein) is a new meadow bird reserve and is managed predominantly by mowing in June and August. The second site (Oukoop) is an intensive dairy farm.
Maximum photosynthetic uptake of the grass sward (range 2 to 34 μmol CO2 m−2 s−1) showed a close and similar linear relationship with Leaf Area Index (LAI; range 1 to 5) except in maturing hay meadows, where maximum photosynthetic uptake did not increase further. Apparent quantum yield varied between 0.02 and 0.08 (mean 0.045) μmol CO2 μmol−1 photons at both sites and was significantly correlated with LAI during the growth season. Ecosystem Respiration at 10°C (R10) calculated from the year round data set was 3.35 μmol CO2 m−2 s−1 at Stein and 3.69 μmol CO2 m−2 s−1 at Oukoop.
Both sites were a source of carbon in winter and a sink during summer with net ecosystem exchange varying between 50 to 100 mmol CO2 m−2 d−1 in winter to below −400 mmol CO2 m−2 d−1 in summer. Periodically, both sites became a source after mowing. Net annual ecosystem exchange (NEE) for Stein was −5.7 g C m−2 a−1 and for Oukoop 133.9 g C m−2 a−1.
When biomass removal, manure applications and estimates of methane emissions ware taken into account, both eutrophic peat meadows are a strong source for C around 420 g C m−2 a−1.