Evaluating the Benefits of Higher Diversity CRP Plantings for At-Risk Species

The Nebraska Legacy Plan lists grassland loss as one of the primary conservation threats in the state. The USDA Conservation Reserve Program (CRP) provides incentives for farmers to take land out of crop production for a 10–15–year period, during which it is frequently planted to grasslands. Land enrolled in CRP covers more than a million acres in Nebraska, but it is planted to a wide range of seed mixes and little is known about how differences in plant diversity and composition may impact faunal biodiversity and conservation threats. This project compared high and low diversity CRP plantings to evaluate potential benefits for at–risk species, including habitat for butterflies, bees and birds, the exclusion of non–native species, and better water infiltration. The collected data from this project may be useful to monitor succession and the impacts of management techniques in future research. Overall, the effect of higher diversity CRP was either neutral or positive, with a few exceptions. 

Goals

• Determine if higher diversity CRP plantings provide habitat and forage for at–risk grassland butterfly species: Higher diversity CRP planting mixes more often contained forage species for at–risk butterflies. CP38 was typically best suited for all species. The exception in all cases was the regal fritillary (Speyeria idalia) since no lists contained violets, which are the only source of larval forage.

• Benefits of planting diversity for native bees and at–risk grassland birds: Although bumble bees (Bombus spp.) responded positively to forbs in pollinator CRP plantings, the effect of forb diversity on these and other wild bees is likely to change over time as the pollinator plantings become better established at this site. This may also influence at–risk bird species by enhancing nesting suitability and invertebrate forage in high diversity plantings. During this study period, the eastern meadowlark (Sturnella magna) was only counted in pollinator plots, for example, and with time other species may also come to nest preferentially in the higher diversity plantings.

• Determine if higher diversity plantings drive changes in soil health and impact the colonization of non–native species: Better infiltration rates were observed in the higher diversity pollinator plantings but it was unclear whether this was an effect of disking, the weedy species of the planting type, or both. Regardless, on these sandy soils a sufficient bulk density for desirable plant growth may only be maintained with disking until the plots are better established. Similarly, although the pollinator plantings had a greater number of non–native species, this may be due to the stage of succession at which the study was done, with weedy species coming in before the deeper–rooted species. Limited spread of invasive and non–native species may be more strongly linked to planting diversity as the pollinator plots become better established. Although this research project has been completed, it has set a foundation for a variety of further work which can explore the role of the successional stages of high diversity CRP plantings.