Seeing the Canopy for the Branches: Improved Within Canopy Scaling of Leaf Nitrogen
Abstract Transitioning across biological scales is a central challenge in land surface models. Processes that operate at the scale of individual leaves must be scaled to canopies, and this is done using dedicated submodels. Here, we focus on a submodel that prescribes how light and nitrogen are dist...
| Main Authors: | , , , , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
American Geophysical Union (AGU)
2020-10-01
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| Series: | Journal of Advances in Modeling Earth Systems |
| Subjects: | |
| Online Access: | https://doi.org/10.1029/2020MS002237 |
| _version_ | 1818354405327503360 |
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| author | Ethan E. Butler Ming Chen Daniel Ricciuto Habacuc Flores‐Moreno Kirk R. Wythers Jens Kattge Peter E. Thornton Peter B. Reich |
| author_facet | Ethan E. Butler Ming Chen Daniel Ricciuto Habacuc Flores‐Moreno Kirk R. Wythers Jens Kattge Peter E. Thornton Peter B. Reich |
| author_sort | Ethan E. Butler |
| collection | DOAJ |
| description | Abstract Transitioning across biological scales is a central challenge in land surface models. Processes that operate at the scale of individual leaves must be scaled to canopies, and this is done using dedicated submodels. Here, we focus on a submodel that prescribes how light and nitrogen are distributed through plant canopies. We found a mathematical inconsistency in a submodel implemented in the Community and Energy Land Models (CLM and ELM), which incorporates twigs, branches, stems, and dead leaves in nitrogen scaling from leaf to canopy. The inconsistency leads to unrealistic (physically impossible) values of the nitrogen scaling coefficient. The mathematical inconsistency is a general mistake, that is, would occur in any model adopting this particular submodel. We resolve the inconsistency by allowing distinct profiles of stems and branches versus living leaves. We implemented the updated scheme in the ELM and find that the correction reduces global mean gross primary production (GPP) by 3.9 Pg C (3%). Further, when stems and branches are removed from the canopy in the updated model (akin to models that ignore shading from stems), global GPP increases by 4.1 Pg C (3.2%), because of reduced shading. Hence, models that entirely ignore stem shading also introduce errors in the global spatial distribution of GPP estimates, with a strong signal in the tropics, increasing GPP there by over 200 g C m−2 yr−1. Appropriately incorporating stems and other nonphotosynthesizing material into the light and nitrogen scaling routines of global land models, will improve their biological realism and accuracy. |
| first_indexed | 2024-12-13T19:24:54Z |
| format | Article |
| id | doaj.art-1300707db4fb4e91b592c528cc0de125 |
| institution | Directory Open Access Journal |
| issn | 1942-2466 |
| language | English |
| last_indexed | 2024-12-13T19:24:54Z |
| publishDate | 2020-10-01 |
| publisher | American Geophysical Union (AGU) |
| record_format | Article |
| series | Journal of Advances in Modeling Earth Systems |
| spelling | doaj.art-1300707db4fb4e91b592c528cc0de1252022-12-21T23:34:03ZengAmerican Geophysical Union (AGU)Journal of Advances in Modeling Earth Systems1942-24662020-10-011210n/an/a10.1029/2020MS002237Seeing the Canopy for the Branches: Improved Within Canopy Scaling of Leaf NitrogenEthan E. Butler0Ming Chen1Daniel Ricciuto2Habacuc Flores‐Moreno3Kirk R. Wythers4Jens Kattge5Peter E. Thornton6Peter B. Reich7Department of Forest Resources University of Minnesota St. Paul MN USADepartment of Forest Resources University of Minnesota St. Paul MN USAEnvironmental Sciences Division, Climate Change Science Institute Oak Ridge National Laboratory Oak Ridge TN USADepartment of Forest Resources University of Minnesota St. Paul MN USADepartment of Forest Resources University of Minnesota St. Paul MN USAMax Planck Institute for Biogeochemistry Jena GermanyEnvironmental Sciences Division, Climate Change Science Institute Oak Ridge National Laboratory Oak Ridge TN USADepartment of Forest Resources University of Minnesota St. Paul MN USAAbstract Transitioning across biological scales is a central challenge in land surface models. Processes that operate at the scale of individual leaves must be scaled to canopies, and this is done using dedicated submodels. Here, we focus on a submodel that prescribes how light and nitrogen are distributed through plant canopies. We found a mathematical inconsistency in a submodel implemented in the Community and Energy Land Models (CLM and ELM), which incorporates twigs, branches, stems, and dead leaves in nitrogen scaling from leaf to canopy. The inconsistency leads to unrealistic (physically impossible) values of the nitrogen scaling coefficient. The mathematical inconsistency is a general mistake, that is, would occur in any model adopting this particular submodel. We resolve the inconsistency by allowing distinct profiles of stems and branches versus living leaves. We implemented the updated scheme in the ELM and find that the correction reduces global mean gross primary production (GPP) by 3.9 Pg C (3%). Further, when stems and branches are removed from the canopy in the updated model (akin to models that ignore shading from stems), global GPP increases by 4.1 Pg C (3.2%), because of reduced shading. Hence, models that entirely ignore stem shading also introduce errors in the global spatial distribution of GPP estimates, with a strong signal in the tropics, increasing GPP there by over 200 g C m−2 yr−1. Appropriately incorporating stems and other nonphotosynthesizing material into the light and nitrogen scaling routines of global land models, will improve their biological realism and accuracy.https://doi.org/10.1029/2020MS002237climatemodelingvegetationland surfacephotosynthesisnitrogen |
| spellingShingle | Ethan E. Butler Ming Chen Daniel Ricciuto Habacuc Flores‐Moreno Kirk R. Wythers Jens Kattge Peter E. Thornton Peter B. Reich Seeing the Canopy for the Branches: Improved Within Canopy Scaling of Leaf Nitrogen Journal of Advances in Modeling Earth Systems climate modeling vegetation land surface photosynthesis nitrogen |
| title | Seeing the Canopy for the Branches: Improved Within Canopy Scaling of Leaf Nitrogen |
| title_full | Seeing the Canopy for the Branches: Improved Within Canopy Scaling of Leaf Nitrogen |
| title_fullStr | Seeing the Canopy for the Branches: Improved Within Canopy Scaling of Leaf Nitrogen |
| title_full_unstemmed | Seeing the Canopy for the Branches: Improved Within Canopy Scaling of Leaf Nitrogen |
| title_short | Seeing the Canopy for the Branches: Improved Within Canopy Scaling of Leaf Nitrogen |
| title_sort | seeing the canopy for the branches improved within canopy scaling of leaf nitrogen |
| topic | climate modeling vegetation land surface photosynthesis nitrogen |
| url | https://doi.org/10.1029/2020MS002237 |
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