Reproductive consequences of farmland heterogeneity in little owls (<Emphasis Type="Italic">Athene noctua</Emphasis>)

The amount of high-quality habitat patches, their distribution, and the resource accessibility therein play a key role in regulating habitat effects on reproductive success. Heterogeneous habitats offer non-substitutable resources (e.g. nest sites and food) and substitutable resources (e.g. different types of food) in close proximity, thereby facilitating landscape complementation and supplementation. However, it remains poorly understood how spatial resource separation in homogeneous agricultural landscapes affects reproductive success. To fill this gap, we investigated the relationships between farmland heterogeneity and little owl (Athene noctua) reproductive success, including potential indirect effects of the heterogeneity-dependent home-range size on reproduction. Little owl home-ranges were related to field heterogeneity in summer and to structural heterogeneity in winter. Clutch size was correlated with the amount of food-rich habitat close to the nest irrespective of female home-range size, suggesting importance of landscape complementation. Nestling survival was positively correlated with male home-range size, suggesting importance of landscape supplementation. At the same time, fledgling condition was negatively correlated with male home-range size. We conclude that decreasing farmland heterogeneity constrains population productivity by two processes: increasing separation of food resources from nest or roost sites results in low landscape complementation, and reduction of alternative food resources limits landscape supplementation. Our results suggest that structural heterogeneity affects landscape complementation, whereas the heterogeneity and management of farmland fields affect landscape supplementation. Thus, to what extent a reduction of the heterogeneity within agricultural landscapes results in species-specific habitat degradation depends on the ecological processes (i.e. landscape complementation or supplementation) which are affected.     

Corridors and barriers in biodiversity conservation: a novel resource-based habitat perspective for butterflies

Habitat loss and fragmentation, exacerbated by projected climate change, present the greatest threats to preservation of global biodiversity. As increasing habitat fragmentation and isolation of residual fragments exceeds the dispersal capacity of species, there is the growing need to address connectivity to maintain diversity. Traditionally, habitat corridors have been proposed as a solution. But, the concept of corridors (barriers) is poorly understood; typically they are defined as linear habitats linking up habitat patchwork, and are advocated without a detailed understanding of the elements making up species’ habitats and the cost-effectiveness of alternative solutions. Yet, landscapes comprise an enormous range of ‘linear’ structures that can function in different ways to promote species’ persistence and diversity. In this review, a functional definition of corridor (barrier) is developed to give prominence to connectivity as opposed to ad hoc structures purported to advance connectivity. In developing the concept, urgency to accommodate environmental changes compels a growing emphasis on organism diversity rather than a preoccupation with single species conservation. The review, in focusing on butterflies to address the issue of corridors for patchwork connectivity, draws attention to fundamental divisions among organisms in any taxon: generalists and specialists. Both groups benefit from large patches as these necessarily house species with specialist resources as well as generalists with very different resource types. But, generalists and specialists require very different solutions for connectivity, from short-range habitat corridors and gateways for specialists to habitat and resource stepping stones (nodes, surfaces) for generalists. Connectivity over extensive areas is most critical for moderate generalists and their conservation requires emphasis being placed on space–time resource heterogeneity; landscape features, of whatever dimensionality and structure, provide a vital framework for developing the variety of suitable conditions and resources for enhancing their diversity.     

Multi-scale habitat selection and foraging ecology of the eurasian hoopoe (<Emphasis Type="Italic">Upupa epops</Emphasis>) in pine plantations

