Landscape management can foster pollinator richness in fragmented high-value habitats.

Landscape context of bee, wasp and parasitoid diversity: grass-strip corridors, fallows and food webs

Agri-environmental schemes (AES) aim to restore biodiversity and biodiversity-mediated ecosystem services in landscapes impoverished by modern agriculture. However, a systematic, empirical evaluation of different AES types across multiple taxa and functional groups is missing. Within one orthogonal design, we studied sown flowering AES types with different temporal continuity, size, and landscape context and used calcareous grasslands as seminatural reference habitat. We measured species richness of 12 taxonomic groups (vascular plants, cicadas, orthopterans, bees, butterflies, moths, hoverflies, flower visiting beetles, parasitoid wasps, carabid beetles, staphylinid beetles, and birds) representing 5 trophic levels. A total of 54,955 specimens were identified using traditional taxonomic methods, and bulk arthropod samples were identified through DNA metabarcoding, resulting in a total of 1,077 and 2,110 taxa, respectively. Species richness of most taxonomic groups, as well as multidiversity and richness of pollinators, increased with temporal continuity of AES types. Some groups responded to size and landscape context, but multidiversity and richness of pollinators and natural enemies were not affected. AES flowering fields supported different species assemblages than calcareous grasslands, but assemblages became more similar to those in seminatural grasslands with increasing temporal continuity. Our results indicate that AES flowering fields and seminatural grasslands function synergistically. Flowering fields support biodiversity even when they are relatively small and in landscapes with few remaining seminatural habitats. We therefore recommend a network of smaller, temporally continuous AES flowering fields of different ages, combined with permanent seminatural grasslands, to maximize benefits for biodiversity conservation and ecosystem service delivery in agricultural landscapes.

Modern agriculture has severely impacted the variety of life on earth. Agricultural expansion has cleared >50% of natural habitats on agriculturally usable land, while agricultural intensification has reduced the abundance and diversity of wildlife in farmed areas. Agri-environment schemes (AESs) offer opportunities to restore habitats for wildlife in farmed landscapes across Europe and elsewhere. This could help to (1) reverse declines in species of conservation concern and (2) provide “ecosystem services”, such as pollination, which contribute to human wellbeing. AES interventions have led to increases in the abundance and diversity of wildlife. However, despite the scale of public investment in AESs, the size and significance of those increases are often unclear. Furthermore, the outcomes of AES interventions vary depending on features of the surrounding landscape, especially semi-natural habitat. Research to date has directed the allocation of AES interventions in a broad sense, for example towards landscapes with <20% coverage of semi-natural habitat. Still, there is a lack of specific advice about how and where to restore habitat on farmland to maximise benefits for priority insect species. I present two field studies of the abundance and species richness of night-flying Lepidoptera (moths) in the UK, aiming to develop advice for land managers implementing AESs. Focussing on moths in three distinct habitat specialism groups, I looked at how the benefits of two types of AES interventions were affected by the coverage of semi-natural calcareous grassland (CG) nearby. In the first field study I investigated the benefits of AES interventions that create wide grass margins on the edges of arable fields. I found that grass margins significantly increased the abundance of grassland generalist moths. Furthermore, grass margins benefitted CG-associated moths if there were large areas of CG habitat nearby. Therefore, spatial targeting of AES interventions towards semi-natural habitat has the potential to improve outcomes for biodiversity. In the second field study I investigated the benefits of AES interventions that restore arable fields to species-rich grassland. Restored grassland fields were similar to semi-natural CG in terms of moth abundance and species richness. Furthermore, CG moths were more abundant on restored grassland where CG indicator wildflowers were established. Grassland restoration is a particularly successful AES intervention, especially if the plant community is enhanced to support priority insect species. Finally, I present the first individual-based model to test how the benefits of AES interventions depend on distance from source populations on semi-natural habitat. By simulating larval and adult life-stages of hypothetical insect species, my model provided a set of mechanisms that help to explain my empirical field observations. Ultimately, this thesis presents two of the most robust field studies on the interaction between AES interventions and the landscape context. By interpreting these field studies in light of a supporting model, I produce clear advice for land managers interested in the conservation of moths and the other species with which they coexist.

