Increasing interest in isolated wetlands requires an understanding of the location, spatial extent, and configuration of the resource. The National Wetlands Inventory (NWI) is the most commonly used data source for this information; however, the accuracy is limited in some contexts, e.g., agricultural, seasonally-ponded, or forested wetlands. This study sought to improve isolated wetland mapping accuracy by integrating currently available NWI maps with other geospatial data sources (i.e., Soil Survey Geographic Database [SSURGO], Digital Raster Graphics [DRGs], and Digital Elevation Models [DEMs]). Relative to NWI, the optimal model (combining data derived from NWI, SSURGO, and DRGs) identified 1,874 additional isolated wetlands and 19,737-ha of additional isolated wetland area. A remote accuracy assessment indicated a high degree of accuracy for the optimal model (Kappa00.88, Sensitivity090%, and Specificity098%), as compared to NWI maps (Kappa 00.70, Sensitivity 068%, and Specificity099%). Small wetlands (< 4-ha) dominated the wetland population and reduced nearest neighbor distances between wetlands. Isolated wetlands were clustered and clustering was strongest among larger wetlands. This study identified a framework for improving the accuracy of wetland maps and serves as a foundation for ongoing wetland studies within the Dougherty Plain.
Se utilizó fotografías aéreas de 1948, 1968, 1993 y 2007 para la construcción de una cronosecuencia de uso del terreno y cubierta terrestre (LULC) que representa el 10 por ciento del distrito fisiográfico de Dougherty Plain en el suroeste de Georgia. Encontramos grandes reducciones en la superficie de bosques y agricultura y el aumento de pino plantado y la agricultura de riego. El paisaje se hizo más fragmentado (por ejemplo, más parchos más pequeños) y dominado por algunas clases. Las tendencias variaron entre clases LULC con parchos de bosque cada vez más pequeños y de regadío cada vez más frecuente, especialmente en la porción central de la Llanura Dougherty donde las limitadas aguas superficiales requieren el uso de pozos de agua subterránea para el riego. Los pinos plantados fueron convirtidos principalmente de tierras agrícolas marginales entre 1948 y 1968, pero cada vez más de bosques en períodos posteriores. Los patrones LULC variaron espacialmente dentro de la Llanura Dougherty indicando que LULC puede ser impulsado por fenómenos a una escala más fina. Los conductores de los cambios observados incluyeron la adopción generalizada de riego de irrigación de pivote-central y programas de conservación de la tierra.
Phytoplankton from NE Do ñana marshland ("El Cangrejo Grande", Do ñana Natural Park, Spain)The study area ("El Cangrejo Grande", Doñana Natural Park) is located at the final section of the Guadiamar River channel and it is a part of the NE Doñana marshland. The hydrological characteristics of the area are complex and dynamic due to the different origin of its water input: the Guadiamar River basin, the Guadalquivir River estuary, and rice paddies outlets. This area is included in the hydrologic regeneration plan for the Doñana marshland ("Doñana 2005"), though the present study was finished before any modification took place. Phytoplankton richness was high since a total of 224 phytoplankton taxa were registered. Diatoms and Clorophytes were the groups that had the highest richness, Nitzschia palea, Cyclotella atomus and Monoraphidium contortum being the most widely distributed and abundant species. Phytoplankton exhibited a strong seasonal variation, in both composition and biomass, segregated in two periods (flood and desiccation) as suggested by the results of the PCA. On the other hand, the spatial differences were less evident according to a multidimensional scaling analysis (MDS). This seasonal pattern was stronger in the ordination of physico-chemical variables (conductivity, nutrient concentration and suspended matter). We conclude that this system is an ecotone zone with a high hydrologic complexity due to a variety of water inputs with a strong seasonality. These hydrologic features would be the determining factor in phytoplankton composition and high taxon richness.
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