Patch Attributes Research Articles

Breeding season microhabitat use by Cerulean Warbler (Setophaga cerulea) in an experimentally-managed forest

Cerulean Warbler (Setophaga cerulea) populations have undergone significant declines over the past four decades, and the species is considered state endangered in Indiana. These migratory songbirds nest in the canopies of mature deciduous forests throughout eastern North America, but local microhabitat preferences vary by geography and scale, and may influence differential nest success rates across the breeding range. Between 2010 and 2015, we searched for nests, mapped out male territories, and monitored nest success in the Hardwood Ecosystem Experiment in central Indiana. We collected data on a variety of microhabitat features at the territory, nest patch, and nest site levels, as well as at non-use points, and evaluated the influence of several characteristics on nest success. We evaluated nest patch and territory attributes using binomial generalized linear models and nest success with a generalized linear mixed-effects model. Cerulean Warblers selected nest patches characterized by taller trees and located on ridges and valleys rather than on mid-slopes, while males selected territories that were located on steeper northeast-facing slopes closer to roadways than random points. Successful nests were placed lower in the nest tree and were found in areas with shorter trees; several features selected by Cerulean Warblers at the nest patch and territory levels were associated with lower nest success rates. As elsewhere in the range, white oak was an important nest tree species. In developing forest management strategies, land managers must strive to balance small-scale microhabitat preferences with the need for regenerating oak-hickory forests to sustain Cerulean Warbler breeding populations.

Fragmentation metric proxies provide insights into historical biodiversity loss in critically endangered grassland

Landscape transformation causes habitat loss and fragmentation, which poses the greatest threat to biodiversity globally. In a fragmented landscape the persistence of species is affected by the amount of habitat and the spatial attributes of individual habitat patches. As baseline biodiversity information is often unavailable to assess the effects of transformation on biodiversity, quantifying changes in patch metrics over time could be a useful indicator of biodiversity changes in fragmented landscapes. We investigate historical land cover changes due to increased anthropogenic land uses in a highly fragmented, critically endangered grassland, the Woodbush Granite Grassland, South Africa. We test how the spatial attributes of habitat patches were affected by habitat loss and fragmentation over two extended time-periods, and use these results to infer likely threats to biodiversity over these periods. We used repeat aerial photography to analyse the drivers and extent of land cover loss and the changes in five fragmentation metrics over a 60year period. The overall grassland extent decreased significantly over the 60-year period, mainly due to increased timber plantations, with an estimated 6.1% of the original extent of the grassland remaining in 2008. Increases in patch isolation due to habitat loss were most pronounced between 1948 and 1977, while between 1977 and 2008 patch sizes decreased and edge effects increased. This extensive habitat loss and increase in fragmentation are likely to have had considerable impacts on the biodiversity of the region, which is supported by anecdotal evidence of species extinctions and local extinctions. Because so little of the vegetation type remains, it is imperative that the last vestiges of this vegetation type are protected from transformation and further habitat degradation. In summary, we show how, faced with a lack of biodiversity data, fragmentation patch metrics can be used to quantify threats to biodiversity.

Rainforest seed rain into abandoned tropical Australian pasture is dependent on adjacent rainforest structure and extent

AbstractIt is well known that the recovery of abandoned tropical pastures to secondary rainforest benefits from the arrival of seeds from adjacent rainforest patches. Less is known, however, about how the structural attributes of adjacent rainforest (e.g. tree density, canopy cover and tree height) impact seed rain patterns into abandoned pastures. Between 2011 and 2013, we used seed traps and ground seed surveys to track the richness and abundance of rainforest seeds entering abandoned pastures in Australia's wet tropics. We also tested how seed rain diversity is related to the distance from forest, the proportion of forest cover in the landscape and several structural attributes of adjacent forest patches, specifically average tree height, canopy cover, tree species richness and density. Almost no seeds were captured in elevated pasture seed traps, even near forest remnants. Abundant forest seeds were found in ground surveys but only within 10 m of forest edges. In ground surveys, seeds from wind‐dispersed species were more abundant, but less species rich, than animal‐dispersed species. A survey of pasture seedling recruits suggested that some forest seeds must be dispersing more than 10 m into pasture at very low frequencies, but only a few species are establishing there. Recruits were predominantly animal‐dispersed not wind‐dispersed species. In addition to distance from forest and the proportion of forest within a 100‐ to 200‐m radius of sampling sites, the richness and density of adjacent forest trees were the most important factors for explaining the probability of seed occurrence in abandoned pastures. Results suggest that without some restoration assistance, the recovery of abandoned pastures into secondary rainforest in Australia's tropical rainforests will likely be limited, at least in part, by a very low rate of seed dispersal away from forest edges and by the diversity and density of trees in adjacent remnant forests.

