Field Margin Vegetation Research Articles

Land consolidation impacts the abundance and richness of natural enemies but not pests in small‐holder rice systems

Abstract Traditional small‐holder agricultural landscapes in southern China are being consolidated to increase mechanisation levels in agriculture, but it is unclear how this influences rice arthropod communities in these landscapes. Here, based on a six‐year study in 20 rice fields, we evaluated the impact of land consolidation on arthropod communities, crop damage, and rice yield. We also analysed how effects of land consolidation were moderated by the proportion of large semi‐natural habitat patches and insecticide use. We found that, compared to consolidated fields, rice fields in traditional farmlands had a higher abundance and family richness of natural enemies, but a similar abundance of rice pests. Land consolidation did not significantly interact with the proportion of large semi‐natural habitat patches or insecticide application, in terms of affecting arthropods. The proportion of semi‐natural habitat reduced the negative effect of insecticide application on key rice pests, but no equivalent interaction occurred for natural enemies. Synthesis and applications: Land consolidation can have negative impacts on the abundance and richness of natural enemies, but not pests in small‐holder rice systems, and these impacts are independent from insecticide application and proportion of semi‐natural habitat in the landscape. We recommend the implementation of agri‐environmental measures or re‐establishing field margin vegetation during the consolidation process to mitigate these potential negative effects, although trade‐off between enhancing crop yields and preserving rice arthropod biodiversity should be considered. We encourage future research to focus on the detailed assessment of the function of linear habitats for a better understanding of the impact of land consolidation.

Lablab (Lablab purpureus L.) genotypes and field margin vegetation influence bean aphids and their natural enemies.

Lablab (Lablab purpureus L.) is an important food and livestock feed legume that can also enhance soil fertility. However, its production is limited by insect pests, notably the black bean aphid (Aphis fabae). The present field study was conducted to determine the difference in the contribution of lablab genotypes and natural field margin vegetation (FMV) to the abundance and diversity of natural enemies and the damage, incidence, and abundance of bean aphids. Eighteen lablab genotypes were planted in the presence or absence of FMV in a randomized complete block design experiment replicated four times. Data on aphid abundance, incidence, and severity of damage were collected at four growth stages of the crop. Lablab genotypes significantly influenced aphid incidence, suggesting some level of tolerance to aphid colonization. Findings showed that lablab genotypes were a significant influence on natural enemy species richness with no statistical difference for abundance and natural enemy species diversity. However, the genotypes did not vary significantly in their influence on the number of aphid natural enemies. FMV was associated with low bean aphid damage. Overall, the presence or absence of FMV did not influence the number of natural enemies caught on the crop. This concurs with recent work that shows a similar number of natural enemies with field margin plants but may reflect the reduced number of pest insects. Cropping seasons influenced aphid abundance and damage severity, with the populations developing at the early stages of lablab development and decreasing as the crop advanced. This pattern was similar both in the presence or absence of FMV. The findings of this study highlight the important contribution of crop genotype together with the presence of field margin species in the regulation of aphids and their natural enemies in lablab.

Major field margin vegetation types in France and their relationships with climate, agricultural landscapes and management intensity

ABSTRACT Arable field margins are an important semi-natural habitat providing multiple functions in agroecosystems. Despite three decades of research, analyses of species assemblage and functional traits are lacking. Leveraging a national monitoring network in metropolitan France, we aim to provide a comprehensive taxonomic and functional synthesis of field margin flora, outline main field margin types and explore their associations with management practices, climate, and agricultural landscapes. We analysed data from 532 field margins surveyed between 2013 and 2017, using both uni- and multivariate analyses. Field margins exhibited great diversity with 711 distinct taxa (12% of all flora in mainland France) at the national scale and an average of 16 species per 10 m2 locally. While field margins contained few species of conservation value, they offered a refuge for many declining species as well as rare arable weed species. We identified seven main field margin types, each linked to distinct conditions of climate, soil, landscape and agricultural practices. Mediterranean field margins notably differed from all others. In the main cluster, vineyard margins also stood out as distinct from annual crop margins. Additionally, field margins in landscapes with a high proportion of grassland differed from those within intensively cultivated field crop plains in conventional agriculture. Overall, our study highlights the high botanical diversity of field margins and their interest for plant conservation in agricultural landscapes. Promoting the installation and/or maintenance of field margins through agri-environmental schemes should thus favour biodiversity conservation and associated ecosystem provision.

