Abstract In the face of a changing climate and increasing human demand for water, an understanding of habitat preference has become critical for managing wild fish populations and projecting ...potential changes in habitat and populations. Two approaches to Physical Habitat Simulation (PHABSIM) modeling of coastal cutthroat trout Oncorhynchus clarkii clarkii spawning habitat were compared by modeling a reach, consisting of eight transects covering a pool and upstream and downstream riffles, of a small Puget Sound stream with two sets of habitat variables. The reach contained a cluster of redds 2 years in a row, assumed to be an indication of preferred spawning habitat and was located in the area of maximum spawning in the watershed, based on multiple years of redd surveys. Two PHABSIM instream flow models of the study site, one based on standard microhabitat (depth D, velocity V, and substrate S) suitabilities and the other based on D, V, and channel unit (CU) suitabilities, were developed and compared for their relative ability to correctly predict coastal cutthroat trout spawning habitat selection at the redd cluster within the PHABSIM study site. One approach was the standard use of habitat suitability criteria (HSC) for D, V, and S to indicate spawning habitat quality. The alternate approach was to replace substrate HSC with CU index HSC that incorporated dominant substrate particle diameter, CU (riffle, deep and shallow pool tail, pool body, deep and shallow pool edge, cascade, waterfall, and terrestrial), where deep and shallow units were based on relative residual depth (RRD), size of CU relative to channel width, and position within CU. Spawning habitat quality was calculated for each transect as weighted usable width with the standard HSC metrics (WUW s ) as well as the modified CU index (WUW m ). WUW m at the transects bracketing the redd cluster exceeded WUW m at the remaining six transects and was outside the 95% confidence interval for WUW m at the remaining transects. In contrast, WUW s varied less between the redd cluster and the remainder of the transects, suggesting the CU index better reflected spawning habitat quality than substrate. Incorporation of elevation relative to SZF addressed vulnerability to declining flow during incubation. Both models resulted in maximum WUA within the range of discharges that coincided with the majority of fresh cutthroat trout redds in Skookum Creek.
RESUMEN Las cuencas que drenan la costa oriental del Lago de Maracaibo en Venezuela se encuentran bajo fuertes impactos con efecto pernicioso sobre los ecosistemas fluviales, pero se desconoce su ...estado de conservación, lo que limita el manejo adecuado de los recursos hidrobiológicos regionales. En los tributarios Machango y Misoa se caracterizaron 16 tramos de ríos según las dimensiones del cauce, la composición del sustrato y las variables físico-químicas del agua, y se recolectaron muestras de insectos. El estado de conservación de las localidades se estimó mediante índices ambientales (IHF: índice de hábitat fluvial; QBR-And: índice de calidad de bosques de ribera andina; HII: índice de integridad de hábitat). Se exploraron las relaciones entre el gradiente del hábitat e índices mediante análisis de clasificación y ordenación multivariada. El hábitat acuático mostró un gradiente de heterogeneidad asociado directa y significativamente con la altura y el estado de conservación de cauces y zonas de ribera. Todos los índices tuvieron puntajes elevados donde hubo mayor cobertura vegetal en zonas de ribera y sustratos más heterogéneos; además, los índices tuvieron correlaciones proporcionales y significativas con el gradiente del hábitat fluvial y el número de familias de insectos acuáticos. Se reconoció un gradiente en el estado de conservación, donde una clase de conservación baja se asoció con hábitats homogéneos e intervenidos y con menor riqueza de insectos acuáticos. Los índices empleados son adecuados para estimar las clases de conservación de los ríos y sus biotas, pudiendo ser útiles para el monitoreo de las cuencas hidrográficas. SUMMARY The drainages of the eastern coast of Lake Maracaibo of Venezuela are subjected to strong disturbances, especially the loss of riparian forests and transformation of riverbeds, with detrimental effect on river ecosystems, but their conservation status is unknown, limiting appropriate management of regional hydrobiological resources. In the tributary rivers Machango and Misoa, 16 drainage sites were evaluated by characterizing the channel dimensions, the substrate composition and the water physicochemical variables. Aquatic insects were also collected using standardized sampling. The conservation status of the sites was estimated using environmental indices (IHF: fluvial habitat index; QBR-And: index of quality of Andean riparian forest; HII: habitat integrity index). Relationships between habitat gradient and the indices were explored by multivariate classification and ordination analysis. The synthetic variables generated were related environmental indices and biotas. The aquatic habitat showed a heterogeneity gradient directly and significantly associated with the variables that determine the structure of the channel and riparian zones. All indices scored higher where there was more vegetation cover in riparian zones and heterogeneous substrates; also, the indices had significant correlations with the gradient of fluvial habitat and number of insect families. A