Intercropping, i.e., association of two or more species, is promising to reduce insect populations in fields. The cereal aphid Rhopalosiphum padi, a vector of the Barley yellow dwarf virus PAV ...(BYDV-PAV), represents a major threat for cereal grain production. In this study, we tested the potential of winter barley intercropped with clover to reduce the size of R. padi populations and to lower the BYDV-PAV incidence in fields. We used arenas (i.e., sets of 36 barley plants) intercropped with or without clover plants (at different sown densities). In each arena, a single viruliferous founder, R. padi, (with an alate or a wingless morph) was deposited to introduce aphids and viruses in the experiment. Thirteen days later, the number of aphids in the arena, the percentage of plants hosting aphids and the infection rates were monitored. Data produced through this experimental design showed that clover alters the distribution of the aphid progeny (lower aphid spread) produced by an alate founder morph. Moreover, clover reduces the size of aphid populations produced by a wingless founder morph. However, despite the effects of clover on biological parameters of R. padi, the presence of clover in barley arena did not modify BYDV infections, suggesting complex mechanisms between partners of the BYDV pathosystem for plant-to-plant virus spread.
Semi-natural habitats are key components of rural landscapes because they shelter a significant number of overwintering arthropods that are beneficial to agriculture. However, woodlots are ...semi-natural habitats with high patch-level heterogeneity and this aspect has been poorly studied. The purpose of this study was to determine the influence of woodlot heterogeneity on overwintering ground beetles. Woodlot heterogeneity was characterized in terms of distance from the woodlot boundary and date of the most recent logging operation. We used emergence traps to quantify the population density of ground beetles that overwintered in the different parts of the woodlot. In woodlot edges the densities and species richness of ground beetles were significantly higher than in the rest of the woodlot. Ground beetles that are active in crop fields overwintered in the edges but not in the inner zone of the woodlot. Species assemblages of ground beetles overwintering in the edges were highly diverse. The date of the most recent logging operation did not explain the distribution of ground beetles that overwintered in the woodlot. Our results show that woodlots, and in particular their edges, are used as a winter shelter by ground beetles that spend part of their life in crops, which potentially favours biological control in adjacent crop fields. PUBLICATION ABSTRACT
Intensification of agriculture, with landscape simplification and reduction of natural habitats, is known to contribute to the decline of arthropods. Implementation of agroecological practices and ...infrastructures in current cropping systems is expected to mitigate this biodiversity loss and provide pest regulation through natural enemies. The aim of this study was to assess the efficiency of an undestroyed strip of winter cover crop within maize fields to promote ground-dwelling arthropod spillover and their predation activity into fields. The field survey was carried out in 2019 and 2020 within 12 fields. Monitoring of ground-dwelling arthropod activity-density, richness, and predation rate, as well as slug activity-density, was conducted in the strip, in the cropped area and in a grassy field margin. The results show that activity-density of carabids, spiders, and slugs, and the predation rate were overall higher in the strip than in the cropped area or the field margin. No clear edge effect of the strip on arthropods in the cropped area was found, but predation rate was enhanced closer to the strip. We did not record a negative effect of the strip on the occurrence of slugs within the maize crop. The study shows that a mid-field strip of winter cover crops can be efficient for biodiversity conservation of ground-dwellings predators in agricultural landscapes and provide a potential pest control service in cropped fields.
•Preserved winter cover crop strips in cropped maize fields benefit natural enemies.•Strips do not lead to higher occurrence of slugs in cropped maize.•No clear spillover of ground-dwelling arthropods from strips toward crops was found.•Predation activity in crops increased with decreasing distance from the strips.
Context
Permanent grasslands have declined across Europe since the agricultural intensification. Grassland vicinity, landscape heterogeneity and vicinity of hedgerows are enhancing factors for ...farmland carabid (ground beetle) diversity. However, interrelation between grassland and cropland communities needs to be better known in various landscape context.
Objectives
In this study we disentangle the effects of different landscape indicators carabid communities of adjacent grasslands and cereal fields to assess mutual benefits of these two land cover types.
