Integrating peatlands into the coupled Canadian Land Surface Scheme (CLASS) v3.6 and the Canadian Terrestrial Ecosystem Model (CTEM) v2.0

Abstract

Abstract. Peatlands, which contain large carbon stocks that must be accounted for in the global carbon budget, are poorly represented in many earth system models. We integrated peatlands into the coupled Canadian Land Surface Scheme (CLASS) and the Canadian Terrestrial Ecosystem Model (CTEM), which together simulate the fluxes of water, energy, and CO 2 at the land surface-atmosphere boundary in the family of Canadian Earth system models (CanESMs). New components and algorithms were added to represent the unique features of peatlands, such as their characteristic ground floor vegetation (mosses), the slow decomposition of carbon in the water-logged soils and the interaction between the water, energy, and carbon cycles. This paper presents the modifications introduced into the CLASS-CTEM modelling framework together with site-level evaluations of the model performance for simulated water, energy and carbon fluxes at eight different peatland sites. The simulated daily gross primary production (GPP) and ecosystem respiration are well correlated with observations, with values of the Pearson correlation coefficient higher than 0.8 and 0.75 respectively. The simulated mean annual net ecosystem production at the eight test sites is 87 g C m −2 yr −1 , which is 22 g C m −2 yr −1 higher than the observed annual mean. The general peatland model compares well with other site-level and regional-level models for peatlands, and is able to represent bogs and fens under a range of climatic and geographical conditions.

ORCHIDEE-PEAT (revision 4596), a model for northern peatland CO<sub>2</sub>, water, and energy fluxes on daily to annual scales

“…The peat-saturated hydraulic conductivity value of 2.45 × 10 −5 m s −1 is comparable to the harmonic mean value (6 × 10 −5 m s −1 ) of Morris et al (2015). The values of the other Van Genuchten parameters for peat (Table 1) are similar to those employed in other peatland models (Wania et al, 2009a;Wu et al, 2016).…”

“…Correct representation of peatland hydrology is a challenging problem in large-scale land surface models (Wania et al, 2009a;Wu et al, 2016). The simulated water table by ORCHIDEE-PEAT depends on water inflows from the surrounding non-peatland areas, and a water-routing analysis on subgrid scales can be included to improve the model performance for water table in the future (Ringeval et al, 2012;Stocker et al, 2014).…”

Modelling northern peatland area and carbon dynamics since the Holocene with the ORCHIDEE-PEAT land surface model (SVN r5488)

“…Another approach to estimate peatland area and peat C is to use a soil organic matter map to outline organic-rich areas, such as Histosols and Histels (Köchy et al, 2015;Spahni et al, 2013). This approach overlooks local hydrological conditions and vegetation composition (Wu et al, 2017). Our model estimates of peatland area and C stock generally fall well within the range of published estimates, except in the southeastern US, where there is only 0.05-0.10 million km 2 of peatland in observations but 0.37 million km 2 in the model prediction (Fig.…”

An assessment of geographical distribution of different plant functional types over North America simulated using the CLASS–CTEM modelling framework

“…The model also does not represent peatlands, and as a result the model grows trees and grasses in regions where peatlands exists. Work is under way to incorporate a peatland model developed for CLASS-CTEM (Wu et al, 2016) into our modelling framework.…”