Landscape Composition Variables Research Articles

Effects of landscape structure and patch characteristics on the density of central populations of the eastern green lizard Lacerta viridis.

A better understanding of the impact of habitat loss on population density can be achieved by evaluating effects of both parameters within remnant habitat patches and parameters of the landscape surrounding those patches. The integration of predictors at the patch and landscape level is scarce in animal ecological studies, especially for reptiles. In this study, a patch-landscape approach was applied to evaluate the combined effects of within-patch habitat quality, patch geometry and landscape configuration and composition on the density of remnant populations of the eastern green lizard, Lacerta viridis, in a highly modified landscape in Bulgaria. Landscape composition variables (proportion of different land covers) were measured at different spatial scales surrounding patches. Single-scale models were built to evaluate combined effects of all predictors on density, when including all landscape composition variables at a specific spatial scale. Multi-scale models were applied to analyze combined effects when including landscape composition variables at the scale of their strongest effect (scale of effect, SoE). Results showed that the SoE of proportion of cropland and urban areas was small (50 m), while for proportion of habitat was large (1.5 km). The overall effect of habitat loss was better explained by the multi-scale model. Population density increased with patch area and decreased with patch shape irregularity and with the proportion of three land cover types surrounding patches-cropland, urban areas, and habitat. Combining patch and landscape parameters is important to identify ecological processes that occur simultaneously at different spatial levels and landscape scales, which would imply the application of multi-scale approaches for the protection of wild animal populations. Results are contrasted with what is known about occupancy patterns of the species in the same region and approaches to integrate both occupancy and density, in the field design of animal ecological studies are suggested.

A global assessment of primate responses to landscape structure.

Land-use change modifies the spatial structure of terrestrial landscapes, potentially shaping the distribution, abundance and diversity of remaining species assemblages. Non-human primates can be particularly vulnerable to landscape disturbances, but our understanding of this topic is far from complete. Here we reviewed all available studies on primates' responses to landscape structure. We found 34 studies of 71 primate species (24 genera and 10 families) that used a landscape approach. Most studies (82%) were from Neotropical forests, with howler monkeys being the most frequently studied taxon (56% of studies). All studies but one used a site-landscape or a patch-landscape study design, and frequently (34% of studies) measured landscape variables within a given radius from the edge of focal patches. Altogether, the 34 studies reported 188 responses to 17 landscape-scale metrics. However, the majority of the studies (62%) quantified landscape predictors within a single spatial scale, potentially missing significant primate-landscape responses. To assess such responses accurately, landscape metrics need to be measured at the optimal scale, i.e. the spatial extent at which the primate-landscape relationship is strongest (so-called 'scale of effect'). Only 21% of studies calculated the scale of effect through multiscale approaches. Interestingly, the vast majority of studies that do not assess the scale of effect mainly reported null effects of landscape structure on primates, while most of the studies based on optimal scales found significant responses. These significant responses were primarily to landscape composition variables rather than landscape configuration variables. In particular, primates generally show positive responses to increasing forest cover, landscape quality indices and matrix permeability. By contrast, primates show weak responses to landscape configuration. In addition, half of the studies showing significant responses to landscape configuration metrics did not control for the effect of forest cover. As configuration metrics are often correlated with forest cover, this means that documented configuration effects may simply be driven by landscape-scale forest loss. Our findings suggest that forest loss (not fragmentation) is a major threat to primates, and thus, preventing deforestation (e.g. through creation of reserves) and increasing forest cover through restoration is critically needed to mitigate the impact of land-use change on our closest relatives. Increasing matrix functionality can also be critical, for instance by promoting anthropogenic land covers that are similar to primates' habitat.

