Ground beetle (Coleoptera: Carabidae) assemblages associated with a satoyama landscape in Japan: the effects of soil moisture,weed height,and distance from woodlands

Agricultural landscapes generally include not only crop fields but also semi-natural habitats. In Japan, such a mixed rural landscape is called “satoyama.” Although ground beetles are potential predators of pests, the environmental factors that determine their distribution in Japanese rural landscapes have not been fully elucidated. To understand the effects of distance from woodland edges, soil moisture, and weed height on assemblages of carabid beetles, we examined the number of adult beetles in pitfall traps placed in a satoyama landscape in the lowlands of western Honshu, Japan. Our results show that the carabid species could be largely differentiated into woodland, intermediate, and open-land species. The “intermediate species” group includes species that depend on woodland or woodland edges for at least part of their life cycles. Paddy fields must have long provided semi-natural habitats that complement those in natural grasslands and wetlands for open-land beetles that prefer wet conditions. Weeds can also increase the abundance of some intermediate and woodland species; thus, the arrangement of such landscape elements as woodlands and paddies can determine the species richness and abundance of ground beetles in agricultural fields.     

Landscape heterogeneity as an ecological filter of species traits

Landscape heterogeneity is a major driver of biodiversity in agricultural areas and represents an important parameter in conservation strategies. However, most landscape ecology studies measure gamma diversity of a single habitat type, despite the assessment of multiple habitats at a landscape scale being more appropriate. This study aimed to determine the effects of landscape composition and spatial configuration on life-history trait distribution in carabid beetle and herbaceous plant communities. Here, we assessed the gamma diversity of carabid beetles and plants by sampling three dominant habitats (woody habitats, grasslands and crops) across 20 landscapes in western France. RLQ and Fourth Corner three-table analyses were used to assess the association of dispersal, phenology, reproduction and trophic level traits with landscape characteristics. Landscape composition and configuration were both significant in explaining functional composition. Carabid beetles and plants showed similar response regarding phenology, i.e. open landscapes were associated with earlier breeding species. Carabid beetle dispersal traits exhibited the strongest relationship with landscape structure; for instance, large and apterous species preferentially inhabited woody landscapes, whereas small and macropterous species preferentially inhabited open landscapes. Heavy seeded plant species dominated in intensified agricultural landscapes (high % crops), possibly due to the removal of weeds (which are usually lightweight seeded species). The results of this study emphasise the roles of landscape composition and configuration as ecological filters and the importance of preserving a range of landscape types to maintain functional biodiversity at regional scales.     

Could Behaviour and Not Physiological Thermal Tolerance Determine Winter Survival of Aphids in Cereal Fields?

Traits of physiological thermotolerance are commonly measured in the laboratory as predictors of the field success of ectotherms at unfavourable temperatures (e.g. during harsh winters, heatwaves, or under conditions of predicted global warming). Due to being more complicated to measure, behavioural thermoregulation is less commonly studied, although both physiology and behaviour interact to explain the survival of ectotherms. The aphids Metopolophium dirhodum, Rhopalosiphum padi and Sitobion avenae are commercially important pests of temperate cereal crops. Although coexisting, these species markedly differ in winter success, with R. padi being the most abundant species during cold winters, followed by S. avenae and lastly M. dirhodum. To better understand the thermal physiology and behavioural factors contributing to differential winter success, the lethal temperature (physiological thermotolerance) and the behaviour of aphids in a declining temperature regime (behavioural thermotolerance) of these three species were investigated. Physiological thermotolerance significantly differed between the three species, with R. padi consistently the least cold tolerant and S. avenae the most cold tolerant. However, although the least cold tolerant of the study species, significantly more R. padi remained attached to the host plant at extreme sub-zero temperatures than S. avenae and M. dirhodum. Given the success of anholocyclic R. padi in harsh winters compared to its anholocyclic counterparts, this study illustrates that behavioural differences could be more important than physiological thermotolerance in explaining resistance to extreme temperatures. Furthermore it highlights that there is a danger to studying physiological thermotolerance in isolation when ascertaining risks of ectotherm invasions, the establishment potential of exotic species in glasshouses, or predicting species impacts under climate change scenarios.     

