The didactic valence of a complex fluvial geomorphosite: dendrochronology, vegetation, petrography and history as tools for an integrated landscape reading

A complex river may represent a precious occasion to understand the dynamicity of a multi disciplinary geo(morpho)site. The Trebbia River, located in the Northern Appennines, is one of the Po tributary flowing towards NE, through Liguria and Emilia Romagna regions. It is well differentiated along its course, so that several geological topics can be analysed in depth through an integrated landscape analysis, conferring the river with an high didactic value. The institution of three SICs (Community Important Sites) along this river represents a starting point that witnesses its importance from a naturalistic point of view as the different morphologies generated by different lithotypes, exemplary of those natural processes that modelled the Earth surface through geological times, witness. The good accessibility to the different scientific and cultural emergences represents in addition an indispensable feature, especially for scholars didactic purposes. Imaging to create an itinerary, particularly addressed to young students, some stops have been chosen to explain the geological and geomorphological setting, vegetation and anthropic settlements characteristics of this fluvial environment. Through the different tools at disposal (dendrochronology, petrography and vegetation) it is possible to configure some exercises to touch by hand the elements constituting the landscape. At last but not the least, the scenic impact of some elements and locations are definitely indisputable and probably means the easiest way to grow curiosity in the public, scholars and not, involved in any didactic or geotourist experience. The upper part of the valley is characterized by two SICs, both instituted in 1995: the San Salvatore Meanders (IT4010006) and the Bobbio-Perino area (IT4010011). This river portion develops across the Bobbio tectonic window and it is characterized by some spectacular scenic valued meanders set on the alternation of the miocenic Arenarie di San Salvatore and Argilliti di Brugnello belonging to the Toscana Nappe. The Trebbia passage through the Bobbio tectonic window, a morphology generated by the concomitant action of the fluvial erosion and tectonic uplifting processes, represents a scientific valence for its geohistorical importance as central tool for the investigation regarding the Northern Appennines thrust belt structure. At the same time it can become a meaningful occasion especially for scholars to approach one of the more complex tectonic concept in a simplified way. At the NE edge of this structure the Barberino Gorges allow the observation of the Ligurian Succession ophiolites relieves. They highlights the linking between geodiversity and biodiversity. The differences in the vegetation that grows on different lithology, as in the specific case on the ophiolites (serpentinofite: Euphorbia spinosa ssp. Ligustica, Sempervivum tectorum), is an evidence of the relation existing between geological substratum and biological diversities, covering the site of an ecological value. The lower valley, from Perino as far as the confluence with the Po River, is characterized by a wider braided riverbed, recognized as a SIC (IT4010016) in 2002. It is a site well predisposed to the examination of the recent evolution of the fluvial terraces and bars through dating of the different geomorphologic surfaces with. Here dendrochronological analysis carried out on bars and at the terrace edges allow to reconstruct the recent river evolution. Some dendrochronological exercises predisposed for the scholars permit them to experiment the scientific methods using the results as a control-instrument. The linkage between geomorphology and human settlements is evident in the case of both the selected cultural emergences located in Bobbio and Rivalta. They allow some reflections on the particular strategies adopted in the settlements choices during medieval and roman times. The scientific attribute, with its geomorphological model, geohistorical, ecological and didactic valences, together with the cultural and scenic attributes, reveal the sites along the Trebbia River to be ideal in order to propose an integrated reading of a river landscape, addressed to different kind of public.