Novel coupled permafrost-forest model revealing the interplay between permafrost, vegetation, and climate across eastern Siberia

Abstract

Abstract. Boreal forests of Siberia play a relevant role in the global carbon cycle. However, global warming threatens the existence of summergreen larch-dominated ecosystems likely enabling a transition to evergreen tree taxa with deeper active layers. Complex permafrost-vegetation interactions make it uncertain whether these ecosystems could develop into a carbon source rather than continuing atmospheric carbon sequestration under global warming. Consequently, shedding light on the role of current and future active-layer dynamics and the feedbacks with the apparent tree species is crucial to predict boreal forest transition dynamics, and thus for aboveground forest biomass and carbon stock developments. Hence, we established a coupled model version amalgamating a one-dimensional permafrost-multilayer forest land-surface model (CryoGrid), with LAVESI, an individual-based and spatially explicit forest model for larch species (Larix Mill.), extended for this study by including other relevant Siberian forest species and explicit terrain. Following parametrization, we ran simulations with the coupled version to the near future to 2030 with a mild climate-warming scenario. We focus on three regions, covering a gradient of summergreen forests in the east at Spasskaya Pad to mixed summergreen-evergreen forests close to Nyurba, and the warmest area at Lake Khamra in the south-east of Yakutia, Russia. Coupled simulations were run with the newly implemented boreal forest species and compared to runs allowing only one species at a time, as well as to simulations using just LAVESI. Results reveal that the coupled version corrects for overestimation of active-layer thickness (ALT) and soil moisture and large differences in established forests are simulated. We conclude that the coupled version can simulate the complex environment of central Siberia reproducing vegetation patterns making it an excellent tool to disentangle processes driving boreal forest dynamics.

Thermohydrological Impact of Forest Disturbances on Ecosystem‐Protected Permafrost

“…(2016, 2018) and Kruse, Stuenzi, Boike, et al. (2022). Newly introduced parameters are provided in Table A2.…”

“…The output generated by the three CryoGrid‐Vegetation instances is extrapolated back to the original resolution of the environmental grid used in LAVESI (see Kruse, Stuenzi, Boike, et al. [2022] for additional model details). The optimum plant available water levels for growth for the simulated Larix gmelinii tree species is between 21.1% and 40% (Sato et al., 2010).…”

“…We apply a dynamic vegetation‐permafrost model (Kruse, Stuenzi, Boike, et al., 2022), based on the one‐dimensional permafrost land surface model, CryoGrid (Westermann et al., 2016), and the individual‐based and spatially explicit larch forest model LAVESI (Kruse et al., 2016). The permafrost model was adapted for use in boreal forest ecosystems (Stuenzi, Boike, Cable, et al., 2021; Stuenzi, Boike, Gädeke, et al., 2021) by adding a state‐of‐the‐art multilayer vegetation model (CLM‐ml v0, originally developed for the Community Land Model (CLM) by Bonan et al.…”

Regional opportunities for tundra conservation in the next 1000 years

“…The source code was updated to LAVESI-WIND version 1.2 on the crutransects branch to be sufficiently light in terms of memory allocation (details in Appendix 1) and including landscape (developed in parallel for Chukotka mixed alpine-latitudinal treeline simulations in Shevtsova et al, 2021 ; Kruse et al, 2021 ). The model is freely available on GitHub ( https://github.com/StefanKruse/LAVESI ; Kruse et al, 2022 ).…”

Regional opportunities for Siberian tundra conservation in the next 1000 years

“…To achieve the most realistic model, each life-history stage of the larch individuals is handled explicitly, and the model’s processes adapted to observed patterns of surveyed tree stands for the dominant larch tree species, Larix gmelinii and Larix sibirica . The source code was updated to version 1.2 on the crutransects branch to be sufficiently light in terms of memory allocation and include landscape (developed in parallel for Chukotka mixed alpine-latitudinal treeline simulations in Shevtsova et al, 2021 ; Kruse et al, 2021 ). The model is freely available on Github https://github.com/StefanKruse/LAVESI.…”