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.
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).
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 semi‐natural habitats (SNHs) in the surrounding landscape. In contrast, floral resource availability in managed vineyards had only marginal effects on above‐ground‐nesting bees.
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.
The abandonment of traditional agricultural practices and subsequent succession are major threats to many open-adapted species and species-rich ecosystems. Viticulture on steep slopes has recently suffered from strong declines due to insufficient profitability, thus increasing the area of fallow land considerably. Changing cultivation systems from vertically oriented to modern vineyard terraces offers an opportunity to maintain management economically viable and thus reduces further abandonment. Hillside parallel terraces favor mechanization, and their embankments offer large undisturbed areas that could provide valuable habitats. We investigated the effects of vineyard abandonment, different vineyard management types (vertically oriented vs. terraced), and local parameters on Orthoptera diversity in 45 study sites along the Upper Middle Rhine Valley in Germany. Our results show that woody structures and vineyard abandonment reduced Orthoptera diversity at the local and landscape scale due to decreased habitat quality, especially for open-adapted species. In contrast, open inter-rows of actively managed vineyard types supported heat-adapted Caelifera species. On terrace embankments, extensive management and taller vegetation benefited Ensifera species, while short and mulched vegetation in vertically oriented vineyards favored the dominance of one single Caelifera species. Our results highlight the significance of maintaining viticultural management on steep slopes for the preservation of both open-adapted Orthoptera species and the cultural landscape.
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