Responses of the antennal bimodal hygroreceptor neurons to innocuous and noxious high temperatures in the carabid beetle,Pterostichus oblongopunctatus

Electrophysiological responses of thermo- and hygroreceptor neurons from antennal dome-shaped sensilla of the carabid beetle Pterostichus oblongopunctatus to different levels of steady temperature ranging from 20 to 35 °C and rapid step-changes in it were measured and analysed at both constant relative and absolute ambient air humidity conditions. It appeared that both hygroreceptor neurons respond to temperature which means that they are bimodal. For the first time in arthropods, the ability of antennal dry and moist neurons to produce high temperature induced spike bursts is documented. Burstiness of the spike trains is temperature dependent and increases with temperature increase. Threshold temperatures at which the two neurons switch from regular spiking to spike bursting are lower compared to that of the cold neuron, differ and approximately coincide with the upper limit of preferred temperatures of the species. We emphasise that, in contrast to various sensory systems studied, the hygroreceptor neurons of P. oblongopunctatus have stable and continuous burst trains, no temporal information is encoded in the timing of the bursts. We hypothesise that temperature dependent spike bursts produced by the antennal thermo- and hygroreceptor neurons may be responsible for detection of noxious high temperatures important in behavioural thermoregulation of carabid beetles.     

The role of various meadow margin types in shaping carabid and staphylinid beetle assemblages (Coleoptera: Carabidae,Staphylinidae) in meadow dominated landscapes

Less intensively managed semi-natural habitats, e.g., field and meadow margins like hedgerows, are thought to be crucial landscape components for maintaining biodiversity in highly disturbed and intensively managed agricultural landscapes. In this study, we focused on the effects of three meadow margin types on activity-density, species richness and species composition of carabid and staphylinid beetles recorded by pitfall traps in Central European landscapes dominated by intensively managed meadows. Carabid activity-density was significantly higher in meadows than in meadow margins and within meadow margins their activity-density increased from grassy meadow margins via shrubby ones to woody meadow margins. We found that recorded species richness of both carabid and staphylinid beetles was not significantly affected by habitat identity (meadow margin or neighbouring meadow) and meadow margin type. Recorded species composition of both investigated taxa was significantly affected by habitat identity and interaction between habitat identity and meadow margin type (i.e. it differed between particular meadow margin types). Assemblages inhabiting various meadow margin types were more dissimilar between each other than assemblages from neighbouring meadows. Meadow margins within grassland dominated landscapes maintain local species richness by hosting different species from those living in surrounding meadows. Dissimilarity of carabid and staphylinid assemblages from meadows neighbouring both sides of particular meadow margin did not differ between meadow margin types. Our results indicate that semi-natural habitats play an important role in maintaining biodiversity not only in agricultural landscapes dominated by arable fields, but also in those dominated by meadows.     

Heterogeneity from increasing crop types: effect on carabid beetles

We investigated the effect of crop type heterogeneity on carabid beetles in intensively managed agricultural landscapes. We compared different crops and habitat type configurations and compositions. In addition we assessed the effect of artificial fragmentation by paved roads and water channels in an agricultural landscape. Crop type heterogeneity negatively affected carabid assemblages. Spatial dissection by artificial structures had an even more negative effect on carabid diversity. The nested structure of the carabid assemblages among crop types was caused by a negative response to heterogeneity in the agricultural landscape. Even though crop types in an intensive agricultural landscape increased, the landscape may tend to fragment habitat. Although artificially fragmented habitats had more unstable carabid assemblages, heterogeneity from different crop types has also been shown to be a characteristic of fragmented landscapes. To produce a positive relationship between biodiversity and heterogeneity in an agricultural landscape, farming intensity should be reduced to allow for the conversion of highly productive lands into more natural habitats.     

