Ricostituzione della vegetazione dopo il taglio delle pinete di Pinus pinea L.

Stone pine (Pinus pinea L.) plantations are typical elements of the Tuscan coastal land-scape. Therefore, the Program of Forest Operations in the San Rossore Estate for 2005-2009 planned that the old plantations should be renewed by means of clear-cut in narrow strips and patches. In order to evaluate the natural regeneration of the vegetation cover, in-vestigations were carried out in four cut strips and two control stands of two stone pine plantations that were over 100-year old. Cutting operations were performed in the period 2006-2008 and investigations were carried out between the first and the fourth vegetative seasons after clearcut. The effects of clearcut were determined on: 1) the main soil physi-cal and chemical properties; 2) the size and composition of the soil seed bank; 3) the re-covery of plant cover, and 4) the impact of browsing and predation on plant regrowth. The clearcut of stone pine plantations reduced the content of organic matter and nutrients in the superficial soil layer and caused their uneven distribution, creating patches com-pletely free from organic soil. The soil seed bank contained from 300 to 3,000 seeds m-2, values corresponding to a poor seed bank typical of mature forests, which is scarcely able to sustain the rapid recovery of vegetation. Seeds were small sized, mostly comprised be-tween 1 and 2 mm and never larger than 4 mm, and, approximately half of the species, had broad ecological amplitude or were aliens. Clearcut reduced the number of larger seeds increasing the proportion of seeds smaller than 1 mm. The vegetation cover increased progressively in the years following clearcut, covering 70% of soil after four vegetative seasons, primary due to the diffusion of graminoid spe-cies, Erica scoparia and Rubus sp, all species able to sprout from roots or below-ground organs. The proportion of alien species in the plant cover never exceeded 2%. Browsing intensity changed among years and was highly selective. Browsing was never observed on saplings of Pinus pinea, Erica scoparia and Myrtus communis, all species that are crucial for the restoration of stone pine forest types. However, wildlife could hinder the recruitment of tree species by means of seed predation and, only for broadleaves, also for the browsing of saplings. Results on soil and soil seed-bank characteristics highlight that the stone pine plantations of the San Rossore Estate and of the Tuscan coast in general, are vulnerable biocoenoses. In consequence, their natural revegetation after severe disturbances such as clearcut could lead to vegetation types with minor biogenetic and lanscape value, in contrast with the role of Biosphere Reserve assigned to the area. We suggest that the rapid regrowth of Erica scoparia and of other understory shrubs is crucial to protect soil from erosion, thus reducing nutrient losses through leaching and mineralization, and to prevent that bare soils are invaded by alien species sprouted from the seed bank or arrived from the surroundings.