gradient in the conservation status was detected, where a class of low conservation was associated with homogeneous and impacted habitats and the lowest richness of insect families. The indices used are suitable to estimate conservation classes of rivers and their biotas, and may be employed for monitoring drainages. RESUMO As bacias que drenam a costa oriental do Lago de Maracaibo na Venezuela se encontram sob fortes impactos com efeito pernicioso sobre os ecossistemas fluviais, mas se desconhece seu estado de conservação, o que limita a manipulação adequada dos recursos hidro biológicos regionais. Nos tributários Machango e Misoa foram caracterizados 16 segmentos de rio segundo as dimensões do leito, a composição do substrato e as variáveis físico-químicas da água, e se recolheram amostras de insetos. O estado de conservação das localidades foi estimado mediante índices ambientais (IHF: índice de hábitat fluvial; QBR-And: índice de qualidade de florestas de ribeira andina; HII: índice de integridade de hábitat). Exploraram-se as relações entre a gradiente do hábitat e índices mediante análises de classificação e ordenação multivariada. O hábitat aquático mostrou uma gradiente de heterogeneidade associada direta e significativamente com a altura e o estado de conservação de leitos e áreas d e r ibeira. T odos o s í ndices t iveram pontuações elevadas onde houve maior cobertura vegetal em áreas de ribeira e substratos mais heterogêneos; além disso, os índices tiveram correlações proporcionais e significativas com a gradiente do habitat fluvial e o número de famílias de insetos aquáticos. Reconheceu-se uma gradiente no estado de conservação, onde uma classe de conservação baixa foi relacionada com habitats homogêneos e modificados, e com menor riqueza de insetos aquáticos. Os índices empregados são adequados para estimar as classes de conservação dos rios e suas biotas, podendo ser úteis para o monitoramento das bacias hidrográficas.
Exploring Spatial Scale in Geography provides a conceptual and practical guide to issues of spatial scale in all areas of the physical and social sciences. Scale is at the heart of geography and ...other spatial sciences. Whether dealing with geomorphological processes, population movements or meteorology, a consideration of spatial scale is vital. Exploring Spatial Scale in Geography takes a practical approach with a core focus on real world problems and potential solutions. Links are made to appropriate software environments with an associated website providing access to guidance material which outlines how particular problems can be approached using popular GIS and spatial data analysis software. This book offers alternative definitions of spatial scale, presents approaches for exploring spatial scale and makes use of a wide variety of case studies in the physical and social sciences to demonstrate key concepts, making it a key resource for anyone who makes use of geographical information.
Many large-scale connectivity initiatives have been proposed around the world with the aim of maintaining or restoring connectivity to offset the impacts on biodiversity of habitat loss and ...fragmentation. Frequently, these are based on the requirements of a single focal species of concern, but there is growing attention to identifying connectivity requirements for multi-species assemblages. A number of methods for modelling connectivity have been developed; likewise, different approaches have been used to construct resistance surfaces, the basic input data for connectivity analyses. In this study we modelled connectivity for a multi-species group of vertebrates representative of heavily fragmented forests in north-central Victoria, Australia. For each species, we used least-cost modelling and compared two alternate resistance surfaces, based on species distribution models and on expert opinion, respectively. We integrated the connectivity results across individual species to obtain a multi-species connectivity map for the region. A resistance surface based on expert assessment of the relative use of land-cover classes by the target species was more informative than one based on species distribution models. The former resulted in pathways more strongly aligned with existing patches and strips of native vegetation. In this region, pathways aligned with streams and their associated riparian vegetation have relatively high ecological potential and feasibility to contribute to regional connectivity for the assemblage of forest vertebrates.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Large-scale conversion of uncultivated land to agriculture threatens wildlife and can diminish ecosystem services provided by nature. Understanding how wildlife provision ecosystem services may ...incentivize wildlife conservation in agricultural landscapes. Attracting Barn Owls (Tyto furcata) to nest on farms for pest management has been implemented worldwide but has not been evaluated in vineyard agroecosystems. Napa Valley, California, is a renowned winegrape growing region, and viticulturists encourage Barn Owl occupancy to help minimize damage from Botta's pocket gophers (Thomomys bottae) and voles (Microtus spp.). This study modeled the use of habitats in space and time by hunting Barn Owls, providing information about their potential to provide the critical ecosystem service of pest consumption. We used global positioning system tags to track hunting owls and used a resource selection