The spatial distribution of birds and carabid beetles in pine plantation forests: the role of landscape composition and structure

Aim To evaluate the joint and independent effects of spatial location, landscape composition and landscape structure on the distribution patterns of bird and carabid beetle assemblages in a mosaic landscape dominated by pine plantation forests. Location A continuous 3000‐ha landscape mosaic with native maritime pine Pinus pinaster plantations of different ages, deciduous woodlands and open habitats, located in the Landes de Gascogne forest of south‐western France. Methods We sampled breeding birds by 20‐min point counts and carabid beetles by pitfall trapping using a systematic grid sampling of 200 points every 400 m over the whole landscape. Explanatory variables were composed of three data sets derived from GIS habitat mapping: (1) spatial variables (polynomial terms of geographical coordinates of samples), (2) landscape composition as the percentage cover of the six main habitats, and (3) landscape structure metrics including indices of fragmentation and spatial heterogeneity. We used canonical correspondence analysis with variance partitioning to evaluate the joint and independent effects of the three sets of variables on the ordination of species assemblages. Moran's I correlograms and Mantel tests were used to assess for spatial structure in species distribution and relationships with separate landscape attributes. Results Landscape composition was the main factor explaining the distribution patterns of birds and carabids at the mesoscale of 400 × 400 m. Independent effects of spatial variables and landscape structure were still significant for bird assemblages once landscape composition was controlled for, but not for carabid assemblages. Spatial distributions of birds and carabids were primarily influenced by the amount of heathlands, young pine plantations, herbaceous firebreaks and deciduous woodlands. Deciduous woodland species had positive responses to edge density, while open habitat species were positively associated with mean patch area. Main conclusions Forest birds were favoured by an increase in deciduous woodland cover and landscape heterogeneity, but there was no evidence for a similar effect on carabid beetles. Fragmentation of open habitats negatively affected both early‐successional birds and carabids, specialist species being restricted to large heathlands and young plantations. Several birds of conservation concern were associated with mosaics of woodlands and grasslands, especially meadows and firebreaks. Conserving biodiversity in mosaic plantation landscapes could be achieved by the maintenance of a significant amount of early‐successional habitats and deciduous woodland patches within a conifer plantation matrix.     

Management intensity at field and landscape levels affects the structure of generalist predator communities

Agricultural intensification is recognised as a major driver of biodiversity loss in human-modified landscapes. Several agro-environmental measures at different spatial scales have been suggested to mitigate the negative impact of intensification on biodiversity and ecosystem services. The effect of these measures on the functional structure of service-providing communities remains, however, largely unexplored. Using two distinct landscape designs, we examined how the management options of organic farming at the field scale and crop diversification at the landscape level affect the taxonomic and functional structure of generalist predator communities and how these effects vary along a landscape complexity gradient. Organic farming as well as landscapes with longer and more diversified crop rotations enhanced the activity-density of spiders and rove beetles, but not the species richness or evenness. Our results indicate that the two management options affected the functional composition of communities, as they primarily enhanced the activity-density of functionally similar species. The two management options increased the functional similarity between spider species in regards to hunting mode and habitat preference. Organic farming enhanced the functional similarity of rove beetles. Management options at field and landscape levels were generally more important predictors of community structure when compared to landscape complexity. Our study highlights the importance of considering the functional composition of generalist predators in order to understand how agro-environmental measures at various scales shape community assemblages and ecosystem functioning in agricultural landscapes.     

Organic Farming: Biodiversity Impacts Can Depend on Dispersal Characteristics and Landscape Context

Organic farming, a low intensity system, may offer benefits for a range of taxa, but what affects the extent of those benefits is imperfectly understood. We explored the effects of organic farming and landscape on the activity density and species density of spiders and carabid beetles, using a large sample of paired organic and conventional farms in the UK. Spider activity density and species density were influenced by both farming system and surrounding landscape. Hunting spiders, which tend to have lower dispersal capabilities, had higher activity density, and more species were captured, on organic compared to conventional farms. There was also evidence for an interaction, as the farming system effect was particularly marked in the cropped area before harvest and was more pronounced in complex landscapes (those with little arable land). There was no evidence for any effect of farming system or landscape on web-building spiders (which include the linyphiids, many of which have high dispersal capabilities). For carabid beetles, the farming system effects were inconsistent. Before harvest, higher activity densities were observed in the crops on organic farms compared with conventional farms. After harvest, no difference was detected in the cropped area, but more carabids were captured on conventional compared to organic boundaries. Carabids were more species-dense in complex landscapes, and farming system did not affect this. There was little evidence that non-cropped habitat differences explained the farming system effects for either spiders or carabid beetles. For spiders, the farming system effects in the cropped area were probably largely attributable to differences in crop management; reduced inputs of pesticides (herbicides and insecticides) and fertilisers are possible influences, and there was some evidence for an effect of non-crop plant species richness on hunting spider activity density. The benefits of organic farming may be greatest for taxa with lower dispersal abilities generally. The evidence for interactions among landscape and farming system in their effects on spiders highlights the importance of developing strategies for managing farmland at the landscape-scale for most effective conservation of biodiversity.     

