POSTFIRE VEGETATION DYNAMICS IN A NATIVE PINUS-HALEPENSIS MILL. FOREST ON MT. CARMEL, ISRAEL

Israel's largest natural Pinus halepensis Mill. forest is on the Mt. C armel range and belongs to the distinct East Mediterranean genetic gro up. Most of this forest is the result of invasion of abandoned fields and grazing lands, resulting in a heterogeneous pine forest with an un derstory of broad-leaf shrubs and trees. Species composition, vegetati on cover, pine-stand structure, and pine genetic diversity of plots in sites of known fire history, burned 5, 11, and 20 years ago, were stu died with adjacent unburned sites forming a chronosequence. Except for annual species, no species replacement took place during post-fire su ccession. The main observed changes were in the cover of species and o f plant life forms. The ratio of tree/dwarf-shrub cover was found to b e linearly related to the number of years elapsed since the last fin. Therefore, this ratio could serve as an index to determine the success ional stage of Aleppo pine stands with unknown fire history. It is est imated that 30-40 years are needed for full recovery of Aleppo pine st ands after fire, depending upon site quality. The stands of post-fire regeneration are of uniform age and are less variable in their structu re than unburned stands. The genetic distance among the various Pinus halepensis subpopulations was found to be very small; most of the gene tic variability was due to within-subpopulations variability, with alm ost no variability among subpopulations. Alleles that an typical of We st Mediterranean P. halepensis populations or of P. brutia, were found in mio post-fire subpopulations (stands), indicating pre-fire cross p ollination between native Pious halepensis trees and trees in adjacent pine plantations of foreign origin. The conclusion is that fin has li ttle effect on species composition and on vegetation structure, but th at it alters the Aleppo pine stand structure.