Agricultural intensification has resulted in a decline in insect biodiversity and threatens the provision of valuable ecosystem services. Agri-environment schemes (AESs) have been implemented in an effort to conserve biodiversity on farmland and increase agricultural sustainability, but their effectiveness can vary widely. To better determine which factors influence AES effectiveness, the relative roles of local habitat features, habitat quality, and landscape context need to be further explored. The aim of this study was to determine the most important factors influencing field margin AES effectiveness in commercial apple orchards, in terms of arthropod biodiversity conservation and ecosystem service provision. We surveyed wild bees and aphid natural enemies in field margins and apple trees in 20 orchards, ten bordered by hedgerow field margins (an AES) and ten with herbaceous field margins (no hedgerows present, not an AES). We considered field margin floral resources and the cover of semi-natural habitat in the surrounding landscape as indicators of local habitat quality and landscape context, respectively. We furthermore quantified pollination and pest control as measures of ecosystem service delivery and the relationship between arthropod communities and apple yield (initial and final fruit set) and quality. We found that hedgerow presence strongly predicted both pollinator and natural enemy communities and that these relationships were more pronounced than those with local habitat quality and landscape context. Hedgerows were negatively related to wild bee richness and abundance within the orchard, and positively related to natural enemy richness and abundance at the field margin but not within the orchard. We found no relationships between local and landscape factors and ecosystem service delivery, and no relationship between wild bee communities and apple yield, suggesting that apple is not pollen limited in our study system. There was, however, a negative relationship between natural enemy richness and initial fruit set. We conclude that annually cut hedgerows can benefit the conservation of natural enemies, but have limited arthropod-mediated private benefits for apple production, and likely need to be supplemented with additional local habitat resources for the conservation of wild bees. Our findings indicate that local habitat factors can strongly influence biodiversity regardless of landscape context, but that AESs likely need to be designed with separate biodiversity and ecosystem service targets, and specific taxonomic groups, in mind.

An important function of agri-environmental schemes (AES) is to change management of pastures to better conserve biodiversity. However, the effects of most AES on biodiversity are poorly understood, especially when it comes to effects of AES management over time. The main aim of this study is to investigate if the species richness and abundance of grassland specialists of vascular plants and two important insect pollinator groups (bumblebees and butterflies) differ over time (5 years) in pastures with AES management (two value levels; general values and special values) and pastures without AES management. We also investigate if local vegetation characteristics and landscape composition relate to species richness in semi-natural grasslands. Using data from more than 400 sites we found that species richness of vascular plants (grassland specialists) was higher in pastures with AES management (for special and general values) compared to those without AES, which implies that these schemes do have value of the conservation of plant diversity. However, species richness and abundance of butterflies (grassland specialists) and bumblebees (all species) did not differ significantly among the three AES categories. We found no evidence that the type of AES management caused any changes in species richness of plants, butterflies or bumblebees during the 5 year period of our investigation. It appears that AES management that encourages uniform and minimum levels of grazing can have both positive and negative effects on biodiversity. For example, pollinators may benefit from a lower grazing intensity that could increase flower richness and heterogeneity in vegetation height. However, low grazing intensity may lead to increased cover of trees and shrubs, which can have negative effects for both insect pollinators and vascular plants. The effects of landscape composition were weak and only species richness of bumble bees were associated with landscape composition. Designing management regimes to maintain suitably heterogeneous vegetation layer, and continued long-term monitoring of biodiversity will be critical for safeguarding culturally and functionally important semi-natural grasslands.

