Mangrove forests submitted to depositional processes and salinity variation investigated using satellite images and vegetation structure surveys

The current paper examines the growth and spatio-temporal variation of mangrove forests in response to depositional processes and different salinity conditions. Data from mangrove vegetation structure collected at permanent plots and satellite images were used. In the northern sector important environmental changes occurred due to an artificial channel producing modifications in salinity. The southern sector is considered the best conserved mangrove area along the coast of São Paulo State, Brazil. Landsat TM5 images from 1997 and 2010 were processed using Geographical Information Systems. Supervised classifications complemented by visual interpretations and ground truth were used to map mangrove areas in both periods. In each permanent plot, all plants were identified and tree diameter, height, and incidence of associated species were recorded. Mean height, basal area dominance, and stem density were also assessed. In the southern sector of the study area, digital image analysis revealed shoreline progradation and mangrove establishment. These sites have demonstrated both vegetation growth and extension. In the northern sector, the satellite image analysis revealed an increase of depositional areas. An important number of associated freshwater plants were observed, inhibiting the establishment of mangrove seedlings or growth of saplings. Despite the high sedimentation rate, which enables mangrove colonization, the low salinity exerts indirect negative influence on mangrove development, considering that it creates good conditions to macrophytes reproduction. Coastal planning requires that the spatial differences be recognized as unique sub-systems due to the hydrodynamic complexity. Both on-theground monitoring of the vegetation structure and space-borne remote sensing are important tools to support coastal zone management.SCOPUS: cp.j