Bird conservation can be challenging in landscapes with high habitat turnover such as planted forests, especially for species that require large home ranges and juxtaposition of different habitats to complete their life cycle. The eurasian hoopoe (Upupa epops) has declined severely in western Europe but is still abundant in south-western France. We studied habitat selection of hoopoes in pine plantation forests using a multi-scale survey, including point-counts at the landscape level and radio-tracking at the home-range scale. We quantified habitat use by systematically observing bird behaviour and characterized foraging sites according to micro-habitat variables and abundance of the main prey in the study area, the pine processionary moth (Thaumetopoea pityocampa). At the landscape scale, hoopoes selected habitat mosaics of high diversity, including deciduous woods and hedgerows as main nesting sites. At the home-range scale, hoopoes showed strong selection for short grassland vegetation along sand tracks as main foraging habitats. Vegetation was significantly shorter and sparser at foraging sites than random, and foraging intensity appeared to be significantly correlated with moth winter nest abundance. Hoopoe nesting success decreased during the three study years in line with processionary moth abundance. Thus, we suggest that hoopoes need complementation between foraging and breeding habitats to establish successfully in pine plantations. Hoopoe conservation requires the maintenance of adjacent breeding (deciduous woods) and foraging habitats (short swards adjacent to plantation edges), and consequently depends on the maintenance of habitat diversity at the landscape scale.     

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.     

Landscape connectivity and the role of small habitat patches as stepping stones: an assessment of the grassland biome in South America

Connectivity losses lead to a reduction of the amount of habitat resources that can be reached and used by species, and hence to a decline in the ranges and abundance of multiple taxa. Despite the recognized important role of small habitat patches for many species inhabiting fragmented landscapes, their potential contribution as stepping stones for maintaining overall landscape connectivity has received less attention. Using connectivity metrics based on a graph-theoretic approach we (i) quantified the connectivity of grassland patches in a sector of the Pampa region in Argentina, using a range of dispersal distances (from 100 to 10,000 m) representative of the scale of dispersal of different species; (ii) identified the most relevant patches for maintaining overall connectivity; and (iii) studied the importance of small patches (defined for different area thresholds of 5, 20, and 50 ha) as connectivity providers in the landscape. Although grassland patches were in general poorly connected at all distances, some of them were critical for overall connectivity and were found to play different crucial roles in the patch network. The location of small patches in the grassland network allowed them to function as stepping stones, yielding significant connectivity gains for species that move large distances (>5000 m) for the three area thresholds considered. Thus, under the spatial pattern of the studied landscape, species that move long distances would benefit from stepping stones, while less mobile organisms would benefit from, and mostly rely on the largest patches. We recommend that future management activities should (i) aim at preserving the grassland patches with the highest potential as stepping stones to promote landscape-level connectivity; and (ii) pay more attention to the conservation of key small patches, particularly given that usually they are those more vulnerable to land clearing for agriculture.     

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).     

Pervasive effects of dispersal limitation on within- and among-community species richness in agricultural landscapes

Aim To determine whether the effect of habitat fragmentation and habitat heterogeneity on species richness at different spatial scales depends on the dispersal ability of the species assemblages and if this results in nested species assemblages. Location Agricultural landscapes distributed over seven temperate Europe countries covering a range from France to Estonia. Methods We sampled 16 local communities in each of 24 agricultural landscapes (16 km²) that differ in the amount and heterogeneity of semi‐natural habitat patches. Carabid beetles were used as model organisms as dispersal ability can easily be assessed on morphological traits. The proximity and heterogeneity of semi‐natural patches within the landscape were related to average local (alpha), between local (beta) and landscape (gamma) species richness and compared among four guilds that differ in dispersal ability. Results For species assemblages with low dispersal ability, local diversity increased as the proximity of semi‐natural habitat increased, while mobile species showed an opposite trend. Beta diversity decreased equally for all dispersal classes in relation to proximity, suggesting a homogenizing effect of increased patch isolation. In contrast, habitat diversity of the semi‐natural patches affected beta diversity positively only for less mobile species, probably due to the low dispersal ability of specialist species. Species with low mobility that persisted in highly fragmented landscapes were consistently present in less fragmented ones, resulting in nested assemblages for this mobility class only. Main conclusions The incorporation of dispersal ability reveals that only local species assemblages with low dispersal ability show a decrease of richness as a result of fragmentation. This local species loss is compensated at least in part by an increase in species with high dispersal ability, which obscures the effect of fragmentation when investigated across dispersal groups. Conversely, fragmentation homogenizes the landscape fauna for all dispersal groups, which indicates the invasion of non‐crop habitats by similar good dispersers across the whole landscape. Given that recolonization of low dispersers is unlikely, depletion of these species in modern agricultural landscapes appears temporally pervasive.     

