Recent channel adjustments and riparian vegetation response: some examples from Molise (Italy)

Abstract

An integrated geomorphological and ecological approach was adopted to investigate the relation between recent channel adjustments and riparian vegetation evolution by performing a large-scale multi-temporal analysis of channel and land cover features and a study of the present-day floristic setting along the three major river systems present in Molise (Southern Italy), the Volturno, Biferno and Trigno. Our results highlight the major channel adjustments that occurred between 1954 and 2009 consisting in progressive morphological changes, extreme channel narrowing (between 84% and 97%) and moderate to very intense channel incision (between 2 and 10.5 m). These channel adjustments led to the progressive stabilization of most of the formerly active channel systems and were accompanied by substantial changes in the riparian vegetation which now appears largely, but not completely, in equilibrium with the present river dynamics. Major differences may be noted between the studied river reaches in relation to their state of naturalness, floristic richness and differentiation in vegetation types, which appear particularly controlled by the amount of channel incision and human disturbance. Our findings underline the importance of fluvial dynamics and trends in controlling the development and structure of riparian vegetation and the connected ecological status of river systems.