Abstract:
Landscapes of farms and adjacent areas are known to influence abundance of various
arthropods such as pollinators in commercial agricultural ecosystems. In this context, we
examined the effect of heterogeneous landscapes surrounding and including commercial
apple orchards on pollinator visitation and foraging distance during bloom period from
2011 to 2013 in Pennsylvania. Our results showed that the frequency of feral honeybees
and solitary bee visits within an apple orchard depends on the proximity of the orchard to
an unmanaged habitat (primarily comprised of forest). At the landscape scale, we found
that the Mean Proximity Index, the Largest Patch Index, and the Number of Patches
positively correlated with the visitation rate of dominant bee taxa (Apis mellifera, Bombus
spp., and solitary bees) visiting apple flowers at low spatial scales (up to 500 m around
the orchards). The Mean Proximity Index at 500 m was related to bee visitation patterns,
especially for solitary bees and A. mellifera. Bees in all our study sites preferred to forage
in areas with large homogenous patches up to 500 m around an apple orchard. This
effect can be attributed to the mass flowering of apples that formed the largest proportion
of the 500 m spatial scale. The Number of Patches at 250 m spatial scale was positively
correlated with bee visitation, especially Bombus spp., probably because these areas had
more habitats and more resources required by these bees. We conclude that retaining
unmanaged habitats closer to commercial apple orchards will maintain biodiversity within
the landscapes and insure pollination services to apples.
