The Effects of Crop Intensification on the Diversity of Native Pollinator Communities.
Increases in agricultural conversion are leading to declines in native grasslands and natural resources critical for beneficial insects. However, little is known regarding how these changes affect pollinator diversity. Land use types were categorized within 300 m and 3 km radii of pollinator sampling locations in Brookings County, SD. Pollinator abundance and species richness were regressed on the proportion of the landscape dedicated to row crops, grass and pasture, forage crops, small grains, and aquatic habitats using variance components modeling. Row crops had a negative effect on bee abundance at 300 m, after fixed effects modeling accounted for outliers skewing this relationship. At 3 km, corn positively affected bee abundance and richness, while soybean acreage decreased species richness. The landscape matrix of outlying sites consisted of large monocultured areas with few alternative habitat types available, leading to inflated populations of Melissodes and Halictidae. Syrphids had a positive parabolic relationship between diversity and row crops, indicating potential for competitive exclusion from intermediate landscapes. Unlike other studies, landscape diversity within 300 m was not found to significantly benefit pollinator diversity. Within especially agriculturally developed areas of the region, high abundances of pollinators suggest selection for a few dominant species. There was no effect of forage crops or aquatic habitats on pollinator diversity, indicating that less highly managed areas still represent degraded habitat within the landscape. Incorporating pollinator-friendly crops at the farm level throughout the region is likely to enhance pollinator diversity by lessening the negative effects of large monocultures.
USDA-ARS, North Central Agricultural Research Laboratory, 2923 Medary Ave., Brookings, SD 57006 (cmogren@gmail.com; jgl.entomology@gmail.com) Current Address: Louisiana State University AgCenter, Entomology Department, 404 Life Sciences, Baton Rouge, LA 70803 cmogren@gmail.com.
Christina L
CL
Mogren
USDA-ARS, Northern Plains Agricultural Research Laboratory, 1500 North Central Ave., Sidney, MT 59270 (tatyana.rand@ars.usda.gov).
Tatyana A
TA
Rand
Economics Department, South Dakota State University, Brookings, SD 57007 (scott.fausti@sdstate.edu).
Scott W
SW
Fausti
USDA-ARS, North Central Agricultural Research Laboratory, 2923 Medary Ave., Brookings, SD 57006 (cmogren@gmail.com; jgl.entomology@gmail.com) Current Address: Ecdysis Foundation, 46958 188th St, Estelline, SD 57234.
Jonathan G
JG
Lundgren
D000383:Agriculture / Q000379:methods*; D000818:Animals; D001516:Bees / Q000502:physiology*; D044822:Biodiversity; D018556:Crops, Agricultural / Q000254:growth & development; D000455:Medicago sativa / Q000254:growth & development; D054817:Pollination; D011156:Population Density; D013023:South Dakota; D013025:Glycine max / Q000254:growth & development; D003313:Zea mays / Q000254:growth & development
Cropland Data Layer; Melissodes; agrobiont; landscape simplification