Field margins and cropping system influence diversity and abundance of aphid natural enemies in Lablab purpureus

AbstractField margin plants around crops are postulated to increase natural enemy abundance to enhance pest management. A trial was conducted to determine the contribution of field margin vegetation and cropping systems to natural enemies of bean aphids (Aphis fabae) on Lablab purpureus, an orphan crop legume. Natural enemy populations were surveyed in plots with a combination of lablab monocrop or maize‐lablab intercrop and with or without planted field margins comprising four plant species (Chenopodium album, Bidens pilosa, Galinsoga parviflora and Tagetes minuta), arranged in a randomized complete block design with four replicates. A cage experiment was also conducted to understand the extent to which these field margin plants supported the parasitoid wasp, Aphidius colemani, to parasitize bean aphids. A total of 2029 insects from 10 families were collected using sticky cards and pan traps. In comparison to plots with no field margin plants, the presence of plant‐rich field margins increased abundance of natural enemies by 9.5% and supported higher populations of Braconidae (parasitoids) and damsel bugs (predators). The maize‐lablab intercrop had 15.5% lower abundance of natural enemies than the lablab monocrop. Higher grain yield was recorded in plots with a field margin vegetation (300 kg ha−1) compared to plots without field margin vegetation (210 kg ha−1). The presence of a companion plant did not significantly affect the performance of parasitoids, in the cage experiment, indicating that parasitoids were not limited by access to food. In supporting aphid parasitization, B. pilosa was associated with the highest number of mummies (8.28). The lowest number of mummies were observed in cages with T. minuta (3.44). These results demonstrate the potential of plant‐rich field margins to augment natural enemy populations and enhance conservation biocontrol of aphids.

Not All Field Margins Are Equally Useful: Effects of the Vegetation Structure of Margins on Cereal Aphids and Their Natural Enemies.

Differences in the semi-natural vegetation of field margins will affect the biological control services derived from the presence of these semi-natural habitats adjacent to fields. Of the plant functional traits that are most relevant for insects, plant life forms reflect different aspects of plant structure and functioning that can help predict the value of marginal vegetation for arthropods in agricultural systems. The aim of this study was to determine the effect of the vegetation structure of field margins on cereal aphids and on some of their natural enemies (parasitoids, hoverflies and ladybugs) in terms of plant life forms. We characterized margin vegetation using the relative cover of each life form and sampled insects in crops along transects parallel to field margins. Our results show that in the studied areas, the abundance of natural enemies was greater near margins dominated by annual plants than in margins dominated by perennial plants. On the other hand, the abundances of aphids and parasitism rates were higher near margins dominated by perennial woody plants than near margins dominated by perennial herbaceous plants. By promoting specific life forms in existing margins, farmers can enhance the conservation biological control and relieve aphid pressure on their crops.

Use of Winery and Animal Waste as Fertilizers to Achieve Climate Neutrality in Non-Irrigated Viticulture

There is a growing interest globally in reducing the environmental impacts of farming by reusing agricultural waste and reducing agricultural greenhouse gas (GHG) emissions. In this work, the potential of Mediterranean viticulture for GHG emissions mitigation and Carbon (C) storage in biomass and soil is examined. In a field experiment, synthetic fertilizer use was reduced by 50 and 100% after applying a winery waste-based biofertilizer, and the C balance was determined at the vineyard level. The Vineyard Carbon Tool (VCT) for GHG emissions estimation in vineyards was developed by tailoring to vineyards the widely used Cool Farm Tool (CFT). Our results show that existing conventional viticulture could be easily transformed into zero-emissions by reducing nitrogen (N) fertilizers, lowering tillage frequency, using less fuel, and maintaining field margin vegetation at the farm level. Use of Life Cycle Analysis (LCA) showed that farm input reductions lead to a vineyard lifetime C storage equal to 25,124 kg CO2-eq ha−1 or 837 kg CO2-eq ha−1 year−1. This approach could be used for the design of eco-schemes related to C farming under the new Common Agricultural Policy (CAP).