Fine Scale Movements of the Butterfly Plebejus argus in a Heterogeneous Natural Landscape as Revealed by GPS Tracking

The study of butterfly movements has focused on dispersal behaviour in the framework of population persistence in heterogeneous landscapes. The ecological significance of routine movements has received less attention. These movements may be influenced by structural attributes of habitat patches or may reflect the distribution of food, mates, host plants or ecological interactions. The relative influence of structural and functional factors on flight patterns is poorly understood, partly because butterfly movements are often described by simplified representations of actual trajectories. Using high-resolution GPS tracking we obtained accurate trajectories of routine movements of Plebejus argus in a heterogeneous natural landscape. Habitat quality in patches was ranked according to the abundance of host and nectar plants as well as the abundance of nests of its mutualistic ant Lasius niger. Movements were slow and winding in high quality habitats whereas faster, straighter flights were observed in poor habitats. At edges, butterflies often crossed without any exploratory behaviour towards patches of better quality, suggesting they may use cues to detect resources at some distance. Conversely, individuals usually stayed in the patch after exploring edges with other patches of lower quality. However, scanning also preceded exits towards clearly unsuitable habitat, compatible with transfers to distant high-quality patches. We conclude that patterns of movement in P. argus were explained by spatial heterogeneity defined by functional rather than structural criteria. We also show that inexpensive handheld GPS receivers allow depicting detailed flying trajectories in open flat terrain revealing complex behavioural patterns.

