Towards the establishment of the Italian network of old-growth forests: the understorey plant diversity perspective

The publication of the Decree that has established the Italian network of old-growth forests opens new opportunities for nature conservation and new challenges for scientists. A fundamental criterion for the identification of old-growth forests is related to a “characteristic biodiversity” due to the absence of disturbances for at least sixty years. In this contribution we mainly discuss shortcomings, potential interpretation and perspectives related to the application of this criterion for the vascular plants living in the understorey. We show that the understorey diversity (both taxonomic and functional) patterns with forest maturity are strongly context-dependent and stand structural features are fundamental drivers. As a consequence, considering the impressive heterogeneity of Italian forests, the strict threshold included in the Decree (sixty years since the last disturbance) can hardly be used to distinguish a “characteristic biodiversity”. Finally, we invite all the Italian scientists dealing with forest ecosystems to strongly collaborate in order to accept the challenge introduced by the Decree.