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Title: Comparing ecosystem and soil respiration: Review and key challenges of tower-based and soil measurements

The net ecosystem exchange (NEE) is the difference between ecosystem CO 2 assimilation and CO 2 losses to the atmosphere. Ecosystem respiration (Reco), the efflux of CO 2 from the ecosystem to the atmosphere, includes the soil-to-atmosphere carbon flux (i.e., soil respiration; Rsoil) and aboveground plant respiration. Therefore, Rsoil is a fraction of Reco and theoretically has to be smaller than Reco at daily, seasonal, and annual scales. But, several studies estimating Reco with the eddy covariance technique and measuring Rsoil within the footprint of the tower have reported higher Rsoil than Reco at different time scales. Here, we compare four different and contrasting ecosystems (from forest to grasslands, and from boreal to semiarid) to test if measurements of Reco are consistently higher than Rsoil. In general, both fluxes showed similar temporal patterns, but Reco was not consistently higher than Rsoil from daily to annual scales across sites. We also identified several issues that apply for measuring NEE and measuring/upscaling Rsoil that could result in an underestimation of Reco and/or an overestimation of Rsoil. These issues are discussed based on (a) nighttime measurements of NEE, (b) Rsoil measurements, and (c) the interpretation of the functional relationships of these fluxes withmore » temperature (i.e., Q10). Finally, we highlight that there is still a need for better integration of Rsoil with eddy covariance measurements to address challenges related to the spatial and temporal variability of Reco and Rsoil.« less
Authors:
 [1] ;  [2] ;  [3] ;  [4] ;  [5] ;  [6] ;  [1] ;  [7] ;  [8] ;  [9] ;  [3] ;  [1]
  1. Univ. of Delaware, Newark, DE (United States). Dept. of Plant and Soil Science
  2. Center for Scientific Research and Higher Education at Ensenada , BC (Mexico). Dept. of Biological Conservation
  3. Univ. of Innsbruck (Austria). Inst. of Ecology
  4. Univ. of Arizona, Tucson, AZ (United States). School of Geography and Development, B2 Earth Science
  5. Pacific Northwest National Lab. (PNNL), Richland, WA (United States). Joint Global Change Research Inst.
  6. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Environmental Science Division
  7. Univ. of Helsinki (Finland). Dept. of Forest Sciences
  8. Univ. of Eastern Finland, Kuopio (Finland). Dept. of Environmental and Biological Sciences
  9. Southwest Watershed Research Center, Tucson, AZ (United States)
Publication Date:
Report Number(s):
PNNL-SA-124283
Journal ID: ISSN 0168-1923; PII: S0168192317303556
Grant/Contract Number:
AC05-76RL01830; 1137178; NNX13AQ06G; 2014-67003-22070
Type:
Accepted Manuscript
Journal Name:
Agricultural and Forest Meteorology
Additional Journal Information:
Journal Volume: 249; Journal ID: ISSN 0168-1923
Publisher:
Elsevier
Research Org:
Pacific Northwest National Lab. (PNNL), Richland, WA (United States)
Sponsoring Org:
USDOE Office of Science (SC); National Science Foundation (NSF); National Aeronautic and Space Administration (NASA); United States Department of Agriculture (USDA)
Country of Publication:
United States
Language:
English
Subject:
54 ENVIRONMENTAL SCIENCES; net ecosystem exchange (NEE); soil CO2 efflux; temperature sensitivity; Q10; eddy covariance; AmeriFlux; FluxNet
OSTI Identifier:
1413484