基于图论的景观连接度量化方法应用研究——以福建省闽清县自然森林为例

PDF HTML阅读 XML下载 导出引用 引用提醒 基于图论的景观连接度量化方法应用研究——以福建省闽清县自然森林为例 DOI: 10.5846/stxb201507301599 作者: 作者单位: 复旦大学环境科学与工程系,复旦大学环境科学与工程系 作者简介: 通讯作者: 中图分类号: 基金项目: 国家社科基金重大资助项目（14ZDB140） Evaluation method for landscape connectivity based on graph theory: a case study of natural forests in Minqing County, Fujian Province Author: Affiliation: Department of Environmental Science and Engineering,Fudan University,Department of Environmental Science and Engineering,Fudan University Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:气候变化和人类活动导致的自然生境丧失和生境片断化使全球生物多样性面临威胁，而有效缓解这类问题的手段之一是维持自然生境的景观连接度。图论分析法作为景观连接度研究的新途径成为研究领域热点，但仍然存在提高距离阈值取值的科学性、充分解读图论连接度指数等有待探究的问题。以闽清县自然森林为对象使用图论分析方法进行了景观连接度的量化研究，提出并使用了距离阈值综合取值方法，联合使用了多种景观连接度指数。研究结果表明，距离阈值综合取值方法能够提高取值的准确性并具有广泛适用性，二进制连接度指数与概率连接度指数能够从不同角度指示景观结构和斑块重要性格局。研究区域90%以上的景观连接度由主要景观组分维持，数量很少的极高重要值斑块数能够对整体连接度水平产生显著影响。面积越大的斑块重要性指数越高，但是极高重要值斑块的重要性指数并不完全取决于斑块面积，而更多的与斑块位置等因素相关。本研究进一步完善图论分析法在景观连接度研究方面的应用，对生物多样性保护工作具有参考价值。 Abstract:The loss of natural habitat and habitat fragmentation, caused by climate change and human activities is a seriously threat global biodiversity. Maintaining landscape connectivity of natural habitats is one of the most effective methods for alleviating these related problems. Landscape connectivity describes the degree to which the landscape facilitates or impedes ecological flow and movement among habitat patches. By integrating information related to landscape structure and ecological processes, landscape connectivity describes the effects of habitat fragmentation on the organisms living within the landscape. Graph theory provides powerful tools for assessing landscape connectivity, and has become a popular research method in recent years. However, some issues related to the application of graph-based methods still need to be discussed and analyzed, such as choosing a proper threshold distance and gaining an understanding of various connectivity indices. This study used the graph theory method to assess the landscape connectivity of natural forest in Minqing County, Fuzhou City, China. A comprehensive method was utilized to assign a reasonable threshold distance, which consisted of three steps:namely, determining the range of the maximum dispersal distance of a focal species, enumerating a gradient distance value, and an experiment using link thresholding. Six indices were used to assess the landscape connectivity of the study area:number of links (NL), number of components (NC), Harary index (H), area-weighted flux (AWF), integral index of connectivity (ⅡC), and probability of connectivity (PC). We harvested data related to the natural commonweal forests of Mingqing County from the data of 2010 National Forest Resource Inventory using ArcGIS 10.2 to define habitat patches in the study area. The six landscape connectivity indices were calculated using Conefor Sensinode 2.6 software. Using the comprehensive method, 1 km was found to be the optimal threshold distance that best presented the structure of the landscape. A medium-level structure, consisting of 56 components was detected using the NL and NC indices. Based on the binary (H, ⅡC) and probability (AWF, PC) indices, the level of landscape connectivity of the natural forests in Minqing is comparatively low. The patch importance indices (dIs) aided in identifying the most important patches that could potentially affect the overall level of connectivity. We determinded that the main component provided 90% of the connecting functions in maintaining the landscape connectivity; however, losing a single critical patch could significantly reduce overall connectivity. The results indicated that this new method involving evaluation of the threshold distance could help researchers determine more accurate distance values for landscape connectivity, and therefore, this method would be applicable for both scientific research and planning. In addition, binary and probability indices could be used together to reveal landscape structure and the spatial patterns of patch importance. In our analysis, we found that the values of dI are generally proportional to the area of patches; however, patch area is not the dominate element that determines the dI values of the most critical patches. Other patch features, such as patch position, may have greater influence on the dI values for the extremely important patches. This may be caused by a commonly used but inaccurate method of evaluating patch attributes. This topic required further investigation and improvement in future studies. In conclusion, this study will help promote the application of graph theory in research studies related to landscape connectivity, and can provide guidance for land managers tasked with conserving biodiversity. 参考文献 相似文献 引证文献

Potential impacts of aridity on structural and functional status of a southern Mediterranean Stipa tenacissima steppe

Over the last decades, there has been a growing interest in evaluating the predicted potential impacts of future climatic conditions on ecosystem functioning. Ecological indicators developed to assess ecosystem functioning strongly rely on soil and vegetation variables.In the current investigation, we evaluated the structural and functional status of a southern Mediterranean Stipa tenacissima steppe along an increasing aridity gradient. We estimated also the predicted effects of aridity on their functioning.The wide variation of LFA indices, vegetation structural attributes and soil properties among the different study sites revealed structural and functional heterogeneity in S. tenacissima steppes with the increasing aridity. Correlations obtained between LFA indices and most patch attributes showed the importance of vegetation structural attributes on the functioning of S. tenacissima steppes. On the other hand, correlations found between LFA indices and most measured soil variables verified the significance of LFA indices in monitoring soil functioning in southern Mediterranean S. tenacissima steppes.The strong negative relationships observed between aridity and stability, nutrient cycling indices demonstrated that increasing aridity can reinforce erosive processes and deteriorate nutrient cycling (i.e. aridity decreased soil carbon, nitrogen and enzymatic activities).Similarly, aridity was negatively related to vegetation structural attributes including patch cover and landscape organization index. This finding suggests that any increase in aridity can promote the loss of perennial vegetation cover.The current investigation highlighted that predicted increasing aridity will dramatically affect the functioning of southern Mediterranean S. tenacissima steppes, especially in the more arid areas.