Field margins and botanical insecticides enhance Lablab purpureus yield by reducing aphid pests and supporting natural enemies.

Botanical insecticides offer an environmentally benign insect pest management option for field crops with reduced impacts on natural enemies of pests and pollinators while botanically rich field margins can augment their abundance. Here, we evaluated the non‐target effects on natural enemies and pest control efficacy on bean aphids in Lablab of three neem‐ and pyrethrum‐based botanical insecticides (Pyerin75EC®, Nimbecidine® and Pyeneem 20EC®) and determine the influence of florally rich field margin vegetation on the recovery of beneficial insects after treatment. The botanical insecticides were applied at the early and late vegetative growth stages. Data were collected on aphids (abundance, damage severity and percent incidence) and natural enemy (abundance) both at pre‐spraying and post‐spraying alongside Lablab bean yield. The efficacy of botanical insecticides was similar to a synthetic pesticide control and reduced aphid abundance by 88% compared with the untreated control. However, the number of natural enemies was 34% higher in botanical insecticide‐treated plots than in plots treated with synthetic insecticide indicating that plant‐based treatments were less harmful to beneficial insects. The presence of field margin vegetation increased further the number of parasitic wasps and tachinid flies by 16% and 20%, respectively. This indicated that non‐crop habitats can enhance recovery in beneficial insect populations and that botanical insecticides integrate effectively with conservation biological control strategies. Higher grain yields of 2.55–3.04 and 2.95–3.23 t/ha were recorded for both botanical insecticide and synthetic insecticide in the presence of florally enhanced field margins in consecutive cropping seasons. Overall, these data demonstrated that commercial botanical insecticides together with florally rich field margins offer an integrated, environmentally benign and sustainable alternative to synthetic insecticides for insect pest management and increased productivity of the orphan crop legume, Lablab.

Role of traditional ecological knowledge on field margin vegetation in sustainable development: A study in a rural-urban interface of Bengaluru

Field Margin Vegetation (FMV) is an important part of agrobiodiversity which provides a range of ecological and economic benefits. Those services are mostly unaccounted in spite of having potential contribution to biodiversity conservation, well-being of farming households, climate change mitigation etc. The structure and composition of FMV and socioeconomic transformation are closely linked to each other. Transformation which influences FMV negatively leads to erosion of traditional ecological knowledge of the community that is associated with the use, management and conservation of native vegetations in the agroecosystems. There has been research on the function and composition of field margin vegetations, more specifically in the West but the documentation of traditional ecological knowledge on field margin vegetation from the viewpoint of socio-ecological sustainability is not readily available. Through this research an attempt is made to understand and document the uses of FMV by farmers and related traditional knowledge in rural-urban interface of Bengaluru, India. The agricultural landscape under study was found to be rich in FMV species belonging to 43 families. These species are used for a variety of purposes by the people l living in the rural-urban fringe of the northern transect of Bengaluru. This is a preliminary, yet substantial attempt that provides insights into the socioecological significance of the FMV component of agroecosystem. The findings would help in strategising actions to enhance its stake in initiatives to achieve sustainable development goals through health and nutrition, sustainable farming, environmental conservation and economic well-being. The study suggests that the scientific assessment of ecosystem services from FMV along with integration of traditional ecological knowledge in contemporary science would certainly contribute towards enhancement of its values.

Role of Traditional Ecological Knowledge on Field Margin Vegetation in Sustainable Development: A Study in a Rural-Urban Interface

Role of Traditional Ecological Knowledge on Field Margin Vegetation in Sustainable Development: A Study in a Rural-Urban Interface