Methods
We sampled carabids in three agricultural plains of southeastern France, each associated with a gradient in grassland coverage. We used regression models to point out effects of landscape indicators on the separate, overall and common carabid species richness of paired cereal crops and grasslands.
Results
Landscape Shannon diversity and field border density explained best gamma species richness. In grasslands, we found a higher species richness when the landscape diversity increased, except in the study region dominated by grasslands. In cereal crops, the landscape parameters showed no significant effect on carabid richness. Finally, the common species richness from cereal fields and grasslands was explained by higher density of field borders between them, but also by higher grassland coverage where grasslands were the scarcest.
Conclusions
Our results suggest that cropland carabid communities may benefit from the habitat and resource complementation provided by grasslands. This finding pleads for the preservation of grasslands in cropped landscapes to favor carabids and illustrates the potential for enhanced biological control in future cropping systems with reduced pesticide inputs.
Carabids (ground beetles) are important beneficial insects that contribute to biological control of pests and weeds in crop production. They can be found in different agricultural landscape habitats. ...However, little has been studied about the composition and similarity of carabid assemblages between two major land covers types: cropland and grassland. In a context of declining grassland areas in farmlands, highlighting complementarities of these two land covers is crucial to encourage land use planning that favors biodiversity. The objective of this study was to evaluate the relative and shared contribution of cereal crops and grasslands to carabid diversity in farmlands. Carabids were sampled in 104 pairs of cereal fields and grasslands in 3 agricultural regions of southeastern France. Carabid diversity was further analyzed with multiple regression models, including different local parameters. The correlations between assemblage similarities and geographical distance of sampled cereal fields and grasslands were also studied. Overall, 115 different species were found, 82 in cereal fields and 95 in grasslands. Per site species number and activity-density were higher in the two study regions with higher grassland cover. Evenness of carabid assemblages were higher in grasslands. Cropland and grassland remained strongly distinct, but assemblages showed higher similarity up to 4 km distance from each other. The study illustrates the major interest in preserving grassland within farmland for land use planners and/or policy makers. We found that grasslands and croplands complement each other. Though they host distinct communities, they provide continuous and different resources to the species throughout the year.
The enhancement of pest regulation service in crops depends for a large part on the capacity of agroecological practices to increase the presence of key species or functional traits in arthropod ...communities within fields.
We investigated the effects of undestroyed strips of winter cover crops in maize fields on carabid community composition, and on the distribution of three ecological traits: diet, wing status and body size.
We found that the community composition and the distribution of ecological traits in the in‐field cover crop strips had commonalities with both adjacent cropped areas and field margins. Some species were recorded mostly or only in the strips indicating that strips could support carabid species and help increase local diversity from the first year of establishment.
The activity‐density of Poecilus cupreus and Pterostichus melanarius was higher in the cropped proximity of the strip, and the body size was influenced by the distance from the strip.
Our results suggest that carabid communities are shaped by the habitat type, but the influence of such agroecological infrastructures on communities of adjacent crops is minor beyond a distance of 10 m. However, overall species abundance was increased and thus potentially provided enhanced pest regulation.
•Microhabitat density was significantly higher in woodland edges than in their interior.•Bark loss, cracks, sap runs and epiphytes were significantly more abundant in woodland edges.•It is important ...to consider woodland edges for forest and non forest biodiversity conservation.
Forest edges are important features of wooded farmland. Their role for biodiversity was investigated using tree microhabitats (TMH) as an indirect indicator of forest biodiversity. Because they are managed more intensively, trees in the edges of fragmented temperate woodlands are likely to host more TMH than trees in their interior. In this study, we tested this hypothesis in relation to tree density, diameter, species composition and the structure and management of woodland edges. We selected 28 woodlands with edges differing by their structure and the adjacent fields. Eleven types of TMH were recorded in two transects set up in the edges and interior of the woodlands. TMH density was significantly higher in the woodland edges (4.67±0.78 per 100m2 area) than in the interior (1.86±0.23 per 100m2 area). Some TMH - patches of bark loss, cracks, sap runs and epiphytes – were significantly more abundant in the edges than in the interior. These results were accounted for by the convergence of several factors: (i) significantly higher tree density in woodland edges, (ii) a significantly higher proportion of TMH host trees in woodland edges, (iii) a larger tree diameter on average in woodland edges and, even in the same given size class, a higher frequency of TMH host trees, and (iv) greater abundance in woodland edges of tree species more likely to host TMH, even with small diameters. The positive relationship found between the height of the bottom of the crown and TMH abundance may have resulted from abiotic factors (micro-climatic conditions) related to long management rotations, but we did not demonstrate any direct effect of management practices. Given the large number of forest taxa, but also farmland taxa, that depend on TMH, woodland edges should be reconsidered as zones of high potential interest for forest biodiversity conservation.
