Postfire, natural regeneration of Pinus brutia forests in Thasos island, Greece

摘要

The natural, postfire regeneration of Pinus brutia forests has been studied in two 40-60-year-old forests of Thasos island, North Aegean sea, Greece, burned in the summers of 1985 and 1989. Within the latter burned area (5 700 ha), forty experimental sites of various aspects and site index values were established and successively monitored for 5 years, at 6-month intervals. Pine seedling emergence took place late in spring (due to a long drought in that particular year) but exclusively during the first postfire year. By the end of the recruitment period (May 1990), mean pine seedling density was considerably high (2-6 seedlings m(-2)) while a significant drop in the first summer was observed. Thereafter, a relatively smooth decline was obtained and the density was almost stabilized to about 0.6-2 seedlings m(-2) after 5 years: the kinetics of survival was found to follow a rectangular hyperbola. Significant differences in seedling density values were detected among site groups of varying aspect or site index: north-facing and index I sites showed the highest density values while south-facing and index V ones the lowest. Similarly, height kinetics showed a significant divergence among site groups; again, the north-facing and the index I sites were the fastest growing. Annual height growth showed a linear regression kinetics throughout the 5- (and conceivably 9-) year-long postfire period of study, with a yearly increment of 17 cm. Starting at an age of 4-6 years, an increasing fraction of the sapling population became reproductive so that after 9 years a considerable portion (5-15 %) had already produced cones with fully germinable seeds. (C) 2000 Editions scientifiques et medicales Elsevier SAS. [References: 41]