Extinction debt of a common shrub in a fragmented landscape

Fil: Gonzalez Varo, Juan P.. Consejo Superior de Investigaciones Cientificas. Estacion Biologica de Donana; Espana

Examining the role of landscape structure and dynamics in alien plant invasion from urban Mediterranean coastal habitats

This paper aims to disentangle the effects of both current landscape structure and recent land use-change on alien plant invasion in urban Mediterranean coastal habitats. Patches of four habitat types (rock outcrops, sand dunes, scrublands and forests) of different sizes and surrounding landscape compositions were selected along the coast of the Metropolitan Region of Barcelona (NE Spain). Attributes of habitat patches, historical (1956) and current landscape composition around them, land-cover changes (1956–2005) and other environmental and geographic factors within these patches were obtained. The association of these attributes with alien plant richness, abundance and composition was investigated using GLM and CCA. Alien species richness was mostly explained by patch size and shape and built-up area proportion from 1956 and 2005 in a 50m buffer around patches. Alien species abundance was mostly related to patch shape, temperature, rainfall, land-cover changes within patches and cropland cover of 1956 in a 50m buffer around patches. Alien species composition was primary related to habitat type, temperature, land-cover changes within patches and the composition of the surrounding landscape. Results suggest that landscape factors affect alien species richness and abundance differently, which are indicative of species colonization and spread, respectively. Landscape history positively affects both colonization and spread, with evidence for a colonization credit related with past urban cover, and the association between recent patch dynamics and present aliens spread. Results highlight the importance of including landscape structure and dynamics in the management of plant invasions in coastal Mediterranean habitats, especially in metropolitan regions.

Community attributes determine facilitation potential in a semi-arid steppe

a b s t r a c t Studies on positive plant-plant relations have traditionally focused on pair-wise interactions. Conversely, the interaction with other co-occurring species has scarcely been addressed, despite the fact that the entire community may affect plant performance. We used woody vegetation patches as models to eval- uate community facilitation in semi-arid steppes. We characterized biotic and physical attributes of 53 woody patches (patch size, litter accumulation, canopy density, vegetation cover, species number and identity, and phylogenetic distance), and soil fertility (organic C and total N), and evaluated their relative importance for the performance of seedlings of Pistacia lentiscus, a keystone woody species in western Mediterranean steppes. Seedlings were planted underneath the patches, and on their northern and south- ern edges. Woody patches positively affected seedling survival but not seedling growth. Soil fertility was higher underneath the patches than elsewhere. Physical and biotic attributes of woody patches affected seedling survival, but these effects depended on microsite conditions. The composition of the community of small shrubs and perennial grasses growing underneath the patches controlled seedling performance. An increase in Stipa tenacissima and a decrease in Brachypodium retusum increased the probability of survival. The cover of these species and other small shrubs, litter depth and community phylogenetic dis- tance, were also related to seedling survival. Seedlings planted on the northern edge of the patches were mostly affected by attributes of the biotic community. These traits were of lesser importance in seedlings planted underneath and in the southern edge of patches, suggesting that constraints to seedling estab- lishment differed within the patches. Our study highlights the importance of taking into consideration community attributes over pair-wise interactions when evaluating the outcome of ecological interac- tions in multi-specific communities, as they have profound implications in the composition, function and management of semi-arid steppes.

The Function of Plant Patches and Woodland Ecosystem in Utilized and Un-Utilized Sites (Case Study: Forest Region of Aloostan, Golestan Province)

Functional and structural features of plant patches in different ecological sites are used as ecological threshold predictors in natural ecosystems. This study aimed to: (i) find the effect of types of plant patches (based on live form) on potential and function of woodland ecosystems and (ii) compare plant patches function in utilized and un-utilized sites on the south slope of Alborz Mountain, Golestan Province. For this purpose, eleven parameters of the soil surface attributes of each plant patches were assessed using the Landscape Function Analysis methodology across four transects of 100 meters located at the highest slope. Then stability, nutrient cycle, and infiltration indicators of each plant patches were calculated using Excel software. These indicators were tested between two sites and within the plant patch groups using Student t-test and Duncan comparison of means analysis, respectively, by SPSS (Statistical Package for the Social Sciences) software. The study did not find a significant difference between the two sites and the plant patches, except for the stability indicator between the sites. Also, results showed different functions within the groups of the sites, especially in the woody plant patches with the highest function in all the indicators in both sites. Woody and woody-grass were the most important ecological indicators at utilized and un-utilized sites. The results of this study suggest that the use of Landscape Function Analysis provides a simple, rapid and consistent method in assessment of the forest ecosystems health.

