Evoluzione del paesaggio e cambiamenti di uso del suolo dal 1954 al 2006 nelle foreste di Tovanella e Cajada (Dolomiti - Belluno).

In this paper we would like to present the results of a work done within the project called “Scientific research to identify good management practices in natural forest reserves” with the collaboration of TeSAF and Corpo Forestale dello Stato. The aim of this work is to define if and how different levels of pressure on the environment within the study sites are able to modify and interfere with the landscape layout and configuration. To do this we have chosen two different study areas which structure, composition and processes have been already studied in previous works. The first one is the Tovanella Valley, which has not been actively managed since the 50’s and it was declared a Natural Reserve in 1971; the second one is the Cajada Valley that has been managed continuously until now, even if with lower levels of intensity. The following step was to collect and analyze different series of historical aerial photographs both in paper and digital supports, considering a time span of 52 years, from 1954 to 2006. These pictures were used to detect five different land use classes on the screen. An irreplaceable tool used during the analytical phase was the GIS (Geographic Information System), through which all the necessary data were extract by “reading” the landscape pattern. After the first phase, during which all the photographs were digitalized and correct by the orthorectification process, the second step was to analyze and differentiate the areas into 5 land use classes (forest - pasture – natural grassland – shurbland - rocks). The results show that changes have interest within the two study sites and that the forest has increased its total surface. The most important change, considering the effect connected to it, was the drastic reduction in open spaces as grasslands and pastures, that are responsible of a consistent part of the total amount of habitat biodiversity. Some landscape metrics were calculated, and then statistically analyzed. They show that the higher effect of the abandonment occurred in Tovanella where the openings were completely fulfilled by the forests, creating a uniform “green sea” of trees. On the other hand, the active management of Cajada Valley through the last decades, has ensured a certain level of habitat fragmentation and interconnectivity. In conclusion it is possible to say that the presence of men with their traditional activities on a local level and based on the ecological laws is the only feasible way to maintain an high biological diversity in these areas.