Linear Landscape Features Research Articles

GPS tracking technology and re-visiting the relationship between the avian visual Wulst and homing pigeon navigation

Within their familiar areas homing pigeons rely on familiar visual landscape features and landmarks for homing. However, the neural basis of visual landmark-based navigation has been so far investigated mainly in relation to the role of the hippocampal formation. The avian visual Wulst is the telencephalic projection field of the thalamofugal pathway that has been suggested to be involved in processing lateral visual inputs that originate from the far visual field. The Wulst is therefore a good candidate for a neural structure participating in the visual control of familiar visual landmark-based navigation. We repeatedly released and tracked Wulst-lesioned and control homing pigeons from three sites about 10–15 km from the loft. Wulst lesions did not impair the ability of the pigeons to orient homeward during the first release from each of the three sites nor to localise the loft within the home area. In addition, Wulst-lesioned pigeons displayed unimpaired route fidelity acquisition to a repeated homing path compared to the intact birds. However, compared to control birds, Wulst-lesioned pigeons displayed persistent oscillatory flight patterns across releases, diminished attention to linear (leading lines) landscape features, such as roads and wood edges, and less direct flight paths within the home area. Differences and similarities between the effects of Wulst and hippocampal lesions suggest that although the visual Wulst does not seem to play a direct role in the memory representation of a landscape-landmark map, it does seem to participate in influencing the perceptual construction of such a map.

Researching, promoting and protecting Welsh toponyms – Challenges and possible solutions

Place names are stepping-stones to our past, connecting us to our ancestors. Once severed, geographical, social and cultural links between local people and place and names cannot be restored. Documentary and mapping research has been conducted in parts of the largely upland, a protected area of Snowdonia National Park. A new methodology reveals a palimpsest of toponyms in Welsh rural landscapes since 1284 and uncovers previously concealed history and untold narratives of Welsh heritage. Toponyms in Wales are under threat. Social and economic changes impose adverse effects on the traditional family farm, relic farm buildings and linear landscape features such as stone walls, banks and woodlands and field patterns. A consequence of this is the reduced use of toponyms. Tourists, walkers, climbers, and divers contribute to this erosion unintentionally. They often translate toponyms literally or make up their own (usually non-Welsh) names, for rock climbs, lakes, peaks, and caves that are considered too difficult to pronounce. These newly invented names quickly replace the original toponyms, often reinforced by guidebooks and maps published in English. New housing estates, homes and tourist businesses frequently adopt English names which are not in keeping with traditional visual signage in rural areas. The Welsh Place Name Society (WPNS) formed in 2013 is a grass roots and academic inclusive organisation which provided robust evidence to the Welsh Government during the consultation stage of the Historic Environment Bill 2016. However, it was decided not to give place names legal protection, unlike historic monuments, country houses and bats. The Office of The Commissioner for Welsh has a well-established panel of experts who determine standardised spellings for towns and villages. Their on-line list provides a useful reference for organisations and individuals, but this list and others have no legal standing. This paper discusses the critical legal issue of protecting place names in Wales and illustrates how the Society has worked alongside organisations and local communities in Wales to promote and defend place names.

An Empirical Bayesian Approach to Quantify Multi-Scale Spatial Structural Diversity in Remote Sensing Data

Landscape structure is as much a driver as a product of environmental and biological interactions and it manifests as scale-specific, but also as multi-scale patterns. Multi-scale structure affects processes on smaller and larger scales and its detection requires information from different scales to be combined. Herein, we propose a novel method to quantify multi-scale spatial structural diversity in continuous remote sensing data. We combined information from different extents with an empirical Bayesian model and we applied a new entropy metric and a value co-occurrence approach to capture heterogeneity. We tested this method on Normalized Difference Vegetation Index data in northern Eurasia and on simulated data and we also tested the effect of coarser pixel resolution. We find that multi-scale structural diversity can reveal itself as patches and linear landscape features, which persist or become apparent across spatial scales. Multi-scale line features reveal the transition zones between spatial regimes and multi-scale patches reveal those areas within transition zones where values are most different from each other. Additionally, spatial regimes themselves can be distinguished. We also find the choice of scale need not be informed by typical length-scales, which makes the method easy to implement. The proposed multi-scale approach can be applied to other contexts, following the roadmap we pave out in this study and using the tools available in the accompanying R package StrucDiv.

