Soil Water Availability and the Renewal of Oak Forest Stands in a Coastal Mediterranean Area: an Experimental Study

this study was aimed to assess the causes of the structural decline in the renewal rate of a pristine oak forest close to Rome (central Italy) by analyzing long-term measurements of the water budget in open and fenced areas. Despite dry climate conditions in the area, long-term soil moisture measurements at 100 cm soil depth indicated that an enough large amount of water is available to oaks during the whole year. Moreover, while trees did not suffer from water deficit during summer, they may experience root asphyxia during rainy years. The analysis of the water budget clarified that, even during exceptionally-dry years, oak renewal was not limited by dry climate conditions. Instead, overgrazing due to the high demographic pressure determined by wild boars which eat almost exclusively oak acorns and deer which eat the leafs of young plants was one of the most important factors affecting oak renewal.