Data from: Seasonal mass-flowering events dominate landscape effects on plant-pollinator network structure
Data files
Apr 01, 2026 version files 11.66 KB
-
data_jappl-2024-01222.csv
7.56 KB
-
README.md
4.10 KB
Abstract
Agricultural landscapes feature marked seasonal changes in the quality and quantity of habitats and floral resources supporting pollinating insects. Seasonal dynamics can affect the structure of plant-pollinator interactions, yet the relative importance of both landscape elements with spatio-temporal dynamics and those elements that are more static in space and time remains largely unknown. Such an understanding is needed to identify resource-mediated modifications of plant-pollinator network structures and their functional and management implications. To understand the spatio-temporal effects of landscape heterogeneity on the structure of plant-pollinator networks, we sampled plant-pollinator (Apiformes - except Apis mellifera; Syrphidae) communities over three seasonal periods in twelve landscapes in central Germany. The landscapes comprised spatial gradients in the proportion of semi-natural habitat cover and edge density. To assess temporal changes, we evaluated the cover of mass-flowering crops in bloom, floral diversity, and honey bee density at each plant-pollinator sampling event. Spatio-temporally dynamic characteristics, particularly the cover of mass-flowering crops, were more important than static characteristics in explaining variation in plant-pollinator network structure across the three seasonal periods. The richness of plants and pollinators was generally lower when the proportion of mass-flowering crops was high. Under such conditions, networks were more connected, with greater niche overlap among pollinators, and decreased network specialization (H2’). Richness was higher in landscapes with high edge density, with an increasing effect on network connectance up to a certain threshold. The proportion of semi-natural habitat cover and floral diversity had differential effects on the richness of plants and pollinators, with strong effects on the dietary niche overlap of the pollinators, potentially indicating a decrease in competition when semi-natural habitat cover and flower diversity are high. Synthesis and application. To better support plant-pollinator communities in agricultural-dominated landscapes, we suggest incentivizing the planting of complementary floral resources and preserving or restoring semi-natural habitat areas. Especially in intensively used agroecosystems, the negative effects of mass-flowering crops can be mitigated by maintaining flower-rich edge habitats and relatively small field sizes, which help support plant and pollinator communities, avoid potential negative effects of exploitative competition, and ensure the sustainability of pollination services via increased functional redundancy.
Dataset DOI: 10.5061/dryad.9s4mw6mxm
Description of the data and file structure
In 2021, plant–pollinator interactions were sampled in 12 study landscapes in Saxony-Anhalt, Germany. Each landscape comprised a 500 m radius core area and spanned a gradient of arable land cover (22–97%). Within each landscape, 20 transect subsections (50 m each) were proportionally distributed across all flowering habitats to capture landscape-wide interaction networks.
Sampling was conducted three times per landscape: spring (May), early summer (June–July), and late summer (August). Surveys took place between 09:00 and 18:00 under suitable weather conditions (≥14 °C, wind speed <6 m/s, no precipitation). Sampling effort was standardized to 120 minutes per landscape (6 min per 50 m), excluding handling time. Flower-visiting Syrphidae and Apiformes were recorded; each observed visit was documented as an interaction between pollinator and plant species. Subsequently, landscape-wide plant-pollinator interaction matrices were build and several network metrics calculated based on these interaction networks.
Landscape variables were assessed during each sampling round. These included the proportional cover of mass-flowering crops, floral resource availability, and the density of Apis mellifera. Floral surveys were conducted along transects using thirty 2 × 0.5 m vegetation plots, recording all flowering species and their number of inflorescences. Additionally, habitat maps within a 1 km radius around the center of the study landscapes were used to quantify semi-natural habitat cover and edge density.
Files and variables
File: data_jappl-2024-01222.csv
Description:
Variables
- sampling_round: Sampling was repeated three times per study site, therefore sampling round was noted as 21.1/21.2/21.3, "21" stands for the year 2021.
- site: Twelve study landscapes were sampled, named S1-12.
- pollinator_richness: Total number of different pollinator species sampled in a study landscape. All individual bees (Apiformes, excl. Apis mellifera) and hoverflies (Syrphidae) that came in contact with the reproductive parts of a flower were defined as pollinators.
- plant_richness: Total number of different flowering plant species sampled in a study landscape.
- connectance: Network metric connectance calculated with the R-package 'bipartite' (Dormann et. al., 2008).
- z-score_connectance: Calculated z-scores for connectance based on 10,000 null models computed with the Patefield algorithm, ‘r2d-table’, which maintains row and column sums but randomizes cell values.
- nicheoverlap_pollinator: Network metric niche overlap of pollinators (HL = higher level) calculated with the R-package 'bipartite' (Dormann et. al., 2008).
- z-score_nicheoverlap_pollinator: Calculated z-scores for niche overlap of pollinators based on 10,000 null models computed with the Patefield algorithm, ‘r2d-table’, which maintains row and column sums but randomizes cell values.
- h2_specialization: Network metric of H2' network specialization calculated with the R-package 'bipartite' (Dormann et. al., 2008).
- z-score_h2_specialization: Calculated z-scores for H2' network specialization based on 10,000 null models computed with the Patefield algorithm, ‘r2d-table’, which maintains row and column sums but randomizes cell values.
- prop_mfc: Proportional cover of mass-flowering crops in bloom during the respective sampling round.
- floral_diversity: Calculated Shannon diversity based on the conducted floral survey.
- honeybee_density: Honey bee (Apis mellifera) density was estimated by recording their abundance for one minute per transect subsection, and calculating the mean at the landscape-level.
- prop_snh: Proportional cover of semi-natural habitat areas in the study landscapes.
- edge_density: Landscape edge density was calculated as the ratio of boundary habitat to total landscape area.
