Annual displacement of soil in nest tumuli of alkali bees (Nomia melanderi) (Hymenoptera: Apiformies: Halictidae) across an agricultural landscape

Thousands of bee species nest in the ground, sometimes gregariously. digging central tunnels whose excavated soil is pushed to the surface its tumuli To quantify tumulus, production across a landscape. nesting female alkali bee, (Nomia imelanderi) were censused for the 155 km(3) Touchet Valley of southeastern Washington. where nest sites of alkali bees are managed to pollinate alfalfa seed fields. Across this landscape in 2001, an estimated 9.1 million nesting females collectively brought 87,500 kg (96 tons) of soil to the surface in their tumuli, much of which is subsequently eroded away by wind or rain. At this rate. the oldest populated nest site would have cumulatively lost four cm to surface Subsidence as a result of the past halt century’s nesting activity. Bees are probably minor agents of biogeomorphology and bioturbation except where nesting females are concentrated in long-lived Populous aggregations