Insect pollination is important in a smallholder bean farming system

BackgroundMany crops are dependent on pollination by insects. Habitat management in agricultural landscapes can support pollinator services and even augment crop production. Common bean (Phaseolus vulgaris L.) is an important legume for the livelihoods of smallholder farmers in many low-income countries, particularly so in East Africa. While this crop is autogamous, it is frequently visited by pollinating insects that could improve yields. However, the value of pollination services to common beans (Kariasii) yield is not known.MethodsWe carried out pollinator-exclusion experiments to determine the contribution of insect pollinators to bean yields. We also carried out a fluorescent-dye experiment to evaluate the role of field margins as refuge for flower-visitors.ResultsSignificantly higher yields, based on pods per plant and seeds per pod, were recorded from open-pollinated and hand-pollinated flowers compared to plants from which pollinators had been excluded indicating that flower visitors contribute significantly to bean yields. Similarly, open and hand-pollinated plants recorded the highest mean seed weight. Extrapolation of yield data to field scale indicated a potential increase per hectare from 681 kg in self-pollinated beans to 1,478 kg in open-pollinated beans indicating that flower visitors contributed significantly to crop yield of beans. Our marking study indicated that flower-visiting insects including bees, flies and lepidopterans moved from the field margin flowers into the bean crop. Overall, these results show that insect pollinators are important for optimising bean yields and an important food security consideration on smallholder farms. Field margin vegetation also provides habitat for flower-visiting insects that pollinate beans. Hence, non-crop habitats merit further research focusing on establishing which field margin species are most important and their capacity to support other ecosystem services such as natural pest regulation or even pests.

Structural field margin characteristics affect the functional traits of herbaceous vegetation.

BackgroundField margins are ecologically important to an agroecosystem as they are a source of biodiversity. They can be composed of a diverse flora which may offer resources to a wide range of insects and birds. The vegetation composition of field margins is determined by soil characteristics, management, and landscape structures. However, little is known about the effect of individual field margin components such as ditches, grass strips, shrubs and trees, and the overall margin’s complexity, on the vegetation composition and its functional effect and response traits.MethodsThis paper reports on the effects of field margin component typology (ditches, grass strips, shrubs, trees, and vehicle tracks) and complexity (the number of components), on the herbaceous vegetation of field margins. Forty field margins were sampled in 2016 in a 200 ha. organic mixed arable livestock farm.ResultsThe factor which was identified as having the most effect on vegetation composition was adjacent land-use type, which reflected the margins’ management regime. However, field margin components were found to affect vegetation response and effect traits. Tree components had less grassweeds than vehicle tracks while more complex field margins also had less grassweeds than simple field margins near cropped fields, most likely due to the lower availability in light and less disturbance from vehicles. Simple grassy margins produced a high proportion of hymenoptera flowers.DiscussionThese results highlight the importance of field margin components in maintaining a high diversity of vegetation typologies differing in effect traits that are relevant for the provisioning of ecosystem services, such as supporting pollen and nectar requirements of beneficial insects, as well as their importance in determining the presence of weed species that could potentially invade the cropped fields.

Structure and composition of field margin vegetation in the rural-urban interface of Bengaluru, India: a case study on an unexplored dimension of agroecosystems.

Field margin vegetation (FMV) refers to the plant community in the interface between agriculture and natural environments. Substantial work has been carried out on the management of field margins in European countries with the aim of conserving field-level biodiversity and enhancing agronomic benefits. India, instead, is lagging behind in the assessment of FMV and formulating subsequent management strategies for biodiversity conservation at the field boundaries. This study is a first step to better understand the structural and functional dimensions of field margin vegetation along an agricultural transformation gradient near the megacity of Bengaluru, India. Empirical field studies along with the detection of vegetation change using remote sensing and geo-informatics technique were used to record information on field margin vegetation. The phytosociological study, revealed a total of 81 species, comprising 29 species of trees, 21 shrubs and 31 herbs at the field margins of six selected villages of northern Bengaluru. Randomly selected 355 field boundaries were delineated from high-resolution Worldview 3 images for the year 2018 and from Google Earth images for the year 2004-2005. The FMV area was around to 85.40ha in 2004-2005 but declined to 76.69ha in 2017-2018. The survey also indicated that local farmers have in-depth ecological knowledge on the importance of FMV in ensuring a sustainable flow of resources within the agricultural landscape. The results demonstrate that rural and transition zones of the study area have higher dominance of planted tree species on the margins, whereas urban zone exhibits comparatively uniform dominance for all species. Our study also highlights the need for conservation of FMV to ensure agroecosystem health as a prerequisite for sustainable socioecological development.

Multiple ecosystem services from field margin vegetation for ecological sustainability in agriculture: scientific evidence and knowledge gaps.

