768 resultados para landscape modification


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1. Landscape modification is often considered the principal cause of population decline in many bat species. Thus, schemes for bat conservation rely heavily on knowledge about species-landscape relationships. So far, however, few studies have quantified the possible influence of landscape structure on large-scale spatial patterns in bat communities. 2. This study presents quantitative models that use landscape structure to predict (i) spatial patterns in overall community composition and (ii) individual species' distributions through canonical correspondence analysis and generalized linear models, respectively. A geographical information system (GIS) was then used to draw up maps of (i) overall community patterns and (ii) distribution of potential species' habitats. These models relied on field data from the Swiss Jura mountains. 3. Fight descriptors of landscape structure accounted for 30% of the variation in bat community composition. For some species, more than 60% of the variance in distribution could be explained by landscape structure. Elevation, forest or woodland cover, lakes and suburbs, were the most frequent predictors. 4. This study shows that community composition in bats is related to landscape structure through species-specific relationships to resources. Due to their nocturnal activities and the difficulties of remote identification, a comprehensive bat census is rarely possible, and we suggest that predictive modelling of the type described here provides an indispensable conservation tool.

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Aim To examine the distributional patterns of vertebrates (including birds, bats, carnivores and lagomorphs) along landscape composition and configuration gradients to better understand the effects of landscape modification on occurrence patterns at both species and community level. Location The region of Alentejo, a forest-dominated area of southern Portugal. Methods The study area was framed using 1647 hexagonal plots, each of 259 ha in size. Composition and configuration gradients were obtained for each plot by integrating the proportions of the main land cover types and their configuration patterns using multivariate analyses. Species-specific vertebrate responses were investigated using data from 75 plots in which carnivores, bats and lagomorphs were sampled, and from 135 plots in the case of birds. Community- level responses were investigated through changes in species richness and beta-diversity in 57 plots where all vertebrate groups were simultaneously sampled. At the species-level, an information-theoretic approach was used to determine the effects of landscape gradients on species’ responses. At the community level, Mantel tests were used to determine between-plot differences in species composition using the Sørensen dissimilarity index. Results We found that the occurrence patterns of most vertebrate species were best predicted by composition-related gradients, although configuration gradients were also frequently included in species-specific occurrence models. We also found a weak correlation between species richness and most landscape gradients suggesting a turnover in the identity of species, something that was corroborated by the stronger correlation between environmental gradients and beta-diversity measures. The amount of forest cover and landscape complexity (estimated as the heterogeneity in the size and number of land cover types) were the main composition and configuration gradients determining vertebrate responses at both species and community level. Main conclusions Our work contributes to a more refined understanding of the mechanisms underlying species distributional patterns in real-world human-modified landscapes. By uncovering generalities of species with multiple ecological requirements and by describing the entire landscape mosaic through landscape gradients, we also suggest that our work greatly helps to fill the gap between existing conceptual landscape models aimed to understand species distributional patterns in human-modified landscapes.

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We quantified differences in the abundance and diversity of bird species at inherent (naturally occurring) and induced (human-created) edges in the Murray Mallee, South Australia, to explore the effects of anthropogenic landscape modification. Bird species were classified into edge response categories based on numerical differences in abundance between the edge and interior of habitat patches. 'Open-country' species (e.g. Australian Magpie and Little Raven) increased in abundance near induced edges, but were rarely recorded > 200 m into patch interiors or at inherent edges. The Australian Ringneck, Red Wattlebird, Spiny-cheeked Honeyeater, Singing Honeyeater and White-eared Honeyeater increased in abundance near each inherent edge and were classified as 'edge-users'. However, their responses at induced edges varied between sites. The Yellow-plumed Honeyeater, Spotted Pardalote, White-browed Babbler, Chestnut Quail-thrush and Southern Scrub-robin decreased in abundance near one or more induced edges and were classified as 'edge-avoiders' at these sites. The Yellow-plumed Honeyeater, Spotted Pardalote, Chestnut Quail-thrush and Southern Scrub-robin are considered mallee habitat specialists in eastern Australia. These species may be particularly affected by anthropogenic modification of mallee vegetation.

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An archaeological survey on Peel Island in Moreton Bay, southeast Queensland, was conducted to assist the conservation planning for the Peel Island Lazaret (PIL), one of a number of institutions housed on the island during the nineteenth and twentieth centuries. The survey revealed a patteming of artefacts across the island as well as landscape modification related to its Aboriginal and European institutional uses.

