Evaluation of CRP contour buffer and filter strips as habitat for native bees and predatory ground beetles

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Moorhouse, Amy
Major Professor
Mary A. Harris
Brian J. Wilsey
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Ecology, Evolution, and Organismal Biology

Suitable habitat for beneficial insects providing ecosystem services has declined greatly in agriculturally dominated landscapes. Iowa’s landscape once dominated by tallgrass prairie is now dominated by monoculture agriculture, in particular corn (Zea mays L.) and soybeans (Glycine max (L.) Merr.). Native bees require resources of pollen and nectar and in return provide the service of pollination. Predatory ground beetles are natural enemies of many agricultural crop pests but require some habitat in undisturbed, non-cropped areas.

Conservation Reserve Program (CRP) contour buffer and filter strips are potential areas of habitat within rowcropped fields. The vegetation mixes commonly planted in these strips range from only grass to more highly diverse mixes of grasses and forbs. We assessed native bee communities and predatory ground beetle assemblages in current CRP contour buffer and filter strips of various forb vegetation mixes using a variety of common sampling methods during the growing seasons in 2014 and 2015 from May to August.

Native bee abundance increased as forb diversity increased whereas species richness and diversity was not significantly different among plant diversity levels. Bee communities at high plant diversity sites were significantly different from communities at medium and low plant diversity sites. Positive trends suggest high plant diversity sites support higher abundances and species richness of all bee guilds except bumble bees.

Predatory ground beetle abundance, tribe richness and tribe diversity were not significantly different among plant diversity levels. The majority of beetles at each site were of medium or large sizes with few to no small or very small sized beetles. Overall, trends showed forb diversity positively influenced the probability of ground beetle assemblages containing beetles from more size classes.

These results suggest that increased forb diversity within contour buffer and filter strips increase available resources for native bee communities but not necessarily for predatory ground beetle assemblages. Overall, increasing the number of forbs in a contour buffer or filter strip to 15 or more species will support a higher abundance and richness of native bees and as few as 5 forb species could be sufficient to support a more functionally diverse ground beetle assemblage.

Fri Jan 01 00:00:00 UTC 2016