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GIS Techniques (gi + techniques)
Selected AbstractsRefining Biodiversity Conservation PrioritiesCONSERVATION BIOLOGY, Issue 6 2005GRANT M. HARRIS Bosque del Atlántico; percepción remota; priorización; SIG; sitios prioritarios para la conservación Abstract:,Although there is widespread agreement about conservation priorities at large scales (i.e., biodiversity hotspots), their boundaries remain too coarse for setting practical conservation goals. Refining hotspot conservation means identifying specific locations (individual habitat patches) of realistic size and scale for managers to protect and politicians to support. Because hotspots have lost most of their original habitat, species endemic to them rely on what remains. The issue now becomes identifying where this habitat is and these species are. We accomplished this by using straightforward remote sensing and GIS techniques, identifying specific locations in Brazil's Atlantic Forest hotspot important for bird conservation. Our method requires a regional map of current forest cover, so we explored six popular products for mapping and quantifying forest: MODIS continuous fields and a MODIS land cover (preclassified products), AVHRR, SPOT VGT, MODIS (satellite images), and a GeoCover Landsat thematic mapper mosaic (jpg). We compared subsets of these forest covers against a forest map based on a Landsat enhanced thematic mapper. The SPOT VGT forest cover predicted forest area and location well, so we combined it with elevation data to refine coarse distribution maps for forest endemic birds. Stacking these species distribution maps enabled identification of the subregion richest in threatened birds,the lowland forests of Rio de Janeiro State. We highlighted eight priority fragments, focusing on one with finer resolved imagery for detailed study. This method allows prioritization of areas for conservation from a region >1 million km2 to forest fragments of tens of square kilometers. To set priorities for biodiversity conservation, coarse biological information is sufficient. Hence, our method is attractive for tropical and biologically rich locations, where species location information is sparse. Resumen:,Aunque hay acuerdo generalizado sobre las prioridades de conservación a escalas mayores (i. e., sitios prioritarios para la conservación de la biodiversidad), los límites son muy gruesos como para definir metas de conservación prácticas. La refinación de la conservación de sitios prioritarios significa la identificación de localidades específicas (parches de hábitat individuales) de tamaño y escala realistas para ser protegidos por gestores y apoyados por políticos. Debido a que los sitios prioritarios han perdido la mayor parte de su hábitat original, las especies endémicas dependen del que permanece. Ahora el asunto es identificar donde están el hábitat y las especies. Logramos lo anterior mediante técnicas directas de percepción remota y de SIG para identificar localidades específicas importantes para la conservación de aves en el sitio prioritario Bosque del Atlántico en Brasil. Nuestro método requiere de un mapa regional de la cobertura forestal actual, así que exploramos seis productos populares para el mapeo y cuantificación de bosques: campos continuos MODIS y una cobertura de suelo MODIS (productos preclasificados), AVHRR, SPOT VGT, MODIS (imágenes de satélite) y un mosaico GeoCover Landsat thematic mapper (jpg). Comparamos subconjuntos de estas coberturas forestales con las de un mapa basado en un Landsat enhanced thematic mapper. La cobertura forestal SPOT VGT predijo bien la superficie y localización del bosque, así que lo combinamos con datos de altitud para refinar los mapas generales de distribución de aves endémicas de bosques. La sobreposición de estos mapas de distribución permitió la identificación de la subregión más rica en aves amenazadas,los bosques en bajíos del Estado de Río de Janeiro. Dimos relevancia a ocho fragmentos prioritarios, con atención en uno con imágenes de resolución fina para estudio en detalle. Este método permite la priorización de áreas para conservación de fragmentos de decenas de kilómetros cuadrados en una región >1 millón km2. La información biológica general es suficiente para definir prioridades de conservación de la biodiversidad. Por lo tanto, nuestro método es atractivo para localidades tropicales y biológicamente ricas, para las que la información sobre la ocalización de las especies es escasa. [source] Upscaling water savings from farm to irrigation system level using GIS-based agro-hydrological modelling,IRRIGATION AND DRAINAGE, Issue 1 2007Shahbaz Khan simulation d'irrigation; extrapolation; efficacité d'utilisation de l'eau; économie de l'eau Abstract Irrigation continues to be the main water user on a global scale despite the increase in water use by sectors other than agriculture. More efficient water application technologies and water management practices are ways of realising potential water savings, thus moderating the negative impacts of higher water use on farm incomes and environmental impact on rivers and groundwater systems. This paper describes an integrated approach of agro-hydrological modelling for determining potential water savings achievable by adopting high-tech irrigation technologies at farm level and application of GIS techniques to upscale those benefits at the regional irrigation system level. The SWAP (Soil,Water,Atmosphere,Plant) model was used for the simulation of water use at the farm level. The results are promising, as