Calcareous grasslands and orchard meadows are among the most species-rich semi-natural habitats in Europe, but they are severely threatened by intensified land use and abandonment. Here, we focus on the effects of management vs. abandonment of these grasslands in agricultural vs. forest-dominated landscapes of Germany. We recorded butterflies and birds and classified them in farmland and woodland species according to their habitat preferences. Species richness and abundance of farmland butterflies were higher on calcareous grasslands than orchard meadows and benefited from forested landscapes in case of orchard meadows. Species richness of woodland butterflies was higher on abandoned than managed grasslands, independent of habitat type and landscape context. Richness and abundance of farmland birds benefited from managed orchard meadows, and were more abundant in agricultural landscapes. On calcareous grasslands, however, the abandonment led to higher richness and abundance of farmland birds. Woodland birds exhibited higher species richness in abandoned than managed grasslands, especially in orchard meadows. Woodland birds and butterflies appeared to be less affected by habitat type, management or landscape context than farmland species. Calcareous grasslands were much more important for butterfly diversity than orchard meadows, but suitability of orchards for butterflies was improved when embedded in forested landscapes. In contrast to butterflies, bird diversity benefited more from orchard meadows than calcareous grasslands, which had higher diversity when management was abandoned. In conclusion, landscape context can shape communities in these two grassland habitat types, so conservation management should consider reserves in both agricultural and forested landscapes and thereby, diversify regional biota.

Pollinating insect populations, essential for maintaining wild plant diversity and agricultural productivity, rely on (semi)natural habitats. An increasing human population is encroaching upon and deteriorating pollinator habitats. Thus the population persistence of pollinating insects and their associated ecosystem services may depend upon on man-made novel habitats; however, their importance for ecosystem services is barely understood. We tested if man-made infrastructure (railway embankments) in an agricultural landscape establishes novel habitats that support large populations of pollinators (bees, butterflies, hoverflies) when compared to typical habitats for these insects, i.e., semi-natural grasslands. We also identified key environmental factors affecting the species richness and abundance of pollinators on embankments. Species richness and abundance of bees and butterflies were higher for railway embankments than for grasslands. The occurrence of bare (non-vegetated) ground on embankments positively affected bee species richness and abundance, but negatively affected butterfly populations. Species richness and abundance of butterflies positively depended on species richness of native plants on embankments, whereas bee species richness was positively affected by species richness of non-native flowering plants. The density of shrubs on embankments negatively affected the number of bee species and their abundance. Bee and hoverfly species richness were positively related to wood cover in a landscape surrounding embankments. This is the first study showing that railway embankments constitute valuable habitat for the conservation of pollinators in farmland. Specific conservation strategies involving embankments should focus on preventing habitat deterioration due to encroachment of dense shrubs and maintaining grassland vegetation with patches of bare ground.

Community structure and interaction webs of flower-visiting and cavity-nesting insects along an experimental plant diversity gradient

Agri-environment schemes and ecosystem services: The influence of different sown flower field characteristics on pollination, natural pest control and crop yield

Summary Agri‐environment scheme (AES) interventions are a major avenue for habitat creation and restoration across Europe. To maximize benefits for biodiversity, AES interventions are sometimes spatially targeted relative to existing semi‐natural habitat (SNH). However, the evidence base for effective spatial targeting is deficient; studies until now have collated data across several taxa and regions, resulting in non‐specific advice that is only useful at the regional scale. We present a field study using macro‐moths (Lepidoptera) to test (i) the impact of creating grassland habitat on arable field margins, (ii) how the impact of this type of AES intervention varies according to species specialism and (iii) the potential impact of spatially targeting AES interventions for proximity to semi‐natural chalk grassland (CG). We surveyed macro‐moths on arable fields with and without AES interventions across a range of levels of connectivity to CG. We also surveyed macro‐moths on CG habitat. Macro‐moth abundance was highest on CG and lowest on arable field centres. The benefits of AES interventions were largest for grassland‐associated macro‐moths: abundance was ∼1·4 times higher on AES margins than on control margins for this group. Chalk grassland‐associated macro‐moths only benefited from AES interventions that were close (&lt;1 km) to large areas (&gt;10 ha) of CG habitat. We estimate that clustering AES interventions around CG could lead to a ∼17% increase in CG macro‐moth abundance on arable margins across our sampled region, leading to an overall increase of 2·6% within the sampled region. Synthesis and applications. We provide evidence that for conservation of species associated with a specific type of semi‐natural habitat (SNH), agri‐environment scheme (AES) interventions are most effectively positioned close to that habitat. Our study on macro‐moths in arable fields with and without AES interventions across a range of levels of connectivity to chalk grassland represents a template for the production of tailored spatial targeting advice. We show that optimal positioning of AES habitat creation depends on the extent of SNH in the surrounding landscape as well as the ecology and life history of species being conserved.

