Preprints
https://doi.org/10.5194/egusphere-2023-2003
https://doi.org/10.5194/egusphere-2023-2003
08 Sep 2023
 | 08 Sep 2023
Status: this preprint is open for discussion.

Implementing a dynamic representation of fire and harvest including subgrid-scale heterogeneity in the tile-based land surface model CLASSIC v1.45

Salvatore R. Curasi, Joe R. Melton, Elyn R. Humphreys, Txomin Hermosilla, and Michael A. Wulder

Abstract. Canada’s forests play a critical role in the global carbon (C) cycle and are responding to unprecedented climate change as well as ongoing natural and anthropogenic disturbances. However, the representation of disturbance in boreal regions is limited in pre-existing land surface models (LSMs). Moreover, many LSMs do not explicitly represent subgrid-scale heterogeneity resulting from disturbance. To address these limitations, we implement harvest and wildfire forcings in the Canadian Land Surface Scheme Including Biogeochemical Cycles (CLASSIC) land surface model alongside dynamic tiling that represents subgrid-scale heterogeneity due to disturbance. The disturbances are captured using 30-m spatial resolution satellite data (Landsat) on an annual basis for 33 years. Using the pan-Canadian domain (i.e. all of Canada south of 76° N) as our study area for demonstration, we determine the model setup that optimally balances detailed process representation and computational efficiency. We then demonstrate the impacts of subgrid-scale heterogeneity relative to standard average individual-based representations of disturbance and explore the resultant model biases. Our results indicate that the modeling approach implemented can balance model complexity and computational cost to represent the impacts of subgrid-scale heterogeneity resulting from disturbance. Subgrid-scale heterogeneity is shown to have impacts 1.5 to 4 times the impact of disturbance alone on gross primary productivity, autotrophic respiration, and surface energy balance processes in our simulations. These impacts are a result of subgrid-scale heterogeneity slowing vegetation re-growth and affecting surface energy balance in recently disturbed, sparsely vegetated, and often snow-covered fractions of the land surface. Representing subgrid-scale heterogeneity is key to more accurately representing timber harvest, which preferentially impacts larger trees on higher quality and more accessible sites. Our results show how different discretization schemes can impact model biases resulting from the representation of disturbance. These insights, along with our implementation of dynamic tiling may apply to other tile-based LSMs. Ultimately our results enhance our understanding of, and ability to, represent disturbance within Canada to facilitate a comprehensive process-based assessment of Canada’s terrestrial C cycle.

Salvatore R. Curasi et al.

Status: open (until 03 Nov 2023)

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Salvatore R. Curasi et al.

Data sets

Implementing a dynamic representation of fire and harvest including subgrid-scale heterogeneity in a tile-based land surface model Salvatore R. Curasi; Joe R. Melton; Elyn R. Humphreys; Txomin Hermosilla; Michael A. Wulder https://doi.org/10.5281/zenodo.8302974

Model code and software

Implementing a dynamic representation of fire and harvest including subgrid-scale heterogeneity in a tile-based land surface model Salvatore R. Curasi; Joe R. Melton; Elyn R. Humphreys; Txomin Hermosilla; Michael A. Wulder https://doi.org/10.5281/zenodo.8302974

Salvatore R. Curasi et al.

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Short summary
Canadian forests are responding to fire, harvest, and climate change. Models need to quantify these processes and their carbon and energy cycling impacts. We develop a scheme that based on satellite records represents fire, harvest, and the sparsely vegetated areas that these processes generate. We evaluate model performance and demonstrate the impacts of disturbance on carbon and energy cycling. This work has implications for land surface modeling and assessing Canada’s terrestrial C cycle.