1
Boundaries between woodlots and agricultural habitats are numerous in temperate agricultural landscapes and influence ecological processes in both woodlots and agricultural habitats.
2
We aimed to ...determine how far the species assemblage of ground beetles in woodlot and open habitats was influenced by the presence of the woodlot–field boundary.
3
We studied the distribution of ground beetles on both sides of the boundaries of four woodlots along transects of pitfall traps (n = 140). The depth of edge influence (i.e. the distance from the boundary at which the presence of the boundary has no more significant influence) on the species assemblage of ground beetles in each woodlot and in each agricultural habitat was determined with nonlinear canonical analysis of principal coordinates, an ordination method that is followed by nonlinear regression of the principal coordinates on distance from the boundary.
4
The depth of edge influence on the species assemblages of ground beetles was asymmetrical relative to the boundary: it was generally higher and had higher variability in open habitats (14.4 ± 12.3 m) than in woodlots (4.9 ± 2.3 m). Species assemblages of ground beetles in edges were a mix between both adjacent species assemblages. Edge effects in woodlots were deeper in the woodlots exhibiting a deeper penetration of open habitat species. Symmetrically, edge effects in open habitat were deeper in the open habitats with a deeper diffusion of forest species into the open habitat.
5
Forest ground beetles were not threatened by edge effects. Rather, edge effects are likely to benefit agriculture, mostly through the dispersal of predatory forest species into agricultural fields.
Pour des raisons patrimoniales autant que pour les services qu'elle rend à l'humanité, il apparaît nécessaire de soutenir la diversité des organismes vivants et, pour cela, de connaître leur ...utilisation des milieux dans les paysages ruraux. En particulier, des travaux récents soutiennent un modèle de colonisation cyclique qui énonce qu'une partie des espèces circulant dans les milieux cultivés en été trouvent un abri propice à l'hivernation dans les milieux semi-naturels. Notre but était ici de mettre au jour les facteurs locaux et paysagers déterminant la répartition spatiale et la structure des assemblages de Carabidae dans un paysage rural des coteaux de Gascogne. Les patrons de répartition des Carabidae, obtenus à deux échelles spatiales différentes, celle du paysage et celle de la parcelle, et à deux moments clés de la vie de ces insectes, la période durant laquelle ils sont actifs (circulants) et la période d'hivernation, ont été interprétés en termes de processus écologiques grâce à la prise en compte des traits biologiques et écologiques des espèces de Carabidae. Les résultats montrent que le type de milieu a un effet structurant majeur sur les assemblages de Carabidae circulants comme hivernants, comparable aux effets des conditions environnementales locales et paysagères réunies. Par ailleurs, les effets de lisière sur les Carabidae circulants, au niveau des interfaces entre les bois et les cultures, sont limités à quelques mètres ou quelques dizaines de mètres. Concernant les Carabidae hivernants, nous avons noté de manière surprenante que leur densité était de deux à six fois plus élevée dans les marges (cultivées) des cultures que dans les milieux semi-naturels. De plus, nous n'avons noté aucun contraste de répartition spatiale entre les Carabidae hivernants et les Carabidae circulants, quels que soient les espèces ou les groupes fonctionnels considérés. Ceci indique donc que les marges des cultures sont des milieux d’hivernation très importants dans le contexte considéré et que si un mouvement de colonisation cyclique existe pour les Carabidae des cultures, il doit se dérouler entre leur zone intérieure et leur marge. L'ensemble de nos résultats soutient l'idée que si l'agencement spatial des milieux seminaturels dans le paysage est important pour promouvoir les populations de Carabidae auxiliaires dans les cultures, la gestion des cultures elles-mêmes, et notamment de leurs marges, est également de première importance.
