Abstract
The accuracy of the description regarding tree architecture is crucial for data processing. LiDAR technology is an efficient solution for capturing the characteristics of individual trees. The aim of the present study was to analyze tree shape variability in a mixed oak forest consisting of four European white oak species: Quercus petraea, Q. frainetto, Q. pubescens, and Q. robur. Moreover, we tested for association between tree shape and individual heterozygosity and whether oak trees identified as pollen donors in a previous genetic study have a larger size in terms of crown and trunk characteristics than non-donors. The woody structure of a tree was defined by the quantitative structure model (QSM) providing information about topology (branching structure), geometry, and volume. For extracting the 3D point clouds a high-speed 3D scanner (FARO FocusS 70) was used. The crown variables were strongly correlated to each other, the branch volume being influenced by branch length, maximum branch order, and the number of branches but not influenced by diameter at breast height (DBH), trunk length, trunk volume, or tree height. There was no relationship between the individual heterozygosity based on nuclear microsatellite genetic markers and crown and trunk characteristics, respectively. Branch volume, total area, DBH, trunk volume, and the total volume of tree were significantly larger in pollen donors compared to non-donor Q. petraea trees. Thus, the mean branch volume was more than three times higher. Pollen donors had nearly two and half times larger total area in comparison to non-donor individuals. Our results suggest that a thorough characterization of tree phenotype using terrestrial laser scanning may contribute to a better understanding of mating system patterns in oak forests.
Highlights
Tree shape variability, the shape of the crown, can vary among and within tree species depending on many factors, influenced by site conditions and tree competition for light [1]
The main objective of the present study was to analyze tree shape variability of different European white oak species growing in similar site conditions
After noise filtering of all elements smaller than 10 mm, which were discarded to avoid misleading information in the quantitative structure model (QSM) reconstruction, the 3D point clouds of each tree were reduced by an average of approx. 5% of the original data
Summary
The shape of the crown, can vary among and within tree species depending on many factors, influenced by site conditions and tree competition for light [1]. It is determined by expansion of lateral and terminal branches, lateral branches that extend from the main stem (first-order branches) being controlled to varying degrees by the terminal branches. There are usually no more than five orders of branches as the branches of higher orders die because of lack of light inside the crown [2,3,4]. In terms of tree architecture, the accuracy and level of characterization is important, as the deeper the characterization goes the harder and more time consuming it is to extract accurate results
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