function to compare used and available habitats. We constructed the intensity of use and home range-movement maps using a time local convex hull analysis from location data. We found that Barn Owls selected uncultivated habitats when hunting, some of which were relatively rare on the landscape. Approximately, one-third of Barn Owl hunting locations occurred in vineyards, but this use was out of proportion to the availability of vineyards, which comprised 50% of the area around nest boxes. The owls' use of vineyards increased with decreasing amount of selected uncultivated habitat in the landscape. However, as reported by a previous study, the occupancy of nest boxes in vineyards increases with uncultivated habitats nearby. Future research should model landscape composition to determine the amount of preferred habitat necessary to support occupancy as well as hunting in vineyards. A true test of pest management by Barn Owls awaits experimentation coupled with monitoring rodent populations. LAY SUMMARY Agricultural landscapes are composed of a variety of habitats, both cultivated and uncultivated, and it is vital to understand how wildlife use these areas, especially for predatory birds that may help control agricultural pests. We used Global Positioning System telemetry to examine the selection of habitats for hunting by Barn Owls breeding in nest boxes in winegrape vineyards. Barn Owls selected uncultivated habitats, such as oak savanna, riparian forest, and grasslands for hunting, some of which were relatively rare on the landscape. Nonetheless, approximately, one-third of Barn Owl hunting locations occurred in vineyards, suggesting their predation of rodent pests could be useful for farmers.
The concept of the ecological trap, a low-quality habitat that animals prefer over other available habitats of higher quality, has appeared in the ecological literature irregularly for over 30 years, ...but the topic has received relatively little attention, and evidence for traps remains largely anecdotal. Recently, however, the ecological trap concept has been the subject of a flurry of theoretical activity that is likely to raise its profile substantially, particularly in conservation biology. Ecological trap theory suggests that, under most circumstances, the presence of a trap in a landscape will drive a local population to extinction. A number of empirical studies, almost all of birds, suggest the existence of traps and demonstrate the difficulties of recognizing them in the field. Evidence for ecological traps has primarily been found in habitats modified by human activities, either directly (e.g., through the mowing of grassland birds' nests) or indirectly (e.g., via human-mediated invasion of exotic species), but some studies suggest that traps may occur even in relatively pristine areas. Taken together, these theoretical and empirical results suggest that traps may be relatively common in rapidly changing landscapes. It is therefore important for conservation biologists to be able to identify traps and differentiate them from sinks. Commonly employed approaches for population modeling, which tend to assume a source-sink framework and do not consider habitat selection explicitly, may introduce faulty assumptions that mask the effects of ecological traps and lead to overly optimistic predictions about population persistence. Given the potentially dire consequences of ecological traps and the accumulating evidence for their existence, greater attention from the community of conservation biologists is warranted. In particular, it is important for conservation biologists and managers to incorporate into conservation planning an explicit understanding of the relationship between habitat selection and habitat quality.
Habitat quality of a bird's breeding grounds has been typically evaluated by investigating patterns in nesting success, whereas events that follow fledging have been largely ignored. One especially ...overlooked aspect of breeding-habitat quality is how habitat affects the survival of young birds after they leave the nest, a period when mortality is notoriously high. We studied survival of fledglings of two mature-forest species, the Ovenbird (Seiurus aurocapilla) and Worm-eating Warbler (Helmitheros vermivorum), to identify intrinsic (e.g., age, condition) and extrinsic (e.g., habitat structure) factors that influence survival. From 2004 to 2007, we radio-tagged 51 Ovenbird and 60 Worm-eating Warbler fledglings in southeast Ohio. We recorded the birds' locations daily and compared vegetation structure at the fledglings' and paired random locations. Using known-fate models in program MARK, we calculated post-fledging survival to be 65% for the Ovenbirds (51 days after fledging) and 67% for the Worm-eating Warblers (31 days after fledging). Fledglings' condition at the time of radio tagging was positively related to survival after fledging, implying carryover effects from the nestling period. Fledglings of both species used dense vegetation with 40–60% more woody stems in the understory than at random locations. Moreover, use of dense vegetation actually promoted survival. Although riparian thickets and tree-fall gaps within some forests may provide abundant habitat for fledglings, other forests may lack the structural attributes that promote fledglings' survival. Our findings highlight the importance of both breeding and post-fledging requirements being considered in avian conservation plans.