Pollinating insects are under high human pressure due to agricultural intensification and urbanization. Although many research and conservation projects have been applied worldwide, there is still a need for a comprehensive approach that meets local conditioning and capabilities. This paper investigated the composition, abundance, richness, alpha, beta, and gamma-diversity of pollinators between unused railway embankments and semi-natural grasslands. On 50 study sites (25 sites in unused railways and 25 their reference on grasslands), we collected data on the abundance, species richness and species diversity of bees, butterflies, and hoverflies. We conducted five samplings yearly (April–September) for two years, 2017–2018. To assess differences in abundance, species richness, alpha and beta diversity of pollinators between unused railways and controls, we used generalized linear mixed models (GLMM). To compare the composition of pollinator species, we applied non-metric multidimensional scaling (NMDS). Abundance, species richness, and Shannon-Wiener diversity index of all three groups of pollinators were significantly higher in unused railway lines than in control grasslands. Pollinator communities were more constant in unused railway lines than in grasslands. The NMDS analysis highlighted the importance of these structures for bee, butterfly and hoverfly communities, which were a subset of grassland species, but were more abundant. We indicated the highest total taxonomic beta-diversity for bees, butterflies, and hoverflies and species turnover for bees and butterflies in control grassland compared with unused railway lines. The taxonomical nestedness was significantly higher in unused railways lines for bees and butterflies than in control grasslands. In the case of hoverflies, we did not found any significant differences in species turnover and nestedness. Unused railway lines may act as a conservation tool for pollinator communities in intensively managed farmland and complement the declining semi-natural habitats.

Restoring intensive agricultural fields to species-rich semi-natural grassland could have profound effects on biodiversity and ecosystem services. However, only a minority of European agri-environment scheme funding is currently devoted to such measures (<1% in the UK) and too few studies compare biodiversity on restored habitats with that on appropriate control and reference sites. As a result, there is a lack of advice for land managers on how to implement habitat restoration to maximise conservation outcomes, especially for insects. We present a landscape-scale field study in which we tested whether the abundance and species-occurrence of moths (Lepidoptera) differed between arable fields, fields restored to species-rich grassland, and semi-natural calcareous grassland (CG). We also tested whether moths were affected by the frequency of CG indicator wildflowers, age of restoration and habitat connectivity of restored grassland. We found that the abundance of CG-associated moths on restored grassland was almost eight times that on arable fields, and abundance and species-occurrence did not differ significantly from that on semi-natural CG. The only group of moths that was more abundant on CG than restored grassland was associated with late successional stage habitats (e.g. woodland), which shows that trees and shrubs are key features maintaining insect biodiversity on CG. CG moths were more abundant on restored grassland sites where CG indicator wildflowers had established, suggesting that active enhancement of the plant community can increase the abundance of target insect groups. Restoring arable fields to species-rich grassland benefits moths over short timescales (as little as 3years) and at great distances from semi-natural CG (up to 7km). It should play a pivotal role in future agri-environment schemes aiming to increase insect biodiversity.