Home range and habitat selection of spotted owls in the central Sierra Nevada

We studied home range and habitat selection of radio-marked adult California spotted owls (Strix occidentalis occidentalis) randomly selected from among the breeding population of owls in the central Sierra Nevada, California from June to October 2006. The most parsimonious home-range estimate for our data was 555 ha (SE = 100 ha). Home-range size was positively correlated with the number of vegetation patches in the home range (habitat heterogeneity). We used resource selection ratios to examine selection of vegetation types by owls within our study area. Owl home ranges contained a high proportion of mature conifer forest, relative to its availability, although the confidence interval for this estimate overlapped one. We also used resource selection functions (RSF) to examine owl foraging habitat selection. Relative probability of selection of foraging habitat was correlated with vegetation classes, patch size, and their interaction. Owls showed highest selection rates for large patches (>10 ha) of pole-sized coniferous forest. Our results suggested that spotted owls in the central Sierra Nevada used habitat that contained a high proportion of mature conifer forest at the home-range scale, but at a finer scale (foraging site selection) owls used other vegetation classes interspersed among mature forest patches, consistent with our hypothesis that spotted owls may use other forest types besides old growth and mature forests when foraging. Our study provides an unbiased estimate of habitat use by spotted owls in the central Sierra Nevada. Our results suggest that forest managers continue to protect remaining mature and old-growth forests in the central Sierra Nevada because owl home ranges contain high proportions of these habitats. However, our results also showed that owls used younger stands as foraging habitat so that landscape heterogeneity, with respect to cover types, may be an important consideration for management but we did not attempt to relate our findings to fitness of owls. Thus management for some level of landscape heterogeneity for the benefit of owls should proceed with caution or under an adaptive management framework. © 2011 The Wildlife Society.     

Assessing the importance of individual habitat patches as irreplaceable connecting elements: An analysis of simulated and real landscape data

Habitat loss and fragmentation are considered to be severe threats to biodiversity, and maintaining natural levels of landscape connectivity may be one of the best responses to these issues. Graph-based habitat availability (reachability) metrics have been shown to be an appropriate method for a multifaceted but coherent landscape connectivity assessment. These metrics can be partitioned into three commensurate fractions (intra, flux, connector) that quantify the different ways in which habitat patches contribute to the overall landscape connectivity and habitat availability. In particular, the connector fraction measures the contribution of patches to the connectivity between other habitat areas as irreplaceable connecting elements or stepping stones. Because many conservation efforts and initiatives are focused on conserving or restoring corridors and other linkages between habitat areas, it is critical to understand more thoroughly the conditions under which investing in these connecting elements is an efficient management strategy. For this purpose, we analysed the contribution of the connector fraction in different simulated habitat patterns under different levels of habitat amount and fragmentation and in natural habitats for endangered forest bird species in Catalonia (Spain). We show that a prominent role of individual stepping stone patches as irreplaceable providers of habitat connectivity and availability arises only under a relatively narrow set of conditions, characterised by low habitat amount, high habitat fragmentation and modest to intermediate species dispersal abilities. We suggest that to support connectivity-related investments, it is necessary to focus on those few species or dispersal distance ranges that are likely to be both most dependent on and most benefited by the conservation or restoration of stepping stone patches. We conclude that the total amount of reachable habitat for a particular species is rarely determined by the contribution of individual connectors as the only dominant factor. Therefore, conservationists should be cautious not to overemphasise the importance of connectivity investments and to balance them with other conservation alternatives and strategies to promote species conservation in heterogeneous landscapes.     

