Investigations on vitality and genetic structure in oak stands

Six oak stands with the two indigenous species Quercus petraea and Q robur were investigated in order to establish relationships between the vitality of oak trees and their genetic structure. The stands were affected by the 'European oak decline'. The registered traits of every tree were branching habits, defoliation, discoloration of foliage, necrosis on stems, epicormic branches at stems and in the crowns. The several traits were integrated into a vitality coefficient. Isozyme analyses were carried out to characterize the genetic structure of oak stands and subpopulations distinguished by their vitality. In principle, the results indicate the same tendency for the relationship between vitality and genetic structure for Q robur and Q petraea: increase of excess of homozygotes from the tolerant group to the sensitive group, decrease of observed heterozygosity from the tolerant to the sensitive group, maximum hypothetical gametic diversity and minimum subpopulation differentiation in the intermediate group as an indication for a directed selection.