Association between Small Rodents and Forest Patch and Landscape Structure in the Fragmented Lacandona Rainforest, Mexico

Identifying the main factors that shape biological communities in human-modified tropical landscapes has key ecological and conservation implications. In these emerging landscapes, the maintenance of biodiversity may depend on both forest patch and landscape attributes, but this topic has been poorly investigated. Here we assessed the landscape (forest cover, degree of fragmentation, and matrix composition) and patch metrics (tree basal area, patch size, and isolation) that best predicted the abundance and diversity of small terrestrial rodents in the Lacandona rainforest, Mexico. In 2011 and 2012, we sampled rodent communities in 12 sites (9 patches and 3 areas within a continuous forest). We assessed the landscape characteristics within a 100-ha buffer from the center of each site. In total, we captured 78 individuals in 2011 and 82 individuals in 2012 from four species: Desmarest's Spiny Pocket Mouse ( Heteromys desmarestianus), Rice Rat ( Oryzomys sp.), Mexican Deermouse ( Peromyscus mexicanus), and Toltec Cotton Rat ( Sigmodon toltecus). Only the abundance of rodents was strongly associated with forest patch and landscape attributes, but the best predictors differed between years. The degree of fragmentation, matrix composition, and patch isolation showed the lowest impact on rodents, probably because the region is dominated by a highly heterogeneous anthropogenic matrix. Community composition was weakly related to patch and landscape attributes in both years. Overall, our findings suggest that almost a half-century of land use in the region has not led to significant changes at the community level, but additional long-term studies including arboreal species are needed before a strong conclusion can be drawn.

Very high resolution Earth Observation features for testing the direct and indirect effects of landscape structure on local habitat quality

Modelling the empirical relationships between habitat quality and species distribution patterns is the first step to understanding human impacts on biodiversity. It is important to build on this understanding to develop a broader conceptual appreciation of the influence of surrounding landscape structure on local habitat quality, across multiple spatial scales. Traditional models which report that ‘habitat amount’ in the landscape is sufficient to explain patterns of biodiversity, irrespective of habitat configuration or spatial variation in habitat quality at edges, implicitly treat each unit of habitat as interchangeable and ignore the high degree of interdependence between spatial components of land-use change. Here, we test the contrasting hypothesis, that local habitat units are not interchangeable in their habitat attributes, but are instead dependent on variation in surrounding habitat structure at both patch- and landscape levels. As the statistical approaches needed to implement such hierarchical causal models are observation-intensive, we utilise very high resolution (VHR) Earth Observation (EO) images to rapidly generate fine-grained measures of habitat patch internal heterogeneities over large spatial extents. We use linear mixed-effects models to test whether these remotely-sensed proxies for habitat quality were influenced by surrounding patch or landscape structure. The results demonstrate the significant influence of surrounding patch and landscape context on local habitat quality. They further indicate that such an influence can be direct, when a landscape variable alone influences the habitat structure variable, and/or indirect when the landscape and patch attributes have a conjoined effect on the response variable. We conclude that a substantial degree of interaction among spatial configuration effects is likely to be the norm in determining the ecological consequences of habitat fragmentation, thus corroborating the notion of the spatial context dependence of habitat quality.

