A major challenge in habitat restoration is establishing diverse vegetative communities, but the factors that influence species establishment are poorly understood. One possible influence on species establishment is the site use history. Tallgrass prairie restorations frequently take place on sites that have been used for agricultural cultivation, which changes soil and soil water characteristics. Some native prairie species have low germination rates, and changes in soil characteristics have the potential to impact germination rates of these species. We used a greenhouse based experiment to test whether germination rates of 13 tallgrass prairie species differed when grown on soil from tallgrass prairie remnants or from cultivated agricultural fields. Of the thirteen species tested, four were grasses, three were leguminous forbs, and six were non-leguminous forbs. We also tested the effects of planting depth (surface and below the surface) and watering frequency (every 2, 5, or 8 days).
Results/Conclusions
The strongest influence on germination rates overall was watering frequency, followed by site history. Germination rates were significantly higher with more frequent watering overall (11.5, 19.4, and 38.8% overall when watered every 8, 5, or 2 days respectively) and for each individual species. Overall germination was significantly higher on prairie remnant soils (26%) than on cultivated soils (21.1%). Six of the 13 species, including all three legumes, had significantly higher germination on remnant soils than on cultivated soils (Chamaecrista fasciculata, Dalea purpurea, Lespedeza capitata, Liatris aspera, Ratibida pinnata, and Rudbeckia hirta). Planting depth did not have an impact on seed germination overall, but three individual species responded significantly to planting depth. Solidago rigida had significantly higher germination when planted on the soil surface while Bouteloua curtipendula and Andropogon gerardii had significantly higher germination when planted below the soil surface.
Our results suggest that changes in soil characteristics resulting from cultivation can reduce germination rates of some tallgrass prairie species. Because germination is sensitive to water availability, and because many of the soil characteristics affected by cultivation are related to soil water characteristics, we suspect that differences in soil water availability are responsible for reduced seed germination in cultivated sites.
