Ground-nesting bee conservation: the effects of soil disturbance and sand hills

Background/Question/Methods

Many bee species spend most of their life time below ground. For successful conservation of ground-nesting bees, we aim at understanding the impacts of sand hill construction (1) and soil disturbance (2) on ground-nesting bees. In the first experiment we tested the effects of sand hillls on ground-nesting bee populations by creating six sand hills each with an area of three squaremeters next to a flower strip and observing the bee community in relation to six flower strips without sand hill (20 min transects walks). In the second experiment we translocated soil cubes with nests during winter before bee emergences. Translocated soil cubes were either heavily or moderately disturbed to mimic ploughing or excavation of soil. Using emergence traps, we quantified the number of bees emerging and compared moderate to heavily disturbed soils with undisturbed control sites.

Results/Conclusions

The first experiment is expected to demonstrate that sand hills are favorable habitats for ground-nesting bees and can alternate the community composition of bees in adjacent flower strips. Field work will be conducted in April, May and June 2022 and results will be presented on the conference. The second experiment revealed that soil disturbance reduced the number of bees from 30 to less than 10 bees per sampling unit and even less than five bees in heavily disturbed soils. This is suggesting that soil treatments such as ploughing can have strong impacts on bee survival.