Thursday, August 6, 2009

PS 63-33: Subalpine vegetation pattern three decades after stand-replacing wildfires in the southern Rocky Mountains

Jonathan D. Coop, Western State College of Colorado, Anna W. Schoettle, Rocky Mountain Research Station, and Robert T. Massatti, Institute for Applied Ecology.

Background/Question/Methods

Our purpose was to characterize tree regeneration, compositional patterns, and richness, and their relationships to landscape context and topography in four ca. 30-year-old, high-elevation burns in the southern Rocky Mountains.  Vegetation and environmental factors were sampled in 200 0.01-ha plots on transects crossing burn edges and stratified by elevation in four large, 1977-1978 subalpine burns east of the Continental Divide in Colorado: Ouzel, a burn near Kenosha Pass, Badger Mountain, and Maes Creek.  We utilized mantel tests, mixed-effects models, and randomization tests to assess relationships between vegetation and environment. 

Results/Conclusions Three decades after wildfire, plant communities exhibited pronounced compositional shifts across burn edges; compositional turnover across burn edges increased with elevation.  Tree regeneration decreased with increasing elevation and distance into burn interiors; concomitant increases in forbs and graminoids were linked to greater light availability.  Richness was nearly doubled in high-severity burn interiors due to the persistence of a suite of native species occurring primarily in this habitat. Richness rose with distance into burns but declined with elevation.  Only three of 188 plant species encountered were non-native; these were widespread, naturalized species that comprised < 1% total cover.  These subalpine wildfires generated considerable long-term increases in diversity at the plant species-, community-, and landscape-level.  Fire suppression in such systems inevitably leads to reductions of such diversity.  Concerns about post-fire invasion by exotic plants appear unwarranted in remote high-elevation settings.