Finding more sustainable ways to produce food is a major challenge for humanity in the face of biodiversity extinction and climate change. Consequently, research on the ability of agroecosystems to provide multiple functions is growing. In this regard, the relative importance of organic farming and landscape-scale measures for improving multifunctionality has recently been debated. We investigated the effects of farming system (conventional vs. organic) at field scale, total length of hedgerows in the landscape and their interaction on the multifunctionality of 40 winter cereal fields in Brittany (France). Our multifunctionality assessment integrated 21 indicators of five agroecosystem goods: biodiversity conservation, nutrient cycling and soil structure, pest and disease regulation, food production and socio-economic performance. Many indicators of biodiversity conservation, pest and disease regulation, and socio-economic performance were higher in organic than in conventional systems. However, indicators of nutrient cycling and soil structure did not improve and food production was much lower in organic systems. Total hedgerow length in the landscape had less influence than organic farming on indicators, although we observed positive interactions. Granivorous carabid abundance and semi-net margin were highest in organic fields located in well-preserved hedgerow landscapes. Synthesis and applications. Our study suggests that field-scale organic farming is necessary to promote biodiversity conservation and associated ecological functioning in crop fields, whereas landscape-scale preservation of semi-natural habitats alone is likely insufficient. Preservation of hedgerows in the landscape brings additional ecological and socio-economic benefits for organic systems without compromising agricultural production. More broadly, our results call for more ambitious research into the myriad possible combinations of farming practices and agri-environmental measures at both field and landscape scales, to improve both below-ground and above-ground functioning. Evoluer vers une production agricole durable est un d & eacute;fi majeur pour l'humanit & eacute; face & agrave; l'extinction de la biodiversit & eacute; et au changement climatique. Par cons & eacute;quent, les recherches sur la capacit & eacute; des agro & eacute;cosyst & egrave;mes & agrave; assurer de nombreuses fonctions se multiplient. & Agrave; cet & eacute;gard, l'importance relative de l'agriculture biologique et des mesures paysag & egrave;res pour am & eacute;liorer la multifonctionnalit & eacute; a r & eacute;cemment & eacute;t & eacute; d & eacute;battue. Nous avons & eacute;tudi & eacute; les effets de l'agriculture biologique, de la longueur totale de haies dans le paysage et de leur interaction sur la multifonctionnalit & eacute; de 40 champs de c & eacute;r & eacute;ales d'hiver en Bretagne (France). Notre & eacute;valuation de la multifonctionnalit & eacute; est bas & eacute;e sur 21 indicateurs de cinq biens agro & eacute;cosyst & eacute;miques : la conservation de la biodiversit & eacute;, le cycle des nutriments et la structure du sol, la r & eacute;gulation des bio-agresseurs et des maladies, la production agricole, et la performance socio-& eacute;conomique. De nombreux indicateurs de conservation de la biodiversit & eacute;, de r & eacute;gulation des bio-agresseurs et des maladies et de performance socio-& eacute;conomique & eacute;taient plus & eacute;lev & eacute;s en agriculture biologique qu'en agriculture conventionnelle. Cependant, les indicateurs du cycle des nutriments et de la structure du sol n'& eacute;taient pas am & eacute;lior & eacute;s et la production agricole & eacute;tait beaucoup plus faible en agriculture biologique. La longueur totale de haies dans le paysage avait moins d'influence que l'agriculture biologique sur les indicateurs, bien que nous ayons observ & eacute; des interactions positives. L'abondance des carabes granivores et la marge semi-nette & eacute;taient plus & eacute;lev & eacute;es dans les champs en agriculture biologique situ & eacute;s dans les paysages bocagers les mieux pr & eacute;serv & eacute;s. Synth & egrave;se et applications. Notre & eacute;tude sugg & egrave;re que l'agriculture biologique est n & eacute;cessaire pour promouvoir la conservation de la biodiversit & eacute; et le fonctionnement & eacute;cologique associ & eacute; dans les champs cultiv & eacute;s, tandis que la pr & eacute;servation des habitats semi-naturels & agrave; l'& eacute;chelle du paysage est probablement insuffisante & agrave; elle seule. La pr & eacute;servation des haies dans les paysages apporte des avantages & eacute;cologiques et socio-& eacute;conomiques suppl & eacute;mentaires en agriculture biologique sans compromettre la production agricole. Plus g & eacute;n & eacute;ralement, nos r & eacute;sultats appellent & agrave; une recherche plus ambitieuse sur la myriade de combinaisons possibles de pratiques agricoles et de mesures agro-environnementales & agrave; l'& eacute;chelle du champ et du paysage, afin d'am & eacute;liorer & agrave; la fois le fonctionnement souterrain et a & eacute;rien des agro & eacute;cosyst & egrave;mes.

