DOI: 10.5061/dryad.h44j0zpq0
title: Contrasting effects of vineyard type, soil and landscape factors on ground- versus above-ground nesting bees

description: 1. Agricultural intensification and abandonment of traditional
 agricultural practices are main drivers of current insect declines. The
 resulting loss of feeding and nesting opportunities has led to a decrease
 in pollinator populations like wild bees. While the restoration of floral
 resources has been widely implemented in wild bee conservation, nesting
 resources, particularly for ground-nesting species, are barely considered.
 2. We assessed wild bee diversity in a wine-growing area in Germany in 15
 study sites along a soil gradient and evaluated whether wild bees were
 distinctly affected by different vineyard types (vertically oriented,
 terraced, abandoned), local conditions (e.g. shrub and flower cover), and
 landscape factors in response to divergent nesting needs (above-ground vs.
 ground-nesting). 3. We found that wild bees responded more strongly to the
 availability of nesting sites than to flower resources. While
 ground-nesting bees were determined by the suitability of soil aspects for
 nesting irrespective of vineyard management types, above-ground nesting
 bees profited from vineyard abandonment and shrub encroachment in vineyard
 fallows and were enhanced by the availability of seminatural habitats
 (SNH) in the surrounding landscape. In contrast, floral resource
 availability in managed vineyards had only marginal effects on
 above-ground-nesting bees. 4. Synthesis and applications:  Life
 history traits like nesting strategies have long been neglected in wild
 bee conservation approaches, but proved to be highly relevant, especially
 for ground-nesting bees. For this, agri-environmental schemes can no
 longer solely focus on the restoration of floral resources, but should
 equally address nesting resources. Therefore, management efforts for
 enhancing wild bees in vineyard landscapes should aim at complementing
 nesting resources for ground-nesting bees (e.g. exposed bare ground
 patches) and above-ground-nesting bees (e.g. woody elements, hedges) in
 addition to floral resources. At the landscape level, conserving
 heterogeneous landscapes at a mixture of actively managed vineyards and
 semi-natural and woody elements is significant to maintain diverse bee
 communities.
description: In brief, more details are
 given in the manuscript: Wild bee sampling was carried out from April to
 August 2019 in a total of three sampling rounds in three vineyard types:
 vertically oriented, terraced, and fallow (abandoned). At each sampling
 round, traps were exposed for three consecutive days per plot (18th–20th
 April, 28th–30th June, 23rd–26th August). For each plot and sampling round
 we used a set of three differently coloured pan traps, the inside was
 painted with blue, white, and yellow UV-reflecting paints and filled with
 water. Traps were placed in the vineyard-type centre at a distance of 3 m
 from each other and adjusted at the level of the surrounding vegetation.
 Wild
 bees were identified to species level. For analysis, all samples per site
 were pooled over the three sampling rounds. We assigned species to be
 ground-nesting or above-ground-nesting following Westrich (2019).
 Parasitic species, do not build their nests but rather depend on their
 hosts and were therefore not considered as having nesting preferences.
 Environmental parameters were assessed for each
 sampling round in parallel with wild bee sampling (April, June, and August
 2019). We recorded local vegetation parameters for each plot (two
 samplings per plot and sampling round). Within each rectangle, we visually
 estimated the percentage cover of bare ground, herbaceous vegetation,
 shrubs, and the cover of all blooming-colored plants. We determined all
 flowering plants to species level and summarized them as the total number
 of flowering plant species in each rectangle. We measured the height of
 vegetation and shrubs (five random measurements) within each rectangle.
 Mean values were calculated and averaged over the three sampling
 rounds. To account for differences in the soil
 composition we defined five categories (hereafter referred to as soil–5)
 along a gradient from fine soil to coarse gravel particles. We visually
 estimated the proportion and size of fine (&lt; 2 mm) and coarse soil
 particles in a rectangle of 0.4 × 0.4 m. Soil 1 and 2 predominantly had
 fine particles and less than 40 % gravel, while soil 3–5 had a minimum of
 40 % gravel that increased in size from soil 3 (&lt; 1 cm), soil 4
 (1–4 cm) to soil 5 (&gt; 5 cm). 
 To analyse the landscape
 structure, we chose a 150 m radius around each study site. Within each
 radius, we calculated the area of semi-natural habitats, forests, and
 vineyards. SNH elements encompassed woody habitats such as vineyard
 fallows (predominantly) and hedges and herbaceous habitats (meadows or
 field margins with extensive vegetation). As a reference, we used the
 digital landscape model for Germany from 2009 (DLM-DE 2009), which we
 matched and updated with orthophotos (resolution of 40 × 40 cm) provided
 by the Hessian State Office of Land Management and the Surveying and
 Geographic Information Office Rhineland-Palatinate. Additionally, we
 measured the distance from the vineyard centre to the closest SNH and
 forest. <em>data processing:
 </em> Since landscape factors and soil composition
 altered alongside the river current, we used Rhine kilometres (a measure
 of overall river channel length) as a proxy to display altering soil and
 environmental conditions. We used Pearson correlation coefficients to
 describe the alteration of landscape parameters, soil aspect, bee species
 richness, bee abundance, and nesting traits with the river current (Rhine
 km). We choose (generalized) linear mixed effect
 models (GLMMs) and direct ordination methods (RDA) for
 analysis.
description: We provide dataframes as CSV files and metadata for the
 respective dataframes in text files.