The role of woodlands in the diversity and resilience of pollinator communities in agricultural landscapes

科学背景集约化农业是授粉昆虫数量和授粉服务减少的关键驱动因素。减轻这些影响的生态强化措施主要集中在恢复农田规模的半自然栖息地，包括花带和其他草地和野花栖息地斑块。这些农业环境方案所提供的对花卉资源的促进通常只跨越授粉昆虫组合的季节性活动期的一部分。在农田上提供授粉服务也取决于更广泛的景观背景，相对较少注意林地斑块对传粉者群落的影响。不确定性仍然存在于哪些植物物种是传粉物种最有价值的食物资源，以及它们的相对价值如何随季节变化。虽然与草地相关的野花对蜜蜂的好处是公认的，但在农业景观中，树木和林地在缓冲传粉媒介资源（花蜜和花粉）提供方面的互补作用却没有得到充分的研究。林地可以为英国的主要栖息地提供最高水平的花蜜生产，树种授粉昆虫的使用可能与景观中林地的丰富程度不成比例。林地树种组成也影响其他植物，对传粉者产生影响。林地和树木廊道（树篱）为一系列传粉昆虫提供筑巢和幼虫的微型场所。目的和目的本项目将研究林地在农业景观中传粉昆虫群落维持和恢复中的作用。昆虫取样将在诺福克选定的研究景观中进行，该研究景观跨越了一系列密度的林地和树篱网络。该项目旨在解决以下关键研究问题：(1)与发生在地面、林地内部和更开放的农田栖息地的传粉者相比，发生在林地冠层的传粉者组合有多相似？我们将研究相对于更开放的生境，哪些传粉媒介物种在林地冠层中出现的比例最大，并测试冠层发生与林地冠层中花粉和/或花蜜来源的可用性之间的相关性。(2)是否有传粉者在林地冠层或其附近寻找树木花粉资源？我们将使用分子技术来确定传粉昆虫分类群的身份，以及它们相关的花粉，从林地冠层和距离林地栖息地不同的距离取样。这项工作将确定哪些种类的树花粉被使用，如果有的话。我们将测试大约20种常见的林地树种，包括一些风媒传粉的树种。(3)林地是否促进了周边景观传粉媒介多样性和丰度的季节性稳定性？研究设计将侧重于在研究区域内的重要林地斑块内取样，以及在农业景观中与这些斑块的不同距离上取样，包括沿着有树和没有树的树篱的不同距离。在春季和夏季重复取样将捕捉传粉媒介组合的季节性变化。(4)在农业景观中，维持有弹性的传粉媒介群落，从而提供授粉服务的最佳林地和木本廊道管理建议是什么？在这里，我们将重点研究树木廊道在景观中的线性特征，以及如何优化它们在林地斑块和耕地景观之间传粉者组合的连通性和维持授粉服务中的作用。

Scientific backgroundIntensive agriculture is a key driver of declines in pollinating insect populations and pollination services. Ecological intensification to mitigate these effects has focused largely on restoring field-scale semi-natural habitat including flower strips and other habitat patches for grassland and wildflowers. The boost to floral resources provided by these agri-environment schemes typically span only a portion of the seasonal activity period for pollinating insect assemblages. Provision of pollination services on farmland is also dependent on wider landscape context, with relatively little attention being paid to the influence of woodland patches upon pollinator communities.Uncertainty remains over which plant species are the most valuable food resources for pollinator species, and how their relative value varies seasonally. While the benefits to bees of grassland-associated wildflowers is well-established, the complementary role of trees and woodland in buffering the provision of pollinator resources (nectar and pollen) is less well-studied in agricultural landscapes. Woodlands can provide among the highest levels of nectar production for a major UK habitat, and the use by pollinating insects of tree species may be disproportionate to the abundance of woodland in the landscape. Woodland tree species composition also influences other plants, with consequences for pollinators. Woodlands and woody corridors (hedgerows) in landscapes provide nesting and larval microsites for a range of pollinator species.Aims and objectivesThis project will investigate the role of woodland in the maintenance and resilience of pollinator insect communities in agricultural landscapes. Sampling of insects will be carried out in a selected study landscape in Norfolk spanning a range of densities of woodland patches and hedgerow networks. The project sets out to address the following key research questions:(1) How similar are pollinator assemblages that occur in woodland canopies compared with those that occur at ground level, in woodland interiors and in more open farmland habitats? We will investigate which pollinator species show the greatest proportional occurrence in woodland canopies relative to more open habitats, and test for correlation between canopy occurrences and availability of either pollen and/or nectar sources in woodland canopies. (2) Are pollinators found in or close to woodland canopies foraging on tree pollen resources? We will use molecular techniques to determine the identity of pollinator insect taxa, and their associated pollen, sampled from woodland canopies and at varying distance from woodland habitat. This work will establish which species of tree pollen, if any, are being used. We will test for circa 20 common woodland tree species, including some wind-pollinated species.(3) Do woodland areas promote seasonal stability in pollinator diversity and abundance in the surrounding landscape? The research design will focus on sampling within significant woodland patches within the study area, and at varying proximities to these patches within agricultural landscapes, including varying distances along hedgerows with and without trees. Repeat sampling in spring and summer will capture seasonal variations in pollinator assemblages. (4) What are the optimal woodland and woody corridor management recommendations for maintaining resilient pollinator communities, hence pollination services, in agricultural landscapes? Here we will focus on the role of woody corridors as linear features in the landscape, and how to optimise their role in connectivity of pollinator assemblages between woodland patches and cultivated landscapes and maintain pollination services.