Faced with the biodiversity extinction crisis and climate change, alternative approaches to food production are urgently needed. Decades of chemical-based weed control have resulted in a dramatic decline in weed diversity, with negative repercussions for agroecosystem biodiversity. The simplification of cropping systems and the evolution of herbicide resistance have led to the dominance of a small number of competitive weed species, calling for a more sustainable approach that considers not only weed abundance but also community diversity and composition. Agroecological weed management involves harnessing ecological processes to minimize the negative impacts of weeds on productivity and maximize biodiversity. However, the current research effort on agroecological weed management is largely rooted in agronomy and field-scale farming practices. In contrast, the contributions of landscape-scale interventions on agroecological weed management are largely unexplored (e.g., interventions to promote pollinators and natural enemies or carbon sequestration). Here, we review current knowledge of landscape effects on weed community properties (abundance, diversity, and composition) and seed predation (a key factor in agroecological weed management). Furthermore, we discuss the ecological processes underlying landscape effects, their interaction with in-field approaches, and the implications of landscape-scale change for agroecological weed management. Notably, we found that (1) landscape context rarely affects total weed abundance; (2) configurational more than compositional heterogeneity of landscapes is associated with higher alpha, beta, and gamma weed diversity; (3) evidence for landscape effects on weed seed predation is currently limited; and (4) plant spillover from neighboring habitats is the most common interpretation of landscape effects on weed community properties, whereas many other ecological processes are overlooked. Strikingly, the drivers of weed community properties and biological regulation at the landscape scale remain poorly understood. We recommend addressing these issues to better integrate agroecological weed management into landscape-scale management, which could inform the movement towards managing farms at wider spatiotemporal scales than single fields in a single season.

Thanks to agroforestry, trees and hedgerows are back in numbers in agricultural landscapes, where they provide many services. Agroforestry also gives pride of place to wild herbaceous vegetation, often perceived as a constraint or neglected by humans. Omnipresent when the soil is not tilled, herbaceous vegetation grows spontaneously at the foot of trees. From alley-cropping agroforestry to bocage landscapes, these 'little' plants are proving to be a major asset for the agroecological transition. Through the presentation of key results, this article explains how to take advantage of the wild herbaceous vegetation in agroforestry systems, in order to conserve biodiversity and promote sustainable agricultural production

Bocage landscapes are characterized by a network of hedgerows that delimits arable fields. Such landscapes provide many ecosystem services, including biodiversity conservation, but their effects on weed communities remain largely unknown. Bocage landscapes could affect weed communities through two main processes: plant spillover from hedgerows and increased environmental heterogeneity in arable fields. These bocage effects are also likely to vary between farming systems (conventional vs. organic) due to differences in management practices. We sampled weed communities more than 20 m from field margins in 74 arable fields (37 per farming system). Fields were located along two independent landscape gradients of total length of hedgerows (with or without a shrub layer) and organic farming cover, in Brittany (France). We analysed the effect of 'bocage' (i.e. the density and complexity of hedgerow networks) and farming systems at field and landscape scales on species and functional diversity of weed communities. Further, we used fidelity to non-crop habitats and Ellenberg indicator values to assess the 'plant spillover' and 'environmental heterogeneity' hypotheses, respectively. Weed communities were more diverse and more abundant in organic farming systems. In addition, weed communities were more diverse, but not more abundant, in denser and more complex bocage landscapes. 'Bocage' increased species diversity of weeds, but also community-weighted variance of specific leaf area, plant height and seed mass. Positive effects of 'bocage' on weed diversity were driven by increased environmental heterogeneity rather than spillover of transient species from hedgerows. 'Bocage' effects were independent of farming systems at field and landscape scales. Synthesis and applications. Maintaining diverse weed communities is key to agroecological weed management and biodiversity conservation in agricultural landscapes. Farmers are often concerned that hedgerows harbour competitive plants spreading into field edges, thereby increasing weed pressure. However, our study shows that dense and complex bocage landscapes promote weed diversity in field cores, most likely by increasing environmental heterogeneity. Thus, bocage landscapes could actually enhance ecosystem services provided by weed communities and reduce weed-crop competition.

