Emergence and mortality of native prairie forbs seeded into an established stand of grasses

Thousands of hectares of warm-season grass plantings in Iowa have few to no native forbs. Diversifying these species poor plant communities with native prairie forbs could result in increased resistance to climatic extremes, increased biodiversity, reduced noxious weedy plant invasion, and reduced geographic isolation between existing native prairie remnants. I hypothesized that frequent mowing in the first one or two years after broadcasting forb seed into an established stand of warm-season grasses can increase forb emergence and reduce forb mortality. I further hypothesized that fall seeded forbs would establish better that those seeded in spring. To test my hypothesis, I seeded 23 forb species at a rate of 3.7 kg/ha or 350 viable seeds/m2. I assessed and compared forb emergence and mortality using three mowing treatments and two seeding treatments; fall seeding with frequent mowing the first growing season (mow-1), spring seeding with frequent mowing the first growing season (mow-1s) winter seeding with frequent mowing two consecutive growing seasons (mow-2), and fall seeding without mowing (no-mow). I also destructive sampled forb plants to assess growth differences between mow-1 and no-mow treatments. Over time, forb emergence was significantly (p Species richness was significantly (p Over time, forb mortality was significantly (p Forbs in mow-1 plots destructive sampled in September of both years had significantly (