Classification of the oldgrowthness of forest inventory plots with dissimilarity metrics in Italian National Parks

The concept of the old-growth forest is highly debated in the literature because of its implications, from close-to-nature forest management to carbon balance. Studies on old-growth forests have multiplied in the last three decades. Most of these studies have focussed on defining the structural features of old-growth forests of non-Mediterranean forest ecosystems or of specific forest types. In Italy, forest structure since Roman times has been greatly influenced by man. For this reason, the concept of old-growth forest in these ecosystems seems more controversial than at the global level. Nonetheless, in the Mediterranean region, there are persistent forest formations that present a certain level of oldgrowthness. These types of forests have been identified mostly in National Parks. The description of forest structure requires a vast amount of information about several biometric attributes. Consequently, the classification of forests as old growth is very time- and resource-consuming. This research aims to describe and test a proposed methodology to classify and determine the relative oldgrowthness of a series of forest inventory plots. Data from 77 beech forest plots located all across Italy were collected and compared with a virtual reference plot. To compare the forest plots, a set of similarity/dissimilarity indexes were tested. The results obtained show that it is possible to accurately rank the oldgrowthness of forest plots and to screen them to exclude non-old-growth forests. The method described was applied for the first time on a set of plots located in the Italian National Parks to determine a priority list of beech forests where further studies need to be conducted.