Sample-based estimation of “contagion metric” using line intersect sampling method (LIS)

Quantification of landscape pattern is of primary interest in landscape ecological studies. For quantification purposes, a large number of landscape metrics have been developed, with definitions based on measurable patch attributes. Calculation of these metrics is commonly conducted on wall-to-wall maps, whereas a new interest is to use sample data. It is argued that a sample survey takes less time and results are more reliable. The overall objective in this paper was to present the potential of the line interest sampling method for estimating a special contagion metric. The specific objective was to assess statistical properties in terms of root mean square error (RMSE) and bias of the contagion metric estimator. This study was conducted on 50.1 km2 already manually delineated land cover maps from the National Inventory of Landscape in Sweden. Monte-Carlo sampling simulation was employed to assess the statistical properties of the estimator. The simulation was conducted for different combinations of two sampling designs, four sample sizes, five lines transect configurations, three lines transect lengths, and two classification systems. The systematic sampling design resulted in lower RMSE and bias compared to a simple random one. Both RMSE and bias of the contagion estimator tended to decrease with increasing sample size and line transect length. We recommend using a combination of systematic sampling design, straight line configuration and long line transect. We conclude that there is no need to use mapped data and thus polygon delineation errors can considerably be reduced or eliminated.

Beneficial insects in urban environments: Parasitism rates increase in large and less isolated plant patches via enhanced parasitoid species richness

In urban habitats, plant resources for herbivorous insects and their parasitoids are spatially subdivided and embedded in a matrix of built environment. These conditions could affect insect colonization and persistence, leading to altered trophic interactions. Here we tested whether spatial attributes (size and isolation) of patches of an urban spontaneous plant (Commelina erecta) affect the parasitism rates on a specialist leaf miner (Liriomyza commelinae) from its diverse parasitoid assemblage. To achieve this goal we performed an observational study in Córdoba city (Argentina), by sampling 893 naturally established C. erecta patches on 18 neighborhoods. Overall parasitism rates of the leaf miner augmented at increasing patch size and decreasing patch isolation, and those effects were mediated by changes in parasitoid richness. Leaf miners in larger or less isolated plant patches supported more parasitoid species which, independently of host abundance, led to higher parasitism rates. Individual parasitoid species showed different responses to patch attributes, with some species being more efficient in large or less isolated plant patches whereas parasitism rates of other species were independent of patch attributes. Our results highlight the importance of spatial availability of urban plant resources for parasitoid diversity and for the key process of biological control in which they are involved. Understanding how natural enemies respond to the patchiness of herbivore resources in the urban context could contribute to the development of strategies to preserve beneficial insects in these highly modified landscapes.

Massive floral display affects insect visits but not pollinator‐mediated pollen transfer inRhododendron ferrugineum

Fragmentation of natural vegetation creates one of the largest threats to plant-pollinator interactions. Although fragmentation impacts on plant populations have been explored in many, mainly herbaceous, species, the response of wild mass-flowering species is poorly known. Here, we studied 28 heathland patches dominated by the mass-flowering shrub Rhododendron ferrugineum, each presenting different R.ferrugineum floral display sizes (total inflorescence number per patch) and patch isolation (median distance to the three nearest patches). We assessed the impacts of these two factors on (i) heathland patch visitor assemblage (considering R.ferrugineum versus surrounding community) and (ii) R.ferrugineum flower visitation rate and pollen transfer limitation (comparing seed set from emasculated to pollen-supplemented flowers). We found that diversity and abundance of bees visiting R.ferrugineum in heathland patches significantly decreased with decreasing R.ferrugineum floral display, while overall visitor density per patch and flower visitation rate increased. Moreover, a decrease in massive floral display and increase in patch isolation resulted in reduced visitor density in the surrounding community. Even in patches with few individuals, we found disproportionate visitor abundance in R.ferrugineum compared to the surrounding community. Finally, pollen transfer limitation in R.ferrugineum was neither affected by visitation rate nor by patch attributes. By disproportionally attracting pollinators from co-flowering species, and probably promoting geitonogamous pollen transfer, the mass-flowering trait appears adequate to compensate, in terms of conspecific pollen transfer, for the decrease in visitor diversity and abundance and in mate availability, which usually result from population fragmentation.