Landscape-scale connectivity and fragment size determine species composition of grassland fragments

As a consequence of agricultural intensification and habitat fragmentation since the mid-20th century, biological diversity has declined considerably throughout the world, particularly in Europe. We assessed how habitat and landscape-scale heterogeneity, such as variation in fragment size (small vs. large) and landscape configuration (measured as connectivity index), affect plant and arthropod diversity. We focused on arthropods with different feeding behaviour and mobility, spiders (predators, moderate dispersal), true bugs (mainly herbivores and omnivores with moderate dispersal), wild bees (pollinators with good dispersal abilities), and wasps (pollinators, omnivores with good dispersal abilities). We studied 60 dry grassland fragments in the same region (Hungarian Great Plain); 30 fragments were represented by the grassland component of forest-steppe stands, and 30 were situated on burial mounds (kurgans). Forest-steppes are mosaics of dry grasslands with small forests in a matrix of plantation forests. Kurgans are ancient burial mounds with moderately disturbed grasslands surrounded by agricultural fields. The size of fragments ranged between 0.16–6.88 ha (small: 0.16–0.48 ha, large: 0.93–6.88 ha) for forest-steppes and 0.01–0.44 ha (small: 0.01–0.10 ha and large: 0.20–0.44 ha) for kurgans. Fragments also represented an isolation gradient from almost cleared and homogenous landscapes, to landscapes with relatively high compositional heterogeneity. Fragment size, connectivity, and their interaction affected specialist and generalist species abundances of forest-steppes and kurgans. Large fragments had higher species richness of ground-dwelling spiders, and the effect of connectivity was more strongly positive for specialist arthropods and more strongly negative for generalists in large than in small fragments. However, we also found a strong positive impact of connectivity for generalist plants in small kurgans in contrast to larger ones. We conclude that besides the well-known effect of enhancing habitat quality, increasing connectivity between fragments by restoring natural and semi-natural habitat patches would help to maintain grassland biodiversity.     

The influence of landscape diversity and heterogeneity on spatial dynamics of agrobiont linyphiid spiders: An individual-based model

Spiders are important generalist predators in natural pest control. However, agricultural fields are highly disturbed and ephemeral habitats, which present a number of challenges to the organisms living there; likewise landscape diversity and heterogeneity are also thought to be important factors in determining spider spatial dynamics. To investigate the interactions between these factors, we present an individual-based simulation model, which integrates life history characteristics of a typical agrobiont linyphiid spider with a dynamic spatially explicit landscape representation. The landscape contains several habitat types of varying quality and varies in time and space. Simulations showed that spatial landscape diversity (number of habitat types available for the spiders) is crucial for the persistence of spiders, but that spatial heterogeneity (spatial arrangement of patches) only had little impact on spider abundance. The necessary landscape diversity could either be provided by a diverse crop rotation or by including refuges in the form of less frequently managed habitats in the landscape. The presence of refuges greatly boosted numbers of spiders in the landscape as a whole. The most important characteristics of refuge were sanctuary from pesticides and extra prey availability, whereas tillage frequency mattered less. The simulations indicated that agrobiont linyphiids combination of high dispersal abilities and high reproductive rate enables it to exploit the transient resources of the different habitats in the agricultural landscape.     

A small mammal’s map: identifying and improving the large-scale and cross-border habitat connectivity for the hazel dormouse <Emphasis Type="Italic">Muscardinus avellanarius</Emphasis> in a fragmented agricultural landscape

Fragmentation and habitat loss pose major threats to global biodiversity. Especially forest dwelling species with small ranges and high habitat specialisation are affected by ongoing land use change. Building projects for infrastructural purposes, expanding settlements, and extensive agricultural areas are assumed to have a high impact on these species. The European Habitat’s Directive aims to conserve and restore habitat networks to lower these impacts. We propose that the idea of securing habitat networks for protected species should be incorporated within large scale landscape planning e.g. by modelling and improving corridors for umbrella species. Within a Danish-German project we developed a model demonstrating potential connecting corridors for Muscardinus avellanarius, a specialised forest dwelling rodent species with low dispersal ability. We used presence data and eco-geographical variables to find a data based time-efficient procedure which may be applied also in other species for future landscape planning. The habitat suitability model shows that the hazel dormouse occupies a narrow niche with highly suitable habitats comprising edge habitats. It indicates the preference of forest patches, linear structures and networks of the mentioned habitats. Along with connectivity the diversity of suitable habitats diversity is the major factor predicting hazel dormouse presence. For conservation management, we calculated habitat corridors and highlight sections with missing connections. This allowed us to accentuate regions of high management interest. The results represent the foundation not only for this cross-border conservation project, but also for long-term dormouse conservation on a federal-state level.     

