Simulating dynamic fire regime and vegetation change in a warming Siberia

Abstract

Background Climate change is expected to increase fire activity across the circumboreal zone, including central Siberia. However, few studies have quantitatively assessed potential changes in fire regime characteristics, or considered possible spatial variation in the magnitude of change. Moreover, while simulations indicate that changes in climate are likely to drive major shifts in Siberian vegetation, knowledge of future forest dynamics under the joint influence of changes in climate and fire regimes remains largely theoretical. We used the forest landscape model, LANDIS-II, with PnET-Succession and the BFOLDS fire extension to simulate changes in vegetation and fire regime characteristics under four alternative climate scenarios in three 10,000-km2 study landscapes distributed across a large latitudinal gradient in lowland central Siberia. We evaluated vegetation change using the fire life history strategies adopted by forest tree species: fire resisters, fire avoiders, and fire endurers. Results Annual burned area, the number of fires per year, fire size, and fire intensity all increased under climate change. The relative increase in fire activity was greatest in the northernmost study landscape, leading to a reduction in the difference in fire rotation period between study landscapes. Although the number of fires per year increased progressively with the magnitude of climate change, mean fire size peaked under mild or moderate climate warming in each of our study landscapes, suggesting that fuel limitations and past fire perimeters will feed back to reduce individual fire extent under extreme warming, relative to less extreme warming scenarios. In the Southern and Mid-taiga landscapes, we observed a major shift from fire resister-dominated forests to forests dominated by broadleaved deciduous fire endurers (Betula and Populus genera) under moderate and extreme climate warming scenarios, likely associated with the substantial increase in fire activity. These changes were accompanied by a major decrease in average cohort age and total vegetation biomass across the simulation landscapes. Conclusions Our results imply that climate change will greatly increase fire activity and reduce spatial heterogeneity in fire regime characteristics across central Siberia. Potential ecological consequences include a widespread shift toward forests dominated by broadleaved deciduous species that employ a fire endurer strategy to persist in an increasingly fire-prone environment.

Will fire-smart landscape management effectively buffer the effects of future climate changes and long-term land abandonment on fire regimes?

“…We acknowledge, however, modelling limitations whose future incorporation in the model would improve the accuracy of our predictions. For example, directly addressing the effects of climate on vegetation is relevant to simulate landscape dynamics in the future (Williams et al 2023), particularly the post-re resprouters dynamics of some oak and shrub species (Batllori et al 2019;Baudena et al 2020) or future expansion of sweet chestnuts (Freitas et al 2021) in Mediterranean landscapes. Also, better integration of re-adaption traits of modelled species would improve the simulation of i) post-re regeneration, for example, by including variability in the degree of serotiny among individuals in P. pinaster stands depending on re regimes since it can affect the capacity of individuals to disperse and persist in the landscape (Hernández-Serrano et al 2013; Tapias et al 2004); or ii) re-resistance, for example, the bark thickness in P. menziesii provides resistance to most surface res (Uchytil 1991), but due to re-vegetation simulation mechanism, the user-de ned threshold in BFOLDS-FRM based on re intensity to kill vegetation (> 500 kW/m) overrides the " re tolerance" trait assigned to the species in the Age-Only extension, thereby potentially modifying species response to re.…”

Mapping Tree Mortality Caused by Siberian Silkmoth Outbreak Using Sentinel-2 Remote Sensing Data

“…The most dramatic changes are expected in the boreal zone, where the temperature could rise by 7 • C [3]. Large carbon pools in boreal forests are vulnerable to climate change, which calls into question the status of these forests as a carbon sink in the near future [1,[4][5][6].…”