Disease-driven suppression of forest carbon uptake rivals mortality-based estimates

Le résumé fourni par la source

While invasive tree pests and pathogens have caused widespread tree mortality events, their subsequent impacts on reduced carbon sequestration remain poorly quantified in the global carbon budget. Previous carbon accounting have focused a lot on the loss of tree biomass rather than the potentially larger reduction of forest carbon sequestration capacity. The present model coupled an epidemiological model and a minimal carbon cycle model (U model) to simulate the impact of ash dieback disease on the reduction of forest carbon sequestration capacity through two mechanisms: a reduction of forest net primary productivity (NPP) through tree crown defoliation, and the release of deadwood to air followed by the attack of the ash dieback pathogen. The ZIP file 'MaxEnt_host_F.excelsior.zip' is the data source for modelling host tree (Fraxinus excelsior L.) distribution using MaxEnt. The output, the host tree distribution, is an important geographic restriction on the main model. The output of the MaxEnt model "Fraxinus_excelsior.tif" is already avilable at 'Ash_dieback_model.zip'. The ZIP file 'Ash_dieback_model.zip' provides data sources and outputs for the main model - the epidemiological model. The model simulates the spread of ash dieback since year 1992, and calculates the reduction of NPP in different places. Code files 'PART1.tree_mortality_and_defoliation.R' and 'PART2.epidemiology.R' can be run sequentially to start the model. The model outputs are predicted reduction of NPP, formatted in TIFF files. The ZIP file 'New_model_20260806.zip' is the minimal carbon cycle model used to simulate the net ecosystem exchange (NEP) with an input of reduction of NPP caused by ash dieback. The code is written using MATLAB. File 'u_model_masterfilequick_necro.mlx' can be used to run the model. The main outputs are maps of NEP, vegetation biomass, and the amount of soil organic carbon. After runnning the U model, script file 'PART3.underestimate.R' can be used to summarise results from U model. The script calculates the proportion of underestimated carbon sequestration capacity compared with an assumption that carbon removal is exclusively from the release of necromass to air (or carbon released from tree mortalities driven by the disease).

Ce résumé expose les affirmations des auteurs. BNTIC ne l’interprète pas comme une validation indépendante des résultats.