Plant establishment in tallgrass prairie plantings

Prairie restorations generally focus on creating plant communities similar to those in remnant habitat. Some native species often fail to become established in restorations, and we have little information on the factors limiting establishment of native species. I used a series of studies to evaluate species richness and establishment patterns in native plantings, to identify points in the life cycle which are most likely limiting establishment, and to examine environmental factors that could be influencing establishment.;I surveyed 30 four to six year old Conservation Reserve Program (CRP) plantings and two prairie remnants in 2005. Total and native species richness was higher in remnants than in CRP plantings. In CRP sites, nearly one third of the 56 planted species were not found. Grasses had higher establishment rates than forbs or legumes. Species with high planting establishment also tended to establish well from background seed sources such as seed rain. In sites of similar size, planting more species resulted in higher native species richness.;Fourteen native species, most of which were also planted in the CRP sites, were used in a field emergence study in 2006. An in vitro germination test was done concurrently on seed from the same lots used in the field testing. Species with low in vitro germination also had low field emergence, and often had low CRP establishment rates, suggesting that germination rates may be limiting establishment of some native species. CRP establishment patterns were best explained by the combination of in vitro germination and seedling survival rates.;Because many prairie restorations take place on soils with a history of agricultural cultivation, I used a greenhouse experiment to determine if germination rates for the 14 species differed on agricultural and prairie remnant soils and to evaluate the effect of varying watering frequency and planting depth. Germination was higher on remnant soils and increased with more frequent watering. Planting depth responses varied by species. Grasses tended to be less affected by soil history differences than forbs or legumes, but were more strongly affected by planting depth, with higher germination rates when planted below the soil surface.