Effects of landscape connectivity on the spatial distribution of insect diversity in agricultural mosaic landscapes

European agricultural landscapes are mosaics of intensively cultivated areas and semi-natural elements. Although comprising only a small fraction of the total area, semi-natural elements provide habitat for most of the landscape biodiversity. Agricultural intensification has increasingly fragmented semi-natural elements and species numbers are in decline. Insights into the effects of landscape structure on species’ distributions within and among semi-natural habitats are needed to conserve biodiversity in agricultural landscapes more effectively. We investigated the landscape- and habitat-specific diversity partitions of wild bees, true bugs, and carabid beetles in two differently structured agricultural landscapes in Switzerland. In each landscape, we partitioned the total species diversity (γ) into its additive components within (_P) and among patches (β_P) and among habitats (β_H). In the landscape characterized by a patchy, isolated distribution of habitat elements, among-patch diversity (β_P) explained 44% of the total species richness (γ) and was significantly higher than expected under a random distribution of samples among habitat patches; in the landscape with higher habitat connectivity, among-patch diversity (β_P) comprised 32% of the total species richness (γ) and did not differ from the random expectation. Habitat-specific within-patch contributions to species richness were similarly low across habitat types (_P=23–24%) in the patchy landscape, whereas in the more connected landscape within-patch partitions tended to be higher and differed among habitat types (_P=22–38%). Functionally different groups of bees, true bugs, and carabids also responded differently to landscape structure in a manner that was consistent with known differences in resource specialization and dispersal ability. Differences in diversity partitions among landscapes and taxa indicate the need for flexible conservation strategies. Conservation of habitat-specific diversity may require more habitat patches in landscapes that have lower habitat connectivity and low within-patch diversity (_P) than in landscapes with higher within-patch diversity (_P).     

Importance of closed landfills as green space in urbanized areas: ecological assessment using carabid beetles

In a closed landfill, we investigated the diversity and ecological characters of carabid beetles to understand the ecological importance of closed landfills that have the potential as a multi-functional habitat for improving biodiversity in urbanized areas. In addition, we studied the influence of environmental factors (vegetation structure, soil) on distribution and diversity of carabid beetles. A total of 92,495 individuals representing 15 carabid species were collected from the closed landfill. Although the species richness of carabid beetles recorded in the closed landfill was not higher than the other green spaces in the city, the closed landfill could sufficiently provides a stable habitat as a semi-natural area for carabid beetles. Soil pH, Na, and tall grass plant cover influenced carabid assemblage in the closed landfill. However, other environmental variables (e.g., K⁺, Na⁺, Mg²⁺, bare land cover, weedy cover, and tree cover) were not correlated with carabid species composition. It is implied that in the closed landfill, which is a highly modified engineered environment, other abiotic environmental (e.g., drainage, soil texture, leachate, and landscape context, etc.) and biotic factors (e.g., intra- and interspecific competition) may have affected carabid assemblage. Although artificial drainages are essential facilities for landfill management, they are a critical factor that affects the species inhabiting the landfill. However, carabid beetles seemed to randomly fall into the artificial drainage. For successful management of closed landfills, it is very important that minimize the intervention and that develop the ecological sensitively management method.     

Cork-oak woodlands as key-habitats for biodiversity conservation in Mediterranean landscapes: a case study using rove and ground beetles (Coleoptera: Staphylinidae, Carabidae)