Monitoring surface urban heat island formation in a tropical mountain city using Landsat data (1987–2015)

Since it was first described about two centuries ago and due to its adverse impacts on urban ecological environment and the overall livability of cities, the urban heat island (UHI) phenomenon has been, and still is, an important research topic across various fields of study. However, UHI studies on cities in mountain regions are still lacking. This study aims to contribute to this endeavor by monitoring and examining the formation of surface UHI (SUHI) in a tropical mountain city of Southeast Asia –Baguio City, the summer capital of the Philippines– using Landsat data (1987–2015). Based on mean surface temperature difference between impervious surface (IS) and green space (GS1), SUHI intensity (SUHII) in the study area increased from 2.7°C in 1987 to 3.4°C in 2015. Between an urban zone (>86% impervious) and a rural zone (<10% impervious) along the urban-rural gradient, it increased from 4.0°C in 1987 to 8.2°C in 2015. These results are consistent with the rapid urbanization of the area over the same period, which resulted in a rapid expansion of impervious surfaces and substantial loss of green spaces. Together with landscape composition variables (e.g. fraction of IS), topographic variables (e.g. hillshade) can help explain a significant amount of spatial variations in surface temperature in the area (R2=0.56–0.85) (p<0.001). The relative importance of the ‘fraction of IS’ variable also increased, indicating that its unique explanatory and predictive power concerning the spatial variations of surface temperature increases as the city size becomes bigger and SUHI gets more intense. Overall, these results indicate that the cool temperature of the study area being situated in a mountain region did not hinder the formation of SUHI. Thus, the formation and effects of UHIs, including possible mitigation and adaptation measures, should be considered in landscape planning for the sustainable urban development of the area.

Does regional landscape connectivity influence the location of roe deer roadkill hotspots?

Linear infrastructures have both direct and indirect effects on ecosystems. Wildlife-vehicle collisions are the most visible direct effect and can result in severe human injuries. In Europe, the roe deer population is growing and roe deer roadkills are becoming more common. Roe deer movements depend on landscape features and regional-scale connectivity. Here, we investigate the influence of the landscape network on the location of roe deer roadkill hotspots. In order to localize new potential hotspots along the national roads of Franche-Comte (Eastern France), we first show that roe deer roadkills are not distributed randomly and we identify hotspots. Then, we explain roe deer hotspot locations using a predictive model by combining landscape composition variables, road-related properties, and graph-based connectivity metrics. We test three centrality metrics at three dispersal distances and we assess the relative contribution of the connectivity metrics to the best model. Finally, in order to define high-risk sections, we find the probability that reduces the costs of misclassification that the model produces. We validate the model with a new set of roe deer roadkills.

Bird metacommunity processes remain constant after 25 years of landscape changes

Metacommunity theory provides a framework to understand how ecological communities vary in space and time. However, few studies have investigated metacommunity processes in a context of long term changes. Environmental changes can impact species distribution and therefore the structure of metacommunities. Using two complementary methods, this study evaluated the temporal variability of bird metacommunity processes in an agricultural landscape after 25 years of changes in land-cover. Bird and landscape data were recorded in the same locations using a series of 256 point counts in 1982 and 2007. First, variance partitioning was applied to quantify the roles of environmental filtering (i.e. landscape composition variables) and spatial variables to organize bird metacommunities each year. Second, changes in the structure of the bird metacommunity were examined by quantifying three of its components: coherence, species turnover and species range boundary clumping. Our results demonstrate that landscape variables explained slightly more bird metacommunity patterns than spatial variation of unknown origin each year. The bird metacommunity had a Clementsian structure (i.e. grouped distribution of species along environmental gradients) which was correlated with a landscape gradient ranging from open farmland to wooded sites. This structure was similar each year. To conclude, the study shows that environmental filtering with specializations to different habitats is a major process in determining bird metacommunities in landscapes. Moreover, our results suggest that metacommunity structure can remain constant over time despite demographic and environmental changes.

Winter habitat selection and partitioning in two sympatric farmland small mammals: Apodemus sylvaticus and Mus spretus

Patterns of small mammal habitat selection vary according to scale, although there are discrepancies about the importance of macro and micro-scale factors in rodent community assembly. We assess whether differences in their micro and macrohabitat selection patterns explain the coexistence of two sympatric rodents, Mus spretus and Apodemus sylvaticus, in an agricultural area of central Spain. We trapped mice in uncultivated and crop fields using a grid of Sherman traps. Food availability and vegetation structure (microhabitat) and landscape composition variables (macrohabitat) were measured in each plot. We used GLMs to determine the scale predictors related to specific abundance. The importance of each scale in the assemblage was assessed by a variance partitioning procedure. At microhabitat scale, A. sylvaticus was positively related to shrub cover and M. spretus to seed availability. At macrohabitat scale, A. sylvaticus was negatively associated with distance to the nearest tree, whereas M. spretus was positively associated with this variable. Macrohabitat explained 39 % and microhabitat 8 % of the variance in the assemblage. Results suggest a relative segregation of food preferences at microhabitat scale, and a habitat partitioning at macrohabitat scale, which may allow spatial coexistence of both species, according to community assembly theory. This study shows the importance of both micro and macrohabitat in the configuration of rodent assemblages.

