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Title: Evaluating the effect of alternative carbon allocation schemes in a land surface model (CLM4.5) on carbon fluxes, pools, and turnover in temperate forests

Abstract

How carbon (C) is allocated to different plant tissues (leaves, stem, and roots) determines how long C remains in plant biomass and thus remains a central challenge for understanding the global C cycle. We used a diverse set of observations (AmeriFlux eddy covariance tower observations, biomass estimates from tree-ring data, and leaf area index (LAI) measurements) to compare C fluxes, pools, and LAI data with those predicted by a land surface model (LSM), the Community Land Model (CLM4.5). We ran CLM4.5 for nine temperate (including evergreen and deciduous) forests in North America between 1980 and 2013 using four different C allocation schemes: i. dynamic C allocation scheme (named "D-CLM4.5") with one dynamic allometric parameter, which allocates C to the stem and leaves to vary in time as a function of annual net primary production (NPP); ii. an alternative dynamic C allocation scheme (named "D-Litton"), where, similar to (i), C allocation is a dynamic function of annual NPP, but unlike (i) includes two dynamic allometric parameters involving allocation to leaves, stem, and coarse roots; iii.–iv. a fixed C allocation scheme with two variants, one representative of observations in evergreen (named "F-Evergreen") and the other of observations in deciduous forests (named "F-Deciduous"). D-CLM4.5 generally overestimatedmore » gross primary production (GPP) and ecosystem respiration, and underestimated net ecosystem exchange (NEE). In D-CLM4.5, initial aboveground biomass in 1980 was largely overestimated (between 10 527 and 12 897 g C m -2) for deciduous forests, whereas aboveground biomass accumulation through time (between 1980 and 2011) was highly underestimated (between 1222 and 7557 g C m -2) for both evergreen and deciduous sites due to a lower stem turnover rate in the sites than the one used in the model. D-CLM4.5 overestimated LAI in both evergreen and deciduous sites because the leaf C–LAI relationship in the model did not match the observed leaf C–LAI relationship at our sites. Although the four C allocation schemes gave similar results for aggregated C fluxes, they translated to important differences in long-term aboveground biomass accumulation and aboveground NPP. For deciduous forests, D-Litton gave more realistic C stem/C leaf ratios and strongly reduced the overestimation of initial aboveground biomass and aboveground NPP for deciduous forests by D-CLM4.5. We identified key structural and parameterization deficits that need refinement to improve the accuracy of LSMs in the near future. These include changing how C is allocated in fixed and dynamic schemes based on data from current forest syntheses and different parameterization of allocation schemes for different forest types. Our results highlight the utility of using measurements of aboveground biomass to evaluate and constrain the C allocation scheme in LSMs, and suggest that stem turnover is overestimated by CLM4.5 for these AmeriFlux sites. Understanding the controls of turnover will be critical to improving long-term C processes in LSMs.« less

Authors:
 [1];  [1];  [1]; ORCiD logo [1]; ORCiD logo [1];  [2];  [3];  [1];  [4];  [2];  [5];  [6];  [7];  [8];  [9];  [10];  [10];  [11];  [1]
  1. Univ. of Arizona, Tucson, AZ (United States)
  2. West Virginia Univ., Morgantown, WV (United States)
  3. Columbia Univ., Palisades, NY (United States). Lamont-Doherty Earth Observatory
  4. Univ. of Arizona, Tucson, AZ (United States); Swiss Federal Research Inst., Birmensdorf (Switzerland); Polish Academy of Sciences (PAS), Krakow (Poland)
  5. Harvard Univ., Cambridge, MA (United States)
  6. Univ. of Colorado, Boulder, CO (United States)
  7. The Ohio State Univ., Columbus, OH (United States)
  8. Virginia Commonwealth Univ., Richmond, VA (United States)
  9. Univ. of New Mexico, Albuquerque, NM (United States)
  10. Indiana Univ., Bloomington, IN (United States)
  11. Univ. of Missouri, Columbia, MO (United States)
Publication Date:
Research Org.:
Univ. of Arizona, Tucson, AZ (United States)
Sponsoring Org.:
USDOE
OSTI Identifier:
1426775
Grant/Contract Number:  
SC0016011
Resource Type:
Journal Article: Accepted Manuscript
Journal Name:
Geoscientific Model Development (Online)
Additional Journal Information:
Journal Name: Geoscientific Model Development (Online); Journal Volume: 10; Journal Issue: 9; Journal ID: ISSN 1991-9603
Publisher:
European Geosciences Union
Country of Publication:
United States
Language:
English
Subject:
54 ENVIRONMENTAL SCIENCES

