Vegetation on the city of Boulder open space grasslands

The grasslands that surround Boulder, Colorado are distinctive in that there is both a diverse array of native plant communities and a significant level of exotic plant invasion. Factors that contribute to community diversity include soil and topographic heterogeneity as well as a variety of land uses. Causes for the exotic plant invasion are primarily related to the process of suburbanization, which includes: habitat fragmentation, increased seed source, terrestrial eutrophication, creation of bare soil, and disruption of the natural disturbance regime.; The composition of grassland plant communities on Boulder grasslands was determined with a cluster analysis of the presence and absence data 177 native species on 1177 quadrats that were located on 68 plots. Eight primary communities were discovered: shale, shortgrass, mixed-grass/foothills, mixed-grass/mesas, xeric tallgrass, mesic tallgrass, ungrazed tallgrass/meadow, and irrigated meadow. The plots on the uplands had a greater richness of native species and a lower richness of exotic species than the lowlands. Most of the exotic species on the uplands were monocarpic, while most of the exotic species from the lowlands were polycarpic. A principal components analysis of eleven cover and diversity variables produced an ordination that ordered the plots along an exotic to native gradient for the first component and along a wet to dry the second. It is suggested that the best method for managing the gradient for Open Space grasslands for the conservation of biodiversity is to attempt replication of pre-historic disturbance regimes, especially bison and fire.