DOI: 10.5061/dryad.9kd51c5qk
title: Floral resource availability and honeybee flower visitations in Oslo, Norway

description: Urban green infrastructure can provide important habitats for pollinators
 and support urban ecosystem services. Therefore, these areas must be
 managed to maximize biodiversity and density of pollinating insects. We
 used DNA metabarcoding to study honeybee pollen resource use over time and
 space in the city of Oslo, Norway, and to assess the role of green
 infrastructure as a resource for pollinators and the services they
 generate. Urban honeybees used diverse pollen resources throughout their
 active season. There was considerable seasonal turnover in pollen resource
 use that reflected flowering phenology. Non-native plants (including
 invasive species) were an important resource early in the season but were
 replaced by native plants later in the season. Hive location was not
 strongly correlated with resource use, likely indicating effective
 long-distance foraging in the fragmented urban landscape. However, flower
 visitation rates and floral resource density in public urban green spaces
 were coupled with pollen use. Honeybees collected pollen from a small
 number of preferred species but also visited other species, likely for
 nectar. To preserve pollinator services, urban planning should consider
 flower resource management, with particular focus on planting native
 species that can act as early season resources for bees. Public campaigns
 and other incentive mechanisms to promote the cultivation of native plants
 that are resources for pollinators and the protection of urban
 semi-natural habitats have the potential to enhance the value of green
 infrastructure to support urban pollinators and pollination services.
description: Floral inventories were conducted in 100 green spaces within the
 Oslo urban area between July 18 and August 4, 2017, generating a
 landscape-level estimate of floral resource abundance for this time
 period. Sampling locations were extensions of previous work, with sites
 selected to capture a range of habitat suitability values as expressed in
 early versions of a model for urban pollinator habitat (Stange et al.
 2017). The urban green spaces investigated were publicly accessible and
 included hedgerow, lawn, meadow, and waste areas containing primarily
 ruderal vegetation, as well as parks and cemeteries containing planted and
 tended vegetation. Green spaces composed of short cut lawns, forests
 lacking flowering ground cover, and private garden green spaces were
 excluded from the inventory. Each green space was visited once to
 determine floral resource density using 1 to 3 transects according to
 vegetation patch size and shape for a total of 20 transect meters. All
 open floral units were recorded within a 40 cm width along each transect.
 The definition of a unit (individual flower, entire inflorescence)
 differed between species. For inflorescences with a high number of
 individual flowers (ex/ racemes, capitula), we used a multiplication
 factor to calculate the total number of flowers of that species in the
 transect. Multiplication factors were based on the average number of
 flowers per recorded unit, retrieved from the literature (Lid and Lid
 2005; Mossberg et al. 1992; and the Nordic virtual flora at the Swedish
 Natural History Museum http://linnaeus.nrm.se/flora/). The mean floral
 resource density for the landscape was calculated per plant species across
 all the inventoried green spaces, as well as within a 1-, 3-, and 5-km
 radius of each individual hive. Landscape-level honeybee visitation rates
 to different floral resources were calculated from 60 transect meters
 within each green space. One to four visits (mean 2.3) were made to each
 green space between July 18 and August 10, 2017, during which we walked
 each transect for approximately 5 min, allowing for additional time for
 specimen handling and species identification. We recorded the number of
 honeybees observed on flowers, including the plant species, within 2.5 m
 on both sides of the transect. Visitation rates were calculated as a mean
 across all transects in the landscape, as well as for all transects within
 a 1-, 3-, and 5-km radius of each individual hive.
description: # Floral resource availability and honeybee flower visitations in Oslo,
 Norway
 [https://doi.org/10.5061/dryad.9kd51c5qk](https://doi.org/10.5061/dryad.9kd51c5qk) The dataset contains locality level floral resource estimates for 100 sites in Oslo, Norway, and pollinator visitation events observed at the same localities. ## Description of the data and file structure The project includes the following data files, all of which use the string "N/A" to indicate missing or non-recorded values: #### floral\_visitation\_data.txt This tab-delimited text file includes observations of flying and sitting pollinators along transects in urban areas in Oslo, Norway. It contains data columns with the following headers: | Column header | Description | | ------------- | ----------- | | trap\_number | a unique identifier for the locality | | inventory\_date | the date on which observations were made | | observer1 | initials of the primary observer on the transect | | observer2 | initials of the secondary observer on the transect (if present) | | observation\_start | time at which survey began | | observation\_end | time at which survey ended | | temperature | air temperature during survey | | sky\_cover | estimate of cloud cover during survey | | wind | wind conditions during survey | | rain | precipitation during survey | | additional\_comments | comments about site, proximity of honeybee hives, and observations made | | pollinator\_species\_latin | scientific name of the pollinator observed | | sex | sex of the pollinator observed | | individuals\_flying | number of individuals observed flying in the transect area | | individuals\_sitting | number of individuals observed sitting in the transect area | | plant\_species\_latin | scientific name of the plant on which the pollinator was seated (if pollinator was sitting) | #### floral\_density\_data.txt This tab-delimited text file includes quantitative inventories of plants occurring along transects in urban areas in Oslo, Norway. It contains data columns with the following headers: | Column header | Description | | ------------- | ----------- | | trap\_number | a unique identifier for the locality | | inventory\_date | the date on which observations were made | | plant\_species\_latin | scientific name of the blooming plant observed | | flower\_number | number of flowers observed | | transect\_width\_cm | width of transect in cm | | transect\_length\_m | length of transect in m | | comments | additional comments about the transect and observations |