Habitat patch size and configuration can affect plant population and plant community dynamics. Therefore, they are important considerations when using spatially-patterned seeding as a restoration method. One such method proposed as a cost-effective grassland restoration strategy is strip-seeding, which involves seeding in linear patches across a site and allowing for natural dispersal into unseeded areas. This method provides the benefits of concentrating seeding effort, increasing establishment, and reducing costs. In order to determine how restoration patch size and configuration alter grassland communities and dispersal, we examined plant communities on a strip-seeding experiment in Davis, CA. Fields were seeded in 2012 with native perennial bunchgrass mixes in different strip widths and configurations (seeding coverage from 0% - 100% of experimental plots). We measured the community diversity and abundance across transects in the middle of the strip, the edge of the strip, and in the unseeded between-strip area. We used PERMANOVA to understand how patch size affected community dynamics across the seeded strips.
We found that patch size alters native species diversity, however it has less of an effect on dispersal and presence of invasive species. Patches that were wider had higher species abundance and richness both within the strips and at the edges of strips. This is likely due to a lower edge to interior ratio of the patch. As expected, 0% seeded control plot had the lowest number of species overall and the highest abundance of invasive species. Strip configuration and size did not have a significant effect on invasive species diversity. Although there was some variation in species, we found that Elymus glaucus (blue wildrye) and Vulpia microstachys (three week fescue) were the only species that were well established in the unseeded strips, regardless of strip width or configuration. Therefore, while wider strips are likely optimal for promoting species diversity, dispersal ability seems to be limited for many species regardless of in-strip diversity. While there was low diversity in between-strip areas, there still was high ground cover. More time may be required for other species to establish in these areas, but because dispersal from the strips was occurring, strip-seeding still could be an effective restoration technique.