PDF HTML阅读 XML下载 导出引用 引用提醒 黄河中下游农业景观中景观简化对传粉昆虫多样性的影响——以巩义市为例 DOI: 10.5846/stxb201511292392 作者: 作者单位: 河南大学,河南大学,河南大学,河南大学 作者简介: 通讯作者: 中图分类号: 基金项目: 国家自然科学基金资助项目（41371195，41071118） Effects of landscape simplification on pollinator diversity in agricultural areas near the lower reaches of the Yellow River: a case study Author: Affiliation: Henan University,Henan University,, Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:在农业景观中，传粉昆虫的生存繁衍与半自然生境的面积大小有关。集约化生产方式使半自然生境比例逐渐减少，农田比例不断增加，随着景观简化梯度的变化（农田比例逐渐增大），传粉昆虫群落多样性将会发生怎样的变化？选择黄河中下游典型农区巩义市为研究区域，采用诱捕盘法（Pan traps）进行农田、林地的传粉昆虫取样，以21个样点作为景观简化梯度（农田比例范围5%-86%）的呈现，基于每个样点的传粉昆虫多度和丰富度变化来探究景观简化对传粉昆虫多样性的影响。结果显示：区内累计捕获传粉昆虫39660头，优势类群包括双翅目（Diptera）、膜翅目（Hymenoptera）、鞘翅目（Coleoptera）等。采用逐步回归分析及线性拟合后发现景观简化程度与传粉昆虫多度和丰富度呈显著负相关（P<0.05）；景观简化对传粉昆虫类群间的影响也是有差异的，其中对鞘翅目多度的影响最为密切（R2=0.27），同时对膜翅目和双翅目也有较大影响（R2=0.14、R2=0.11），景观简化与鳞翅目多度呈正相关；随景观简化的程度加深，农田生境中膜翅目多度呈显著下降趋势（P<0.05），而林地中膜翅目多度变化不明显。在未来的景观规划中，应着重考虑传粉昆虫中鞘翅目类群的栖息地变化及食物资源状况。依据研究结果建议林地生境中应注重保护现有的自然植被群落，在人工林中可以种植一定面积的蜜粉源植物；农田生境内对杂草群落、半自然生境斑块进行合理规划的基础上，还可以种植线性景观植物作为传粉昆虫的食物源。 Abstract:In agricultural landscapes, the survival and reproduction of pollinators depends on the size of semi-natural habitats. The intensive agricultural production model has caused a decrease in semi-natural habitats and an increase in the proportion of land dedicated to agriculture. This study aimed to quantify any changes in the diversity of pollinators following this increase in the proportion of land dedicated to agriculture. Our study area was in Gongyi City, which is a typical agricultural region located near the lower reaches of the Yellow River. Twenty-one study sites were collected from the northeast to the central area. Pan traps were used to capture pollinators from farmland and woodland habitats. Using the Akaike Information Criterion (AIC), we calculated the optional characteristics scales of the pollinators and landscape features by 500m, where landscape simplifying was determined in terms of farmland proportion. Finally, the proportion of farmland was chosen as the basis of landscape simplification, which provided us with 21 sample points as the simplified gradient of the landscape (the ratio of farmland should be between 5% and 86%). We then explored the impact of landscape simplification on pollinator diversity, which was based on the species abundance and richness of pollinators at each sample point. We caught a total of 39660 individual pollinators. The most common orders caught included Diptera (26236 individuals), Hymenoptera (13893 individuals), and Coleoptera (2033 individuals). Stepwise analysis and linear fitting showed that landscape simplification directly influenced the richness and abundance of pollinators, with greater proportions of farmland significantly negatively correlating with the richness and abundance of species caught (P<0.05). The effect of landscape simplification on different pollinator groups was variable. The effect of landscape simplification was most significant on Coleoptera (R2=0.27), followed by Hymenoptera (R2=0.14), and Diptera (R2=0.11). Landscape simplification was correlated with an increase in the number of Lepidoptera individuals caught (R2=0.09). Hymenoptera abundance was significantly decreased in farmland habitats, while there was no observable change in Hymenopteran abundance in woodlands. Overall, as the proportion of farmland increased, we observed significant changes in the abundance and richness of species caught. Our results showed that the proportion of farmland directly affected the abundance and richness of pollinators caught. In certain areas the balance between farmlands and semi-natural habitats is inappropriate and needs to be carefully reconsidered by decision makers and stakeholders. During land use planning, there should be an emphasis on the habitat and food resources needed by the Coleoptera taxa of pollinating insects in particular. Our results also suggested that more attention needed to be paid to the protection of existing natural vegetation communities in woodland habitats, while nectar-producing plants could be planted in artificial forests. Moreover, linear landscape plants could be planted as a food source for pollinators alongside farmlands. To protect natural habitats, such as weed communities, linear artificial landscapes of a suitable size could be planted on the boundary of farmlands, which would have a significant ecological impact and help to protect resource insects, such as Hymenopterans. 参考文献 相似文献 引证文献

