Satellite data analysis for identification of groundwater salinization effects on coastal forest for monitoring purposes

The unconfined aquifer below the San Vitale pinewood (Ravenna, Italy) contains mainly salt and brackish groundwater because of excessive mechanical drainage, over-exploitation, and high rates of both natural and anthropogenic subsidence. Changes in the groundwater salinity concentration induce variations in the leaf properties and vegetation cover, recognizable by surveys carried out in different spectral bands. Therefore, a comparison between satellite images with different spatial and spectral resolutions, ASTER and Worldview-2, was made using the Normalized Difference Vegetation Index (NDVI). The aim is to identify portions of pinewood affected by groundwater salinization through a procedure that could reduce the expensive and time consuming ground monitoring campaigns. Moreover, the Worldview-2 high resolutions were used to investigate the Thermophilic Deciduous Forest (TDF) spectral behavior, chosen as a vegetation sample, without the influence of the allochthonous Pinus pinea species that is scattered inside the whole pinewood. The NDVI, calculated with traditional bands, identified the same stressed areas in both satellite data. Instead, using the new Red-Edge band of the Worldview-2 image, a greater correlation between NDVI and groundwater salinity was detected. Inside the TDF, the high resolution data showed that Pinus pinea species is an element of stress for the whole pine forest.