I castagneti delle colline a sud-ovest di Siena: Origine e attuali modificazioni

Abstract

The chestnut woods on the hills South-West of Siena: their past origin and present modifications.—Phytosociological methods have been used to ascertain the origin and recent hystory of chestnut groves in the South-western Siennese hills. The present analysis was based on the assumption that chestnut (Castanea sativa) is autochthonous in this area, frequently occurring in mixed oakwoods of the order Quercetalia robori-petraeae and particularly abundant in the cooler and less dry sites. Several stands of chestnut coppices, fruit bearing chestnut groves, and mixed oakwoods (in which chestnut is relatively abundant and certainly autochthonous), have been analysed and compared. The floristic analysis shows that all the studied chestnut woods derive from mixed oakwoods in which man has eliminated all the woody species except the chestnut. These conclusions are in disagreement with the often held opinion that all chestnut woods of the Italian peninsula are artificial plantations established in preroman times. The main changes occurred in chestnut woods during the last 40–50 years, after the heavy damages caused by the parasitic fungi Endothia parasitica and Phytophtora cambivora, are outlined. Some modifications are due to man's action such as the conversion from chestnut groves to coppices or the substitution of chestnut with Conifers, especially Pinus pinaster. The main « spontaneous » modifications lead on the colder slopes to the reestablishment of a mixed forest with oaks, Turkey oaks and chestnuts; on the warm slopes, where the chestnut trees had probably been planted outside their ecologically optimal area, to a Calluna heath (Tuberario lignosae-Callunetum, ass. nova, Calluno-Genistion). These heaths can be spontaneously colonized by Pinus pinaster from adjacent reafforested areas.