Identification of the Key Determinants of Bats’ Altitude Increase over the S3 Expressway in Poland with Mesh Screens Applied

The continuing increase in motorisation and the resulting development of the road infrastructure puts increasing demands on environmental protection, and on the protection of bats in particular. One of the available mitigation measures is mesh screen structures installed on dual carriageways. However, not all the mitigating measures turn out to be effective and functional. Mesh screens were installed along a road section over a dozen kilometres long near a large bat reserve in Poland (40,000 bats). As part of post-construction work, bat mortality monitoring was conducted over a 3–4 year period in order to assess the effectiveness of the mesh screens in raising the height of bat flyways. An analysis of the mortality surveys and the locations of bat carcasses found along the expressway allowed the authors to confirm that the screens may contribute to raising the height of bat flyways, yet this effect should be considered in combination with other determinants identified during the surveys. The article presents the main determinants, which together with the mesh screens installed along a dual carriageway road over the length of several kilometres, can contribute to the effective raising of the height at which bats fly across the road. The most important determinants included: retaining the continuity of linear landscape features along the confirmed bat commuting and migration routes, no gaps in the tree line greater than 30 m, use of natural funnels for bats to fly through, and sizing of culverts and underpasses appropriate for the specific bat species, as identified in the pre-construction surveys. The conclusion drawn from the research was the need for interdisciplinary studies to be carried out already during preliminary design work, to ensure a sustainable approach on the part of the road engineers, structural engineers, chiropterologists, and landscape architects involved in the road project. A detailed analysis of numerous factors relevant to the analysed dual carriageway demonstrated the importance of following the principles of sustainable design and collaboration within interdisciplinary design teams to select the best mitigation measures already at the pre-construction stage of the project.

A conceptual-model-based sediment connectivity assessment for patchy agricultural catchments

Abstract. The accelerated sediment supply from agricultural soils to riverine and lacustrine environments leads to negative off-site consequences. In particular, the sediment connectivity from agricultural land to surface waters is strongly affected by landscape patchiness and the linear structures that separate field parcels (e.g. roads, tracks, hedges, and grass buffer strips). Understanding the interactions between these structures and sediment transfer is therefore crucial for minimising off-site erosion impacts. Although soil erosion models can be used to understand lateral sediment transport patterns, model-based connectivity assessments are hindered by the uncertainty in model structures and input data. Specifically, the representation of linear landscape features in numerical soil redistribution models is often compromised by the spatial resolution of the input data and the quality of the process descriptions. Here we adapted the Water and Tillage Erosion Model and Sediment Delivery Model (WaTEM/SEDEM) using high-resolution spatial data (2 m × 2 m) to analyse the sediment connectivity in a very patchy mesoscale catchment (73 km2) of the Swiss Plateau. We used a global sensitivity analysis to explore model structural assumptions about how linear landscape features (dis)connect the sediment cascade, which allowed us to investigate the uncertainty in the model structure. Furthermore, we compared model simulations of hillslope sediment yields from five subcatchments to tributary sediment loads, which were calculated with long-term water discharge and suspended sediment measurements. The sensitivity analysis revealed that the assumptions about how the road network (dis)connects the sediment transfer from field blocks to water courses had a much higher impact on modelled sediment yields than the uncertainty in model parameters. Moreover, model simulations showed a higher agreement with tributary sediment loads when the road network was assumed to directly connect sediments from hillslopes to water courses. Our results ultimately illustrate how a high-density road network combined with an effective drainage system increases sediment connectivity from hillslopes to surface waters in agricultural landscapes. This further highlights the importance of considering linear landscape features and model structural uncertainty in soil erosion and sediment connectivity research.

