Three-dimensional quantification of tree architecture from mobile laser scanning and geometry analysis

Yonten Dorji,Peter Annighöfer,Emilie Isasa,Bernhard Schuldt,Kali Middleby,Liane Neudam,Klaus Körber,Christian Ammer,Dominik Seidel,Rinzin Dorji

doi:10.1007/s00468-021-02124-9

Abstract

Key messageMobile laser scanning and geometrical analysis revealed relationships between tree geometry and seed dispersal mechanism, latitude of origin, as well as growth.The structure and dynamics of a forest are defined by the architecture and growth patterns of its individual trees. In turn, tree architecture and growth result from the interplay between the genetic building plans and environmental factors. We set out to investigate whether (1) latitudinal adaptations of the crown shape occur due to characteristic solar elevation angles at a species’ origin, (2) architectural differences in trees are related to seed dispersal strategies, and (3) tree architecture relates to tree growth performance. We used mobile laser scanning (MLS) to scan 473 trees and generated three-dimensional data of each tree. Tree architectural complexity was then characterized by fractal analysis using the box-dimension approach along with a topological measure of the top heaviness of a tree. The tree species studied originated from various latitudinal ranges, but were grown in the same environmental settings in the arboretum. We found that trees originating from higher latitudes had significantly less top-heavy geometries than those from lower latitudes. Therefore, to a certain degree, the crown shape of tree species seems to be determined by their original habitat. We also found that tree species with wind-dispersed seeds had a higher structural complexity than those with animal-dispersed seeds (p < 0.001). Furthermore, tree architectural complexity was positively related to the growth performance of the trees (p < 0.001). We conclude that the use of 3D data from MLS in combination with geometrical analysis, including fractal analysis, is a promising tool to investigate tree architecture.

Highlights

The science of tree structure and form dates back to Leonardo da Vinci, who investigated the cross-sectional area of branches and found it to be maintained across branching orders (Richter 1970)
It is already known that tree architecture is not entirely random (Valladares and Niinemets 2007), and that it is determined by the dynamic response of tree growth to its abiotic and biotic environment, in the context of its genetic code (Hallé et al 1978; Scorza et al 2002; Busov et al 2008; Burkardt et al 2020)
For analysis of the relationship between seed dispersal strategy and the tree architectural complexity, we considered tree species for which the major seed dispersal strategy was animal-based or wind-based

Summary

Introduction

The science of tree structure and form dates back to Leonardo da Vinci, who investigated the cross-sectional area of branches and found it to be maintained across branching orders (Richter 1970). Tree shape has been shown to be influenced by environmental factors such as wind (Noguchi 1979; Watt et al 2005; De Langre 2008), water availability (Archibald and Bond 2003), light availability (Kuuluvainen 1992; Niinemets and Kull 1995), terrain slope (Barij et al 2007), and competition (Bayer et al 2013; Juchheim et al 2017) This adaptive geometry of trees (Horn 1971; Borchert and Slade 1981) is likely the result of an individual’s need to optimize fitness in a given location, which would include the need for structural stability, light interception, and reproductive success (Valladares and Niinemets 2007; Honda and Fisher 1978; Hollender and Dardick 2015). Depending on the environmental conditions at the growing site, many trees have a particular form that is distinguishable (Lindh et al 2018; Malhi et al 2018)

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Conclusion