Less fuel for the next fire? Short-interval fire delays forest recovery and interacting drivers amplify effects

Area of Science:

• Ecology
• Forestry
• Climate Change Science

Background:

• 21st-century climate and disturbance dynamics challenge historical ecosystem resilience.
• Subalpine forests in Greater Yellowstone were historically resilient to infrequent, severe fires.
• Interacting environmental drivers may amplify ecosystem vulnerability.

Purpose of the Study:

• To investigate how short-interval fire, climate, topography, and proximity to unburned forest affect post-fire regeneration.
• To compare forest biomass and fuels after short-interval versus long-interval severe fires.

Main Methods:

• Sampled paired short-interval (<30-year) and long-interval (>125-year) post-fire plots in Greater Yellowstone.
• Analyzed live tree stem density, seedling density, biomass, and dead woody fuels.
• Assessed interactions between fire interval, climate, topography, and distance to live forest edge.

Main Results:

• Mean post-fire live tree stem density was 10x lower after short-interval fires.
• Warmer-drier climates correlated with higher seedling densities, potentially due to lodgepole pine's serotiny.
• Aspen (Populus tremuloides) density increased with short-interval fires, unlike conifers.
• Live biomass and canopy fuels remained low nearly 30 years post-short-interval fire.
• Short-interval plots had half the dead woody biomass, lacking large snags.

Conclusions:

• Short-interval fires significantly diminish tree regeneration and live biomass, especially where historical serotiny was high.
• Propagule limitation interacts with short-interval fires to reduce regeneration but also lessen subsequent burn severity.
• Interacting drivers threaten forest resilience under future fire regimes.