Field margins are major habitats for biodiversity conservation and ecosystem functioning in agricultural landscapes, but biotic homogenization of plant communities threatens their ecological and agronomic functions. Our objective is to determine the drivers of plant diversity in field margins for conservation and restoration purposes. To do so, we assessed the effects of field margin structure and long-term management over 20 years (1995-2015) on the taxonomic and functional α- and β-diversity, and the functional composition of herbaceous plant communities. In 2015, we surveyed 302 field margins in bocage landscapes of Brittany, northwestern France. Results were very similar between taxonomic and functional diversity but revealed important discrepancies between the drivers of α- and β-diversity. Deep ditches, mowing and grazing increased α-diversity but did not affect β-diversity. Denser hedgerows had lower α-diversity than other field margins but strongly contributed to β-diversity by harbouring more unique sets of species or life strategies. Long-term herbicide spraying in field margins and cropping intensity in adjacent habitats did not affect α-diversity, but had more complex effects on β-diversity and selected for common weeds. All in all, preservation of dense hedgerows, abandonment of herbicide spraying, and protection against agrochemical drifts are key measures to prevent the establishment of common weeds and biotic homogenization of herbaceous plant communities in field margins. Above all, our study shows how important it is to go beyond α-diversity to make robust conservation and restoration decisions.

Hedgerows are key wildlife habitats in agricultural landscapes, with presumably high multifunctionality - that is the capacity to provide multiple ecological, agronomic or cultural functions. However, knowledge gaps remain regarding the drivers of hedgerow multifunctionality and potential synergies and trade-offs between functions. In particular, it is unknown in which landscapes hedgerows best support a range of taxa and associated functions. We assessed the effects of hedgerow features, adjoining farming systems, landscape context, and their in-teractions on hedgerow multifunctionality based on four ecological functions - biodiversity conservation, po-tential pollination, potential predation, and pest colonization. We estimated these functions by the abundance and diversity of plant and arthropod taxa in 40 hedgerows, in Brittany (France). Results support previous studies showing the beneficial effects of flower cover, margin width, adjacent organic farming, and other variables related to hedgerow structural complexity on individual taxa or proxies of functions. Most importantly, our study reveals that hedgerows are more multifunctional in landscapes with dense hedgerow networks (so-called 'bocage' landscapes), which is likely the result of greater habitat amount, connectivity, and environmental heterogeneity. In addition, we find weak correlations between proxies of functions, and more synergies than trade-offs in response to the explanatory variables, indicating that there is considerable scope for improving the ecological value of hedgerows. We draw attention to the fact that ongoing destruction of hedgerow networks, including wide and structurally complex hedgerows, might lead to long-term or irretrievable loss of associated species and ecological functions, jeopardizing restoration and replanting efforts.

Through a meta-analysis, Mupepele et al. (BMC Ecol Evol 21:1-193, 2021) assessed the effects of European agroforestry systems on biodiversity, estimated by species richness or species diversity. They showed that the effects of silvoarable and silvopastoral systems depend on the systems they are compared to and the taxa studied. Further, they found that only silvoarable systems increased species richness or diversity, compared to cropland. The authors conclude that agroforestry systems have weak effects on biodiversity and that landscape context or land-use history are probably more important than the practice of agroforestry in itself. However, we draw attention to important shortcomings in this meta-analysis, which downplay the potential of agroforestry for biodiversity conservation in agricultural landscapes. We hope that the meta-analysis by Mupepele et al. (BMC Ecol Evol 21:1-193, 2021), and our comments, will contribute to improving the quality of research on agroforestry systems and biodiversity conservation.

Grâce à l’agroforesterie, les arbres et les haies sont de retour dans les paysages agricoles, où ils rendent de nombreux services. L’agroforesterie fait également la part belle à la végétation herbacée sauvage, souvent perçue comme une contrainte ou négligée par les humains. Omniprésente dès lors que le sol n’est pas travaillé, la végétation herbacée pousse spontanément au pied des ligneux. Des paysages bocagers à l’agroforesterie intra-parcellaire, ces « petites » plantes s’avèrent être un atout de taille pour la transition agroécologique. À travers la présentation de résultats marquants, cet article explique comment profiter de la végétation herbacée sauvage des systèmes agroforestiers, en vue de conserver la biodiversité et de favoriser une production agricole durable.