Contributions of Hedgerows to People: A Global Meta-Analysis

Hedgerows are linear landscape features of woody vegetation usually located around agricultural fields. An increasing number of studies have addressed the effects of hedgerows on biodiversity and ecosystem services. This study is aimed to synthesize these effects and compare the levels of biodiversity and ecosystem services in farmland with hedgerows and (1) farmland without hedgerows and (2) nearby natural habitat at the global scale. We hypothesized that farmland with hedgerows (1) enhances biodiversity and ecosystem services as compared to farmland without hedgerows but (2) supports lower levels of biodiversity and ecosystem services than natural habitat. Our systematic literature review retained 835 observations from 170 primary studies, which were analyzed following the standard methodology in meta-analyses. Our results partially support both hypotheses. Farmland with hedgerows exhibited higher levels of biodiversity and provisioning services than farmland without hedgerows (H1). Farmland with hedgerows provided similar levels of biodiversity (edge effects) but lower levels of ecosystem services than natural habitat (H2). The effects of hedgerows on biodiversity and ecosystem services depended on control ecosystem type (grassland/meadow or forest/woodland) but were largely independent of climate type (temperate or tropical) and the focus of spatial scale (field or landscape). In conclusion, conservation and restoration of hedgerows contribute to people in several ways by enhancing biodiversity and multifunctionality in agricultural landscapes.

On this side of the fence: Functional responses to linear landscape features shape the home range of large herbivores.

Understanding the consequences of global change for animal movement is a major issue for conservation and management. In particular, habitat fragmentation generates increased densities of linear landscape features that can impede movements. While the influence of these features on animal movements has been intensively investigated, they may also play a key role at broader spatial scales (e.g. the home range scale) as resources, cover from predators/humans, corridors/barriers or landmarks. How space use respond to varying densities of linear features has been mostly overlooked in large herbivores, in contrast to studies done on predators. Focusing on large herbivores should provide additional insights to understand how animals solve the trade-off between energy acquisition and mortality risk. Here, we investigated the role of anthropogenic (roads and tracks) and natural (ridges, valley bottoms and forest edges) linear features on home range features in five large herbivores. We analysed an extensive GPS monitoring database of 710 individuals across nine populations, ranging from mountain areas mostly divided by natural features to lowlands that were highly fragmented by anthropogenic features. Nearly all of the linear features studied were found at the home range periphery, suggesting that large herbivores primarily use them as landmarks to delimit their home range. In contrast, for mountain species, ridges often occurred in the core range, probably related to their functional role in terms of resources and refuge. When the density of linear features was high, they no longer occurred predominantly at the home range periphery, but instead were found across much of the home range. We suggest that, in highly fragmented landscapes, large herbivores are constrained by the costs of memorising the spatial location of key features, and by the requirement for a minimum area to satisfy their vital needs. These patterns were mostly consistent in both males and females and across species, suggesting that linear features have a preponderant influence on how large herbivores perceive and use the landscape.

Juvenile Barn Owl Tyto alba dispersal: a radio-tracking study of roost site selection in relation to landscape features

ABSTRACT Capsule Radio-tracking of 19 juvenile Barn Owls Tyto alba alba in England revealed different spatial patterns for males and females, that tree branches were frequent roost sites, and that altitudinal distribution changed after owls acquired home ranges. Aims To gain new understanding of the natal dispersal of Barn Owls by identifying roost sites and analysing their spatial pattern, site type, altitude, and location in relation to linear features. Methods Diurnal roost sites of 19 juvenile Barn Owls were located by radio-tracking in southwest England. We evaluated the possibility of sex-bias in natal and between-roost dispersal distances and tested for change in the site types used as natal sites and daytime roosts. We tested for differences in the altitude of roosts used during the dispersal phase and those used once the birds acquired a home range, and we analysed the location of roost sites in relation to major roads, railways, and rivers. Results Barn Owls commenced dispersal when they were between 63 and 122 days after hatching (median = 94). Roost sites used by females were more widely scattered than those used by males. Owls roosted most frequently in trees, despite most natal sites being in buildings. The altitude of roost sites during dispersal in elevated landscapes was higher than those on their acquired home range. We could find no evidence that owls followed linear features during dispersal, nor that hills were barriers to dispersal. Conclusion Post-fledging roosting behaviour of female and male Barn Owls differed spatially and was congruent with a wider pattern of sex-bias in avian natal dispersal. Frequent roosting on tree branches had implications for exposure to adverse weather. Some juveniles roosted at altitudes that were higher than subsequent roosts on their acquired home range. We found no evidence to support the proposal that linear landscape features constituted dispersal corridors.

