Crown architecture of mature Quercus robur L. (Fagaceae) trees in a floodland oak grove near the northern border of the area (Yaroslavl region)

The structural organization of the crown has been studied in middle-aged reproductive individuals of Quercus robur L., growing in a floodplain oak grove with a horizontal mosaic of the forest stand on the right bank of the river Volga in the vicinity of Yaroslavl. In total, 312 individuals of the one trunk and a few trunk life forms were studied. Quantitative relationships between the vertical zones and branches and trunk in the crown, direction of growth, growth, plan of organization and pattern of branching of the trunk and the largest and longest-lived branches from the trunk were analyzed. It has been established that in the studied cenopopulation, individuals with an orthotropic trunk predominate, the organization plan of which is hierarchical with polyarchic elements. The trunk and the axes that replace the trunk are characterized mainly by unstable monopodial growth. A wide variety of options for the combination of polyarchic elements on the trunk and the patterns of direction of the branches from the trunk are described. In a closed tree stand, the most common variant is that with a trunk with single fork structures, which forms branches that have an almost vertical growth direction. As light levels increase, the variety of options increases. In more illuminated habitats, the height of the crown attachment of individuals decreases, the ratio of the crown width to the height of the individual increases, the proportion of branches with a significant participation of sympodia and pseudodichotomous structures increases, and a larger number of pseudowhorls are formed on the trunk.