Mapping land cover change in an Alpine protected area through historical aerial photos and object-based approach

The landscape pattern change, occurred in the last few decades, should to be monitored to understand the possible effects on ecological process. The aerial photos are a valuable tool to delineate landscape composition and configuration over large areas recognizing the vegetation patterns and their phisyognomy. Several drawbacks as data availability, software cost, image preparation and data mining affect the effective usability of aerial images. Here are shown a repatable workflow to retrieve quantitative data from different type of aerial photos using only free and open source geographical software (GFOSS). Two aerial photos (1975 and 2011), collected by Gran Paradiso National Park (GPNP), representing an altitudinal transect composed by 7 plot of 100 m of radius ranging from 1240-2440 m a.s.l. were used. Images were orthorectified, smoothed and similar group of neighbouring pixels were grouped in maningfull objects. Pixel groups were manually labeleld creating a spatial explicit databases. Using a priori defined minimum mapping unit (MMU), the two different altitutinal transect configurations were compared showing a strong change in vegetation pattern in Montane belt with a strong increase in tree cover and a shrink of pastures and meadows. Implemented method ensured a strong repeatability and suitability over different aerial images and represented scene, but there is the need to overcome challenge as the possibility to automatize the object labelling-step providing consistent results.