Scale-dependent diversity effects of seed dispersal by a wild herbivore in fragmented grasslands

Dispersal limitation between habitat fragments is a known driver of landscape-scale biodiversity loss. In Europe, agricultural intensification during the twentieth century resulted in losses of both grassland habitat and traditional grassland seed dispersal vectors such as livestock. During the same period, populations of large wild herbivores have increased in the landscape. Usually studied in woodland ecosystems, these animals are found to disperse seeds from grasslands and other open habitats. We studied endozoochorous seed dispersal by roe deer (Capreolus capreolus) in fragmented grasslands and grassland remnants, comparing dispersed subcommunities of plant species to those in the established vegetation and the seed bank. A total of 652 seedlings of 67 species emerged from 219 samples of roe deer dung. This included many grassland species, and several local grassland specialists. Dispersal had potentially different effects on diversity at different spatial scales. Almost all sites received seeds of species not observed in the vegetation or seed bank at that site, suggesting that local diversity might not be dispersal limited. This pattern was less evident at the landscape scale, where fewer new species were introduced. Nonetheless, long-distance dispersal by large wild herbivores might still provide connectivity between fragmented habitats within a landscape in the areas in which they are active. Finally, as only a subset of the available species were found to disperse in space as well as time, the danger of future biodiversity loss might still exist in many isolated grassland habitats.     

Salinisation reduces biodiversity in neighbouring freshwater patches in experimental metacommunities

1. Aquatic ecosystems are biodiversity hot spots across many landscapes; therefore, the degradation of these habitats can lead to decreases in biodiversity across multiple scales. Salinisation is a global issue that threatens freshwater ecosystems by reducing water quality and local biodiversity. The effects of salinity on local processes have been studied extensively; however, the effects of salinisation or similar environmental stressors within a metacommunity (a dispersal network of several distinct communities) have not been explored.
2. We tested how the spatial heterogeneity and the environmental contrast between freshwater and saline habitat patches influenced cladoceran biodiversity and species composition at local and regional scales in a metacommunity mesocosm experiment. We defined spatial heterogeneity as the proportion of freshwater to saltwater patches within the metacommunity, ranging from a freshwater-dominated metacommunity to a saltwater-dominated metacommunity. Environmental contrast was defined as the environmental distance between habitat patches along the salinity gradient in which low-contrast metacommunities consisted of freshwater and low-salinity patches and high-contrast metacommunities consisted of freshwater and high-salinity patches.
3. We hypothesised that the α-richness of freshwater patches and metacommunity γ-richness would decrease as freshwater patches became less abundant along the spatial heterogeneity gradient in both low- and high-contrast metacommunities, because there would be fewer freshwater patches that could serve as source populations for declining populations. We hypothesised that low-contrast metacommunities would support more species across the spatial heterogeneity gradient than high-contrast metacommunities, because, via dispersal, low-salinity patches can support halotolerant freshwater species that can mitigate population declines in neighbouring freshwater patches, whereas` high-salinity patches will mostly support halophilic species, providing fewer potential colonisers to freshwater patches.
4. We found that α-richness of freshwater mesocosms and metacommunity γ-richness declined in saline-dominated metacommunities regardless of the environmental contrast between the freshwater and saline mesocosms. We found that environmental contrast influenced freshwater and saline community composition in low-contrast metacommunities by increasing the abundances of species that could tolerate low-salinity environments through dispersal, whereas freshwater and high-salinity communities showed limited interactions through dispersal.
5. Freshwater mesocosms had a disproportionate effect on the local and regional biodiversity in these experimental metacommunities, indicating that habitat identity may be more important than habitat diversity for maintaining biodiversity in some metacommunities. This study further emphasises the importance in maintaining multiple species-rich habitat patches across landscapes, particularly those experiencing landscape-wide habitat degradation.