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In Argentina, the incidence of American Cutaneous Leishmaniasis (ACL) has shown a steady increase over the last few decades. In the Chaco biogeographical region, specifically, several outbreaks of ACL were recently reported in addition to the usual time-space scattering of ACL cases. However, little is known about the sandfly composition in the eastern, humid Chaco (HC) region or the western, dry Chaco (DC) region. Therefore, phlebotomine captures were performed throughout this region and an analysis of the distribution of reported ACL cases was conducted in order to assess the vector diversity in ACL endemic and epidemic scenarios in the Chaco region. The results support the hypothesis of two distinct patterns: (1) the DC, where Lutzomyia migonei was the most prevalent species, had isolated ACL cases and a zoonotic cycle; (2) the HC, where Lutzomyia neivai was the most prevalent species, had an increase in ACL incidence and outbreaks and an anthropozoonotic cycle. The epidemic risk in the Chaco region may be associated with the current climate trends, landscape modification, connection with other ACL foci, and Lu. neivai predominance and abundance. Therefore, changes in sandfly population diversity and density in the Chaco region are an indicator of emergent epidemic risk in sentinel capture sites.

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Chagas disease is one of the most important yet neglected parasitic diseases in Mexico and is transmitted by Triatominae. Nineteen of the 31 Mexican triatomine species have been consistently found to invade human houses and all have been found to be naturally infected with Trypanosoma cruzi. The present paper aims to produce a state-of-knowledge atlas of Mexican triatomines and analyse their geographic associations with T. cruzi, human demographics and landscape modification. Ecological niche models (ENMs) were constructed for the 19 species with more than 10 records in North America, as well as for T. cruzi. The 2010 Mexican national census and the 2007 National Forestry Inventory were used to analyse overlap patterns with ENMs. Niche breadth was greatest in species from the semiarid Nearctic Region, whereas species richness was associated with topographic heterogeneity in the Neotropical Region, particularly along the Pacific Coast. Three species,Triatoma longipennis, Triatoma mexicana and Triatoma barberi, overlapped with the greatest numbers of human communities, but these communities had the lowest rural/urban population ratios. Triatomine vectors have urbanised in most regions, demonstrating a high tolerance to human-modified habitats and broadened historical ranges, exposing more than 88% of the Mexican population and leaving few areas in Mexico without the potential for T. cruzitransmission.

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Radiocarbon-dated palaeoecological records from the upland zone of the northern Apennines spanning the Mid-Late Holocene (last 7000 years) have been evaluated using established criteria for detecting anthropogenic impact on the landscape and environment. The integrated palaeoecological records across the study area collectively indicate human interference with natural vegetation succession and landscape modification from at least the Middle Neolithic. These activities resulted in the progressive decline of Abies, Ulmus, Fraxinus and Tilia, and the spread of Fagus, from ∼7000 cal BP, accompanied at various times by evidence for biomass burning, soil erosion, the expansion of shrubland and herbaceous taxa, and the possible cultivation of Olea, Juglans and Castanea. Comparison of these data with the archaeological scheme for the region, and the climate history of the central-western Mediterranean, has revealed that the palaeoecological records broadly support the archaeological evidence, but suggest that several key vegetation changes also coincide with important periods of climate change, especially at ∼7800–5000 cal BP.

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Landscape heterogeneity (the composition and configuration of matrix habitats) plays a major role in shaping species communities in wooded-agricultural landscapes. However, few studies consider the influence of different types of semi-natural and linear habitats in the matrix, despite their known ecological value for biodiversity. Objective To investigate the importance of the composition and configuration of matrix habitats for woodland carabid communities and identify whether specific landscape features can help to maintain long-term populations in wooded-agricultural environments. Methods Carabids were sampled from woodlands in 36 tetrads of 4 km2 across southern Britain. Landscape heterogeneity including an innovative representation of linear habitats was quantified for each tetrad. Carabid community response was analysed using ordination methods combined with variation partitioning and additional response trait analyses. Results Woodland carabid community response was trait-specific and better explained by simultaneously considering the composition and configuration of matrix habitats. Semi-natural and linear features provided significant refuge habitat and functional connectivity. Mature hedgerows were essential for slow-dispersing carabids in fragmented landscapes. Species commonly associated with heathland were correlated with inland water and woodland patches despite widespread heathland conversion to agricultural land, suggesting that species may persist for some decades when elements representative of the original habitat are retained following landscape modification. Conclusions Semi-natural and linear habitats have high biodiversity value. Landowners should identify features that can provide additional resources or functional connectivity for species relative to other habitat types in the landscape matrix. Agri-environment options should consider landscape heterogeneity to identify the most efficacious changes for biodiversity.