Mangroves as maternity roosts for a colony of the rare east-coast free-tailed bat (Mormopterus norfolkensis) in south-eastern Australia

Context Maternity roosts of insectivorous bats (where females raise young) are critical to the conservation of threatened species as roost quality can influence reproductive success. Additionally, threatened species may have specialised requirements or unusual behaviour, which may be overlooked without targeted investigation. Aims To explore which factors influence the roost selection of Mormopterus norfolkensis, by comparing day roosts, identified via radio-tracking, with environmental variables collected at tree, patch and landscape scales. Methods We collected a range of variables describing maternity roosts and surrounding patches, including internal measurements of hollows and microclimate. Additionally, we derived landscape-scale variables using a geographic information system. We then explored which variables best explained roost occurrence using logistic regression. Key results Nineteen lactating females and two male M. norfolkensis were tracked to 40 roost trees, mostly grey mangrove, Avicennia marina subsp. australasica. Lactating females were found to be faithful to two patches of mangrove forest close to where they were captured, regularly switched roosts and roosted in hollows singularly or in small groups. The attributes of mangrove patches, especially a high proportion of hollows, better predicted roosting by lactating females than roost-tree or landscape characteristics. Additionally, although the microclimate of roost hollows was not significantly different from ambient mangrove conditions, the mangrove forest was slightly more stable and had higher humidity than did other nearby habitats. Conclusions Contrary to predictions, maternity roosting group sizes were relatively small, indicating that bats were not deriving thermoregulatory benefits from communal living. However, we suggest that lactating females may benefit from the operation of a fission–fusion society among the colony as a whole. Additionally, the mature mangrove forest could offer unique roosting opportunities for bats because they support high densities of hollow-bearing trees, a stable microclimate and potentially low abundances of predators and competitors. Implications This is one of few international bat–mangrove studies and it illustrates that threatened species can behave unexpectedly and may be overlooked in conservation strategies that are based largely on anecdotal observations. We encourage further research into the value of mangrove forests to terrestrial fauna globally.

Assessing environmental requirements effects on forest fragmentation sensitivity in two arboreal rodents

The study of the effect of habitat fragmentation on species that inhabit residual patches requires the investigation of the relationship existing between species distribution and landscape components. To understand which components of landscape mosaics are more influential for species’ persistence, we compared the distribution of two arboreal rodents proved to be sensitive to habitat fragmentation, the hazel dormouse Muscardinus avellanarius and the red squirrel Sciurus vulgaris. Their occurrence in residual oak woods in central Italy was studied with nest-boxes and hair-tubes, developing a new method for hair analysis. Their distributions were analysed considering patch, matrix composition and configuration, and landscape vegetation variables. The two species showed a different degree of plasticity, with the squirrel being significantly more specialised at the landscape scale. The comparison of the two distribution patterns highlighted the influence of different ecological constraints and the existence of different strategies to cope with fragmentation. Patch size and patch attributes were generally weaker determinants of occurrence, compared to landscape metrics. The squirrel presence was significantly influenced by the presence of shared perimeter between hedgerows and woods and by the lack of isolation of the residual patches, suggesting the use of several fragments to compensate the low habitat quality. Conversely the hazel dormouse seemed to be more affected by the internal management of the woods, and in particular by the mean DBH. Our results highlight how the recognition of the extrinsic constraints and the influence of multi-scale habitat selection may help guiding land use management, to ensure species conservation in profoundly exploited landscapes.

Effects of multiple factors on plant diversity of forest fragments in intensive farmland of Northern Portugal

