EAS Seminar Series: Jackie Shuman - Exploring fire-climate-vegetation feedbacks with a modeling framework
The EAS Department Seminar Series will be held virtually for the Spring of 2021.
Exploring fire-climate-vegetation feedbacks with a modeling framework
Project Scientist, Terrestrial Sciences Section, NCAR
Fire is an integral part of the climate system coupled to both ecosystems and the atmosphere. Climate influences fire regimes through changes in precipitation and temperature and their impact on vegetation and fuels. Fire occurrence in turn impacts climate by modifying the land surface and impacting water, carbon and energy cycling. Globally, anthropogenic change in the form of heating, longer dry seasons, and high land use pressure increases the risk of more frequent and severe fires, which is expected to continue into the future. Within the tropics, fire acts to determine vegetation size structure, biomass accumulation, and the dominance or coexistence of trees and grasses in part setting the forest-savanna biome boundary. Increases in wildfire has the potential to convert tropical forests to grasslands or fire-adapted woodland savannas with implications for carbon and water cycling. The approaches used in many Earth System Models generally simplify the complexities of fire behavior and effects, ignoring complex multi-scale feedbacks between vegetation structure and risk. To address these feedbacks the SPITFIRE module has been modified and integrated into the size-structured demographic vegetation model the Functionally Assembled Terrestrial Ecosystem Simulator (FATES). Utilizing FATES with the fire behavior and effects module SPITFIRE we explore functional thresholds of trees and grass across South America with an active fire regime. FATES-SPITFIRE causes size-structured plant mortality during fire and captures ‘fire-trap’ dynamics where trees escape fire by achieving a canopy height above the flames or through fire resistant traits. In simulations, fire limits tree extent, with wetter areas retaining a higher stable tree fraction under active fire simulations with or without an initial fire-free period. These results capture critical size-structured competitive interactions, degradation and loss. Interactions between vegetation, climate and fire limit the extent of tropical forest. The ability to capture fire-climate-vegetation feedbacks are critical for projection for ecosystem resilience and shifts under future conditions.
Dr. Shuman is motivated by an interest in the complex organization of vegetation and feedbacks between vegetation and the local, regional, and global system. Dr. Shuman’s work focuses on the development and application of models for improved representation of vegetation response to altered climate and disturbance. Past research has focused on applications in the boreal forests of Russia and North America, including development of tree mortality due to fire based on tree size and species. Current research involves the development, testing and application of the SPITFIRE module embedded within the size-structured vegetation model FATES with application across the tropics, and at sites in Canada.
Seminars are loosely organized around the theme of “Hazards.”