Metapopulation theory predicts that species richness and total population density of habitat specialists increase with increasing area and regional connectivity of the habitat. To test these predictions, we examined the relative contributions of habitat patch area, connectivity of the regional habitat network and local habitat quality to species richness and total density of butterflies and day-active moths inhabiting semi-natural grasslands. We studied butterflies and moths in 48 replicate landscapes situated in southwest Finland, including a focal patch and the surrounding network of other semi-natural grasslands within a radius of 1.5 km from the focal patch. By applying the method of hierarchical partitioning, which can distinguish between independent and joint contributions of individual explanatory variables, we observed that variables of the local habitat quality (e.g. mean vegetation height and nectar plant abundance) generally showed the highest independent effect on species richness and total density of butterflies and moths. Habitat area did not show a significant independent contribution to species richness and total density of butterflies and moths. The effect of habitat connectivity was observed only for total density of the declining butterflies and moths. These observations indicate that the local habitat quality is of foremost importance in explaining variation in species richness and total density of butterflies and moths. In addition, declining butterflies and moths have larger populations in well-connected networks of semi-natural grasslands. Our results suggest that, while it is crucial to maintain high-quality habitats by management, with limited resources it would be appropriate to concentrate grassland management and restoration to areas with well-connected grassland networks in which the declining species currently have their strongest populations.

Increased farming intensity led to massive declines across multiple farmland taxa. In Europe, measures introduced to counteract these losses include those considered agronomically productive, such as organic farming, as well as those that support no direct production of crops, such as non‐crop flowering fields in conventional farming systems. We studied biodiversity effects of non‐productive flowering fields managed under conventional farming compared to both an organically managed cereal mono‐crop (organic winter spelt fields) and a flowering mixed‐crop (organic lentil mixed‐crop fields) as well as conventionally managed winter wheat fields, which served as control crop. These four crop‐use types were studied on six sites over 3 years (17 sites in total) to assess their impact on the activity density (cover for plants), species richness and community composition of wild plants, carabids, spiders, butterflies and wild bees. Species richness of wild plants was highest under organic farming and at field edges when compared to the interior. In the case of carabids and spiders, species richness was highest at the field edges, but there was no difference between the four crop‐use types. In contrast, activity density and species richness of butterflies and wild bees responded only to flowering crop‐use types, showing no edge effects. Arable land cover in 500 m buffer area also affected community composition of all taxa, with the exception of spiders, but had only minor effects on activity densities and species richness. Synthesis and applications. Our findings underline that there is no single best measure to promote biodiversity on arable land. Instead a mosaic of non‐productive and productive measures such as conventional flowering fields, organic crops and field edge habitats might be more appropriate to support the regional species pool in arable‐dominated landscapes. To support a range of complementary biodiversity‐promoting farming practices, agricultural policy should foster the coordination and collaboration between multiple farmers within the same region by covering additional costs for coordination and prioritizing collaborative schemes.