Due to habitat loss and degradation, many species of pollinators are declining in abundance and this can have impacts on rates of pollination in natural and managed ecosystems. Habitat restoration can be useful in rebuilding ecosystems, but often focuses only on plant community reestablishment, with non-plant components of ecosystems, such as pollinators and pollination, often assumed to reestablish passively. Yet, restoration outcomes are notoriously variable and little is known about whether or why rates of pollination may vary among restoration efforts. We tested what variables affect pollination rates among restored prairies in southwestern Michigan, testing biomass, floral cover, landscape, site size, site age, management and fire history. We did this using a sentinel plant approach, grew 120 individuals of a native annual prairie forb (Chamaecrista fasiculata) in a greenhouse. Chamaecrista was chosen because it is buzz pollinated and thought to be mostly outcrossing. Once they started flowering we put four out in each of 17 restored prairies. After one week, we moved plants to a greenhouse, and allowed them to produce seeds. We then evaluated rates of seed set per flower as a function of measured field variables to evaluate mechanisms for variation in pollination between the restored prairies.
Results/Conclusions
From the 1,217 flowers monitored, we found that out of all 60 bagged plants, only one of their flowers produced a fruit—indicating that Chamaecrista requires pollinators to reproduce. Additionally, we found that floral cover was the most important predictor of fruit production (p=0.049) as well as for seed production, although for seed production it was even more closely related (p=0.0001). Fruit production and seed production are indicators of pollination rates, and this data shows that in order for restored prairies to facilitate pollination and have high pollination rates, there needs to be floral cover.