Land-use intensification in Mediterranean agro-forest systems became a pressure on biodiversity, concerning particularly the woodland sensitive species. In 2001, the effects of a land-use gradient from old-growth cork-oak forest to a homogeneous agricultural area were assessed using rove beetles as indicators in a Mediterranean landscape. The aim was to find which species were negatively affected by land-use intensification at the landscape level and whether they benefited from cork-oak patches occurring along the land-use gradient. A total of 3,196 rove beetles from 88 taxa were sampled from all landscape types. Agricultural area recorded significantly higher numbers of abundance and species richness in relation to the cork-oak mosaics, i.e. the old-growth forest and the managed agro-forest landscapes (montados). Moreover, 70% of rove beetle indicator species common enough to be tested by IndVal displayed their highest indicator value for agriculture, showing a lower number of woodland indicators in comparison to ground beetles. Nevertheless, one rove beetle taxon was considered a specialist of closed woodland mosaics while no specialist ground beetle was found for that landscape typology. Some rare rove beetle species were also important in typifying diversity patterns of old-growth cork-oak forests. Hence, future management in Mediterranean landscapes should take into account not only indicator species common enough to be tested by IndVal, but also rare and endemic species. Considering the added value of cork-oak woodland cover for sensitive rove and ground beetle diversity, the strengthening of cork-oak woodland connectivity seems to be a crucial management that is required in agricultural Mediterranean landscapes.     

Effects of landscape structure and land-use intensity on similarity of plant and animal communities

Aim Species richness in itself is not always sufficient to evaluate land management strategies for nature conservation. The exchange of species between local communities may be affected by landscape structure and land‐use intensity. Thus, species turnover, and its inverse, community similarity, may be useful measures of landscape integrity from a diversity perspective. Location A European transect from France to Estonia. Methods We measured the similarity of plant, bird, wild bee, true bug, carabid beetle, hoverfly and spider communities sampled along gradients in landscape composition (e.g. total availability of semi‐natural habitat), landscape configuration (e.g. fragmentation) and land‐use intensity (e.g. pesticide loads). Results Total availability of semi‐natural habitats had little effect on community similarity, except for bird communities, which were more homogeneous in more natural landscapes. Bee communities, in contrast, were less similar in landscapes with higher percentages of semi‐natural habitats. Increased landscape fragmentation decreased similarity of true bug communities, while plant communities showed a nonlinear, U‐shaped response. More intense land use, specifically increased pesticide burden, led to a homogenization of bee, bug and spider communities within sites. In these cases, habitat fragmentation interacted with pesticide load. Hoverfly and carabid beetle community similarity was differentially affected by higher pesticide levels: for carabid beetles similarity decreased, while for hoverflies we observed a U‐shaped relationship. Main conclusions Our study demonstrates the effects of landscape composition, configuration and land‐use intensity on the similarity of communities. It indicates reduced exchange of species between communities in landscapes dominated by agricultural activities. Taxonomic groups differed in their responses to environmental drivers and using but one group as an indicator for ‘biodiversity’ as such would thus not be advisable.     

Habitat structure and neighbor linear features influence more carabid functional diversity in olive groves than the farming system

The effects of land-use management and environmental features at different scales on carabid beetle diversity and trait structure were assessed across olive groves in northeastern Portugal. We selected organic and integrated olive groves that were distinct in terms of specific management practices, local linear features and landscape configurations. Besides the management intensification levels, differences in carabid diversity and community traits were mainly due to local habitat and ecological linear structures at a finer spatial scale. Carabid community traits related to disturbance, namely traits of body size and species dispersal ability, responded to land-use intensity and particular olive grove features were influencing diversity patterns. Within the olive grove patches, larger and brachypterous species were associated to plots with more dense vegetation cover while macropterous and small-sized species were more associated to open areas. Also, larger carabid species benefitted from higher patch size heterogeneity within the landscape mosaics. Our findings indicate that the effects of farming system is contingent on the specific management practices, local and linear features present in agroecosystems such as olive groves. Particularly, the influence of local features on carabid diversity patterns and community traits linked to dispersal and movement may be crucial in maintaining pest control at a landscape scale.     

