Journal cover Journal topic
Biogeosciences An interactive open-access journal of the European Geosciences Union
doi:10.5194/bg-2017-35
© Author(s) 2017. This work is distributed
under the Creative Commons Attribution 3.0 License.
Research article
06 Mar 2017
Review status
This discussion paper is under review for the journal Biogeosciences (BG).
An assessment of geographical distribution of different plant functional types over North America simulated using the CLASS-CTEM modelling framework
Rudra K. Shrestha1, Vivek K. Arora1, Joe R. Melton2, and Laxmi Sushama3 1Canadian Centre for Climate Modelling and Analysis, Environment and Climate Change Canada, University of Victoria, Victoria, BC, V8W 2Y2, Canada
2Climate Research Division, Environment and Climate Change Canada, Toronto, Ontario, Canada
3Département des sciences de la Terre et de l'atmosphère, Université du Québec à Montréal, Canada
Abstract. The performance of the competition module of the CLASS-CTEM (Canadian Land Surface Scheme and Canadian Terrestrial Ecosystem Model) modelling framework is assessed at 1° spatial resolution over North America by comparing the simulated geographical distribution of plant functional types (PFTs) with two observation-based estimates. The model successfully reproduces the broad geographical distribution of trees, grasses and bare ground although limitations remain. In particular, compared to the two observation-based estimates, the simulated fractional vegetation coverage is lower in the arid south-west North American region and higher in the Arctic region. The lower than observed simulated vegetation coverage in the south-west region is attributed to lack of representation of shrubs in the model and plausible errors in the observation-based data sets. The observation-based data indicates vegetation fractional coverage of more than 60 % in this arid region, despite only 200–300 mm of precipitation that the region receives annually and observation-based leaf area index (LAI) in the region are lower than one. The higher than observed vegetation fractional coverage in the Arctic is due to the lack of representation of moss and lichen PFTs and also likely because of inadequate representation of permafrost in the model as a result of which the C3 grass PFT performs overly well in the region. The model generally reproduces the broad spatial distribution and the total area covered by the two primary tree PFTs (needleleaf evergreen and broadleaf cold deciduous trees) reasonably well. The simulated fractional coverage of tree PFTs increases after 1960s in response to the CO2 fertilization effect and climate warming. Differences between observed and simulated PFT coverages highlight limitations in the model and provide insight into physical and structural processes that need improvement.

Citation: Shrestha, R. K., Arora, V. K., Melton, J. R., and Sushama, L.: An assessment of geographical distribution of different plant functional types over North America simulated using the CLASS-CTEM modelling framework, Biogeosciences Discuss., doi:10.5194/bg-2017-35, in review, 2017.
Rudra K. Shrestha et al.
Rudra K. Shrestha et al.
Rudra K. Shrestha et al.

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Short summary
Computer models of vegetation provide a tool to assess how future changes in climate may affect geographical distribution of vegetation. However, such models must first be assessed for their ability to reproduce present day geographical distribution of vegetation. Here, we assess the ability of one such dynamic vegetation model. We find that while the model is broadly successful in reproducing the geographical distribution of trees and grasses in North America some limitations remain.
Computer models of vegetation provide a tool to assess how future changes in climate may affect...
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