Coastal ecosystems and the services they provide are adversely affected by a wide variety of human activities. In particular, seagrass meadows are negatively affected by impacts accruing from the ...billion or more people who live within 50 km of them. Seagrass meadows provide important ecosystem services, including an estimated $1.9 trillion per year in the form of nutrient cycling; an order of magnitude enhancement of coral reef fish productivity; a habitat for thousands of fish, bird, and invertebrate species; and a major food source for endangered dugong, manatee, and green turtle. Although individual impacts from coastal development, degraded water quality, and climate change have been documented, there has been no quantitative global assessment of seagrass loss until now. Our comprehensive global assessment of 215 studies found that seagrasses have been disappearing at a rate of 110 km² yr⁻¹ since 1980 and that 29% of the known areal extent has disappeared since seagrass areas were initially recorded in 1879. Furthermore, rates of decline have accelerated from a median of 0.9% yr⁻¹ before 1940 to 7% yr⁻¹ since 1990. Seagrass loss rates are comparable to those reported for mangroves, coral reefs, and tropical rainforests and place seagrass meadows among the most threatened ecosystems on earth.
Flying animals use aerial habitats to forage, communicate and travel. However, human activities that fragment aerial habitat with built structures, noise, and chemical or light pollution, may limit ...the ability of wildlife to use airspace efficiently. Applying landscape connectivity theory to aerial habitats could reveal how long‐distance migrants respond to sources of aerial habitat fragmentation along their migratory routes. Artificial light at night is a major component of urbanization that fragments dark skies across North America. Attraction of nocturnal migrants to urban light is well documented, but species‐specific responses, especially throughout a full migration from breeding to wintering grounds, are not. We tested hypotheses about long‐distance migratory movements in relation to artificial light using a highly nocturnal, Nearctic‐Neotropical avian migrant (Eastern whip‐poor‐will Antrostomus vociferus). We applied a resource selection framework at multiple spatial scales to explore whether GPS‐tracked birds (n = 10) responded to urbanization in general, or artificial light specifically, during migratory flights. We found little evidence of attraction to artificial light during nocturnal flights. Artificial light and urbanization were highly correlated and difficult to disentangle, but the birds generally avoided urban areas and selected dark‐connected skies for travel. Migratory stopovers (locations where GPS‐tracked birds (n = 20) paused for at least one night), were located almost exclusively in dark, rural areas. Our results illustrate that considering how nocturnal aerial migrants respond to both aerial and terrestrial habitat elements can improve our understanding of what may facilitate their long‐distance movements.
Context
An understanding of species-habitat relationships is required to assess the impacts of habitat fragmentation and degradation. To date, habitat modeling in fragmented landscapes has relied on ...landscape composition and configuration metrics and the importance of habitat quality in determining species distributions has not been sufficiently explored.
Objectives
We evaluated how habitat use by herbivores and frugivorous mammals is shaped by a potential interaction of habitat amount and quality in the Brazilian Pantanal wetland. We also assessed if the contribution of habitat quality to species´ habitat use varies according to the species sensitivity to habitat loss.
Methods
We combined mammal detection data obtained from camera traps with thematic maps to estimate the amount of habitat and measured habitat quality using local environment variables and distance to waterbodies. Specifically, we used a single-season occupancy approach to evaluate the relative support of univariate, additive, and interactive relationships between species-specific habitat use and measures of habitat quality and quantity.
Results
Habitat quality was more important than habitat amount in determining species habitat use (occupancy) in a naturally fragmented landscape. Habitat quality alone was the best predictor of habitat use for two of the six species (white lipped peccary and collared peccary), but no species’ habitat use was explained solely by habitat amount. Habitat amount was influential only when considered in conjunction with habitat quality covariates and only for two sensitive species to habitat loss (agouti and red brocket deer). Habitat quality alone was the best predictor of habitat use for two of the less sensitive species (white lipped peccary and collared peccary). Habitat use for two species was not explained by any covariate (tapir and gray brocket deer).
Conclusions
Conservation programs should incorporate both habitat quality and amount when dealing with sensitive species and prioritize habitat quality management when focusing in less sensitive species.
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