Effects Of Landscape Variables Research Articles

Combining roadkill hotspots and landscape features to guide mitigation measures on highways

Identifying highway sections with high vertebrate roadkill and associated landscape features is crucial for proposing mitigation measures to reduce the negative impacts of wildlife-vehicle collisions on biodiversity, human safety, and the economy. Focusing on highways in the State of Mato Grosso do Sul, Brazil, this study proposes a prioritization of road segments for implementing mitigation measures based on landscape characteristics and roadkill hotspots recorded between 2016 and 2018. Roadkills distribution was assessed using Hotspot Identification, detecting sections with the highest collision intensity. The effect of landscape variables, such as the area and distance of natural vegetation and anthropic land use within 1 km of the highways, on roadkill was modelled using General Linear Mixed Models, which were evaluated based on two response variables: (1) roadkill presence/absence and (2) roadkill abundance, with model selection by the Akaike information criterion. Based on roadkill hotspot identification analysis and predictive models of the influence of landscape elements on roadkill occurrence and abundance, an evaluation criterion was proposed to determine the priority sites for installing wildlife crossings, speed bumps, and signposts. Wildlife-vehicle collisions were positively associated with riparian vegetation areas and urban areas, while negatively associated with silviculture and distance to “cerradão” (forest Cerrado) patches. Eleven road sections were identified as top priority, two as high priority and 78 as medium priority for the installation of mitigation measures with varying cost-benefit ratios. Our results can potentially guide decision-making at broader scales and provide mitigating alternatives applicable to dry ecosystems such as the Cerrado (Brazilian Savanna).

Effects of Landscape Variables on Exchangeable Potassium Content in the Floodplain Soils of the Amur River

This article considers exchangeable potassium levels in the floodplain soils of the Amur River. The accumulation of exchangeable potassium in these soils was found to be largely determined by their age and weathering extent. In the young and highly weathered soils, the content of exchangeable potassium was lower than in the middle-aged soils. In the humus-accumulating horizon, it was 100–400 mg/kg and 200 mg/kg in the Upper and Middle Amur River, respectively. As for the mineral horizons, it ranged from 20 mg/kg in the young alluvial soils to 150 mg/kg in the residual-floodplain rusty soils. Interestingly, a significant increase in exchangeable potassium was observed for the coniferous-birch forests of the Upper Amur River (reaching an average of 400 mg/kg), but not for the oak forests in the Middle Amur River. Due to the asymmetry of the rate and ratio of zonal processes in the floodplain soils of the Upper and Middle Amur River, the residual-alluvial soils turned out to be sharply differentiated by the exchangeable potassium profiles. On average, the brown soils (Fluvic Cambisols) of the Upper Amur River contained up to 350 mg/kg of exchangeable potassium. The Fluvic Cambisols of the Middle Amur River had the lowest content of exchangeable potassium as compared to other studied soils.

Effects of landscape characteristics, anthropogenic factors, and seasonality on water quality in Portland, Oregon

Urban areas often struggle with deteriorated water quality because of complex interactions between landscape factors and climatic variables. However, few studies have considered the effects of landscape variables on water quality at a sub-500-m scale. We conducted a spatial statistical analysis of six pollutants for 128 water quality stations in four watersheds around Portland, Oregon, using data from 2015 to 2021 for the wet season at two microscales (100m and 250m buffers). E. coli was associated with land cover, soil type, topography, and pipe length, while lead variations were best explained by topographic variables. Developed land cover and impervious surface explained variations in nitrate, while orthophosphate was associated with mean elevation. Models for zinc included land cover and topographic variables in addition to pipe length. Spatial regression models better explain variations in water quality than ordinary least squares models, indicating strong spatial autocorrelation for some variables. Our findings provide valuable insights to city planners and researchers seeking to improve water quality in metropolitan areas by manipulating city landscapes.

Breeding habitat and nest-site selection by an obligatory "nest-cleptoparasite", the Amur Falcon Falco amurensis.