Moths Consumed by the Barbastelle Barbastella barbastellus Require Larval Host Plants that Occur within the Bat's Foraging Habitats

Loss of foraging habitat and reductions in insect prey are key factors responsible for declines in bat populations. Identifying important bat foraging habitats and the ecological requirements and conservation status of prey provides evidence for appropriately targeted conservation management strategies. We examined the foraging habits of the barbastelle, Barbastella barbastellus, at the northern edge of its European range using a combination of radio tracking, to determine home range use and habitat selection, and DNA metabarcoding, to identify prey items consumed. Riparian vegetation and broadleaved woodland were the habitat types most strongly selected by foraging bats. Hedgerows within pastoral habitats were also important foraging features within the landscape. We identified 120 different prey items within faecal pellets, the majority of which were moths (97.5%). The large majority (97%) of prey items consumed have larval stages dependent on host plants that are typically found within habitats selected by foraging B. barbastellus. Almost half of all moth prey species identified have undergone considerable population declines in recent decades. We present the most comprehensive list to date of prey consumed by B. barbastellus and provide evidence that conservation management policies should target the protection and enhancement of key B. barbastellus foraging habitats within a 6.5 km sustenance zone around maternity roost sites. Riparian habitat, broadleaved woodland and linear landscape features such as hedgerows should be managed to improve their value to foraging B. barbastellus as well as the developmental stages of their preferred moth prey.

The Mostela: an adjusted camera trapping device as a promising non-invasive tool to study and monitor small mustelids

In spite of their potential important role in shaping small mammal population dynamics, weasel (Mustela nivalis) and stoat (Mustela erminea) are understudied due to the difficulty of detecting these species. Furthermore, their conservation status in many countries is unknown due to lack of monitoring techniques. There is thus an important need for a method to detect these small mustelids. In this study, we tested the efficiency of a recently developed camera trapping device, the Mostela, as a new technique to detect mustelids in a study area near Dieren, the Netherlands. We placed Mostelas in linear landscape features, and other microhabitats thought to be frequently visited by weasels, from March to October 2017 and February to October 2018. We tested for yearly and monthly differences in site use and detectability, as well as the effect of entrance tube size, using an occupancy modelling framework. We found large seasonal differences in site use and detectability of weasels with the highest site use in June to October and highest detection probability in August and September. Detection probability was approximately two times higher for Mostelas with a 10-cm entrance tube compared with 8-cm. Furthermore, we were able to estimate activity patterns based on the time of detection, identify the sex in most detections (69.5%), and distinguish several individuals. Concluding, the Mostela seems promising as a non-invasive monitoring tool to study the occurrence and ecology of small mustelids. Further development of individual recognition from images would enable using the Mostela for density estimates applying capture-recapture models.

Assessing the use of rivers as migratory corridors for temperate bats

AbstractInvestigating landscape-level movement patterns of migratory animals can be challenging, but this is a major component of some animal’s life history and behavior. In particular, bat migration has been difficult to characterize, yet recent research on bat migratory ecology has made major advances. It has been largely accepted that rivers and other linear landscape features may be important migratory corridors for bats during both long- and short-distance migrations. We assessed the migratory behavior of multiple temperate bat species along the Missouri River, a major river corridor in North Dakota, during March through October of 2016–2017. Bat detectors with paired microphones were deployed and oriented parallel to the riverbank. This configuration permitted detection of directional passes of bats, approximately 10–20 m above the microphones and 40 m into the river, which were used as an estimate of migratory behavior. We found the effects of season and species explained less than 2% of the variation of directional passes, indicating an absence of season-specific movement patterns along the studied river corridor. Although our study only assessed a portion of a major river corridor, the results suggest that migratory movements of bats along rivers may not be as straightforward as once thought, highlighting the need for future studies investigating the fine-scaled movement patterns of bats during migration.

Use of linear features by the common vampire bat (Desmodus rotundus) in a tropical cattle-ranching landscape

Linear landscape features are used by many species of insectivorous bats as flight routes and foraging zones, as well as for providing protection against environmental factors and predation. However, very little is known about the role that these landscape features play for non-insectivorous species. In this study, we evaluated the use of linear features by the common vampire bat (Desmodus rotundus) in a cattle-ranching landscape in the state of Tabasco, Mexico. We selected 24 sampling sites in 2014 and 24 independent sites in 2016 to 2017, all adjacent to three types of linear landscape features: forest edges, live fences and streams . We monitored each site for two non-consecutive nights between February and April 2014, and every two months from February 2016 to June 2017. We placed 24 m (2014) or 12 m (2016 to 2017) of mist nets perpendicular to the linear feature from its edge. We recorded the height and distance from the edge for each individual captured. In total we captured 50 D. rotundus individuals in 2014 and 58 in 2016 to 2017. The average flight height was 77 cm for the 2014 data and 69 cm for 2016 to 2017. According to our results, the most used linear features were forest edges, followed by live fences and streams. Overall, 52 % of the 2014 captures and 62 % of the 2016 to 2017 ones occurred in the first 2 m from the edge, with the number of captures gradually decreasing with increasing distance. This study provides information on the commuting patterns of D. rotundus in predominantly open cattle-ranching landscapes.

