C4. Vegetation changes in future climate

When vegetation is modelled as a dynamic component of the climate system, then the structural attributes of vegetation (leaf area index, vegetation height and rooting depth) are able to respond to changes in climate and this in turn also affects the climate. Studies have shown that these bi-directional interactions, between the vegetation and climate, increase the variability of climate (Crucifix et al., 2005; Wang et al., 2011). In this regard, vegetation influences the extremes of climate. The Canadian Terrestrial Ecosystem Model (CTEM) has recently been implemented in CRCM5. CTEM is the dynamic vegetation component of the CCCma’s Earth System Models.

While the current version of CTEM models vegetation as a dynamic component of the climate system in the vertical direction, it does not do so in the horizontal direction. That is, while the vegetation responds to changes in climate by changing its leaf area index, its height and the depth of its roots, it does not change its fractional coverage. This requires modelling of competition between different plant functional types (PFTs) for available space in a climate model grid cell. While CTEM includes a parameterization of competition between PFTs (Arora and Boer, 2006), the competition between PFTs cannot be realistically modelled unless each PFT in a climate model grid cell is allowed to maintain its own energy and water balance. This requires the mosaic/tiling capability within the land-surface scheme to which CTEM is coupled. The recent version of CLASS includes this capability and therefore now it is possible to switch on the competition parameterization of CTEM.

This project will quantify the effects of dynamic vegetation on the simulated variability of the climate system and climate extremes and will include the modelling of competition between PFTs within the CRCM5 framework and investigate how changing distribution of PFTs, e.g. northward movement of boreal forests, affects the future climate and its variability.