<div>Figure 1. Examples of objects with box dimension ranging from one
(cylindrical pole) to three (solid cube) in between two real-life trees
and a Menger sponge (box dimension = 2.72).</div><div>Box dimension is a relatively new measure for assessing structural
complexity of trees and forests in relation to TLS. Seidel et al.
(2019b) studied the relationship between structural complexity (i.e. box
dimension) and horizontal and vertical architectural characteristics
(i.e. tree height and volume, crown radius and surface area, branching
angles) of deciduous trees (<i>Fagus sylvatica, Fraxinus excelsior,
Acer pseudoplatanus, Carpinus betulus</i> ) of varying size. They concluded
that structural complexity was related to crown radius and surface area
of deciduous trees. Dorji et al. (2019) studied how competition affects
structural complexity of European beech (<i>Fagus sylvatica</i> L.)
trees and concluded that their crowns were influenced by competition, as
measured through box dimension. Seidel et al. (2019a), on the other
hand, reported decreasing structural complexity when competition (i.e.
light availability) increased for deciduous trees. Previous work (Seidel
et al. 2018, 2019a, b) demonstrated the potential of box dimension as a
meaningful measure for structural complexity of individual trees.
However, how this measure can be used to quantify forest structure of
conifers and how it can expand our understanding about effects of
anthropogenic activities (e.g. forest management) on tree structure is
largely unexplored.</div><div>Although forest management affects growing conditions of trees as well
as their size and shape (Mäkinen &amp; Isomäki 2004, Saarinen et al. 2020),
it is unclear how forest management affects structural complexity of
conifers. This study aims at identifying relationships between a variety
of attributes (e.g. characterizing stem, crown, and competition) and
structural complexity of individual Scots pine (<i>Pinus sylvestris</i>L.) trees in even-aged and
single-layered managed boreal forest conditions. We aim to understand
how structural complexity is driven by forest management and underlying
structural attributes. We hypothesize that thinning intensity affects
structural complexity of Scots pine trees (H1). It is also hypothesized
that horizontal and vertical measures (e.g. stem and crown dimensions)
are related to structural complexity of Scot pine trees (H2). Finally,
we hypothesize (H3) that there is a relationship between structural
complexity and i) crown dimensions, ii) architectural benefit-to-cost
ratio (i.e. surface-to-volume ratio), iii) tree growth (i.e. DBH,
height, volume, and Δheight/DBH), and iv) the availability of light
(i.e. competition). In other words, structural complexity of individual
Scots pine trees can be explained by these attributes.</div>