     

Trophic Niche in a Raptor Species: The Relationship between Diet Diversity,Habitat Diversity and Territory Quality

Recent research reports that many populations of species showing a wide trophic niche (generalists) are made up of both generalist individuals and individuals with a narrow trophic niche (specialists), suggesting trophic specializations at an individual level. If true, foraging strategies should be associated with individual quality and fitness. Optimal foraging theory predicts that individuals will select the most favourable habitats for feeding. In addition, the “landscape heterogeneity hypothesis” predicts a higher number of species in more diverse landscapes. Thus, it can be predicted that individuals with a wider realized trophic niche should have foraging territories with greater habitat diversity, suggesting that foraging strategies, territory quality and habitat diversity are inter-correlated. This was tested for a population of common kestrels Falco tinnunculus. Diet diversity, territory occupancy (as a measure of territory quality) and habitat diversity of territories were measured over an 8-year period. Our results show that: 1) territory quality was quadratically correlated with habitat diversity, with the best territories being the least and most diverse; 2) diet diversity was not correlated with territory quality; and 3) diet diversity was negatively correlated with landscape heterogeneity. Our study suggests that niche generalist foraging strategies are based on an active search for different prey species within or between habitats rather than on the selection of territories with high habitat diversity.     

Effects of matrix heterogeneity on animal dispersal: from individual behavior to metapopulation-level parameters

Mounting theoretical and empirical evidence shows that matrix heterogeneity may have contrasting effects on metapopulation dynamics by contributing to patch isolation in nontrivial ways. We analyze the movement properties during interpatch dispersal in a metapopulation of Iberian lynx (Lynx pardinus). On a daily temporal scale, lynx habitat selection defines two types of matrix habitats where individuals may move: open and dispersal habitats (avoided and used as available, respectively). There was a strong and complex impact of matrix heterogeneity on movement properties at several temporal scales (hourly and daily radiolocations and the entire dispersal event). We use the movement properties on the hourly temporal scale to build a simulation model to reconstruct individual dispersal events. The two most important parameters affecting model predictions at both the individual (daily) and metapopulation scales were related to the movement capacity (number of movement steps per day and autocorrelation in dispersal habitat) followed by the parameters representing the habitat selection in the matrix. The model adequately reproduced field estimates of population-level parameters (e.g., interpatch connectivity, maximum and final dispersal distances), and its performance was clearly improved when including the effect of matrix heterogeneity on movement properties. To assume there is a homogeneous matrix results in large errors in the estimate of interpatch connectivity, especially for close patches separated by open habitat or corridors of dispersal habitat, showing how important it is to consider matrix heterogeneity when it is present. Movement properties affect the interaction of dispersing individuals with the landscape and can be used as a mechanistic representation of dispersal at the metapopulation level. This is so when the effect of matrix heterogeneity on movement properties is evaluated under biologically meaningful spatial and temporal scales.     