BackgroundField margin and non-crop vegetation in agricultural systems are potential ecosystem services providers because they offer semi-natural habitats for both below and above ground animal groups such as soil organisms, small mammals, birds and arthropods that are service supplying units. They are considered as a target area for enhancing farm biodiversity.MethodologyTo explore the multiple potential benefits of these semi-natural habitats and to identify research trends and knowledge gaps globally, a review was carried out following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. A total of 235 publications from the year 2000 to 2016 in the Scopus and Web of Science databases were reviewed.ResultsThe literature showed an increasing trend in the number of published articles over time with European studies leading in the proportion of studies conducted, followed by North America, Asia, South America, Africa and Australia. Several functional groups of organisms were studied from field margin and non-crop vegetation around agricultural lands including natural enemies (37%), insect pests (22%), birds (17%), pollinators (16%), soil macro fauna (4%) and small mammals (4%). Ecosystem services derived from the field margin included natural pest regulation, pollination, nutrient cycling and reduced offsite erosion. Some field margin plants were reported to host detrimental crop pests, a major ecosystem dis-service, potentially leading to increased pest infestation in the field.ConclusionThe majority of studies revealed the importance of field margin and non-crop vegetation around arable fields in enhancing ecosystem biodiversity. Promotion of field margin plants that selectively enhance the population of beneficial organisms would support sustainable food security rather than simply boosting plant diversity. Our analyses also highlight that agro-ecological studies remain largely overlooked in some regions.

Field Margin Vegetation in Tropical African Bean Systems Harbours Diverse Natural Enemies for Biological Pest Control in Adjacent Crops

Non-crop vegetation around farmland can be valuable habitats for enhancing ecosystem services but little is known of the importance of field margins in supporting natural enemies of insect pests in tropical agriculture. This study was conducted in smallholder bean fields in three elevation zones to assess the importance of field margin vegetation to natural enemy populations and movement to the bean crop for biological pest control. The pests and natural enemies were assessed using different coloured water pan traps (to ensure the capture of insects with different colour preferences) and the interactions of the two arthropod groups with the margin vegetation and their movement to the bean crop were monitored using fluorescent dye. Sentinel plants were used to assess predation and parasitism levels. A total of 5003 natural enemies were captured, more in the field margin than within the bean field for low and mid elevation zones, while in the high elevation zone, they were more abundant within the bean field. Pests were more abundant in the crop than margins for all the elevation zones. The use of a dye applied to margin vegetation demonstrated that common natural enemy taxa moved to the crop during the days after dye application. The proportion of dye-marked natural enemies (showing their origin to be margin vegetation) sampled from the crop suggest high levels of spatial flux in the arthropod assemblage. Aphid mortality rates (measured by prey removal and parasitism levels on sentinel plants) did not differ between the field edges and field centre in any of the three elevation zones, suggesting that for this pest taxon, the centre of the fields still receive comparable pest control service as in the field edges. This study found that field margins around smallholder bean fields are useful habitats to large numbers of natural enemy taxa that move to adjacent crops providing biological pest control service.

Reduced species richness of native bees in field margins associated with neonicotinoid concentrations in non-target soils

Native bees are in decline as many species are sensitive to habitat loss, climate change, and non-target exposure to synthetic pesticides. Recent laboratory and semi-field assessments of pesticide impacts on bees have focused on neonicotinoid insecticides. However, field studies evaluating influences of neonicotinoid seed treatments on native bee communities of North America are absent from the literature. On four Conservation Areas of Missouri, we sampled row-cropped (treated, n = 15) and reference (untreated, n = 9) agricultural fields, and their surrounding field margins for neonicotinoids in soil and non-target vegetation (i.e., native wildflowers). Wildflowers were further collected and screened for the presence of fungicides. Concurrently, we sampled native bees over three discrete time points throughout the agricultural growing season to assess potential impacts of seed treatment use on local bee populations over time. Neonicotinoids were detected in 87% to 100% of treated field soils and 22% to 56% of reference field soils. In adjacent field margin soils, quantifiable concentrations were measured near treated (53% to 93% detection) and untreated fields (33% to 56% detection). Fungicides were detected in < 40% of wildflowers, whereas neonicotinoids were rarely detected in field margin vegetation (< 7%). Neonicotinoid concentrations in margin soils were negatively associated with native bee richness (β = −0.21, P < 0.05). Field margins with a combination of greater neonicotinoid concentrations in soil and fungicides in wildflowers also contained fewer wild bee species (β = −0.21, P < 0.001). By comparison, bee abundance was positively influenced by the number of wildflower species in bloom with no apparent impact of pesticides. Results of this study indicate that neonicotinoids in soil are a potential route of exposure for pollinator communities, specifically ground-nesting species. Importantly, native bee richness in non-target field margins may be negatively affected by the use of neonicotinoid seed treatments in agroecosystems.