Winter site occupancy patterns of the northern flying squirrel in boreal mixed-wood forests

We assessed habitat use by the northern flying squirrel (Glaucomys sabrinus) to test the hypothesis that the species is not a late-seral coniferous forest specialist in boreal mixedwood forests of northwestern Québec. We monitored 149 pairs of nest boxes over 3 visits during February–April 2008. A total of 31 pairs of nest boxes were occupied during the study. The average (3.7, 2.8, and 1.8) and maximum (8, 6, and 4) numbers of individuals in nest boxes decreased from the first to last visit. Average air temperatures were below freezing and increased with the arrival of spring (−23.9, −14.5, and −3.7°C). Using GIS software, we created a 430-m (median dispersal distance) buffer around each pair of nest boxes and extracted landscape composition variables from digital forest inventory maps. We created models that potentially explained site occupancy by the northern flying squirrel as well as detection probability. Model selection indicated that the area of coniferous forests negatively affected site occupancy by flying squirrels while temperature positively influenced detection probability. Our results support the hypothesis that the northern flying squirrel is not a habitat specialist, but can occupy a wider range of forest cover types than previously recognized in various landscape contexts.

Modeling wildlife damage to crops in northern Indiana

Comprehensive information on crop damage by wildlife species is critical if effective strategies for controlling wildlife damage are to be formulated. Discriminating how landscape composition and configuration attributes influence crop damage is important for implementing landscape management techniques to resolve human-wildlife conflicts. We analyzed crop damage data from 100 corn fields and 60 soybean fields located in the Upper Wabash River Basin of northern Indiana during 2003 and 2004. We used negative binomial regression to model the rate of damage to corn and soybean crops in response to local and landscape variables. Rate of crop damage was best predicted by a combination of local and landscape variables for both corn and soybeans. Models with landscape configuration variables were better able to explain patterns of corn damage, and models with landscape composition variables (specifically, amount of wooded areas) were better able to explain patterns of soybean damage. In general, rate of crop damage was negatively related to size of the crop field and positively related to proportion of a field's perimeter that was adjacent to wooded areas, amount of wooded areas, amount of forest edge, and mean size of forest patches. Specific associations between local and landscape variables and rates of crop damage may serve as a guide to planting strategies and landscape management to minimize wildlife damage to crops.

Vascular plant and Orthoptera diversity in relation to grassland management and landscape composition in the European Alps

Summary Several recent studies have considered the relative effects of local vs. landscape factors on diversity of several animal taxa in grasslands. However, very few have considered vascular plant or Orthoptera species, both of which are important biotic components of grassland ecosystems. The general aim of this study was to determine the effect of grassland management and landscape composition, and their potential interactions, on diversity patterns of vascular plants and Orthoptera in Alpine hay meadows. We considered three groups of management regimes defined by different amounts of fertilizer nitrogen applied and cutting frequency: (i) extensive, (ii) low intensive and (iii) intensive meadows situated in different landscape contexts. To evaluate the relative importance of meadow management and landscape composition on diversity patterns, we applied analysis of covariance and variation partitioning analyses. Diversity patterns of both taxonomic groups were affected primarily by grassland management. The extensive management regime was most suitable for conserving high species richness of both taxonomic groups. The intensive meadows were characterized by plant communities dominated by a few ruderal and competitor species, and by Orthoptera communities composed of only a few abundant Caelifera species (e.g. Chorthippus parallelus), while Ensifera species had very low individual densities. Regarding the landscape determinants, plant diversity patterns were not significantly related to any landscape composition variables. In contrast, a high proportion of urban elements and grassland in the surrounding landscape (radius 500 m) affected Orthoptera species richness negatively. Synthesis and applications. The implementation of well‐targeted agri‐environment schemes for compensation payments against intensification and abandonment of extensive hay meadows seems to be a promising tool to protect both taxonomic groups. In this context, we suggest that the existing Swiss ecological compensation area (ECA) hay meadow agri‐environment scheme, which requires at least one cut every year and no fertilizer application, might also be suitable for the Italian Alps. Moreover, the significant influence of landscape composition on Orthoptera diversity suggests that the effectiveness of measures applied at a field scale may be improved by integration of protected area schemes, promoting extensive management at a farm scale.