the potential water saving ranges from 0.1 to 2.2,ML,ha,1 (10,220,mm) for different broad-acre crops, 1.0 to 2.0,ML,ha,1 (100,200,mm) in sprinkler and 2.0 to 3.0,ML,ha,1 (200,300,mm) in drip irrigation for citrus, 1.0 to 1.5,ML,ha,1 (100,150,mm) in sprinkler and up to 4.0,ML,ha,1 (400,mm) in drip irrigation for vineyards and 0.5 to 1.0,ML,ha,1 for vegetables (50,100,mm). SWAP simulations show crop water saving potential of 7% for maize, 15% for soybean, 17% for wheat, 35% for barley, 17% for sunflower and 38% for fababean from the current water use statistics in Australia. Spatial analysis in GIS environment is carried out to investigate the spatial variations of water use for a particular crop under different depths to water table and varying soil types. Maps of water need for all broad-acre crops are drawn and pixel-to-pixel comparison is performed to determine the water saving potential per unit area. The upscaling approach shows that considerable water amounts could be saved both in Murrumbidgee Irrigation Area (MIA) and Coleambally Irrigation Area (CIA) with potential water saving of 36 to 95,GL (MCM) in MIA and 42 to 72,GL (MCM) in CIA. Copyright © 2007 John Wiley & Sons, Ltd. L'irrigation reste l'usage principal de l'eau à l'échelle mondiale en dépit de l'augmentation des volumes utilisés par les secteurs autres que l'agriculture. L'amélioration des techniques d'irrigation et des procédures de gestion de l'eau permet de réaliser des économies d'eau potentielles, modérant ainsi les impacts négatifs d'une surconsommation d'eau sur les revenus agricoles et ses incidences sur l'environnement des cours d'eau et des aquifères. Cet article décrit comment un modèle agro-hydrologique intégré peut déterminer les économies d'eau réalisables grâce à l'adoption de technologies de pointe dans l'irrigation au niveau de l'exploitation agricole et à l'application des techniques de SIG à l'extension de ces avantages au niveau d'un système régional d'irrigation. Le modèle SWAP (Sol-Eau-Atmosphère-Plante) a été employé pour simuler l'utilisation de l'eau au niveau de l'exploitation. Les résultats sont prometteurs car l'économie d'eau potentielle va de 100 à 2 200 m3/ha (10 à 220 millimètres) pour différentes cultures de plein champ, de 1 000 à 2 000 m3/ha (100 à 200 millimètres) en aspersion et de 2 000 à 3 000 m3/ha (200 à 300 millimètres) en goutte à goutte sur des citronniers, de 1 000 à 1 500 m3/ha (100 à 150 millimètres) en aspersion et jusqu'à 4 000 m3/ha (400 millimètres) en goutte à goutte sur de la vigne, et de 500 à 1 000 m3/ha pour des légumes (50 à 100 millimètres). Les simulations de SWAP à partir de données statistiques australiennes courantes montrent un potentiel d'économie d'eau de 7% pour le maïs, 15% pour le soja, 17% pour le blé, 35% pour l'orge, 17% pour le tournesol et 38% pour les fèves. Une analyse par SIG permet d'étudier les variations spatiales de l'utilisation de l'eau pour une récolte particulière selon la profondeur de la nappe et le type de sol. Les besoins en eau de toutes les cultures de plein champ sont cartographiés et le potentiel d'économie d'eau par unité de surface est estimé pixel par pixel. L'extrapolation des résultats montre que des volumes d'eau considérables pourraient être économisés dans les zones irriguées de Murrumbidgee (MIA, économie potentielle de 36 à 95 millions de m3) et de Coleambally (CIA, économie potentielle de 42 à 72 m3). Copyright © 2007 John Wiley & Sons, Ltd. [source] Density effects on life-history traits in a wild population of the great tit Parus major: analyses of long-term data with GIS techniquesJOURNAL OF ANIMAL ECOLOGY, Issue 2 2006TEDDY A. WILKIN Summary 1Population density often has strong effects on the population dynamics and reproductive processes of territorial animals. However, most estimates of density-dependent effects use the number of breeding pairs per unit area in a given season and look for correlations across seasons, a technique that assigns the same density score to each breeding pair, irrespective of local spatial variation. 2In this study, we employed GIS techniques to estimate individual breeding densities for great tits breeding in Wytham Woods UK, between 1965 and 1996. We then used linear mixed modelling to analyse the effect of density on reproductive processes. 3The areas of Thiessen polygons formed around occupied nestboxes were used to approximate territory size (necessarily inverse of breeding density). There were significant, independent and positive relationships between clutch size, fledging mass and the number of offspring recruited to the population, and territory size (all P < 0·001), but no effect of territory size on lay-date or egg mass. 4Thiessen polygons are contiguous and cover all of the available area. Therefore, at low nest densities territory polygons were excessively oversized. Using a novel procedure to address this limitation, territory sizes were systematically capped through a range of maxima, with the greatest effect in the models when territories were capped at 0·9,2·3 ha. This figure approximates to the maximum effective territory size in our population and is in close agreement with several field-based studies. This capping refinement also revealed a significant negative relationship between lay-date and territory size capped at 0·9 ha (P < 0·001). 