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An important challenge for conservation today is to understand the endangerment process and identify any generalized patterns in how threats occur and aggregate across taxa. Here we use a global database describing main current external threats in mammals to evaluate the prevalence of distinct threatening processes, primarily of anthropogenic origin, and to identify generalized drivers of extinction and their association with vulnerability status and intrinsic species' traits. We detect several primary threat combinations that are generally associated with distinct species. In particular, large and widely distributed mammals are affected by combinations of direct exploitation and threats associated with increasing landscape modification that go from logging to intense human land-use. Meanwhile, small, narrowly distributed species are affected by intensifying levels of landscape modification but are not directly exploited. In general more vulnerable species are affected by a greater number of threats, suggesting increased extinction risk is associated with the accumulation of external threats. Overall, our findings show that endangerment in mammals is strongly associated with increasing habitat loss and degradation caused by human land-use intensification. For large and widely distributed mammals there is the additional risk of being hunted.

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The maned wolf Chrysocyon brachyurus is the largest canid inhabiting South America. Its geographic distribution includes the open fields of Brazil's central area, which is currently undergoing agricultural expansion. The diet of the maned wolf and its seasonal variation was determined on a dairy cattle ranch (Sao Luis farm, 566 ha) in the State of Minas Gerais, Brazil. From January to December faeces of the maned wolf were collected monthly (n = 150 scats; 397 food item occurrences). Twenty-nine taxa were identified from scats, 18 of animal origin (46% or 183 occurrences) and 11 of plants (54% or 214 occurrences). The fruits of Solanum lycocarpum were the dominant food item in our study (29%). Mammals contributed 13%, arthropods 12%, birds 11% and reptiles 2% of the food items. Arthropods and fruits were prevalent in the rainy season and mammals in the dry season. As expected for a heavily fanned region, frugivory results were at the lower end of the diversity scale (9-33 species) and included four old garden species. No previous study of the diet of maned wolf has registered as many species of Solanaceae as this one. Although dietary richness was lower, the main food items (wolf fruit, armadillos, rodents, birds) were the same as study sites in 'cerrado' and upland meadows. In this region, the open habitats occupied by the maned wolf were previously covered by Atlantic forest, suggesting that landscape modification such as cattle ranching has opened new frontiers for distribution expansion of the maned wolf. The impact of loss of dietary richness and the increase in Solanaceae on the survival of the maned wolf need to be evaluated.

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La provincia de Mendoza, ubicada en el centro-oeste de la Argentina, tiene una extensión de 150 830 km2. Prácticamente todas las actividades agropecuarias y forestales están concentradas en el 3 % de su territorio que es posible irrigar. Al oeste, en el límite con Chile, está la cadena montañosa que forma parte de la región fitogeográfica del Desierto Andino que se extiende por más de 500 km, con un ancho promedio de 100 km. El objetivo del trabajo fue introducir algunas especies de coníferas y evaluar su comportamiento en dicha región fitogeográfica, con la finalidad de lograr un aprovechamiento forestal, proteger el suelo contra la erosión hídrica y/o eólica, modificar el paisaje y desarrollar áreas de explotación turística. Las especies seleccionadas en esta primera etapa fueron: Cedrus deodara, Cupressus arizonica, Cupressus macrocarpa, Juniperus virginiana, Pinus griffithii, Pinus halepensis, Pinus nigra, Pinus pinaster, Pinus pinea y Pinus radiata. Las experiencias se llevaron a cabo en dossitios, separados por más de 150 km, y situados a 1 050 y 2 000 msnm, respectivamente. Se tomaron datos de supervivencia, altura y diámetro de los individuos, y se efectuaron observaciones sobre su hábito de crecimiento y condiciones fitosanitarias. Las principales conclusiones fueron las siguientes: 1. Todas las especies mostraron buen estado fitosanitario sin haberse detectado ninguna plaga o enfermedad de importancia. 2. El hábito de crecimiento fue el correspondiente a cada especie; sólo hubo fustes bifurcados en algunos individuos de Pinus pinea. 3. Las especies que evidenciaron mayor aptitud fueron: Juniperus virginiana, Cupressus arizonica, Pinus pinea, Pinus pinaster y Cupressus macrocarpa.

