PS 31-4 - Effects of interseeded cover crop mixtures on ground beetle community composition

Wednesday, August 9, 2017
Exhibit Hall, Oregon Convention Center
Sara Carabajal1, Randa Jabbour2 and Andrew R. Kniss1, (1)Plant Science, University of Wyoming, Laramie, WY, (2)University of Wyoming

Cover crops provide a plethora of ecosystem services within agronomic systems. The extent of their impact varies by region and species. Though they are not directly economically beneficial, if interseeded in corn they can be used as forage for grazing livestock. However, the best methods associated with interseeding cover crops are not thoroughly understood, especially in semi-arid climates. Functional diversity of cover crops may influence cover crop establishment, affect crop yield, and impact other organisms in the ecosystem. I focus on how these variables impact ground beetle communities. Ground beetles (Coleoptera:Carabidae) are abundant within agroecosystems, and have a potential role in weed management given their seed feeding behavior.

At the University of Wyoming Sustainable Agriculture Research and Extension Center, six cover crop species -- red clover, winter pea, triticale, winter wheat, turnip and rapeseed— were seeded into standing corn at the V6 stage of growth. Ten treatments were applied to the field plot: a monoculture of each species, 2 mixtures with 3 species, a 6 species mixture, and control plots with no cover crops, each replicated 4 times. Pitfall traps were used to estimate activity-density, genus richness, and evenness of carabids three times in the season.


Pitfall traps were placed in the field following cover crop seeding and after seedling emergence. Five days after seeding, crop diversity had no significant effect on overall beetle abundance (p=0.24). Four weeks after seeding, there was a non-significant trend of higher beetle abundance in more diverse cover crop mixtures (p=0.07). The six species cover crop mixtures tended to have higher beetle activity density compared to monoculture and control plots. We are currently identifying beetles to genus, which will allow us to compare richness, evenness, and beetle community composition. The presence or absence of highly granivorous ground beetle genera may leave seeds broadcast on the soil surface vulnerable to predation and affect cover crop establishment. Plant emergence and ground cover is also being analyzed to assess plant establishment. If functional cover crop diversity affects granivorous carabids, this could alter the impact carabids have on both crop establishment and the weed seed bank. The results of this experiment will help to address whether short-term bursts of planned diversity in the form of cover crops impact associated biodiversity.