Ongoing declines of bees and other pollinators are driven in part by the loss of critical floral resources and nesting substrates. Most conservation/restoration efforts for bees aim to enhance floral abundance and continuity but often assume the same actions will bolster nesting opportunities. Recent research suggests that habitat plantings may not always provide both forage and nesting resources. We evaluated wildflower plantings designed to augment floral resources to determine their ability to enhance nesting by soil-nesting bees over 3 study years in Northern California agricultural landscapes. We established wildflower plantings along borders of annual row crops and paired each with an unplanted control border. We used soil emergence traps to assess nest densities and species richness of soil-nesting bees from spring through late summer at paired field borders planted with wildflowers or maintained conventionally as bare or sparsely vegetated areas, as is typical for the region. We also quantified soil-surface characteristics and flower resources among borders. Wildflower plantings significantly increased nest densities and the richness of bee species using them. Such benefits occurred within the first year of planting and persisted up to 4 years post establishment. The composition of nesting bee communities also differed between wildflower and unenhanced borders. Wildflower plantings differed from controls in multiple characteristics of the soil surface, including vegetation cover, surface microtopography and hardness. Surprisingly, only vegetation cover significantly affected nest densities and species richness. Wildflower plantings are a widespread habitat action with the potential to support wild bees. The demonstrated benefit wildflower plantings had for increasing the nesting of soil-nesting bees greatly augments their relevance for the conservation of wild bee communities in agricultural and other landscapes. Identifying soil-surface characteristics that are important for nesting provides critical information to guide the implementation and management of habitats for bees.

中文翻译：

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野花种植增加了土壤筑巢蜜蜂的筑巢机会

蜜蜂和其他传粉媒介持续减少的部分原因是关键花卉资源和筑巢基质的丧失。大多数蜜蜂保护/恢复工作的目的是提高花朵的丰富度和连续性，但通常认为相同的行动将增加筑巢机会。最近的研究表明，栖息地种植可能并不总是提供饲料和筑巢资源。我们对旨在增加花卉资源的野花种植进行了评估，以确定其在北加州农业景观中增强土壤筑巢蜜蜂筑巢能力的能力，历时三年。我们沿着一年生中行作物的边界种植野花，并将每种野花与未种植的对照边界配对。我们使用土壤出苗诱捕器来评估从春季到夏末在成对的田野边界上筑巢的土壤筑巢蜜蜂的巢密度和物种丰富度，这些田野边界种植有野花或传统上保持为裸露或稀疏植被区域，就像该地区的典型情况一样。我们还量化了边界之间的土壤表面特征和花卉资源。野花种植显着增加了巢穴密度和使用它们的蜜蜂物种的丰富度。这种效益在种植的第一年就出现了，并持续到种植后的 4 年。野花和未强化边界之间筑巢蜜蜂群落的组成也有所不同。野花种植与对照土壤表面的多个特征不同，包括植被覆盖、表面微地形和硬度。令人惊讶的是，只有植被覆盖显着影响巢穴密度和物种丰富度。野花种植是一项广泛的栖息地行动，有可能支持野生蜜蜂。事实证明，种植野花对于增加土壤筑巢蜜蜂的筑巢量有好处，这极大地增强了野花种植对农业和其他景观中野生蜜蜂群落保护的相关性。识别对筑巢很重要的土壤表面特征为指导蜜蜂栖息地的实施和管理提供了关键信息。