ContextBiodiversity
monitoring programs require fast, reliable and cost-effective methods
for biodiversity assessment in landscapes. Sampling pollinators across
entire landscapes is challenging, as trapping needs to cover many
habitat types.ObjectivesWe
developed and tested a landscape-wide sampling design for pollinators.
We assessed the predictability and stability of pollinator biodiversity
estimates in agricultural landscapes, and tested how estimates were
affected by sampled habitat, landscape composition and spatial scale.MethodsWe
sampled pollinators using pan traps at 250 locations in 10 replicated
landscapes measuring 1 × 1 km and calculated bee richness predictions
based on different sample sizes. Traps were placed regularly in each
landscape, sampling each habitat proportionally to its area. Landscapes
contained semi-natural habitats, crop fields and forests and differed in
the amount of a mass-flowering crop (oilseed rape).ResultsRegular
sampling reflected local habitat amount. Compared with cereal fields,
significantly more pollinators occurred in oilseed rape, and fewer in
forests. Sampling in only one habitat type led to biased estimates of
landscape-wide bee species richness, even when sample size was
increased. The spatial scale of best predictions depended on the sampled
habitat. Species richness was overestimated when sampling was limited
to semi-natural habitats and underestimated in oilseed rape fields.
Precision increased with the number of sampling points per landscape.ConclusionsTo
study landscape-wide pollinator biodiversity, we suggest to sample
multiple sites per landscape in a broad range of resource-providing
habitat types, with sample sizes proportional to habitat amount. Our
approach will also be useful for biodiversity monitoring programs in
general.</div
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