Decadal wildfire effects on melittophily and bee communities in a ponderosa pine forest

The absence of frequent, low severity surface fires in many ponderosa pine (Pinus ponderosa) forests has led to an increase in size and severity of wildfires seen today. There is often a temporary increase in understory plant richness and abundance following wildfires which is expected to affect local pollinators. Bees, both managed and wild bees, are the primary animal pollinators for a variety of flowering plant species. Although many agricultural and native ecosystems depend on bee pollination, little is known about pollinator communities in forested ecosystems or how pollinator communities respond following wildfires. We documented differences in melittophily among the summer months in 2017 and between burned and unburned sites ten years after the 2007 Egley Fire Complex in Oregon, USA. Bee community differences were assessed among summer months, between burned and unburned sites, and between yellow and blue cross-vane traps. Melittophily and flower communities differed among summer months; generally, melittophily and flower abundance, richness, and diversity decreased as the summer progressed, as did bee richness and diversity. Melittophily, flower, and bee richness were all found to be higher in burned sites, as were flower and bee abundance. We found cross-vane traps successful for trapping bees, with yellow traps having higher abundance (individual bees) and richness than blue traps. These results demonstrate the importance of fire to understory plant and bee communities in a ponderosa pine forest. Additionally, we demonstrate differences in melittophily and bee communities among summer months that should be considered in experimental design.