Influences of blackberry margins on population dynamics of Drosophila suzukii and grape infestation in adjacent vineyards

AbstractUnderstanding the dynamics of pest insect populations in relation to the presence of non‐crop habitats and infestation levels of adjacent crops is essential to develop sustainable pest management strategies. The invasive pest species Drosophila suzukii (Diptera: Drosophilidae) is able to utilize a broad range of host plants. In viticulture, scientific risk assessment for D. suzukii has only recently started and studies assessing the effects of field margins containing wild host plants on D. suzukii population dynamics and on infestation risks in adjacent vineyards are lacking. Thus, in a one‐year field study, the role of different field margins on fly abundance and crop infestation in adjacent vineyards of Vitis vinifera, variety “Pinot Noir,” were investigated. Different monitoring methods were conducted to assess fly distribution, sex ratio and grape infestation in 14 vineyards adjacent to field margins containing either blackberry (BB) Rubus spp. or non‐host (NH) plants. Our results show that blackberries strongly enhanced D. suzukii abundance within field margin vegetation all year long, whereas fly abundance in vineyards adjacent to BB margins was just enhanced in some seasonal periods. Moreover, the influence of BB margins was limited by distance. However, high fly numbers in BB field margins did result in zero egg infestation of “Pinot Noir” berries. These results may have important implications for winegrowers to make efficient management decisions: regardless of high abundance of adult D. suzukii, only grape berry monitoring can assess the actual infestation risk and the potential need to take management action.

Sowing of margin strips rich in floral resources improves herbivore control in adjacent crop fields

Field margin vegetation provides resources for natural enemies of crop herbivores. Thus, the design of plant mixtures improving resource provisioning is being discussed increasingly with respect to improving herbivore control. We set up a field experiment to assess the effect of (i) a wildflower strip optimized for nectar provisioning; (ii) a grass strip and (iii) spontaneous vegetation on herbivore regulation in oilseed rape and wheat. We also analyzed the attractiveness of plant species to natural enemies. The cover of flowering entomophilous plant species as a proxy of floral resource provisioning was twice as high in wildflower strips compared with the other strip treatments. Natural enemy densities were higher within and close to wildflower strips in the field. A corresponding effect on aphid predation and aphid infestation was observed. Significant negative correlations between natural enemy abundance in the margin and aphid infestation in the fields supported a causal relationship. The sown wildflower strip species were more attractive to natural enemies than spontaneous vegetation. The results of the present study demonstrate that improved nectar provisioning increased the predation and parasitism of crop herbivores. Further research on the spatio‐temporal dynamics of interactions is needed to determine why not all crop herbivores respond to an increase of natural enemies in field margins.

Assessing non-intended effects of farming practices on field margin vegetation with a functional approach

To assess the unwanted side effects of farming practices on non-target plants, we used a nationwide survey of the vegetation of arable field margin strips. The vegetation was surveyed during two years (2013, 2014) in 430 field margins distributed over all agricultural regions of France. We used two complementary multivariate, trait-based approaches to examine how ten plant traits were related to ten environmental variables describing abiotic conditions, landscape factors, field margin management and in-field practices. Generalized additive mixed models were also developed to assess how the same environmental variables correlated with species richness, functional diversity and relative richness of agrotolerant versus hemerophobic species. Traits responded primarily to an environmental gradient of landscape diversity and field margin management. For instance, narrow field margin strips, frequent management and presence of a ditch favoured annual plants, small size at maturity and perennial plants, respectively. The second environmental gradient affecting plant traits was related to field size and intensity of in-field farming practices. On this gradient, fertilizer drift appeared to have a much stronger effect on plant trait composition of field margin strips than herbicide drift. The relationship between species richness, or functional diversity, and environment was consistent with the trait-based approach: the two former variables were negatively correlated with agriculture intensification (e.g. field size). However, this analysis also highlighted new covariates, such as a negative relationship between frequency of herbicide use and species richness. Some of the observed patterns seemed to be driven by differential responses of agrotolerant versus hemerophobic species, with the latter being more species-rich under organic than under conventional farming. Despite efforts to reduce nitrogen inputs since the 2000s, our results shows that N-fertilization still has significant non-intended effects on field margin vegetation. More generally, increasing the width of field margin strips, keeping or restoring semi-natural elements (ditches, hedges) in the field boundary, and lowering the number of management events may promote grassland plant species more typical of semi-natural habitats.