Hedgerows are among the most stable refugia for biodiversity in agricultural landscapes, providing food and shelter to many living organisms. However, the destruction and alteration of hedgerow ground vegetation compromise their potential for biodiversity conservation. The purpose of this study was to find local and landscape-scale drivers that promote plant diversity in hedgerows and prevent their colonization by troublesome weeds. Using a functional approach, we assessed the effects of hedgerow features, adjacent farming systems (conventional vs organic) and landscape context (bocage, semi-natural habitat cover, organic farming cover) on the diversity and composition of plant communities in 40 hedgerows, in Brittany (France). Hedgerow features had no effect on species diversity, but influenced functional diversity measured as a standardized effect size (SES), i.e. independent of species diversity. Organic farming at local scale was the main driver increasing both species and functional diversity (SES), doubling the cover of insect-pollinated forbs. High organic farming cover in the landscape increased species diversity, but not functional diversity (SES), of hedgerows adjoining conventional farming systems. Besides, high cover of semi-natural habitats and organic farming in the landscape prevented colonization of hedgerows by troublesome weeds. Promoting extensive management at both local and landscape scale is thus necessary for successful restoration of hedgerow ground vegetation, which should favour biodiversity conservation and ecosystem service provision.

Developing agroecological practices that enhance biological control of crop pests is a major issue for the transition of agriculture towards sustainable and biodiversity-friendly systems. Agroecological infrastructures (AEI) are devoted to the support of ecosystem service providers, although they have mixed effects on natural enemies of crop pests. In temperate regions, alley cropping agroforestry involves within-field AEI, in the form of tree rows and associated understory vegetation strips. The objective of this study was to assess the potential of generalist predators (carabid beetles and cursorial spiders) to control weed seeds and invertebrate pests in alley cropping vs pure crop systems, under two contrasting farming systems (conventional vs organic). Predator surveys were carried out in May and June 2017 in South-Western France over 12 winter cereal fields. Our study revealed that the effect of alley cropping was modulated by the farming system. Under conventional farming, alley cropping had a negative effect on the activity-density and species richness of generalist predators, especially regarding carnivorous carabids whose activity-density was reduced by nearly 50%. Under organic farming, alley cropping enhanced both the activity-density and complementarity of generalist predators, with a two-fold increase in the activity-density of seed-feeding carabids (predominantly granivorous and omnivorous), potentially promoting weed seed and invertebrate pest control. Our results suggest that the effectiveness of AEI in promoting natural enemies depends on the farming system at the field scale, which affects resource availability and determines spillover intensity between habitats. AEI are often perceived as sources of natural enemies. However, sink and retention effects (i.e. reduced or delayed spillover into crop fields due to higher attractiveness of AEI) should not be overlooked as they can explain the mixed impacts of AEI on natural enemy communities.

Le systeme de production agricole actuel est la principale cause d'extinction globale de la biodiversite. L'agroforesterie intra-parcellaire, qui consiste a associer arbres et grandes cultures sur une meme parcelle, represente une grande opportunite pour la reintegration des habitats semi-naturels dans les champs. Les rangees d'arbres sont associees a des bandes de vegetation non cultivees, que l'on appelle lineaires sous-arbores (LSA). Etant donne la configuration spatiale et la surface occupee par les LSA, il est probable que la dispersion des organismes et la quantite de refuges pour la biodiversite soient augmentees en agroforesterie intra-parcellaire, en comparaison de temoins agricoles. Cela pourrait resulter en une augmentation des services et/ou dis-services ecosystemiques en fonction de la nature des especes favorisees (adventices competitives, ravageurs ou auxiliaires de culture). L'objectif de cette these etait de decrire la reponse des communautes de plantes et invertebres aux systemes agroforestiers et au mode de production (agriculture conventionnelle vs biologique) et d'evaluer les effets positifs et negatifs des LSA sur la conservation de la biodiversite et le controle biologique des ravageurs. Les communautes de plantes et invertebres des systemes agroforestiers et des temoins agricoles ont ete echantillonnees sur un reseau de parcelles, tandis qu'un site experimental servit a l'etude de l'hivernation des invertebres en agroforesterie. Nous avons decrit la structure taxonomique et fonctionnelle des communautes pour comprendre leurs reponses aux systemes agroforestiers et, pour les invertebres, leurs potentiels effets sur le controle biologique des ravageurs. Nos etudes ont confirme que les LSA sont des habitats favorables au maintien de la biodiversite dans les champs. Les LSA ne semblent guere constituer une source d'adventices ou de ravageurs dominants, mais affectent grandement la dispersion des predateurs terrestres, de facon positive ou negative selon le mode de production. Les resultats obtenus au cours de cette these comblent un manque de connaissance sur la biodiversite des systemes agroforestiers temperes et fournissent des pistes de gestion des infrastructures agroecologiques, qui sont implantees afin de favoriser la biodiversite fonctionnelle et reduire l'utilisation de produits phytosanitaires.