The relative importance of landscape properties for woodland birds in agricultural environments

Summary Studies of landscape change are seldom conducted at scales commensurate with the processes they purport to investigate. Landscape change is a landscape‐level process, yet most studies focus on patches. Even when landscape context is considered, inference remains at the patch‐level. The unit of investigation must be extended beyond individual patches to whole mosaics in order to advance understanding of faunal responses to landscape change. In this study, we aggregated data from multiple sites per landscape such that both the response and explanatory variables characterized ‘whole’ landscapes, allowing for landscape‐level inference about factors influencing species’ incidence. We used hierarchical partitioning and Bayesian variable selection methods to develop species‐specific models that examined the influence of four categories of landscape properties – habitat extent, habitat configuration, landscape composition and geographical location – on the incidence of 58 species of woodland‐dependent birds in 24 agricultural landscapes (each 100 km2) in south‐eastern Australia. There was strong evidence for a positive effect of habitat extent for 27 species. Thirty species were related to at least one of the four landscape composition variables, and geographical location was important for 19 species. Habitat configuration was influential for 13 species and where important, the impacts of fragmentation per se were detrimental. Variation among species in the influential landscape variables indicates that different species respond to different sets of cues in land mosaics. Thus, although all species were grouped a priori as ‘woodland‐dependent’, expectations based on general ecological characteristics may prove unreliable. Synthesis and applications. These results underscore the value of moving beyond the fragmentation paradigm focused on the spatial pattern of habitat vs. non‐habitat, to a greater appreciation of the composition and heterogeneity of land mosaics. Landscape‐level inference will enable improved conservation outcomes by recognizing the influence of landscape properties on biota and devising strategies at this scale to complement patch‐based management. We provide strong empirical evidence that biodiversity management in agricultural landscapes must focus on habitat extent. Complementary management of other landscape attributes, such as habitat aggregation and intensity of agricultural land‐use, will also enhance the value of agricultural landscapes for woodland birds.

Independent Effects Of Fragmentation On Forest Songbirds: An Organism-Based Approach

The degree to which spatial patterns influence the dynamics and distribution of populations is a central question in ecology. This question is even more pressing in the context of rapid habitat loss and fragmentation, which threaten global biodiversity. However, the relative influence of habitat loss and landscape fragmentation, the spatial patterning of remaining habitat, remains unclear. If landscape pattern affects population size, managers may be able to design landscapes that mitigate habitat loss. We present the results of a mensurative experiment designed to test four habitat loss vs. fragmentation hypotheses. Unlike previous studies, we measured landscape structure using quantitative, spatially explicit habitat distribution models previously developed for two species: Blackburnian Warbler (Dendroica fusca) and Ovenbird (Seiurus aurocapilla). We used a stratified sampling design that reduced the confounding of habitat amount and fragmentation variables. Occurrence and reoccurrence of both species were strongly influenced by characteristics at scales greater than the individual territory, indicating little support for the random-sample hypothesis. However, the type and spatial extent of landscape influence differed. Both occurrence and reoccurrence of Blackburnian Warblers were influenced by the amount of poor-quality matrix at 300- and 2000-m spatial extents. The occurrence and reoccurrence of Ovenbirds depended on a landscape pattern variable, patch size, but only in cases when patches were isolated. These results support the hypothesis that landscape pattern is important for some species only when the amount of suitable habitat is low. Although theoretical models have predicted such an interaction between landscape fragmentation and composition, to our knowledge this is the first study to report empirical evidence of such nonlinear fragmentation effects. Defining landscapes quantitatively from an organism-based perspective may increase power to detect fragmentation effects, particularly in forest mosaics where boundaries between patches and matrix are ambiguous. Our results indicate that manipulating landscape pattern may reduce negative impacts of habitat loss for Ovenbird, but not Blackburnian Warbler. We emphasize that most variance in the occurrence of both species was explained by local scale or landscape composition variables rather than variables reflecting landscape pattern.