Effects of spontaneous field margin vegetation on the regulation of herbivores in two winter crops

Non-crop vegetation of field margins provides resources for natural enemies of crop herbivores. However, it is still not well known whether this resource provisioning effect is strong enough to improve herbivore regulation within crop fields and which plant species and functional groups favour this ecosystem service. A better understanding of the interactions between field margin vegetation and herbivore regulation is crucial to evaluate management strategies and to design suppressive plant mixtures. We surveyed 64 wheat and oilseed rape fields of Western France for two years (16 fields per year and crop) in order (1) to identify plant diversity or group effects on herbivore regulation within crop fields and (2) to identify species within plant groups that improve regulation. Herbivores, herbivore damage and natural enemies were monitored on crop plants at a distance of 5 and 50m from the field margin. At the same time, the cover and phenological stage of all vascular plants were estimated in the adjacent field margin. The study demonstrated a positive relationship between the cover of entomophilous plant species that were flowering at the survey date and response variables related to herbivore regulation. Plant species richness and the cover of plant species taxonomically close to crop plants had a small influence on herbivores and natural enemies in wheat whereas related wild Brassicaceae increased herbivory and decreased herbivore regulation in oilseed rape. Within the entomophilous flowering plants, several species were significantly related to a better herbivore regulation in univariate analyses. Multivariate ordination techniques allowed the identification of plant species influencing several response variables of herbivore regulation at the same time. Our study demonstrated the importance of entomophilous species that flowered at peak infestation of crop herbivores. Spontaneous field margins rich in flowering entomophilous species provide an important ecosystem service without expensive sowing of seed mixtures.

Ecobordure: A flora-based indicator to assess vegetation patterns of field margins and infer its local drivers. Design in Brittany (France)

Field margins are key landscape elements contributing to maintain biodiversity in agricultural landscapes. Yet, their ecological value is often poorly assessed and restricted to landscape descriptors, e.g. density or structure of hedgerows. We introduce Ecobordure, a flora-based indicator designed to describe vegetation patterns of field margins and infer on drivers leading to these patterns, i.e. structure and management practices of field margins. Ecobordure first targets agricultural teachers and advisers, who want to learn and help students and farmers to learn about patterns and drivers of field margin vegetation, for promoting management practices favorable to this biodiversity. Here, we present the stages of the Ecobordure design and output validation. The first stage consisted of elucidating the relationship between vegetation composition and structural and management characteristics of field margins. Canonical Correspondence Analyses were performed on empirical datasets derived from field work in bocage regions of Brittany (north-western France). This first stage led to the selection of 31 reference species, quite common, easy-to-recognize and representative of i) the whole community and ii) a wide range of ecological attributes. The 31 reference species were classified in three groups sharing similar life history traits and ecological attributes: “forest-edge”, “grassland” and “weed” species. The second stage consisted of the graphical representation of field margins in a triplot diagram, the “Ecobordure triangle”, according to the relative percentage of the three species groups. The representation of the Ecobordure triangle was then refined through segmentation in seven sectors to facilitate the reading and interpretation of results. Finally, the output validation of the indicator was performed by testing the consistency between Ecobordure outputs and structural and management characteristics of field margins, using an independent dataset. Our results demonstrate that Ecobordure is a simple, efficient and reliable indicator allowing users to characterize vegetation patterns of field margins and identify potential drivers leading to these patterns. In its original form, Ecobordure can be applied to a broad spectrum of field margins in European bocage regions with temperate oceanic climate, on acidic to neutral soil. However, its use can be extended to other agricultural regions through adaptation of the species list. We conclude by giving some information about Ecobordure use and appropriation by end users.