Constructed wetlands support bats in agricultural landscapes

Bats are known to use aquatic habitats as foraging habitats. Agricultural intensification is perceived to be a main reason for the loss of wetlands. However, artificial wetland creation (i.e. the construction of retention-ponds) in the agricultural landscape aiming at water or nutrient retention has recently gained importance. We evaluated to what extent bats use these artificial wetlands as foraging habitats in an agricultural landscape.Bat activity and prey density were compared in matched pairs at retention-ponds and neighbouring vineyard sites using stationary bat-detectors and sticky-traps, respectively. To examine if bat activity is related to the number of bat individuals, a thermal infrared imaging camera was used. Pipistrellus pipistrellus, the dominant species, served as an example to assess habitat selection between retention-ponds and vineyards. This was performed by relating foraging activity to the available area available within the potential home-range.Total bat activity and nocturnal prey density were significantly higher above the retention-ponds than above vineyards. High differences of activity levels between the ponds and the respective vineyard sites were found for Pipistrellus spp. (P. pipistrellus and P. nathusii) and Myotis spp. (M. daubentonii and M. mystacinus), being about 180 times and 50 times higher above the retention-ponds, respectively. A significant correlation was found between recorded bat activity and the maximum number of bat individuals observed with a thermal infrared imaging camera. When relating foraging activity to habitat availability within the assumed home-range of P. pipistrellus, retention-ponds had on average a higher importance as a foraging habitat than the complete vineyard area although they covered less than 0.1% of its area.This study indicates that artificial wetlands such as retention-ponds provide foraging habitats for bats. Therefore, creation of wetlands in intensively used agricultural landscapes benefits bats.     

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.     

Practical tool for landscape planning? An empirical investigation of network based models of habitat fragmentation

This study presents a graph-theoretical modelling approach using daily movements and habitat demands of different target bird species in an urban context to assess: 1) habitable land cover types, 2) threshold distances between patches of habitat, 3) the required minimum accessible habitat areas and 4) the effects of barriers and stepping stones. The modelling approach is tested using empirical data from field surveys in the urban area of Stockholm, Sweden.
The results show that groups of small habitat patches can house the same species as larger contiguous patches as long as they are perceived as functionally connected by the inhabitant organisms. Furthermore, we found that binary habitat/non-habitat representations of the landscape could roughly explain the variation in species occurrence, as long as habitat was properly defined. However, the explanatory power of the landscape models increased when features of matrix heterogeneity such as stepping stones and barriers were accounted for.
Synthesis and application: in a world where forest ecosystems are becoming increasingly fragmented there is an urgent need to find comprehensive and scientifically relevant methods for managing and planning ecosystems. This study shows that: 1) groups of well placed small habitat patches can, together, be sufficient to attract birds in intensively developed areas, 2) the presented modelling approach can help identify such groups of patches, 3) matrix heterogeneity should preferably be accounted for, and 4) proper assessments of habitable land cover types are important. Finally, we argue that the modelling approach applied here may substantially improve landscape management and planning at scales ranging from whole landscapes down to neighbourhoods.     

Foraging habitats and foraging distances of bumblebees, Bombus spp. (Hym., Apidae), in an agricultural landscape

Abstract: In selected foraging habitats of an agricultural landscape flower visits of bumblebees and community structure of foraging bumblebees were studied, with special regard to the role of crops as super-abundant resources. Most crops represent temporal foraging habitats with high abundance of bumblebees but mainly with low diversity in the bumblebee forage community, in contrast to permanent foraging habitats such as, for example, a hedgerow. The high numbers of bumblebees in the monoculture of crop plantations consisted mainly of short-tongued bumblebee species. The role of foraging distances for the visitation rate of foraging habitats was studied by performing capture–recapture experiments with natural nests of Bombus terrestris , Bombus lapidarius and Bombus muscorum . Differences were found on the species as well as the individual level. The foraging distances of B. muscorum were more restricted to the neighbourhood of the nesting habitat than the foraging activity of B. terrestris and B. lapidarius . High percentages of B. terrestris workers were recaptured while foraging on super-abundant resources in distances up to 1750 m from the nest. Isolated patches of highly rewarding forage crops, in agricultural landscapes, are probably only accessed by bumblebee species with large mean foraging distances, such as the short-tongued B. terrestris . Species like the rare, long-tongued B. muscorum depend on a close connection between nesting and foraging habitat. A restricted foraging radius might be one important factor of bumblebee species loss and potential pollinator limitation in modern agricultural landscapes. Furthermore, long-distance flights of bumblebee pollinators have to be considered in the present discussion on gene flow from transgenic plant species on a landscape scale.