5These density-dependent effects were also detected when analyses were restricted to changes within individual females, suggesting that density effects do not merely result from either increased proportions of low-quality individuals, or increased occupation of poor sites, when population density is high. 6Overall, these results suggest that, in the current population, great tits with territories smaller than c. 2 ha independently lay smaller and later clutches, have lighter fledglings, and recruit fewer offspring to the breeding population. These analyses thus suggest a pervasive and causal role of local population density in explaining individual reproductive processes. [source] Identification of sediment source and sink areas in a Himalayan watershed using GIS and remote sensingLAND DEGRADATION AND DEVELOPMENT, Issue 6 2009M. K. Jain Abstract Erosion is a natural geomorphic process occurring continually over the Earth's surface and it largely depends on topography, vegetation, soil and climatic variables, and therefore, exhibits pronounced spatial variability due to catchment heterogeneity and climatic variation. This problem can be circumvented by discretizing the catchment into approximately homogeneous sub-areas using GIS. In this study, the remote sensing and GIS techniques (through Imagine®8.6 and ArcGIS®9.1 software) were used for derivation of spatial information, catchment discretization, data processing etc. for the Himalayan Chaukhutia watershed (India). Various thematic layers for different factors of USLE were generated and overlaid to compute spatially distributed gross soil erosion maps for the watershed using 18-year rainfall data. The concept of transport limited accumulation was formulated and used in ArcGIS® for generating the transport capacity maps. Using these maps, the gross soil erosion was routed to the catchment outlet using hydrological drainage paths, for derivation of transport capacity limited sediment outflow maps. These maps depict the amount of sediment rate from a particular grid in spatial domain and the pixel value of the outlet grid indicates the sediment yield at the outlet of the watershed. Up on testing, the proposed method simulated the annual sediment yield with less than ±40% error. Copyright © 2009 John Wiley & Sons, Ltd. [source] The nature and extent of landscape change under land resettlement programmes in ZimbabweLAND DEGRADATION AND DEVELOPMENT, Issue 5 2006J. A. Elliott Abstract Issues of land and further resettlement are central within the inter related crises that Zimbabwe is currently understood to be experiencing. This paper presents objective data that has not been available to date, concerning the landscape outcomes of the resettlement programme in Zimbabwe as it was implemented in the first two decades after independence. Sequential aerial photograph interpretation and GIS techniques are used to document and explore spatial patterns of resource use, landscape structure and change. Based on 21 resettlement villages across three scheme areas, the analysis explicitly considers the role of national drivers (of the relatively consistent policy and procedures during that time), of agro-ecology and of multidirectional transformations at the village level to raise understanding of these outcomes. The implications of these findings and the value of the methodological techniques for the design and monitoring of further resettlement in the country and the wider region are suggested. Copyright © 2006 John Wiley & Sons, Ltd. [source] Mapping data on enrolled studentsNEW DIRECTIONS FOR INSTITUTIONAL RESEARCH, Issue 120 2003Manuel Granados This chapter illustrates application of GIS techniques to analysis of student enrollment at a major university. [source] Thermokarst ponds as indicators of the former distribution of palsas in Finnish LaplandPERMAFROST AND PERIGLACIAL PROCESSES, Issue 1 2003Miska Luoto Abstract Thermokarst ponds resulting from thawing of palsas were mapped in a 95 km-long transect area in northern Finland. The spatial distribution of thermokarst was related to palsa distribution and to geographical variables using GIS techniques and multivariate spatial modelling. In our 3370 km2 study area, the former distribution of palsas was about three times larger than the present one. This indicates that the formation and thawing of permafrost are not in balance; palsas are collapsing and melting more often than palsas are forming. Copyright © 2003 John Wiley & Sons, Ltd. [source] Effects of modernisation on desired fertility in EgyptPOPULATION, SPACE AND PLACE (PREVIOUSLY:-INT JOURNAL OF POPULATION GEOGRAPHY), Issue 5 2007Angela Baschieri Abstract Using a conceptual framework that borrows notions both from the economic theory of fertility and social interaction theory, this paper assesses the relative importance of social and economic modernisation at the individual and community level in explaining geographical differentials in desired fertility in Egypt. Using the 2000 Egyptian Demographic Health Survey and an up-to-date map of land cover in Egypt, this paper provides an application of an advanced methodology which uses a combination of multilevel modelling and geographical information system (GIS) techniques. The paper shows how GIS techniques facilitate the construction of several variables representing the level of economic modernisation, such as land use, road density and urbanisation. It illustrates how GIS techniques and multilevel modelling can help us to move forward a step in substantiating theories of community influences on fertility. This study also analyses the effect of current family composition on desired fertility in Egypt and reveals the desire of Egyptian society to have at least two children and at least one boy. Copyright © 2007 John Wiley & Sons, Ltd. [source] | |||||||||||||