PARENT SESSION
Contributed Oral Session 127: Forest Structure and Communities
Thursday, August 11, 1:30 PM - 5:00 PM, Meeting Room 513 A, Level 5, Palais des congrès de Montréal
Biotic and abiotic effects on plant species richness and community composition in post-fire Yellowstone forests.
Tinker, Daniel*,1, Turner, Monica2, Romme, William3, 1 University of Wyoming, Laramie, Wyoming, USA2 University of Wisconsin-Madison, Madison, Wisconsin, USA3 Colorado State University, Ft. Collins, Colorado, USA
ABSTRACT- Landscape-scale variability in post-fire lodgepole pine seedling density has been shown to be a primary driver in the variability in aboveground net primary production and leaf area, but its effect on understory plant species composition and richness is not well understood. We measured plant species richness in 90 sites in Yellowstone National Park that burned during 1988, and varied substantially across gradients of lodgepole pine sapling density, elevation, precipitation and substrate. We used Analysis of Variance (ANOVA) and Canonical Correspondence Analysis (CCA) to test for significant treatment effects and to describe patterns of community composition within the 90 sites. ANOVA identified significant effects of both biotic (sapling density) and abiotic variables on plant species richness (Model adj. R2 = 0.72; p < 0.001). Plant species richness was significantly lower in sites with the highest sapling density (n = 14.8) than sites with lower sapling density (n = 19.0–24.8). Richness was also lower in sites located at lower elevations (n = 16.9) versus sites at higher elevations (n = 22.6). Sites that occurred on fertile andesite soils showed significantly higher species richness (n = 33.5) than sites found on infertile rhyolite (n = 17.9–19.2; p < 0.001). Interestingly, sites that receive the lowest annual precipitation exhibited higher species richness (n = 25.6) than other sites (n = 16.1–20.5; p < 0.001). CCA identified four primary groups of species assemblages, which appear to respond most strongly to gradients of precipitation and elevation. Low elevation, dry sites were characterized by abundant graminoids and a higher proportion of nitrogen-fixing plants. High elevation, wet sites were dominated by a ground-covering shrub, Vaccinium scoparium, upland sedges, and fewer species of grasses. Sites at mid-elevation that experience intermediate levels of precipitation were characterized by abundant forbs and shrubs other than Vaccinium scoparium. Current patterns in plant species richness and composition may change as post-fire stands mature, but long term studies are necessary to identify such dynamics.
Key words: plant species richness, fire ecology, Yellowstone National Park, plant community composition