EGUsphere

Copernicus Publications

Göttingen, Germany

10.5194/egusphere-2023-1167

Optimizing maximum carboxylation rate for North America’s boreal forests in the Canadian Land Surface Scheme Including Biogeochemical Cycles (CLASSIC) v.1.3

¹ ² ³ Roy

Alexandre

² ³ Melton

Joe R.

https://orcid.org/0000-0002-9414-064X

⁴ Baltzer

Jennifer L.

https://orcid.org/0000-0001-7476-5928

⁵ Ryu

Youngryel

https://orcid.org/0000-0001-6238-2479

⁶ Detto

Matteo

⁷ Sonnentag

Oliver

¹ ²

Département de géographie, Université de Montréal, Montréal, QC H2V 0B3, Canada

Centre d’Études Nordiques, Université Laval, Québec, QC G1V 0A6, Canada

Centre de recherche sur les interactions bassins versants-écosystèmes aquatiques (RIVE), Université du Québec à Trois-Rivières, Trois-Rivières, QC G8Z 4M3, Canada

Climate Research Division, Environment and Climate Change Canada, Victoria, BC V8W 2Y2, Canada

Biology Department, Wilfrid Laurier University, Waterloo, ON N2L 3C5, Canada

Department of Landscape Architecture and Rural Systems Engineering, College of Agriculture and Life Sciences, Seoul National University, Seoul 08826, Republic of Korea

Department of Ecology and Evolutionary Biology, Princeton University, Princeton, NJ 08544, USA

19 07 2023

2023 1 19

2023

This work is licensed under the Creative Commons Attribution 4.0 International License. To view a copy of this licence, visit https://creativecommons.org/licenses/by/4.0/

This article is available from https://egusphere.copernicus.org/preprints/2023/egusphere-2023-1167/

The full text article is available as a PDF file from https://egusphere.copernicus.org/preprints/2023/egusphere-2023-1167/egusphere-2023-1167.pdf

The maximum carboxylation rate (Vcmax) is an important parameter for the coupled simulation of gross primary production (GPP) and evapotranspiration (ET) in terrestrial biosphere models (TBMs) such as the Canadian Land Surface Scheme Including biogeochemical Cycles (CLASSIC). Observations of Vcmax show it to vary both spatially and temporally, but it is often prescribed as constant in time and space for plant functional types (PFTs) in TBMs, which introduces large errors over North America’s boreal biome. To reduce this uncertainty, we used a Bayesian algorithm to optimize Vcmax25 (Vcmax at 25 °C) in CLASSIC against eddy covariance observations at eight mature boreal forest stands in North America for six representative PFTs (two trees, two shrubs, and two herbs). As expected, the simulated GPP and ET using the optimized parameters generally obtained reduced root mean square deviation values compared with eddy covariance observations and corresponding stand-level estimates obtained from gridded global data products. The optimized Vcmax25 values for each PFT compared reasonably well with reported estimates derived from leaf-level gas exchange measurements. However, a large spatial variability of Vcmax25 was identified, especially for the shrub and herb PFTs. We found that the site characteristics, particularly latitude for the shrub PFTs and air temperature for evergreen needleleaf tree, explained much of the spatial variability, providing a basis to improve Vcmax25 parameterizations in TBMs at regional scales.