Pollinator guilds respond contrastingly at different scales to landscape
parameters of land-use intensity
Abstract
Land-use intensification is the main factor for the catastrophic decline
of insect pollinators. However, land-use intensification includes
multiple processes that act across various scales and should affect
pollinator guilds differently depending on their ecology. We aimed to
reveal how two main pollinator guilds, wild bees (specialists) and
hoverflies (generalists), respond to different land-use intensification
measures, i.e. arable field cover (AFC), landscape heterogeneity (LH)
and functional flower composition of local plant communities as a
measure of habitat quality. We sampled wild bees and hoverflies on 22
dry grassland sites within a highly intensified landscape (NE Germany)
within three campaigns using pan traps. We estimated AFC and LH on
consecutive radii (60-3000m) around the dry grassland sites and
estimated the local functional flower composition. Wild bee species
richness and abundance was positively affected by LH and negatively by
AFC at small scales (140-400m). In contrast, hoverflies were positively
affected by AFC and negatively by LH at larger scales (500-3000m), where
both landscape parameters were negatively correlated to each other. At
small spatial scales, though, LH had a positive effect on hoverflies
abundance. Functional flower diversity had no positive effect on
pollinators, but conspicuous flowers seem to attract abundance of both
guilds. In conclusion, landscape parameters contrarily affect two
pollinator guilds at different scales. The correlation of landscape
parameters may influence the observed relationships between landscape
parameters and pollinators. Hence, effects of land-use intensification
seems to be highly landscape-specific.