Stand structure and foliage distribution in Quercus pubescens and Quercus cerris forests in Tuscany (central Italy)

Abstract

We examined vertical foliage distribution (based on destructive harvesting) in the deciduous oak species Quercus pubescens and Quercus cerris, at the level of the entire tree and the forest community, in two adjacent stands in Tuscany (central Italy). The study was aimed at characterizing the structure of these stands in a manner suitable as a biometric background for comparison with canopy processes of other forest sites. The leaf study was based on the ‘cloud’ technique described earlier, characterizing the aggregation of leaves on branches and their position in the canopy. We used regressions (based on coefficients of the double-Gauss equation) to generalize leaf distribution in individual trees and to up-scale the data for whole stands. Q. cerris trees were about six meters taller than Q. pubescens, which grew in a more xeric site. The leaf area index was lower in the stand mainly composed of Q. pubescens (LAI = 2.8) than in the Q. cerris stand (LAI = 4.7). Oak canopies occupied about one half of the stand volume and about 40% of that were ‘clouds’. The leaf area index expressed on the area of projected crown and social trees differed substantially in individual trees of different size. The projected crown to social tree area ratio (an indicator of the structural balance of a tree) reached its minimum in a defined range of tree size; such an unfavourable balance may represent a risk to the survival of trees.