Progress

Objective: Development of a fire recovery chronosequence

Wells et al (in review) developed an alternative fire recovery chronosequence methodology that couples 100+ years of aerial photography data (1900-2000) with Landsat imagery (1984-2007) to create a continuous temporal series of vegetation mortality from fires for 346,266 ha. There is no other data set like this available that includes spatially explicit patches by burn severity class for such a large area and long time. 

  • Results: Quantifying how the proportion of area burned severely has changed over time is critical to understanding trends in the ecological effects of fire. Most assessments over large areas are limited to 30 years of satellite data, so we know little about multi-decadal trends in burn severity and patch size yet both are important to ecosystem function and vegetation recovery.

 

Objective: Assessing ecological recovery following extreme fires

Kemp et al (ongoing) are evaluating vegetation recovery at 183 sites through analyzing seedling densities following 21 individual extreme fires events within lower montane forests, focusing on understanding how environmental gradients (e.g., climate, elevation, heat loading, aspect) and post-fire legacies (e.g., burn severity, patch size, canopy cover) influence spatial patterns of tree regeneration in forests of the Northern Rockies.

  • Results: Distance to the nearest live seed source has an overriding influence on seedling presence and abundance in burned areas. Beyond approximately 300 m from a live seed source, the probability of seedling recruitment drops below 20%. Of the four most common species found in sampled lower montane forest sites (Douglas-fir, ponderosa pine, lodgepole pine, and grand fir), only lodgepole pine does not exhibit this relationship between distance to seed trees and regeneration success. Our results highlight the overarching importance of nearby live seed sources for post-fire regeneration, across broad gradients in climate. The size of high burn severity patches, especially in extreme fire events, will strongly determine patterns of reestablishment.

Bowman-Prideaux et al (in prep) are evaluating how post-fire rehabilitation treatments alter the effects of fire frequency, intensity, or fire interval on plant community trajectories.

  • Results: In a factorial analysis that included post-fire rehabilitation seeding application methods and the number of fires at a site, they found significant differences among post-fire rehabilitation seeding strategies: drill-seeding, drop-seeding, both, or none (P <0.001) (Appendix B, Figures 17 and 18). Three potential mechanisms for differences include seed density, historic seeding efforts, and bias in management decisions for determining seeding method.