Citation Formats

Montané, Francesc, Fox, Andrew M., Arellano, Avelino F., MacBean, Natasha, Alexander, M. Ross, Dye, Alex, Bishop, Daniel A., Trouet, Valerie, Babst, Flurin, Hessl, Amy E., Pederson, Neil, Blanken, Peter D., Bohrer, Gil, Gough, Christopher M., Litvak, Marcy E., Novick, Kimberly A., Phillips, Richard P., Wood, Jeffrey D., and Moore, David J. P. Evaluating the effect of alternative carbon allocation schemes in a land surface model (CLM4.5) on carbon fluxes, pools, and turnover in temperate forests. United States: N. p., 2017. Web. doi:10.5194/gmd-10-3499-2017.
Montané, Francesc, Fox, Andrew M., Arellano, Avelino F., MacBean, Natasha, Alexander, M. Ross, Dye, Alex, Bishop, Daniel A., Trouet, Valerie, Babst, Flurin, Hessl, Amy E., Pederson, Neil, Blanken, Peter D., Bohrer, Gil, Gough, Christopher M., Litvak, Marcy E., Novick, Kimberly A., Phillips, Richard P., Wood, Jeffrey D., & Moore, David J. P. Evaluating the effect of alternative carbon allocation schemes in a land surface model (CLM4.5) on carbon fluxes, pools, and turnover in temperate forests. United States. doi:10.5194/gmd-10-3499-2017.
Montané, Francesc, Fox, Andrew M., Arellano, Avelino F., MacBean, Natasha, Alexander, M. Ross, Dye, Alex, Bishop, Daniel A., Trouet, Valerie, Babst, Flurin, Hessl, Amy E., Pederson, Neil, Blanken, Peter D., Bohrer, Gil, Gough, Christopher M., Litvak, Marcy E., Novick, Kimberly A., Phillips, Richard P., Wood, Jeffrey D., and Moore, David J. P. Fri . "Evaluating the effect of alternative carbon allocation schemes in a land surface model (CLM4.5) on carbon fluxes, pools, and turnover in temperate forests". United States. doi:10.5194/gmd-10-3499-2017. https://www.osti.gov/servlets/purl/1426775.
@article{osti_1426775,
title = {Evaluating the effect of alternative carbon allocation schemes in a land surface model (CLM4.5) on carbon fluxes, pools, and turnover in temperate forests},
author = {Montané, Francesc and Fox, Andrew M. and Arellano, Avelino F. and MacBean, Natasha and Alexander, M. Ross and Dye, Alex and Bishop, Daniel A. and Trouet, Valerie and Babst, Flurin and Hessl, Amy E. and Pederson, Neil and Blanken, Peter D. and Bohrer, Gil and Gough, Christopher M. and Litvak, Marcy E. and Novick, Kimberly A. and Phillips, Richard P. and Wood, Jeffrey D. and Moore, David J. P.},
abstractNote = {How carbon (C) is allocated to different plant tissues (leaves, stem, and roots) determines how long C remains in plant biomass and thus remains a central challenge for understanding the global C cycle. We used a diverse set of observations (AmeriFlux eddy covariance tower observations, biomass estimates from tree-ring data, and leaf area index (LAI) measurements) to compare C fluxes, pools, and LAI data with those predicted by a land surface model (LSM), the Community Land Model (CLM4.5). We ran CLM4.5 for nine temperate (including evergreen and deciduous) forests in North America between 1980 and 2013 using four different C allocation schemes: i. dynamic C allocation scheme (named "D-CLM4.5") with one dynamic allometric parameter, which allocates C to the stem and leaves to vary in time as a function of annual net primary production (NPP); ii. an alternative dynamic C allocation scheme (named "D-Litton"), where, similar to (i), C allocation is a dynamic function of annual NPP, but unlike (i) includes two dynamic allometric parameters involving allocation to leaves, stem, and coarse roots; iii.–iv. a fixed C allocation scheme with two variants, one representative of observations in evergreen (named "F-Evergreen") and the other of observations in deciduous forests (named "F-Deciduous"). D-CLM4.5 generally overestimated gross primary production (GPP) and ecosystem respiration, and underestimated net ecosystem exchange (NEE). In D-CLM4.5, initial aboveground biomass in 1980 was largely overestimated (between 10 527 and 12 897 g C m-2) for deciduous forests, whereas aboveground biomass accumulation through time (between 1980 and 2011) was highly underestimated (between 1222 and 7557 g C m-2) for both evergreen and deciduous sites due to a lower stem turnover rate in the sites than the one used in the model. D-CLM4.5 overestimated LAI in both evergreen and deciduous sites because the leaf C–LAI relationship in the model did not match the observed leaf C–LAI relationship at our sites. Although the four C allocation schemes gave similar results for aggregated C fluxes, they translated to important differences in long-term aboveground biomass accumulation and aboveground NPP. For deciduous forests, D-Litton gave more realistic Cstem/Cleaf ratios and strongly reduced the overestimation of initial aboveground biomass and aboveground NPP for deciduous forests by D-CLM4.5. We identified key structural and parameterization deficits that need refinement to improve the accuracy of LSMs in the near future. These include changing how C is allocated in fixed and dynamic schemes based on data from current forest syntheses and different parameterization of allocation schemes for different forest types. Our results highlight the utility of using measurements of aboveground biomass to evaluate and constrain the C allocation scheme in LSMs, and suggest that stem turnover is overestimated by CLM4.5 for these AmeriFlux sites. Understanding the controls of turnover will be critical to improving long-term C processes in LSMs.},
doi = {10.5194/gmd-10-3499-2017},
journal = {Geoscientific Model Development (Online)},
number = 9,
volume = 10,
place = {United States},
year = {Fri Sep 22 00:00:00 EDT 2017},
month = {Fri Sep 22 00:00:00 EDT 2017}
}

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