Long-term effects of experimental cutting to convert an abandoned oak coppice into transitional high forest in a protected area of the Italian Mediterranean region

Abstract This paper reports the results 20 years after undertaking experimental cutting to convert an abandoned Turkey oak ( Quercus cerris ) coppice into transitional high forest. The basic idea was to convert the coppice into high forest in a single intervention, by way of which an agametic high forest is shaped into an almost permanent compositional and structural arrangement. Two very low release densities, which were unusual both due to legal provisions and to that already tested in Italy, were applied and compared to natural evolution. The experimental thinnings were sustainable from a social and economic perspective, having given rise to positive revenue and not having limited the economic activities of the region. From an ecological perspective, the treated areas experienced an increase in volume between 77% and 80% – recovering from 91% to 100% of the harvested volume – and maintained a persistently low mortality rate for the entire period of observation. In the same period, the areas with natural evolution experienced an increase in volume of less than 14% and a high mortality rate, which, in addition to the Turkey oak individuals, also drastically reduced the presence of other tree species. The experimental thinnings modified the dimensional structure of the treated areas, making it almost uniform and physiognomically similar to that of a one-layer high forest. In the untreated areas, natural evolution produced a dimensional structure that is not very different from that of the treated areas, but over longer times and with selective processes occurring by chance. Twenty years later, the initial hypothesis of undertaking a conversion in a single intervention is corroborated by the results obtained.