Representative estimates of soil and ecosystem respiration in an old beech forest |
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Authors: | Alexander Knohl Astrid R B Søe Werner L Kutsch Mathias Göckede Nina Buchmann |
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Institution: | 1. Max Planck Institute for Biogeochemistry, Hans Kn?ll Str. 10, 07745, Jena, Germany 2. Institute of Plant Sciences, ETH Zürich, Universit?tstrasse 2, LFW C38, CH-8092, Zürich, Switzerland 3. Fertin Pharma, Dandyvej 19, DK-7100, Vejle, Denmark 4. Department of Forest Science, Oregon State University, Corvallis, OR, 97331, USA
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Abstract: | Respiration has been proposed to be the main determinant of the carbon balance in European forests and is thus essential for
our understanding of the carbon cycle. However, the choice of experimental design strongly affects estimates of annual respiration
and of the contribution of soil respiration to total ecosystem respiration. In a detailed study of ecosystem and soil respiration
fluxes in an old unmanaged deciduous forest in Central Germany over 3 years (2000–2002), we combined soil chamber and eddy
covariance measurements to obtain a comprehensive picture of respiration in this forest. The closed portable chambers offered
to investigate spatial variability of soil respiration and its controls while the eddy covariance system offered continuous
measurements of ecosystem respiration. Over the year, both fluxes were mainly correlated with temperature. However, when soil
moisture sank below 23 vol.% in the upper 6 cm, water limitations also became apparent. The temporal resolution of the eddy
covariance system revealed that relatively high respiration rates occurred during budbreak due to increased metabolic activity
and after leaf fall because of increased decomposition. Spatial variability in soil respiration rates was large and correlated
with fine root biomass (r
2 = 0.56) resulting in estimates of annual efflux varying across plots from 730 to 1,258 (mean 898) g C m−2 year−1. Power function calculations showed that achieving a precision in the soil respiration estimate of 20% of the full population
mean at a confidence level of 95%, requires about eight sampling locations. Our results can be used as guidelines to improve
the representativeness of soil respiration measurements by nested sampling designs, being applied in long-term and large-scale
carbon sequestration projects such as FLUXNET and CarboEurope. |
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Keywords: | Carbon flux Eddy covariance Footprint Soil CO2 efflux Sampling design Uncertainty analysis Monte Carlo simulation |
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