Prescribed fire is associated with increased floral richness and promotes short‐term increases in bee biodiversity in the ponderosa pine forest of the Southern Rocky Mountains

Abstract

Managed low‐severity surface fires are frequently implemented in efforts to restore disturbance processes to forests of North America; although the effects of managed fire on forest structure are well‐studied, few studies investigate whether these disturbances cascade to impact pollinator communities. We analysed bee‐habitat relationships in fire‐treated (1‐ and 3‐years post‐treatment) and non‐treated ponderosa pine stands in Colorado to test wild bee population responses. Observed bee richness and α‐diversity were highest in stands 1‐year post‐fire and had more Anthophora, Bombus, Osmia and Lasioglossum spp. in comparison to 3‐year post‐fire and non‐treated stands. Bee functional groups were responsive to treatments, with more below‐ground nesting taxa present in stands 3 years post‐fire. Floral richness was the highest mid‐growing season (June, July) and within 1‐year post‐fire stands. A model analysing the effects of foraging and nesting habitat variation on bee assemblages indicated positive association between floral richness and bee α‐diversity, but negative relationships with stand basal area. Nesting habitat was not associated with variation in bee assemblages. We conclude that managed fire has positive short‐term effects on bee biodiversity that are likely mediated by floral richness. However, these effects were not detectable by 3 years post‐treatment in the southern Rocky Mountain region.