LANDSCAPE-SCALE DISTURBANCES AND CHANGES IN BIRD COMMUNITIES OF BOREAL MIXED-WOOD FORESTS

Bird community response to both landscape-scale and local (forest types) changes in forest cover was studied in three boreal mixed-wood forest landscapes modified by different types of disturbances: (1) a pre-industrial landscape where human settlement, agriculture, and logging activities date back to the early 1930s, (2) an industrial timber managed forest, and (3) a forest dominated by natural disturbances. Birds were sampled at 459 sampling stations distributed among the three landscapes. Local habitat and landscape characteristics of the context surrounding each sampling station (500-m and 1-km radius) were also computed. Bird communities were influenced by landscape-scale changes in forest cover. The higher proportion of early-successional habitats in both human-disturbed landscapes resulted in significantly higher abundance of early-successional bird species and generalists. The mean number of mature forest bird species was significantly lower in the industrial and pre-industrial landscapes than in the natural landscape. Landscape-scale conversion of mature forests from mixed-wood to deciduous cover in human-disturbed landscapes was the main cause of changes in mature forest bird communities. In these landscapes, the abundance of species associated with mixed and coniferous forest cover was lower, whereas species that preferred a deciduous cover were more abundant. Variation in bird community composition determined by the landscape context was as important as local habitat conditions, suggesting that predictions on the regional impact of forest management on songbirds with models solely based on local scale factors could be misleading. Patterns of bird species composition were related to several landscape composition variables (proportions of forest types), but not to configuration variables (e.g., interior habitat, amount of edge). Overall, our results indicated that the large-scale conversion of the southern portion of the boreal forest from a mixed to a deciduous cover may be one of the most important threats to the integrity of bird communities in these forest mosaics. Negative effects of changes in bird communities could be attenuated if current forestry practices are modified toward maintaining forest types (deciduous, mixed-wood, and coniferous) at levels similar to those observed under natural disturbances.

The conservation of arboreal marsupials in the montane ash forests of the central highlands of Victoria, south-eastern Australia. VIII. Landscape analysis of the occurrence of arboreal marsupials

We describe the results of landscape analysis of the occurrence of a suite of species of arboreal marsupials in the montane ash forests of the central highlands of Victoria, south-eastern Australia. The species targeted for study were: Yellow-bellied Glider ( Petaurus australis), Mountain Brushtail Possum ( Trichosurus caninus), Greater Glider ( Petauroides volans) and Leadbeater's Possum ( Gymnobelideus leadbeateri). Our analyses involved exploring statistical relationships between the presence/absence of these four species and compositional variables used to characterise the landscape within 20 and 80 ha circles surrounding each of 166, 3 ha, sites surveyed for arboreal marsupials. Many potential statistical models were examined for each of the four species targeted for analysis. With the exception of P. australis, the final model chosen was the null model; i.e. none of the landscape variables were statistically significant as predictors of the presence of animals at a site. In the case of P. australis, three measures of the landscape within the 80 ha circles surrounding our survey sites were found to be statistically significant: (1) the presence of old forest, (2) the steepness of the forest terrain, and, (3) the area of forest on different aspects. There was a significantly higher probability of detecting the species on northerly and westerly aspects, on either steep or flat terrain, and within circles supporting old growth montane ash forest. P. australis has a home range of 40–60 ha which is at least an order of magnitude larger than the other species of arboreal marsupials examined. Thus, the size of the 80 ha circle used to capture data on landscape composition matched the home range size of P. australis more closely than other species of arboreal marsupials examined in this study. This may, in part, explain why it was the only species for which landscape composition variables were found to be significant predictors of occurrence. Our findings tentatively suggest that changes in the spatial coverage of old growth forest that have resulted from past wildfires, post-fire salvage logging and more recent intensive and extensive clearfell logging operations, have created landscape patterns unsuitable for P. australis. The implications of our results for the conservation of the species are discussed. In addition, some difficulties were experienced in the use of landscape-scale data in our statistical analyses, such as identifying attributes of landscape composition that are biologically relevant to the taxa targeted for analysis. We briefly discuss the nature of these problems.