UNDERSTORY COMMUNITIES OF WARM-DRY, MIXED-CONIFER FORESTS IN SOUTHWESTERN COLORADO

Abstract Mixed conifer of southwestern Colorado is poorly understood in comparison to other common forests in this area, in part due to its compositional complexity. We identified four stand types in warm-dry, mixed-conifer forests; Abies concolor (white fir), Pinus ponderosa (ponderosa pine), Pseudotsuga menziesii (Douglas-fir), and Populus tremuloides (aspen). We examined how composition and abundance of understory varied across these four types, and assessed the correlation between biotic and abiotic variables and understory vegetation. Composition of understory community differed significantly among stand types, with aspen plots having the most distinct understory plant community. Total plant cover was significantly higher in aspen, and shrub richness was significantly higher in the Douglas-fir stand type. On average, for all stand types combined, shrubs dominated the understory cover (11.35%), followed by forbs (7.89%), and graminoids (4.34%). Multivariate multiple regression showed that several topo...