Methods for assessing small-scale variation in the abundance of a generalist mesopredator.

Estimating animal abundance is essential for research, management and conservation purposes. Although reliable methods exist to estimate absolute density for populations with individually marked animals, robust relative abundance indices (RAIs) may allow to track changes in population size when individual identification is not possible. Their performance, however, needs be thoroughly evaluated. We investigated the relative performance of several common faeces-based and camera-based RAIs for estimating small-scale variation in red fox abundance, a mesopredator of high relevance for management, in two different study areas. We compared precision, cost and performance of the methods in capturing relationships with covariates of local abundance. Random transect-based RAIs had a low mean, a comparatively high coefficient of variation and a high proportion of zeros, prohibiting or impeding analysis in relation to environmental predictors. Rectangular scat plots and transects along linear landscape features had an intermediate amount of zeros while retaining a high precision, but were less sensitive to local variation in abundance related to environmental predictors and required a large field effort. Camera trap-based RAIs yielded low to intermediate precision, but were more sensitive to small-scale variation in relative abundance than faeces-based methods. Camera traps were the most expensive methods for an initial monitoring session, but required the lowest field effort, were cheapest in the long run and were the least susceptible to observer bias and detection error under a robust sampling protocol. Generally, faeces count-based RAIs appear more suitable for studies that aim to compare local abundance between several study sites of equal landscape composition under constant detection probability. Camera traps provide more flexible data for studies that require accounting for influences of landscape composition on local abundance and are more cost-effective for long-term or continuous monitoring and more suitable to achieve high replication. Accordingly, the choice of the most suitable method and plot design is context-dependent.

Landscape genetics matches with behavioral ecology and brings new insight on the functional connectivity in Mediterranean mouflon

In natural populations, gene flow often represents a key factor in determining and maintaining genetic diversity. In a worldwide context of habitat fragmentation, assessing the relative contribution of landscape features to gene flow thus appears crucial for sustainable management of species. We addressed this issue in Mediterranean mouflon (Ovis gmelini musimon × Ovis sp.) by combining previous knowledge on behavioral ecology with landscape genetics. We also assessed how sex-specific behavioral differences translated in term of functional connectivity in both sexes. We relied on 239 individuals genotyped at 16 microsatellite markers. We applied a model optimization approach in a causal modeling framework of landscape genetics to test for the effects on gene flow of habitat types and linear landscape features previously identified as important for movements and habitat selection in both sexes. Five resistance values were alternately assigned to these landscape characteristics leading to a comprehensive set of resistance surfaces. Isolation by resistance shaped female gene flow, supporting the central role of linear landscape features as behavioral barriers for animal movements. Conversely, no isolation by resistance was detected in males. Although a lack of statistical power cannot be discarded to explain this result, it tended to confirm that males are less influenced by landscape structures during the mating period. Combining previous knowledge on behavioral ecology with results from landscape genetics was decisive in assessing functional landscape connectivity in both sexes. These results highlighted the need to perform sex-specific studies for management and conservation of dimorphic species.

Ecological landscape elements: long-term monitoring in Great Britain, the Countryside Survey 1978–2007 and beyond