The joint and independent effects of dominant tree species, forest patch spatial attributes, and forest structure and management as drivers of plant species richness and composition in small forest patches scattered within an intensive agricultural landscape were addressed. In a landscape with scattered urban and intensive dairy agricultural areas in north-west Portugal, within which small forest patches (dominated by pines, eucalypts, or both) represent semi-natural habitat islands, 50 small forest patches, with areas ranging between 0.3 and 3 ha, were selected and surveyed for vascular plant diversity, within dairy farming landscape mosaics dominated by annual forage crops. Explanatory variables were composed of three datasets derived either from GIS mapping or field observations: forest type (dominant tree species), forest patch spatial attributes (patch area and shape index), and measures of forest management and structure (diameter at breast height, tree density per hectare, and percentage cover of vegetation strata). Variations in these forest patch attributes were assessed across forest types, and related to measures of plant diversity (total, native, alien, woody, and herbaceous species richness). Redundancy analysis with variance partitioning was applied to evaluate the joint and independent effects of the three sets of variables on species assemblages. The recent shift in canopy dominance from pine to eucalypt observed in the region appears to be related to a (nonsignificant) tendency for the increase of patch area and to the decrease of patch complexity, as well as several changes in forest structure and management, expressed as a trend to denser tree canopies and lower cover of understory plants. Dominant tree species and attributes related to forest structure and management were the most important factors determining plant diversity. The joint effect of the dominant tree species and forest structure and management resulted in lower levels of plant species richness in eucalypt plantations. These were also more prone to invasion by alien species, probably due to decreased biotic resistance from unsaturated native plant assemblages. Our results draw attention to the importance of dominant tree species and management practices for the maintenance of plant diversity levels (species richness and composition) in dairy landscape mosaics, highlighting the importance of the remnants of semi-natural forests as refuges for plant diversity in the landscape context. Nonetheless, forest plant diversity could further be fostered by promoting naturalness of pine stands and the regeneration of native oak woodlands in some forest areas. This would also diversify the range of ecosystem services that could be provided by forest areas in these peri-urban farmlands.

Historical changes in caribou distribution and land cover in and around Prince Albert National Park: land management implications

In central Saskatchewan, boreal woodland caribou population declines have been documented in the 1940s and again in the 1980s. Although both declines led to a ban in sport hunting, a recovery was only seen in the 1950s and was attributed to wolf control and hunting closure. Recent studies suggest that this time, the population may not be increasing. In order to contribute to the conservation efforts, historical changes in caribou distribution and land cover types in the Prince Albert Greater Ecosystem (PAGE), Saskatchewan, were documented for the period of 1960s to the present. To examine changes in caribou distribution, survey observations, incidental sightings and telemetry data were collated. To quantify landscape changes, land cover maps were created for 1966 and 2006 using current and historic forest resources inventories, fire, logging, and roads data. Results indicate that woodland caribou are still found throughout the study area although their distribution has changed and their use of the National Park is greatly limited. Results of transition prob¬abilities and landscape composition analyses on the 1966 and 2006 land cover maps revealed an aging landscape for both the National Park and provincial crown land portions of the PAGE. In addition, increased logging and the development of extensive road and trail networks on provincial crown land produced significant landscape fragmentation for woodland caribou and reduced functional attributes of habitat patches. Understanding historical landscape changes will assist with ongoing provincial and federal recovery efforts for boreal caribou, forest management planning activities, and landscape restoration efforts within and beyond the Park boundaries.

Length and classification of natural and created forest edges in boreal landscapes throughout northern Sweden

Forest edges have numerous implications for structure and function of forest ecosystems. Previous studies on edge quantity have used broad classifications. However, edge influence is driven by the contrast in vegetation structure between adjoining ecosystems, and thus we need detailed site-specific data to assess the role of edges in forests. We studied the variability of sharp edges in 28 boreal landscapes (4 km × 4 km) across an 830 km gradient throughout northern Sweden. Our objectives were: (1) to compare the length of natural and created edges, (2) to classify edges in detail by edge origin, maintenance and forest attributes, and (3) to examine relationships between length of edge and landscape variables. Data were collected using stereo-interpretation of high spatial resolution colour infrared aerial photographs, in combination with line intersect sampling and plots. The length of edge varied from 12 to 102 m ha −1 among landscapes, with an overall mean of 54 m ha −1. Created edges dominated most landscapes (mean 33 m ha −1) and had greater variability than natural edges (mean 21 m ha −1). Maintained edges (e.g. roads, agricultural land) were more abundant than regenerating edges caused by logging. Thirty percent of total edges adjoined narrow linear features. Seventy percent adjoined wider patches and showed high variability (35 classes). Overall, high-contrast edges towards mature forest dominated, i.e. ones that may experience strong edge influence. The amount of edge increased with percent of landscape affected by disturbance, and decreased with latitude and elevation. This study shows that edges are both abundant and highly variable in boreal forests and that forestry is the main driver behind edge creation. Detailed classification of edges based on site-specific forest and patch attributes may help to estimate edge influence at landscape level, and can guide experimental design for examining the impact of edges on structure and function of forest ecosystems.