Variability of annual CO<sub>2</sub> exchange from Dutch grasslands

Abstract

Abstract. An intercomparison is made of the Net Ecosystem Exchange of CO 2 , NEE, for eight Dutch grassland sites: four natural grasslands, two production grasslands and two meteorological stations within a rotational grassland region. At all sites the NEE was determined during at least 10 months per site, using the eddy-covariance (EC) technique, but in different years. The NEE does not include any import or export other than CO 2 . The photosynthesis-light response analysis technique is used along with the respiration-temperature response technique to partition NEE into Gross Primary Production (GPP) and Ecosystem Respiration (R e ) and to obtain the eco-physiological characteristics of the sites at the field scale. Annual sums of NEE, GPP and R e are then estimated using the fitted response curves with observed radiation and air temperature from a meteorological site in the centre of The Netherlands as drivers. These calculations are carried out for four years (2002)(2003)(2004)(2005). Land use and management histories are not considered. The estimated annual R e for all individual sites is more or less constant per site and the average for all sites amounts to 1390±30 gC m −2 a −1 . The narrow uncertainty band (±2%) reflects the small differences in the mean annual air temperature. The mean annual GPP was estimated to be 1325 g C m −2 a −1 , and displays a much higher standard deviation, of ±110 gC m −2 a −1 (8%), which reflects the relatively large variation in annual solar radiation. The mean annual NEE amounts to -65±85 gC m −2 a −1 . From two sites, four-year records of CO 2 flux were available and analyzed (2002)(2003)(2004)(2005). Using the weather record of 2005 with optimizations from the other years, the standard deviation of annual GPP was estimated to be 171-206 gC m −2 a −1 (8-14%), of annual R e 227-247 gC m −2 a −1 (14-16%) and of annual NEE 176-276 gC m −2 a −1 . TheCorrespondence to: C. M. J. Jacobs (cor.jacobs@wur.nl) inter-site standard deviation was higher for GPP and R e , 534 gC m −2 a −1 (37.3%) and 486 gC m −2 a −1 (34.8%), respectively. However, the inter-site standard deviation of NEE was similar to the interannual one, amounting to 207 gC m −2 a −1 . Large differences occur due to soil type. The grasslands on organic (peat) soils show a mean net release of CO 2 of 220±90 g C m −2 a −1 while the grasslands on mineral (clay and sand) soils show a mean net uptake of CO 2 of 90±90 g C m −2 a −1 . If a weighing with the fraction of grassland on organic (20%) and mineral soils (80%) is applied, an average NEE of 28 ±90 g C m −2 a −1 is found. The results from the analysis illustrate the need for regionally specific and spatially explicit CO 2 emission estimates from grassland.

The impacts of drainage, nutrient status and management practice on the full carbon balance of grasslands on organic soils in a maritime temperate zone

“…fertilisation) of organic soils stimulate the aerobic oxidation of previously accumulated organic matter, promoting CO 2 and nitrous oxide (N 2 O) emissions while reducing methanogenesis (Byrne et al, 2004;Freibauer et al, 2004;Nieveen et al, 2005;Jacobs et al, 2007;Drösler et al, 2013;Schrier-Uijl et al, 2013). However, inter-regional spatio-temporal variability of CO 2 flux is high, particularly in western Europe.…”

Climate and site management as driving factors for the atmospheric greenhouse gas exchange of a restored wetland

“…However, the exact budget will depend on the vegetation and its canopy photosynthetic capacity and can be difficult to predict if a wetland is not yet in equilibrium, for example following restoration . It is known that site management plays a role, too, and Jacobs et al (2007) reported a rather unexpected average annual CO 2 release of 220±90 g C m −2 for four Dutch grasslands on organic soils having a relatively high water table and including both managed and unmanaged sites. In contrast, Hendriks et al (2007) observed a consistent net CO 2 uptake between 232 and 446 g C m −2 a −1 for a restored wet grassland with neither grazing nor cutting.…”

Grain Yield Observations Constrain Cropland CO2 Fluxes Over Europe

“…with R 10 the base respiration rate at 10 ∘ C, E a the ecosystem sensitivity coefficient in K, R * the universal gas constant, and T s (t) the instantaneous upper soil layer temperature in K. This Lloyd and Taylor (1994) (Jacobs et al, 2007). Also, since we do not have soil temperature in the reanalysis weather data, we replace T s in equation (10) with the 2 m air temperature (T air ), assuming that the error introduced by the larger diurnal amplitude of T air will average out over 24 h. We hence compute the daily soil respiration (R soil , in g C m −2 d −1 ) by integrating R s over a day and converting it from mg CO 2 to g C with a conversion factor (C f ):…”

“…Note that in practice, the R 10 and E a parameters from equation (10) were estimated from nighttime eddy-covariance NEE measurements, when no GPP and no R growth occur (see Jacobs et al, 2007). As a result, R soil represent not only R het as originally intended but also the whole plant maintenance respiration, both variables dependent on T air .…”