“Relatively little is known about the nesting requirements of ground-nesting wild bees, although nesting sites are of central importance for most wild bee species. There are almost 600 wild bee species in Germany and 75% nest in the soil. To date, however, most of the research has concentrated on the wild bee species that nest above ground in cavities.
Now, researchers at the University of Göttingen have shown in a study on calcareous grasslands that the removal of vegetation in small areas led to a significant increase in ground nests, especially if there was a high abundance of flowering plants nearby…”

https://phys.org/news/2022-11-vegetation-free-patches-ground-nesting-wild-bees.html?