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New Guinea's mountains provide an important case study for understanding early modern human environmental adaptability and early developments leading to agriculture. Evidence is presented showing that human colonization pre-dated 35ka (ka = thousands of uncalibrated radiocarbon years before present) and was accompanied by landscape modification using fire. Sorties into the subalpine zone may have occurred before the Late Glacial Maximum (LGM), and perhaps contributed to megafaunal extinction. Humans persisted in the intermontane valleys through the LGM and expanded rapidly into the subalpine on climatic warming, when burning and clearance may have retarded vegetation re-colonization. Plant food use dates from at least 31ka, confirming that some of New Guinea's distinctive agricultural practices date to the earliest millennia of human presence.

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Glacier and ice sheet retreat exposes freshly deglaciated terrain which often contains small-scale fragile geomorphological features which could provide insight into subglacial or submarginal processes. Subaerial exposure results in potentially rapid landscape modification or even disappearance of the minor–relief landforms as wind, weather, water and vegetation impacts on the newly exposed surface. Ongoing retreat of many ice masses means there is a growing opportunity to obtain high resolution geospatial data from glacier forelands to aid in the understanding of recent subglacial and submarginal processes. Here we used an unmanned aerial vehicle to capture close-range aerial photography of the foreland of Isfallsglaciären, a small polythermal glacier situated in Swedish Lapland. An orthophoto and a digital elevation model with ~2 cm horizontal resolution were created from this photography using structure from motion software. These geospatial data was used to create a geomorphological map of the foreland, documenting moraines, fans, channels and flutes. The unprecedented resolution of the data enabled us to derive morphological metrics (length, width and relief) of the smallest flutes, which is not possible with other data products normally used for glacial landform metrics mapping. The map and flute metrics compare well with previous studies, highlighting the potential of this technique for rapidly documenting glacier foreland geomorphology at an unprecedented scale and resolution. The vast majority of flutes were found to have an associated stoss-side boulder, with the remainder having a likely explanation for boulder absence (burial or erosion). Furthermore, the size of this boulder was found to strongly correlate with the width and relief of the lee-side flute. This is consistent with the lee-side cavity infill model of flute formation. Whether this model is applicable to all flutes, or multiple mechanisms are required, awaits further study.

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Objetivou-se com este trabalho avaliar qualitativamente a atividade de mineração de areia por draga na dinâmica fluvial do Rio Tocantins, no limítrofe do município de Imperatriz. A pesquisa foi realizada entre 2013 e 2014, com base na abordagem e na metodologia qualitativa. Foram realizadas visitas aos locais de extração, observação, registro por meio de imagens fotográficas, aplicação de questionário, estudo bibliográfico e consultas a sites. A mineração de areia tornou-se, um dos grandes contribuintes para o desenvolvimento socioeconômico do município, por gerar serviço direto e indireto. Porém, ao mesmo tempo, expõe traço impactante de ordem antrópica, representado pela modificação paisagística ribeirinha, dos logradouros e via de acesso das jazidas aos pontos de comercialização e aplicação da areia. Nos dados colhidos durante o período da pesquisa, não foram observados políticas ou projetos que viabilizem a mineração de forma sustentável no município, nem tão pouco a revitalização para as áreas degradadas.

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Eukaryotic cells make many types of primary and processed RNAs that are found either in specific subcellular compartments or throughout the cells. A complete catalogue of these RNAs is not yet available and their characteristic subcellular localizations are also poorly understood. Because RNA represents the direct output of the genetic information encoded by genomes and a significant proportion of a cell's regulatory capabilities are focused on its synthesis, processing, transport, modification and translation, the generation of such a catalogue is crucial for understanding genome function. Here we report evidence that three-quarters of the human genome is capable of being transcribed, as well as observations about the range and levels of expression, localization, processing fates, regulatory regions and modifications of almost all currently annotated and thousands of previously unannotated RNAs. These observations, taken together, prompt a redefinition of the concept of a gene.