Abstract. The Countryside Survey (CS) of Great Britain (GB) provides a unique and statistically robust series of datasets, consisting of an extensive set of repeated ecological measurements at a national scale, covering a time span of 29 years. CS was first undertaken in 1978 to provide a baseline for ecological and land use change monitoring in the rural environment of GB, following a stratified random design, based on 1 km squares. Originally, eight random 1 km squares were drawn from each of 32 environmental classes, thus comprising 256 sample squares in the 1978 survey. The number of these sites increased to 382 in 1984, 506 in 1990, 569 in 1998 and 591 in 2007. Detailed information regarding vegetation types and land use was mapped in all five surveys, allowing reporting by defined standard habitat classifications. Additionally, point and linear landscape features (such as trees and hedgerows) are available from all surveys after 1978. From these stratified, randomly located sample squares, information can be converted into national estimates, with associated error terms. Other data, relating to soils, freshwater and vegetation, were also sampled on analogous dates. However, the present paper describes only the surveys of landscape features and habitats. The resulting datasets provide a unique, comprehensive, quantitative ecological coverage of extent and change in these features in GB. Basic results are presented and their implications discussed. However, much opportunity for further analyses remains. Data from each of the survey years are available via the following DOIs: Landscape area data 1978: https://doi.org/10.5285/86c017ba-dc62-46f0-ad13-c862bf31740e, 1984: https://doi.org/10.5285/b656bb43-448d-4b2c-aade-7993aa243ea3, 1990: https://doi.org/10.5285/94f664e5-10f2-4655-bfe6-44d745f5dca7, 1998: https://doi.org/10.5285/1e050028-5c55-42f4-a0ea-c895d827b824, and 2007: https://doi.org/10.5285/bf189c57-61eb-4339-a7b3-d2e81fdde28d; Landscape linear feature data 1984: https://doi.org/10.5285/a3f5665c-94b2-4c46-909e-a98be97857e5, 1990: https://doi.org/10.5285/311daad4-bc8c-485a-bc8a-e0d054889219, 1998: https://doi.org/10.5285/8aaf6f8c-c245-46bb-8a2a-f0db012b2643 and 2007: https://doi.org/10.5285/e1d31245-4c0a-4dee-b36c-b23f1a697f88, Landscape point feature data 1984: https://doi.org/10.5285/124b872e-036e-4dd3-8316-476b5f42c16e, 1990: https://doi.org/10.5285/1481bc63-80d7-4d18-bcba-8804aa0a9e1b, 1998: https://doi.org/10.5285/ed10944f-40c8-4913-b3f5-13c8e844e153 and 2007: https://doi.org/10.5285/55dc5fd7-d3f7-4440-b8a7-7187f8b0550b.

Combining familiarity and landscape features helps break down the barriers between movements and home ranges in a non-territorial large herbivore.

Recent advances in animal ecology have enabled identification of certain mechanisms that lead to the emergence of territories and home ranges from movements considered as unbounded. Among them, memory and familiarity have been identified as key parameters in cognitive maps driving animal navigation, but have been only recently used in empirical analyses of animal movements. At the same time, the influence of landscape features on movements of numerous species and on space division in territorial animals has been highlighted. Despite their potential as exocentric information in cognitive maps and as boundaries for home ranges, few studies have investigated their role in the design of home ranges of non-territorial species. Using step selection analyses, we assessed the relative contribution of habitat characteristics, familiarity preferences and linear landscape features in movement step selection of 60 GPS-collared Mediterranean mouflon Ovis gmelini musimon × Ovis sp. monitored in southern France. Then, we evaluated the influence of these movement-impeding landscape features on the design of home ranges by testing for a non-random distribution of these behavioural barriers within sections of space differentially used by mouflon. We reveal that familiarity and landscape features are key determinants of movements, relegating to a lower level certain habitat constraints (e.g. food/cover trade-off) that we had previously identified as important for this species. Mouflon generally avoid crossing both anthropogenic (i.e. roads, tracks and hiking trails) and natural landscape features (i.e. ridges, talwegs and forest edges) while moving in the opposite direction, preferentially toward familiar areas. These specific behaviours largely depend on the relative position of each movement step regarding distance to the landscape features or level of familiarity in the surroundings. We also revealed cascading consequences on the design of home ranges in which most landscape features were excluded from cores and relegated to the peripheral areas. These results provide crucial information on landscape connectivity in a context of marked habitat fragmentation. They also call for more research on the role of landscape features in the emergence of home ranges in non-territorial species using recent methodological developments bridging the gap between movements and space use patterns.

