AUTHORS: Cassidy Lathrom, Kansas State University; Dave Haukos, United States Geological Survey; Caroline Skidmore, Kansas State University; Brian Monser, Fort Riley Environmental Division; Derek Moon, Fort Riley Environmental Division
ABSTRACT: We assessed the influence of management actions on the occurrence and density of native bumblebee populations in the Great Plains region. Occurrence, density, and distribution of native bumblebees (Bombus spp.) were assessed relative to landscape characteristics and environmental conditions (e.g., fire, haying, mechanical and herbicide control of invading trees and herbaceous plants) on Fort Riley, Kansas. Multi-scale assessments were used to estimate distribution and density of species-specific Bombus at landscape and unit scales across accessible areas of the study area. Unit scales were categorized by dominant cover type (e.g., natural prairie, go-back land, woodland, cultivated/crop land, water, burned, and hayed). Distance sampling was used to estimate distribution and density of species-specific Bombus at landscape scales across accessible areas of the study area. Site locations within predetermined unit scales were selected using randomized surveys resulting in 151, 500-m transects. We conducted sampling during early summer (May and June) and late summer (July and August). Location of all bumblebees observed along the transect were recorded using a Trimble GPS unit. Package Distance in Program R was used to estimate density of Bombus spp. across Fort Riley, within certain cover types, and by management action. Data were comprised of six species including American (B. pensylvanicus), Southern Plains (B. fraternus), Black and Gold (B. auricomus), Common Eastern (B. impatiens), Brown-Belted (B. griseocollis), and Two Spotted (B. bimaculatus). We estimated 1.30 Bombus/ha (CV = 0.184) and 1.40 Bombus/ha (CV = 0.122) during 2022 and 2023, respectively. These data are the first known estimates of Bombus density in tallgrass prairie and serve as a baseline for future assessments.