The selection of a nest site is crucial for successful reproduction of birds. Animals which re‐use or occupy nest sites constructed by other species often have limited choice. Little is known about the criteria of nest‐stealing species to choose suitable nesting sites and habitats. Here, we analyze breeding‐site selection of an obligatory “nest‐cleptoparasite”, the Amur Falcon Falco amurensis. We collected data on nest sites at Muraviovka Park in the Russian Far East, where the species breeds exclusively in nests of the Eurasian Magpie Pica pica. We sampled 117 Eurasian Magpie nests, 38 of which were occupied by Amur Falcons. Nest‐specific variables were assessed, and a recently developed habitat classification map was used to derive landscape metrics. We found that Amur Falcons chose a wide range of nesting sites, but significantly preferred nests with a domed roof. Breeding pairs of Eurasian Hobby Falco subbuteo and Eurasian Magpie were often found to breed near the nest in about the same distance as neighboring Amur Falcon pairs. Additionally, the occurrence of the species was positively associated with bare soil cover, forest cover, and shrub patches within their home range and negatively with the distance to wetlands. Areas of wetlands and fallow land might be used for foraging since Amur Falcons mostly depend on an insect diet. Additionally, we found that rarely burned habitats were preferred. Overall, the effect of landscape variables on the choice of actual nest sites appeared to be rather small. We used different classification methods to predict the probability of occurrence, of which the Random forest method showed the highest accuracy. The areas determined as suitable habitat showed a high concordance with the actual nest locations. We conclude that Amur Falcons prefer to occupy newly built (domed) nests to ensure high nest quality, as well as nests surrounded by available feeding habitats.

Non-crop habitats modulate alpha and beta diversity of flower flies (Diptera, Syrphidae) in Brazilian agricultural landscapes

Non-crop habitats play a key role in maintaining functional diversity and ecosystem services in farmland. However, the interplay between beneficial insects and landscape variables has rarely been investigated in Neotropical agroecosystems. We used flower flies as a model group to investigate the effects of landscape attributes on beneficial insects in agroecosystems across a gradient of landscape complexity. We specifically ask: (i) Do the abundance and species richness of flower flies in cereal crops increase with increasing landscape complexity? (ii) Do the effects of landscape variables on local flower fly communities differ between spatial scales? (iii) How do landscape complexity and local factors (crop size, altitude and insecticide applications) affect beta diversity? We sampled flower flies in 54 edges within 18 wheat crops in Parana State, southern Brazil. The percentage of non-crop habitats, landscape diversity and edge density were the explanatory variables, which were calculated at multiple spatial scales for each landscape. We collected 8340 flower flies, distributed in 12 genera and 52 species. Species richness was positively associated with the percentage of non-crop habitats, but total abundance presented non-clear pattern. However, abundance without the dominant species was also positively associated with the percentage non-crop habitats. Similarly, beta diversity was related to non-crop habitats, suggesting that the reduction in non-crop habitats implies in species loss. We have provided the first insights into the importance of non-crop habitats on the conservation of beneficial insects within Neotropical farmlands. To guarantee high levels of biodiversity within agroecosystems we need to promote the conservation and restoration of non-crop habitats in the surrounding landscapes.

Effect of landscape variables on the long-term decline of Great Argus in the rainforest of Southern Thailand

SummaryIn Thailand, as for most of South-East Asia, large vertebrates are declining rapidly due to habitat degradation and increasing hunting pressure. Once relatively common in the evergreen forest of Southern Thailand, the Great ArgusArgusianus argusis currently limited to a few populations, whose status is currently unknown. In this study we investigated changes in Great Argus abundance over the past 13 years in Hala-Bala Wildlife Sanctuary. Our aim was to estimate and compare the abundance and density of this species from an earlier two-year survey in 2001–2002 and ours in 2014, and to assess the effect of landscape change on its status of the species. We conducted surveys from March to August 2014 during the breeding season. We placed point counts that overlapped the line transects from the 2001–2002 survey. The results indicated a decline of > 35% in mean abundance from 2001 to 2014. In addition, male abundance has shifted and is now positively related to distance from the forest edge. High levels of human disturbance close to the forest edge may have resulted in the birds moving to the core of the forest, suggesting a need to increase protection and management of forest edge areas. In common with other studies of large vertebrates, our results confirm the importance of long-term studies to highlight the negative effects of human disturbance.

