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Environ Entomol. 2016 Apr;45(2):338-47. doi: 10.1093/ee/nvw005. Epub 2016 Feb 26.

Bee Abundance and Nutritional Status in Relation to Grassland Management Practices in an Agricultural Landscape.

Author information

1
Department of Ecology, Evolution, and Organismal Biology, Iowa State University, Ames, IA 50011 (griffinwsmith@gmail.com; debinski@iastate.edu; nicole.a.scavo@gmail.com; coreyjlange@gmail.com; johntdelaney@gmail.com; raymoranz@yahoo.com; amytoth@iastate.edu).
2
Department of Natural Resources and Environmental Sciences, University of Illinois, Urbana, IL 61801 (jrmillr@illinois.edu).
3
Department of Natural Resource Ecology and Management, Oklahoma State University, Stillwater, OK 74078 (david.engle@okstate.edu).
4
Department of Ecology, Evolution, and Organismal Biology, Iowa State University, Ames, IA 50011 (griffinwsmith@gmail.com; debinski@iastate.edu; nicole.a.scavo@gmail.com; coreyjlange@gmail.com; johntdelaney@gmail.com; raymoranz@yahoo.com; amytoth@iastate.edu), amytoth@iastate.edu.

Abstract

Grasslands provide important resources for pollinators in agricultural landscapes. Managing grasslands with fire and grazing has the potential to benefit plant and pollinator communities, though there is uncertainty about the ideal approach. We examined the relationships among burning and grazing regimes, plant communities, and Bombus species and Apis mellifera L. abundance and nutritional indicators at the Grand River Grasslands in southern Iowa and northern Missouri. Treatment regimes included burn-only, grazed-and-burned, and patch-burn graze (pastures subdivided into three temporally distinct fire patches with free access by cattle). The premise of the experimental design was that patch-burn grazing would increase habitat heterogeneity, thereby providing more diverse and abundant floral resources for pollinators. We predicted that both bee abundance and individual bee nutritional indicators (bee size and lipid content) would be positively correlated with floral resource abundance. There were no significant differences among treatments with respect to bee abundance. However, some of the specific characteristics of the plant community showed significant relationships with bee response variables. Pastures with greater abundance of floral resources had greater bee abundance but lower bee nutritional indicators. Bee nutritional variables were positively correlated with vegetation height, but, in some cases, negatively correlated with stocking rate. These results suggest grassland site characteristics such as floral resource abundance and stocking rate are of potential importance to bee pollinators and suggest avenues for further research to untangle the complex interactions between grassland management, plant responses, and bee health.

KEYWORDS:

bumble bee; grassland management; honey bee; patch-burn grazing; pollinator nutrition

PMID:
26921883
DOI:
10.1093/ee/nvw005
[Indexed for MEDLINE]

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