Mesurer l'impact des entités linéaires paysagères sur les dynamiques spatiales du ruissellement : une approche par simulation multi-agents

De nombreux enjeux socio-economiques et environnementaux sont associes aux transferts hydro-sedimentaires qui s’organisent au sein des hydrosystemes, depuis les parcelles agricoles jusqu’aux cours d’eau : pollution diffuse, diminution de la fertilite des sols, pertes en sol, crues turbides, etc. Si les conditions d’initiation de ces transferts sont bien connues a l’echelle de la parcelle agricole, les dynamiques d’ecoulements qui se produisent sur les versants restent mal connues, et ce particulierement dans les petits hydrosystemes bocagers du nord-ouest de la France, ou la mosaique paysagere et notamment la presence plus ou moins importante de reseaux lineaires (haies, routes, fosses…) tend a complexifier leur dynamique spatiale. Connaitre les conditions de transfert est pourtant necessaire en vue d’une gestion integree des bassins versants. Aussi, cette etude propose d’utiliser la simulation multi-agents comme outils d’aide a la decision pour mieux apprehender le role des reseaux lineaires d’origines anthropiques sur le parcours des ecoulements de surface. L’approche menee, dite ascendante, permet d’analyser l’importance des interactions locales qui ont lieu entre chaque entite lineaire pour mieux comprendre le comportement hydrologique global d’un bassin versant. Un premier indice d'analyse spatiale, caracterisant l’impact des reseaux lineaires sur le parcours des ecoulements de surface, est propose ici a partir des simulations numeriques. Cet article ouvre egalement une discussion methodologique en analysant la pertinence des systemes multi-agents en tant qu’outils de diagnostic et d’aide a la gestion des espaces sensibles aux processus de transferts hydro-sedimentaires.

Responses of grassland arthropods to various biodiversity-friendly management practices: Is there a compromise?

The rich species pool in semi-natural grasslands is associated with high spatial and temporal heterogeneity. This empirical study is one of the first to jointly analyze the response of orders, individual species and functional richness of arthropods to particular management practices and to linear landscape features, such as strips of grass and belts of trees. Mostly it was the less mobile, flightless taxa that were negatively affected by immediate disturbance caused by mowing. At a larger time-scale, grasslands managed by mow- ing once every year, and especially by a combined regime of mowing and grazing, supported the highest species richness of butterflies and beetles. Most functional diversity measures reached maximum values soon after mowing. Both strips of grass and belts of trees substantially affected the invertebrate community structure as the majority of taxa were positively associated with these linear features. Based on our results, we propose postponing mowing to later in the year, mowing in gradual stages, maintaining uncut strips primar - ily along permanent landscape features and establishing both strips of grass and belts of trees in submontane grassland environments.

Farm Boundaries as Agroecological Systems

South-central Pennsylvania, framed by the great folds of the Appalachians to the north and west, by the Mason-Dixon Line to the south, and by the rise of hills that bound the lower Susquehanna River to the east, was claimed by settler-farmers of western European descent during the early and mid-eighteenth century. They utilized river and stream valleys to gain access to the fertile lowlands and rich uplands of the region, following in the steps of surveyors to mark farm boundaries with timber fences cut from the cloak of forest. The social and ecological imprint of these boundary structures has endured for hundreds of years.

Landscape structure influences pollinator movements and directly affects plant reproductive success

Pollinators play a key role within most terrestrial communities in maintaining plant populations, as well as pollinating many agricultural crops for seed and fruit production. The mobility of pollinating animals is significant to their importance but we know little about how landscape structure influences pollinator movements. Linear landscape features such as hedgerows and embankments are conspicuous features of agricultural landscape structure and are important artificial habitats in their own right. However, there has been some debate as to the function of these landscape elements as corridors between larger expanses of semi‐natural habitat separated by urban and agricultural habitats. Few studies have specifically studied insect flight responses to linear landscape elements. By observing bumblebee flight behaviour along hedgerows and, by creating a medium‐scale experimental array of flower patches using an artificial linear feature, we examined whether such structures can elicit an oriented flight response along them and therefore facilitate insect movement through the landscape. We found that both hedgerows and artificial linear landscape features can influence the flight directions of bumblebees (Bombus spp. Hymenoptera, Apidae), one of Europe's most important groups of pollinators. A bioassay experiment in which Salvia pratensis (Lamiaceae) was planted into landscape patches with differing numbers of connecting hedgerows showed that this directional response can have a profound effect on plant reproductive success – plants had increased pollinator activity, pollen receipt and subsequent seed set in patches with more connections. The overall hedgerow connectedness of a landscape is therefore important both to bumblebee movement and to those plants which depend on bumblebees for pollination services.