The dramatic decline of invertebrates at a global scale is mainly driven by habitat loss, agricultural intensification and urbanization. Alley cropping agroforestry is a land use practice in which arable crops are grown between tree rows. In such systems, understory vegetation strips (UVS) develop in the tree rows, providing habitats undisturbed by soil tillage. We investigated whether UVS are major overwintering habitats for invertebrates. We focused on carabid communities, which are dominant beneficial invertebrates in crop fields, but suffer from agricultural intensification. We described carabid communities with functional traits related to sensitivity to agricultural disturbances and ecological functions (i.e. pest control). Sampling of invertebrates were carried out from February to June 2018 over seven agroforestry fields in Restinclieres Estate (South France), one of the oldest experimental sites in Europe. The study revealed that 55% of invertebrate taxonomic groups were more abundant in UVS, whereas only 14% were more abundant in crop alleys. Crop pests were overwintering mainly in crop alleys while beneficial invertebrates were more dependent on UVS. Finally, UVS hosted carabids sensitive to agricultural disturbances, characterized by large body length, predominantly granivorous diet and overwintering in adult stage. On the other hand, crop alleys were home to smaller carnivorous species overwintering in both larval and adult stages, which can tolerate high levels of disturbance. Environmental and agricultural policies should consider agroforestry systems, especially understory vegetation strips, as valuable habitats for biodiversity conservation and biological control in agricultural landscapes.

Alley cropping agroforestry is a land use practice in which arable crops are grown between tree rows. In such agroforestry systems, non-crop herbaceous vegetation develops on the tree rows, resulting in understory vegetation strips (UVS). UVS are perceived both as reservoirs for weeds and opportunities for biodiversity conservation. The purpose of this study was to assess the contribution of UVS to (i) plant spillover and (ii) plant diversity conservation, depending on their functional structure and the farming system. Vegetation surveys were carried out in May 2017 in South-Western France over 16 winter cereal fields (8 alley cropping agroforestry systems and 8 pure crop controls), half under conventional farming and half under organic farming. Using data on plant functional traits related to dispersal strategies and response to agricultural disturbances, we explained the mechanisms involved in plant spillover between habitats. The study revealed that very few species were able to disperse far into crop alleys, except perennial species producing rhizomes and stolons whose spread has been favored by tillage. The presence of UVS in agroforestry fields did not increase weed-crop ratio (i.e. weed coverage / weed and crop coverage) in adjacent crop alleys. On the other hand, UVS harbored richer and more abundant floras (with high proportions of species rarely found in arable habitats) compared to crop alleys and pure crop controls, especially under conventional farming. The functional approach provided insights for weed management in alley cropping agroforestry systems in order to optimize plant diversity conservation without increasing weed-crop ratio. This study showed the relevance of using the functional approach to understand the mechanisms behind plant spillover in cropping systems that integrate semi-natural habitats.

In arable fields, plant species richness consistently increases at field edges. This potentially makes the field edge an important habitat for the conservation of the ruderal arable flora (or 'weeds') and the invertebrates and birds it supports. Increased diversity and abundance of weeds in crop edges could be owing to either a reduction in agricultural inputs towards the field edge and/or spatial mass effects associated with dispersal from the surrounding landscape.We contend that the diversity of weed species in an arable field is a combination of resident species, that can persist under the intense selection pressure of regular cultivation and agrochemical inputs (typically more ruderal species), and transient species that rely on regular dispersal from neighbouring habitats (characterised by a more 'competitive' ecological strategy).We analysed a large dataset of conventionally managed arable fields in the UK to study the effect of the immediate landscape on in-field plant diversity and abundance and to quantify the contribution of spatial mass effects to plant diversity in arable fields in the context of the ecological strategy of the resulting community.We demonstrated that the decline in diversity with distance into an arable field is highly dependent on the immediate landscape, indicating the important role of spatial mass effects in explaining the increased species richness at field edges in conventionally managed fields.We observed an increase in the proportion of typical arable weeds away from the field edge towards the centre. This increase was dependent on the immediate landscape and was associated with a higher proportion of more competitive species, with a lower fidelity to arable habitats, at the field edge. Synthesis and applications. Conserving the ruderal arable plant community, and the invertebrates and birds that use it as a resource, in conventionally managed arable fields typically relies on the targeted reduction of fertilisers and herbicides in so-called 'conservation headlands'. The success of these options will depend on the neighbouring habitat and boundary. They should be placed along margins where the potential for ingress of competitive species, that may become dominant in the absence of herbicides, is limited. This will enhance ecosystem services delivered by the ruderal flora and reduce the risk of competitive species occurring in the crop.