Bumble bee foraging and nest success on a chronosequence of reclaimed Ohio coal mines

Reclamation of former mine lands creates pockets of long-standing grassland habitat in a predominantly forested region that may act as resource islands for local plants and wildlife.  In particular, reclamations may provide critical habitat for native bee conservation and contribute to the stability of local pollination services. In this study I will determine: (1) which flowers are most valuable to bees in mine-impacted areas, (2) to what extent bees rely on resources from reclamation habitat, and (3) if reclamations increase in value to bees over time.  In summer 2014 I monitored productivity and resource use of 24 sentinel bumble bee colonies on 12 reclaimed surface mines (aged 2-30+ years). The 20 colonies surviving until early August produced on average 125.75 ± 116.25 (stdev) workers per nest, 36.50 ± 36.55 males, and 21.00 ± 37.01 queens.  High variation largely masked the effects of site age on colony fitness, although nests on old sites produced more males. The largest colonies were those on old, recently-disturbed sites. New queen production and overall colony weight were positively correlated with floral richness and abundance. Floral community composition was strongly influenced by percent forest, crop, and pasture in the surrounding 2km landscape. Herbaceous legumes (e.g. Trifolium pratense, Lotus corniculatus) used in reclamation plantings were a staple of bees’ diets regardless of site age.  The majority of pollen loads from returning foragers were mixed, rather than monospecific. Egg clusters were provisioned with a wide variety of pollen species from adjacent habitats, which varied by site. Tracking which wildflowers bees rely on in mine-impacted landscapes will allow us to recommend to reclamation project managers practices that encourage native pollinators.