THE INITIAL EFFECTS OF COMMUNITY VARIABLES ON SAND PRAIRIE RESTORATION: SPECIES ESTABLISHMENT AND COMMUNITY RESPONSES

摘要

The tallgrass prairie was one of the most wide-ranging and diverse ecosystems in North America. This diverse ecosystem comprises a mosaic of prairie types that, in northern Lower Michigan, was historically dominated by dry sand prairie. As a result offire suppression, silvicultural and agricultural activities, and degradation by invasive species, only approximately 4% of the original extent of sand prairie remains intact in the state. Despite the important ecological role and increasing scarcity ofsand prairie, restoration and management of this ecosystem has been severely understudied. In order to gain a better understanding of this ecosystem and of potential restoration techniques that might influence its community variables, a sand prairie restoration experiment was established in the pine-oak barrens of northern Lower Michigan to analyze how different seeding treatments affect certain community variables, including vegetative cover, species richness, diversity, and floristic quality. The seeding treatments were varied with respect to seeding concentrations (1,000 seeds/m2 and 10,000 seeds/m2); and the inclusion of grasses and/or forbs with diverse ecological characteristics, such as early flowering, late flowering, and nitrogen fixers (i.e.,legumes). Measurements of the community variables were taken during each of the first three growing seasons following seeding. In general, treatments that included a high concentration of grass and/or an early season forb component had the greatest overall positive impact on plant community development. These treatments resulted in significantly greater diversity and higher floristic quality, as well as a lower percentage of non-native or invasive cover than other treatments. The benefit of high concentrations of grasses and early season forbs may play a critical role in initial species establishment of a sand prairie restoration due to the facilitative and competitive advantages they may provide in these harsh environments. However, it remains to beseen if these initially successful communities will have continued success over longer periods of time.