Shelterbelts in agricultural landscapes enhance ladybeetle abundance in spillover from cropland to adjacent habitats

The natural enemies of herbivorous pests in cropping systems may relocate to adjacent habitats in response to declining habitat quality in heterogeneous landscapes. In this study, we measured the cross-edge spillover of ladybeetles from wheat fields to shelterbelts, and tested how landscape variables at various spatial scales influence ladybeetle populations. We conducted a large-scale sampling study of agricultural landscapes differing in structural complexity during 2012 and 2013. The effects of landscape variables (i.e., landscape diversity and the percentage of woody habitats) on the ladybeetle abundance were investigated. Propylea japonica (Thunberg) and Harmonia axyridis (Pallas) were the dominant ladybeetle species. The abundances of ladybeetles in spillover were positively correlated with the percentage of woody area, and negatively correlated with landscape diversity and edge density of crop habitats. It indicates that a low diversity landscape with a large area of shelterbelts supports larger ladybeetle abundance in spillover compared with a high diversity landscape with a limited area of shelterbelts. By contrast, greater numbers of within-field ladybeetles were associated with landscape diversity increase. Landscape features at the spatial scale of 2.5–3 km could best predict the abundance of ladybeetles in spillover, whereas the best prediction model for ladybeetle abundance within field was at the 1.5 km scale. These results suggest that the landscape variables influence ladybeetle abundance differently in spillover and within fields. The introduction of shelterbelts in the agricultural landscape could enhance the conservation of ladybeetle populations.

Scale‐dependent effects of landscape variables on gene flow and population structure in bats

AbstractAimA common pattern in biogeography is the scale‐dependent effect of environmental variables on the spatial distribution of species. We tested the role of climatic and land cover variables in structuring the distribution of genetic variation in the grey long‐eared bat, Plecotus austriacus, across spatial scales. Although landscape genetics has been widely used to describe spatial patterns of gene flow in a variety of taxa, volant animals have generally been neglected because of their perceived high dispersal potential.LocationEngland and Europe.MethodsWe used a multiscale integrated approach, combining population genetics with species distribution modelling and geographical information under a causal modelling framework, to identify landscape barriers to gene flow and their effect on population structure and conservation status. Genotyping involved 23 polymorphic microsatellites and 259 samples from across the species' range.ResultsWe identified distinct population structure shaped by geographical barriers and evidence of population fragmentation at the northern edge of the range. Habitat suitability (as captured by species distribution models, SDMs) was the most important landscape variable affecting genetic connectivity at the broad spatial scale, while at the fine scale, lowland unimproved grasslands, the main foraging habitat of P. austriacus, played a pivotal role in promoting genetic connectivity.Main conclusionsThe importance of lowland unimproved grasslands in determining the biogeography and genetic connectivity in P. austriacus highlights the importance of their conservation as part of a wider landscape management for fragmented edge populations. This study illustrates the value of using SDMs in landscape genetics and highlights the need for multiscale approaches when studying genetic connectivity in volant animals or taxa with similar dispersal abilities.

The Effects of Landscape Variables on the Species-Area Relationship during Late-Stage Habitat Fragmentation

Few studies have focused explicitly on the later stages of the fragmentation process, or “late-stage fragmentation”, during which habitat area and patch number decrease simultaneously. This lack of attention is despite the fact that many of the anthropogenically fragmented habitats around the world are, or soon will be, in late-stage fragmentation. Understanding the ecological processes and patterns that occur in late-stage fragmentation is critical to protect the species richness in these fragments. We investigated plant species composition on 152 islands in the Thousand Island Lake, China. A random sampling method was used to create simulated fragmented landscapes with different total habitat areas and numbers of patches mimicking the process of late-stage fragmentation. The response of the landscape-scale species-area relationship (LSAR) to fragmentation per se was investigated, and the contribution of inter-specific differences in the responses to late-stage fragmentation was tested. We found that the loss of species at small areas was compensated for by the effects of fragmentation per se, i.e., there were weak area effects on species richness in landscapes due to many patches with irregular shapes and high variation in size. The study also illustrated the importance of inter-specific differences for responses to fragmentation in that the LSARs of rare and common species were differently influenced by the effects of fragmentation per se. In conclusion, our analyses at the landscape scale demonstrate the significant influences of fragmentation per se on area effects and the importance of inter-specific differences for responses to fragmentation in late-stage fragmentation. These findings add to our understanding of the effects of habitat fragmentation on species diversity.

Effects of landscape variables and season on reference water chemistry of coastal marshes in eastern Georgian Bay

We surveyed 34 marshes in relatively pristine Precambrian Shield catchments in Georgian Bay and related water chemistry to a suite of landscape-level variables, including characteristics of the marsh and its drainage basin. The first landscape principal component (explained 48% of variation) ordered marshes along a gradient with high values corresponding to marshes with large watersheds that contain extensive upstream wetland and that receive relatively high precipitation inputs. This axis was negatively related to specific conductivity, pH, nitrate nitrogen, and SO42– concentrations and positively related to total phosphorus, colour, suspended solids, ammonia nitrogen, and summer dissolved organic carbon. Stepwise regression models built using catchment- and marsh-level variables explained up to 64% of the variation in water chemistry variables. Average precipitation and snowmelt inputs to the catchments were first to enter the majority of models, alone explaining up to 43% of the variation (in the case of water colour), while drainage area alone explained 44% of the variation in pH. Concentrations of catchment-derived constituents in marshes were highest in spring, reflecting greater loadings from the watersheds, while ionic strength was highest during summer, reflecting increased contributions form other sources (i.e., lake water).

