Tallgrass prairie is one of the most endangered ecosystems worldwide, with less than 3% of its original extent remaining. Much of the remnant prairie exists as small, isolated fragments in a largely agricultural matrix. Prairie reconstruction, or developing a prairie from a former agricultural field, has the potential to increase connectivity of these remnants and provide essential habitat and forage for pollinators [3]. To gain an understanding of how early restoration practices can influence longer term establishment and success of prairie reconstructions, we established an experimental study across nine locations in Minnesota and Iowa. In 2004-2005 we planted plots using one of three planting methods (dormant broadcast, growing-season broadcast, growing-season drill) fully crossed with one of three species richness categories (10, 20, or 34 species) in a completely randomized design. We measured individual species cover in 2005-2007, 2010, and 2015. Five years post-planting, the optimal planting method with regard to planted cover differed between Minnesota and Iowa; dormant broadcast produced greater planted cover in Minnesota while growing-season drill proved more effective in Iowa. Increasing seed mix richness led to greater planted species richness but did not improve outcomes with regard to exotic species invasion. Ten years post planting, we saw little variation among treatments with regard to cover of planted, native non-planted, and exotic species, indicating that there is no best planting method in the longer term. Of particular note, cover of the noxious weed Cirsium arvense declined over the course of the study, without herbicide. However, the cool-season, invasive grasses Poa pratensis and Bromus inermis continued to increase, and there was no planting method or seed richness treatment combination that slowed this growth. Management targeting these cool-season grasses will be key to long-term success of tallgrass prairie reconstructions.
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