Get reliable rangeland science

Non-native invasive plant species have led to changes in plant community composition by displacing native species, ultimately decreasing species richness and diversity. Kentucky bluegrass (Poa Pratensis), a non-native grass, has invaded a majority of rangelands within the Northern Great Plains. Prescribed fire can potentially reduce Kentucky bluegrass and increase native grass and forb richness and diversity in the tallgrass prairie. Our objectives were to investigate the effects of burn season and frequency on Kentucky bluegrass and native plant community composition. We conducted this study in a non-grazed pasture within the tallgrass prairie of the Sheyenne National Grasslands in southeastern North Dakota, USA. To assess effects of burn season on plant community composition and Kentucky bluegrass suppression, we burned 3 ha plots at mid-growing season and dormant season, and a non-burned control with six replicates. To assess the effect of burning frequency on plant community composition and Kentucky bluegrass suppression, three mid-growing season plots were burned a second time the following year. Prior to the initial burn, species composition, abundance, litter and bare ground were recorded within 30 random 1 m2 frames within each replicate using a modified Daubenmire cover-class method. Post-fire composition and abundance were recorded at mid-summer for three growing seasons. Standing biomass was collected within each replicate using 12 randomly distributed quarter meter frames clipped to ground level and oven dried to constant weight. We used nonmetric multidimensional scaling to compare plant community composition of treatments. Kentucky bluegrass was strongly correlated with fall and non-burned treatments, while native grasses were correlated to summer burns. Restoring fire to native prairie appears to be a viable option to reduce exotic species while promoting natives.