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| Titel |
Variability of annual CO2 exchange from Dutch grasslands |
| VerfasserIn |
C. M. J. Jacobs, A. F. G. Jacobs, F. C. Bosveld, D. M. D. Hendriks, A. Hensen, P. S. Kroon, E. J. Moors, L. Nol, A. Schrier-Uijl, E. M. Veenendaal |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1726-4170
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| Digitales Dokument |
URL |
| Erschienen |
In: Biogeosciences ; 4, no. 5 ; Nr. 4, no. 5 (2007-10-08), S.803-816 |
| Datensatznummer |
250001963
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| Publikation (Nr.) |
 copernicus.org/bg-4-803-2007.pdf |
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| Zusammenfassung |
| An intercomparison is made of the Net Ecosystem Exchange of CO2, 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 CO2. 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 (Re) and to obtain the
eco-physiological characteristics of the sites at the field scale. Annual
sums of NEE, GPP and Re 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 (2002–2005). Land use and management histories are not
considered. The estimated annual Re 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 CO2 flux were available and analyzed (2002–2005).
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 Re 227–247 gC m−2 a−1
(14–16%) and of annual NEE 176–276 gC m−2 a−1. The inter-site
standard deviation was higher for GPP and Re, 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
CO2 of 220±90 g C m−2 a−1 while the grasslands on
mineral (clay and sand) soils show a mean net uptake of CO2 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 CO2
emission estimates from grassland. |
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