Land-cover Classes (land-cover + class)

Distribution by Scientific Domains

Selected Abstracts

Urban Textural Analysis from Remote Sensor Data: Lacunarity Measurements Based on the Differential Box Counting Method

Soe W. Myint
Lacunarity is related to the spatial distribution of gap or hole sizes. For low lacunarity, all gap sizes are the same and geometric objects are deemed homogeneous; conversely, for high lacunarity, gap sizes are variable and objects are therefore heterogeneous. Textures that are homogeneous at small scales can be quite heterogeneous at large scales and vice versa, and hence, lacunarity can be considered a scale-dependent measure of heterogeneity or texture. In this article, we use a lacunarity method based on a differential box counting approach to identify urban land-use and land-cover classes from satellite sensor data. Our methodology focuses on two different gliding box methods to compute lacunarity values and demonstrate a mirror extension approach for a local moving window. The extension approach overcomes, or at least minimizes, the boundary problem. The results from our study suggest that the overlapping box approach is more effective than the skipping box approach, but that there is no significant difference between window sizes. Our work represents a contribution to not only advances in textural and spatial metrics as used in remote-sensing pattern interpretation but also for broadening understanding of the computational geometry of nonlinear shape models of which lacunarity is the reciprocal of fractal theory. [source]

A new land-cover map of Africa for the year 2000

Philippe Mayaux
Abstract Aim, In the framework of the Global Land Cover 2000 (GLC 2000), a land-cover map of Africa has been produced at a spatial resolution of 1 km using data from four sensors on-board four different Earth observing satellites. Location, The map documents the location and distribution of major vegetation types and non-vegetated land surface formations for the entire African continent plus Madagascar and the other surrounding islands. Methods, The bulk of these data were acquired on a daily basis throughout the year 2000 by the VEGETATION sensor on-board the SPOT-4 satellite. The map of vegetation cover has been produced based upon the spectral response and the temporal profile of the vegetation cover. Digital image processing and geographical information systems techniques were employed, together with local knowledge, high resolution imagery and expert consultation, to compile a cartographic map product. Radar data and thermal sensors were also used for specific land-cover classes. Results, A total of 27 land cover categories are documented, which has more thematic classes than previously published land cover maps of Africa contain. Systematic comparison with existing land cover data and 30-m resolution imagery from Landsat are presented, and the map is also compared with other pan-continental land cover maps. The map and digital data base are freely available for non-commercial uses from Main conclusions, The map improves our state of knowledge of the land-cover of Africa and presents the most spatially detailed view yet published at this scale. This first version of the map should provide an important input for regional stratification and planning purposes for natural resources, biodiversity and climate studies. Résumé Objet, Dans le cadre du projet Global Land Cover 2000 (GLC 2000), une carte d'Afrique d'occupation du sol a été produite à la résolution spatiale de 1 km à partir de données satellitales de 4 capteurs différents. Localisation, La carte représente la distribution des principaux types de végétation et des surfaces non-végétales du continent africain plus Madagascar et les autres îles voisines du continent. Méthodes, La plupart des données fut acquise durant l'année 2000 par le capteur VEGETATION, embarquéà bord du satellite SPOT-4. La réponse spectrale et le profil temporel des formations végétales ont permis la production de la carte d'occupation du sol. Des techniques de traitement d'image et de systèmes d'information géographique ont été combinées à la consultation d'experts locaux et à l'utilisation de cartes nationales et de données à haute résolution spatiale. Des images radar et thermiques ont servi à cartographier des classes spécifiques. Résultats, Un total de 27 classes est cartographié, ce qui est plus que les précédentes cartes basées sur l'imagerie satellitale. Une comparaison systématique avec les cartes publiées et des images Landsat à 30 m est présentée. Les données sont libres d'accès pour un usage non-commercial à l'adresse Conclusion, Cette carte accroît notre connaissance de l'occupation du sol de l'Afrique et présente la vue la plus détaillée jamais publiée à cette échelle. La première version de la carte devrait fournir une base importante pour une stratification régionale et pour la planification d'études sur les ressources naturelles, la biodiversité et le climat. [source]

Niche breadth rather than reproductive traits explains the response of wetland monocotyledons to land-cover change

Joan Pino
Abstract Question: We hypothesised that, even within the same plant functional group, there are specific distributions in land-cover classes and with land-cover change that are associated with niche breadth rather than reproductive strategy, and that the broader the niche of the species the better they cope with different land-cover classes and changes over time. Location: The Llobregat Delta (Barcelona, Spain). Methods: We analysed the distribution pattern of eight coexisting wetland perennial monocotyledons within human disturbance classes (obtained from the classification of land-cover categories in relation to their level of human disturbance) and changes in such classes from 1956 to 1999. We then compared species regional abundance and distribution patterns with seed dispersal type (wind dispersed versus non-wind dispersed species), vegetative spread (tussock versus caespitose-running species), and niche breadth (the number of phytosociological alliances in which each species is found). Results: Regional abundance of the species was positively related to niche breadth, but was independent of reproductive traits. Similarly, distribution in human disturbance classes and their changes were associated with niche breadth rather than reproductive traits. In general, the more specialist the species, (i) the more they are concentrated in natural habitats, (ii) the less land-cover changes they are able to cope with, and (iii) the more they are restricted to stable change types, particularly to longstanding natural areas. Conclusions: Ecological plasticity rather than dispersal capacity of dominant perennial monocotyledons determines their regional abundance and their ability to cope with recent and future land-cover changes in Mediterranean wetlands. As habitat specialists are less resistant to landscape change than generalists, floristic homogenisation may progress in these habitats with the likely scenario of increasing land-cover turnover. [source]