Supporting biodiversity is an ethical as well as a practical issue since it provides numerous ecosystem services. In that purpose, it is necessary to determine how organisms use the different habitats in rural landscapes. In this view, recent studies suggest that a number of arthropods cyclically colonise cultures, where they feed and reproduce, and semi-natural areas, where they overwinter. We aimed to determine the local and landscape determinants of spatial distribution and structure of ground beetle (Coleoptera: Carabidae) assemblages in a rural landscape of south-western France. We studied spatial distribution patterns of ground beetles at landscape and habitat scales, and at two key periods of their life, that when they are active, and winter. We then considered biological and ecological traits to deduce from these spatial patterns ecological processes affecting ground beetles. Our results show that habitat type has a major effect on species assemblages of active (circulating) as well as overwintering ground beetles, equivalent to that of local conditions and landscape context combined. Edge effects on circulating ground beetles at the woodlot-filed interface were limited to a few meters or a few dozen of meters in both habitats. Amazingly, we found that the density of overwintering ground beetles was two-to six-fold higher in crop margins than in semi-natural habitats. Moreover, we failed to show any difference between the spatial distribution of overwintering ground beetles and circulating ground beetles, whatever the species or functional group considered. Crop margins are thus major overwintering sites in the context studied and cyclic colonisation of ground beetles in crops, if real, may take place between the inner zone and the margins of crops. These results suggest that, in addition to spatial arrangement of semi-natural habitats, crop management, and in particular management of crop margins, is important to promote ground beetles and their beneficial effects on crop protection in agro-forested landscapes.
Pour des raisons patrimoniales autant que pour les services qu'elle rend à l'humanité, il apparaît nécessaire de soutenir la diversité des organismes vivants et, pour cela, de connaître leur ...utilisation des milieux dans les paysages ruraux. En particulier, des travaux récents soutiennent un modèle de colonisation cyclique qui énonce qu'une partie des espèces circulant dans les milieux cultivés en été trouvent un abri propice à l'hivernation dans les milieux semi-naturels. Notre but était ici de mettre au jour les facteurs locaux et paysagers déterminant la répartition spatiale et la structure des assemblages de Carabidae dans un paysage rural des coteaux de Gascogne. Les patrons de répartition des Carabidae, obtenus à deux échelles spatiales différentes, celle du paysage et celle de la parcelle, et à deux moments clés de la vie de ces insectes, la période durant laquelle ils sont actifs (circulants) et la période d'hivernation, ont été interprétés en termes de processus écologiques grâce à la prise en compte des traits biologiques et écologiques des espèces de Carabidae. Les résultats montrent que le type de milieu a un effet structurant majeur sur les assemblages de Carabidae circulants comme hivernants, comparable aux effets des conditions environnementales locales et paysagères réunies. Par ailleurs, les effets de lisière sur les Carabidae circulants, au niveau des interfaces entre les bois et les cultures, sont limités à quelques mètres ou quelques dizaines de mètres. Concernant les Carabidae hivernants, nous avons noté de manière surprenante que leur densité était de deux à six fois plus élevée dans les marges (cultivées) des cultures que dans les milieux semi-naturels. De plus, nous n'avons noté aucun contraste de répartition spatiale entre les Carabidae hivernants et les Carabidae circulants, quels que soient les espèces ou les groupes fonctionnels considérés. Ceci indique donc que les marges des cultures sont des milieux d’hivernation très importants dans le contexte considéré et que si un mouvement de colonisation cyclique existe pour les Carabidae des cultures, il doit se dérouler entre leur zone intérieure et leur marge. L'ensemble de nos résultats soutient l'idée que si l'agencement spatial des milieux seminaturels dans le paysage est important pour promouvoir les populations de Carabidae auxiliaires dans les cultures, la gestion des cultures elles-mêmes, et notamment de leurs marges, est également de première importance.
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