Bo Qu
Ph.D. student
Department of geography
University of Montreal

Supervised by:

Oliver Sonnentag (Regular member)

Research project description

Assimilation of satellite-based passive microwave data products into a terrestrial ecosystem model for refined boreal forest productivity estimates across Canada

The world’s boreal forests constitute an integral component of the climate system, affecting land surface-atmosphere interactions and large-scale circulation patterns. About 80% of the world’s boreal forests contain permafrost, perennially cryotic ground. For example, in northwestern North America, the northernmost boreal forests grow on relatively cold permafrost at the transition from continuous to discontinuous permafrost. Further south, boreal forests occur in areas with relatively warm and thin permafrost that can be isolated, sporadic, and discontinuous. There, permafrost is in disequilibrium with the current climate, and its presence is driven by abiotic and biotic ecosystem properties (e.g., vegetation, soil organic layer thickness, snow, local topography). The permafrost region of the Northern Hemisphere has been warming twice the global rate yet our understanding of how warming may affect boreal forest productivity, and thus how boreal forests function as part of the climate system, remains limited. Thawing permafrost, wildfires, insect outbreaks, and water limitations and heat stress represent major natural disturbances leading to short- or long-term decline in boreal forest composition, structure and function. At the same time, climate warming and post-fire succession have been shown to enhance vegetation productivity. Regional thaw-induced forest loss and a decline in satellite-based measures of forest productivity have been reported for boreal forests along the southern margin of permafrost distribution especially in northwestern North America. In contrast, increased productivity has been detected in northern boreal forests where the treeline is advancing into some areas presently occupied by subarctic woodlands and Arctic tundra. Changes in extent and productivity of boreal forests will alter boreal land surface-atmosphere interactions in the near future under rapidly changing climatic conditions. The inter- and intra-species divergence in observed boreal forest productivity trends in response to disturbances and climate change may stem from poorly understood spatial heterogeneities in changing biotic (i.e., plant functional traits) and abiotic factors (e.g., thawing permafrost and resulting changes in hydrological conditions) and their interactions. The goal of my doctoral research is to provide refined boreal forest productivity estimates for Canada by improving the land surface component of the Canadian Terrestrial Ecosystem Model (CTEM), the terrestrial carbon cycle component of the Canadian Global Coupled Carbon Cycle Model (CGC3M). Specific attention will be paid to the soil moisture and thermal components of CTEM simulated through the Canadian Land Surface Scheme (CLASS). The current implementation of CLASS-CTEM has limited skill to accurately simulate stand-level boreal forest productivity, partly because the model fails to accurately describe the wide range of soil moisture and thermal conditions characteristic for different boreal forest stands. After stand-level testing and refining (e.g., root water-uptake scheme, permafrost and resulting soil moisture and thermal dynamics) the current version of CLASS-CTEM against ecosystem carbon, water and energy fluxes from different permafrost-free and permafrost boreal forest sites across Canada (e.g., Southern Old Black Spruce in central Saskatchewan: permafrost-free boreal forest; Scotty Creek in the southern Northwest Territories: forested boreal peat landscape with sporadic permafrost; Chibougamou in central Québec: permafrost-free boreal forest), various satellite-based passive microwave data products (soil moisture and landscape freeze/thaw from Soil Moisture Ocean Salinity [SMOS], Soil Moisture Active Passive [SMAP] and Advanced Microwave Scanning Radiometers [AMSR-2]) will be assimilated into CLASS-CTEM to improve regional boreal forest productivity estimates across Canada through improved CLASS simulations of spatially and temporally varying soil moisture and thermal conditions under the influence of climate change. 

Research Site Coordinates

Scientific Communications

Qu, B., Roy, A.R., Melton, J., Black, T., Amiro, B., Euskirchen, E., Ueyama, M., Kobayashi, H., Schulze, C., Gosselin, G., Cannon, A., Detto, M., Sonnentag, O., 2023. A boreal forest model benchmarking dataset for North America: a case study with the Canadian Land Surface Scheme Including Biogeochemical Cycles (CLASSIC). <strong>Environmental Research Letters</strong>, 18, 085002. DOI: <a href="" target="_blank">10.1088/1748-9326/ace376</a>.

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