Assessing Arthropod Communities during Bermudagrass Pasture Conversion to Diverse Native Grassland on the Southern Great Plains of North America

Plant communities change during the process of converting bermudagrass (Cynodon dactylon [L.] Pers.) pasture monocultures to diverse native grasslands. Our hypothesis was that suppression of bermudagrass and grazing of seeded post-native grassland affected composition of arthropod communities in small plots. Our objectives were to use sweep nets and pitfall traps to collect insects and study their diversity and abundance as affected by four bermudagrass suppression methods and two post-management grazing regimes during 2 years following treatment applications at a Cross Timbers Ecoregion site in northcentral Texas. The first year after suppression of bermudagrass, plant diversity was greatest in plots treated with glyphosate, effectively removing exotic grass and allowing establishment of diverse native vegetation. This resulted in greater insect diversity but less abundance compared to treatments in which bermudagrass was not effectively removed. In plots where residual imazapyr prevented establishment of native seedlings, insect diversity and abundance were less. Short-duration, intensive grazing by cattle increased insect diversity 18% the first year. The second year after suppression of bermudagrass, treatments affected insect abundance only when grazing had not occurred. As in the first year, insects were more abundant in check plots dominated by bermudagrass; however, abundance in imazapyr-treated plots was comparable to glyphosate-treated plots because the residual effects of imazapyr were less after 20 months and weeds volunteered in those plots and attracted canopy-dwelling insects. Results support the use of glyphosate to remove bermudagrass if greater arthropod diversity is desired. Results also indicated that short-term grazing post-seeding promoted greater plant and subsequent insect diversity, but only during establishment of native grassland species.