Decline of nest site availability and nest density of underground bees along a distance gradient from human settlements.

摘要

Anthropogenic disturbances have caused pollinator decline by affecting the abundance and diversity of foraging plants. Anthropogenic disturbances are also thought to drive pollinator decline by reducing nest site availability, but the exact mechanisms by which human activities influence nest site availability are not currently well understood. In this study, we investigated nesting site preference of underground bee Andrena camellia Wu in two orchards. Principal component analysis of environmental factors (bulk density, penetration resistance, water content and temperature) indicated that A. camellia preferred loose, moist and low-temperature habitats. The favored habitats were located at the bases of the foothills a long distance from human settlements. At the bases, favored nesting substrates decreased along the distance gradient, and nest densities of digger bees increased along the distance gradient. On the summit, however, nesting substrates were compacted, dried with high temperature regardless of distance from human settlements, and the nest densities were all low along the distance gradient. In summary, anthropogenic soil disturbances in the vicinity of human settlements threaten digger bees by altering soil characteristics. The conservation of the soil substrates is addressed in terms of its role in governing the population of digger bee A. camellia.