Forest edge contrasts have a predictable effect on the spatial distribution of carabid beetles in urban forests

Fragmented urban forest remnants are characterised by sharp edges and are bordered by various land-use types, which may have a considerable effect on the fauna and flora at forest edges, and into forest interiors. To investigate the effects of differentially contrasting edges (low vs. intermediate vs. high) on carabid beetle assemblages in urban boreal forests, we placed pitfall traps along a gradient from 6?m into three matrix types (secondary forest vs. grassland vs. asphalt) up to 60?m into urban forest patches in the cities of Vantaa and Helsinki, southern Finland. Individual species and carabid beetle assemblages were strongly affected by edge contrasts and distance from the forest edge. The strongest effect on individual species was caused by high contrasting edges: generalist and open-habitat species were favoured or not affected while forest specialists were affected negatively. Effects of the abundances of potential prey and competitors on the carabid beetles were also evaluated. Forest and moisture-associated carabid species were negatively to neutrally associated with springtail abundances while generalist and open habitat, and dryness associated species were more positively related to springtail abundances (a potential food source). In terms of potential competitors, forest and moisture-associated carabid species were negatively and/or neutrally affected by ant and wood ant numbers, while generalist and open-habitat species were neutrally to positively associated with these taxa. It appears that carabid beetle habitat associations are more important in the responses of these beetles across edges of different contrast than are the prey and competitor numbers collected there. We recommend the creation of “soft” or low-contrast urban edges if the aim of urban management is to protect forest carabids in cities.     

Does the presence of grassy strips and landscape grain affect the spatial distribution of aphids and their carabid predators?

• 1 We investigated, over the course of 2 years, the spatial distribution and abundance of two species of aphid, Metopolophium dirhodum and Sitobion avenae, and predatory species of carabid. This was undertaken in 24 wheat fields in ‘coarse‐grain’ and ‘fine‐grain’ landscapes in western France. A greater percentage of the latter landscape was covered by hedgerows and grassland and the total area covered by fields and the average size of the fields were smaller.
• 2 The effects on aphid abundance of the distance from field margins, the presence of grassy strips and carabid abundance were determined in both landscapes.
• 3 Both aphid species were more abundant in the ‘fine‐grain’ landscape, which may have been a result of the higher density of semi‐natural elements. In both types of landscape, the total numbers of aphids were negatively correlated with the distance from the field margin. This may have been because aphids were dispersing from overwintering sites in field margins. The abundance of M. dirhodum was strongly negatively correlated with the presence of grassy strips in the ‘coarse‐grain’ landscape, although there were no such significant correlations for either of the aphid species in the ‘fine‐grain’ landscape.
• 4 Aphid and carabid abundances were negatively correlated in the ‘fine‐grain’ and positively in ‘coarse‐grain’ landscape.
• 5 The results obtained in the present study emphasize the importance of semi‐natural areas in agricultural landscapes in shaping the spatial distribution of aphids and carabid beetles, their natural enemies, at different spatial scales.

     

Multiscale and surface pattern analysis of the effect of landscape pattern on carabid beetles distribution

It has been often shown that spatial distribution of species can be related to the main characteristics of their habitat. Usually, such relationships refer to point pattern analysis and try to determine whether the distribution of species is conditioned by their surroundings or not. They often seek correlations at a given place, date and scale and neglect the information potentially extracted from detailed surface pattern analyses that would require extended data. This study investigated the impact of landscape pattern and landscape context (of habitats) on carabid beetles assemblages in each place and on a continuous range of scales of a landscape. For this purpose, we develop a tool able to visualize and quantify the spatial variations of indices commonly used in point pattern analyses, such as contagion (heterogeneity) of a landscape and abundance (counts) of species. Using moving windows, we plotted contagion maps of two Brittany sites (France) and cross-correlation maps between the latter and carabid beetles spatial distributions, in order to study their local relationships. Associated landscape and insect index scaling profiles helped to interpret the correlations found. A rather good agreement with landscape ecology predictions over both sites has been found: significant relationships between land cover contagion and total carabid abundance on one hand, between agricultural intensification (mainly maize fields) and carabid body size on the other hand, have been observed. Nevertheless, detailed surface pattern analyses over a wide range of scales show quite high deviations from empirical results with no correlation, or even negative correlation, in some places between otherwise correlated indices.     