The role of landscape configuration in plant composition of floodplain forests across different physiographic areas

Questions: What is the relative importance of landscape variables compared to habitat quality variables in determining species composition in floodplain forests across different physiographic areas? How do species composition and species traits relate to effects of particular landscape variables? Do lowland and mountain areas differ in effects of landscape variables on species composition? Location: Southern Czech Republic. Methods: A total of 240 vegetation relevés of floodplain forests with measured site conditions were recorded across six physiographic areas. I tested how physiographic area, habitat quality variables and landscape variables such as current land-cover categories, forest continuity, forest size and urbanization influenced plant species composition. I also compared how mountain and lowland areas differ in terms of the relative importance of these variables. To determine how landscape configuration affects the distribution of species traits, relationships of traits and species affinity with landscape variables were tested. Results: Among landscape variables, forest continuity, landscape forest cover and distance to nearest settlement altered the vegetation. These variables also influenced the distributions of species traits, i.e. life forms, life strategies, affinity to forest, dispersal modes, seed characteristics, flooding tolerance and Ellenberg indicator values for nitrogen, light, moisture and soil reaction. Nevertheless, physiographic area and habitat quality variables explained more variation in species composition. Landscape variables were more important in lowland areas. Forest continuity affected species composition only in lowlands. Conclusions: Although habitat quality and physiographic area explained more vegetation variability, landscape configuration was also a key factor influencing species composition and distribution of species traits. However, the results are dependent on forest geographical location, with lowland forests being more influenced by landscape variables compared to mountain forests.

Effects of stand, landscape, and spatial variables on bird communities in larch plantations and deciduous forests in central Japan

We examined the effects of stand, landscape, and spatial variables on bird communities in deciduous forests and Japanese larch ( Larix leptolepis (Sieb & Zucc.) Gord.) plantations in a montane region of Nagano Prefecture, central Japan. We used plot-transect methods at 97 sites: 33 in winter 2003 and 18 sites were added in the 2004 breeding season in deciduous forests, and 32 in winter 2004 and 14 sites were added in the 2005 breeding season in larch plantations. Bird–environment relationships were explored using partial redundancy analysis and partial regression analysis. We used spatial variables derived from principal coordinates of neighbor matrices as explanatory variables to detect nonrandom spatial structure of bird communities. Variation in bird communities was mainly explained by stand and spatial variables for both forest types, whereas the effects of landscape variables were small. In plantations, important stand variables for both seasons included stand height, elevation, and the basal area of vines, whereas shrubs, dwarf bamboo ( Sasa senanensis (Franch. & Savat.) Rehd.), and larch snags were important in the breeding season. In deciduous forests, the most important stand variable for both seasons was the basal area of northern Japanese hemlock ( Tsuga diversifolia (Maxim.) Mast.) and Nikko fir ( Abies homolepis Sieb. & Zucc.) trees. Spatial variables showed that bird communities had large-scale (>10 km) spatial variation that could not be explained by stand or landscape variables.

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

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

Landscape Design in Clear Zone: Effect of Landscape Variables on Pedestrian Health and Driver Safety

The relationship between landscape installations and safety or pedestrian activity was evaluated in pilot studies. The sites selected for study were those adjacent to or within the areas often referred to as the “clear zone” of the transportation corridor, an area shared by pedestrians and driver perception. Case study research on the impact of environmental mitigation on driver safety is summarized to identify the landscape installations in the clear zone that appear to have an effect on safety. This is followed by case study research on the identification of variables that encourage walking for health purposes. Preliminary findings indicate that the improved definition of spatial edge resulting from typical curbside and median landscape treatment in the clear zone appears to solicit positive behavioral responses by either attracting pedestrian activity or improving driver safety. It is not possible to draw definitive conclusions from the results because of the small sample sizes in the pilot studies (a pedestrian survey included 52 responses), but indications are that the landscape in the clear zone may be having a positive impact on safety or pedestrian activity under certain circumstances. Both pilot studies were conducted separately in Canada and the United States.