Abundant, distinct, and seasonally dynamic bee community in the
canopy-aerosphere interface above a temperate forest
Abstract
1. Our understanding of how bees (Apoidea) use temperate forests is
largely limited to sampling the understory and forest floor. Studies
over the last decade have demonstrated that bee communities are
vertically stratified within forests, yet the ecology of bee assemblages
immediately above the canopy, the canopy-aerosphere interface, remains
unexplored. 2. We sampled and compared bee communities above the canopy
of a temperate forest to the understory (1 m), midstory (10 m), and
canopy (20 m) on the campus of the University of Massachusetts, in
Amherst, Massachusetts, USA from April – August, 2021. 3. Overall, we
found that assemblages above the canopy had more bees than in the
understory, were distinct in composition from all other strata, and
included the greatest proportion of unique species. Bee abundance and
species richness were highest in the understory throughout the spring
(April and May) and decreased as the season progressed, while bee
abundance and species richness at higher strata increased into the
summer months. We also found that bees with preferences to nest in moist
and rotting wood were largely restricted to canopy and midstory strata.
4. We conclude that bee assemblages occupying the space above the forest
canopy are abundant and diverse, and their unique composition suggests
that this canopy-aerosphere interface plays an additional role in the
bee community of temperate forests. Alternatively, our findings question
how forest bee communities should be defined while highlighting the need
for research on fundamental processes governing species stratification
in and above the canopy.