The value of semi-natural grasslands for the conservation of carabid beetles in long-term managed forested landscapes

Species rich semi-natural grasslands are disappearing across Europe, affecting invertebrate diversity negatively. In NW Spain, the recent abandonment of traditional farming practices and the gradual decrease in grazing pressures are reducing the number and extent of montane grasslands. In this context, we investigated the composition of carabid beetle (Coleoptera, Carabidae) assemblages that inhabit semi-natural grasslands situated in long-term managed oak and beech forested landscapes. According to their spatial arrangement, the studied grasslands were classified into: (1) interior or gap grasslands (small and completely surrounded by continuous forest) and (2) exterior grasslands (large and connected to a variety of habitat types). Our results indicate that, within each forested landscape, the gap and exterior grasslands harboured particular carabid assemblages (i.e. exclusive or abundantly collected species), which were also distinct from the surrounding forest carabid fauna. Dissimilarities between gap and exterior grasslands in each landscape suggest great carabid diversity at the regional scale. We also detected species-specific responses as several carabids were mainly associated with gap or exterior grasslands. Consequently, in highly modified forested landscapes, semi-natural grassland remnants may constitute great value for the protection of the carabid fauna. Specifically, we recommend conservation strategies that preserve variety in grassland features and maintain proper management activities to prevent the loss of specialised species and a decrease in regional carabid diversity.     

Structural complexity of arthropod guilds is affected by the agricultural landscape heterogeneity generated by fencerows

Intensive farming imposes harsh conditions impeding the persistence of most arthropod species within crop fields. Hence, arthropods surviving the unfavourable conditions prevailing within crop fields may disperse towards nearby uncropped margins, such as fencerows. Here, we evaluate the influence of landscape heterogeneity on the abundance of different guilds, particularly herbivores and their natural enemies. Said heterogeneity mostly derives from fencerow network density. Hence, we developed an approach based on fitting linear‐mixed models to elucidate the effects of landscape heterogeneity and field position (fencerows and crop interiors) on arthropod diversity. Mixed models were fitted to arthropod data obtained by pitfall trap samplings in 36 crop fields. Arthropod communities were structurally and functionally more complex along fencerows than within nearby crop interiors. Arthropods abundance was modulated by landscape heterogeneity, increasing the abundance of natural enemies as the landscape heterogeneity increased. On the contrary, herbivores abundance decreased as landscape heterogeneity increased. Consequently, the ratio between herbivores and natural enemies also decreased as landscapes became more heterogeneous. Natural enemies with larger body sizes, mostly carabid beetles, were more sensitive to landscape homogenisation. Our study reveals that, despite the coarse‐grained landscapes in the Rolling Pampa, fencerow density appears as a key factor for structuring complex arthropod guilds in intensively farmed agricultural mosaics. In landscapes with higher density of fencerows, arthropods tend to concentrate along them, thus increasing the community structural complexity as well as the predation pressure over herbivores. This structural complexity of upper trophic levels enhances the ‘top‐down’ regulation of herbivore populations, consequently decreasing the probability of pest outbreaks within crop fields.     

Local vs. landscape controls on diversity: a test using surface-dwelling soil macroinvertebrates of differing mobility

Aim A better understanding of the processes driving local species richness and of the scales at which they operate is crucial for conserving biodiversity in cultivated landscapes. Local species richness may be controlled by ecological processes acting at larger spatial scales. Very little is known about the effect of landscape variables on soil biota. The aim of our study was to partly fill this gap by relating the local variation of surface‐dwelling macroarthropod species richness to factors operating at the habitat scale (i.e. land use and habitat characteristics) and the landscape scale (i.e. composition of the surrounding matrix). Location An agricultural landscape with a low‐input farming system in Central Hesse, Germany. Methods We focused on five taxa significantly differing in mobility and ecological requirements: ants, ground beetles, rove beetles, woodlice, and millipedes. Animals were caught with pitfall traps in fields of different land use (arable land, grassland, fallow land) and different habitat conditions (insolation, soil humidity). Composition of the surrounding landscape was analysed within a radius of 250 m around the fields. Results Factors from both scales together explained a large amount of the local variation in species richness, but the explanatory strength of the factors differed significantly among taxa. Land use particularly affected ground beetles and woodlice, whereas ants and rove beetles were more strongly affected by habitat characteristics, namely by insolation and soil characteristics. Local species richness of diplopods depended almost entirely on the surrounding landscape. In general, the composition of the neighbouring landscape had a lower impact on the species richness of most soil macroarthropod taxa than did land use and habitat characteristics. Main conclusions We conclude that agri‐environment schemes for the conservation of biodiversity in cultivated landscapes have to secure management for both habitat quality and heterogeneous landscape mosaics.