Ecological assessment of a restored tallgrass prairie in Minnesota

Background/Question/Methods

Less than 1% of tallgrass prairie remains; the majority has been converted to agriculture or less diverse vegetation.  In 2008, Gustavus Adolphus College (St. Peter, Minnesota) recreated a 70 acre prairie on formerly cultivated land.  The prairie was planted with 163 species in five constructed habitats typical of tallgrass systems.  The intent of our research was: 1) to compare the planted species with established; 2) to record and control invasive species; 3) to establish permanent plots and develop a management plan, and 4) to record demographic information and model populations of three species: Eryngium yuccifolium, Rudbeckia hirta and Echinacea angustifolia. We established 12 linear transects (280 1-m² quadrats), one belt transect (20 points), and four circular transects with a 2-4m radius. Within each plot all plants were identified and percent cover of each species was estimated. Weedy species were defined as non-native or native species that were not planted.   For each species in the demographic study we marked 20 flowering adults and all juveniles in five-m²patches.   Germination, survivorship and transitions will be monitored over time. In August 2014 we will develop models to estimate population sustainability from the demographic data.

Results/Conclusions

Similarities between composition and cover suggest that only three vegetation types exist, dry, mesic, and wet, rather than five habitats.  Overall native species richness was 79 while 34 weedy species were detected. Of native grasses 19 of 37 planted species were found while 60 of 126 native forbs were encountered. More grass species established in the dry habitat (12 of 14) while the mesic area had the greatest percentage of established forbs (41% of all planted species). The mesic area also had the greatest cover of grasses (68%) while cover of forbs was similar in the mesic and dry habitats (25%). The wet habitat had the fewest established species with only 33% of planted species establishing after three years.  Three areas with high densities of invasive species were identified: Cirsium vulgare, which was immediately controlled, Populus and Ulmus spp. along the edges, and Melilotus officinalis, Salix spp. and Populus  in wet areas where native species did not establish well.  Our management plan recommends a prescribed burn every two years to control the woody species, continued monitoring, and to re-plant the wet areas after a burn to facilitate native community development.