Sowing strips of prairie vegetation into cropland is a relatively new conservation practice that integrates native habitat into working farms in the Midwestern USA. In addition to providing critical habitat in an agriculturally-dominated landscape, these strategically planted, functional restorations can reduce erosion and nutrient export. It has been suggested that to ensure prairie strips provide these desired ecosystem services and aren’t refugia for agricultural weeds, the plantings should be diverse, generate consistent cover by native species, and maintain a balance of grasses and forbs.
During the summers of 2018 and 2019, we investigated factors affecting the species composition of prairie strips by surveying the vegetation in 20-25 sites that had installed prairie strips between 2012 and 2016. While sites varied in a myriad of ways, we focused our analysis on the seed mix, as it is the biggest economic investment a landowner makes in a restoration and it varied greatly among our sites (15 to 54 species seeded). We hypothesized that increasing the diversity of the seed mix would result in communities that were more diverse and had a higher abundance of prairie plants and a lower abundance of weeds.
Results/Conclusions
We found that the richness of the seed mix was positively related to the gamma and beta, but not the alpha, diversity of sites. We did not find any evidence that variation in the seed mix richness explained variation in the abundance of weedy species. Furthermore, we didn’t see any evidence that variation in the grass: forb ratio of the seed mix explained any variation in the abundance of weedy species. In the summer of 2019 we visited 6 sites that planted the same seed mix and found that those sites that were planted in the summer had a higher coverage of weedy species than sites that were planted in the fall or the spring.
This study allowed us to glean broad scale patterns that appear on working lands with independent managers. While we were unable to control for many factors, we still found compelling evidence that species composition of the seed mix and planting season can affect the diversity and the “weedy-ness” of the vegetative community in prairie strips.