Growth analysis of an aged Turkey oak coppice under conversion into high forest

Abstract

Most Italian research concerning the conversion of coppices analyse growth response at the stand level and adopt absolute growth as reference metric. Nonetheless, inter-individual interactions are lost when averaging tree level information at the stand level. Moreover, absolute growth ignores the initial size of individuals under comparison, the growth of large trees will thus always outperform that of small trees, and nothing can be inferred about tree-to-tree competition. We modelled the growth response after conversion thinning at the tree level using relative growth rate as a function of the initial diameter of individuals, stand density and time. Twenty years later, thinned treatments still yielded larger growth than the reference unthinned aged coppice. In the first 10-year period, the relative growth rate in all treatments decreased with increasing tree size. In the second 10-year period, the relative growth rate still decreased with increasing tree size in thinned treatments, whereas in the unthinned aged coppice, it increased with increasing tree size. The model we applied shows to what extent released individuals have grown in relation to their size and, at same time, provides information on their competitive state in relation to the overall density of stands over time.