Response of Beech (Fagus sylvatica L.) Trees to Competition—New Insights from Using Fractal Analysis

Individual tree architecture and the composition of tree species play a vital role for many ecosystem functions and services provided by a forest, such as timber value, habitat diversity, and ecosystem resilience. However, knowledge is limited when it comes to understanding how tree architecture changes in response to competition. Using 3D-laser scanning data from the German Biodiversity Exploratories, we investigated the detailed three-dimensional architecture of 24 beech (Fagus sylvatica L.) trees that grew under different levels of competition pressure. We created detailed quantitative structure models (QSMs) for all study trees to describe their branching architecture. Furthermore, structural complexity and architectural self-similarity were measured using the box-dimension approach from fractal analysis. Relating these measures to the strength of competition, the trees are exposed to reveal strong responses for a wide range of tree architectural measures indicating that competition strongly changes the branching architecture of trees. The strongest response to competition (rho = −0.78) was observed for a new measure introduced here, the intercept of the regression used to determine the box-dimension. This measure was discovered as an integrating descriptor of the size of the complexity-bearing part of the tree, namely the crown, and proven to be even more sensitive to competition than the box-dimension itself. Future studies may use fractal analysis to investigate and quantify the response of tree individuals to competition.

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Quantifying Understory Complexity in Unmanaged Forests Using TLS and Identifying Some of Its Major Drivers

Remote Sensing ◽

10.3390/rs13081513 ◽

2021 ◽

Vol 13 (8) ◽

pp. 1513

Author(s):

Dominik Seidel ◽

Peter Annighöfer ◽

Christian Ammer ◽

Martin Ehbrecht ◽

Katharina Willim ◽

...

Keyword(s):

Laser Scanning ◽

Structural Equation Models ◽

Light Availability ◽

Structural Complexity ◽

Basal Area ◽

Ecosystem Functions ◽

Canopy Openness ◽

Seasonal Precipitation ◽

Wide Range ◽

Precipitation And Temperature

The structural complexity of the understory layer of forests or shrub layer vegetation in open shrublands affects many ecosystem functions and services provided by these ecosystems. We investigated how the basal area of the overstory layer, annual and seasonal precipitation, annual mean temperature, as well as light availability affect the structural complexity of the understory layer along a gradient from closed forests to open shrubland with only scattered trees. Using terrestrial laser scanning data and the understory complexity index (UCI), we measured the structural complexity of sites across a wide range of precipitation and temperature, also covering a gradient in light availability and basal area. We found significant relationships between the UCI and tree basal area as well as canopy openness. Structural equation models (SEMs) confirmed significant direct effects of seasonal precipitation on the UCI without mediation through basal area or canopy openness. However, annual precipitation and temperature effects on the UCI are mediated through canopy openness and basal area, respectively. Understory complexity is, despite clear dependencies on the available light and overall stand density, significantly and directly driven by climatic parameters, particularly the amount of precipitation during the driest month.

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Assessing Understory Complexity in Beech-dominated Forests (Fagus sylvatica L.) in Central Europe—From Managed to Primary Forests

Sensors ◽

10.3390/s19071684 ◽

2019 ◽

Vol 19 (7) ◽

pp. 1684 ◽

Cited By ~ 9

Author(s):

Katharina Willim ◽

Melissa Stiers ◽

Peter Annighöfer ◽

Christian Ammer ◽

Martin Ehbrecht ◽

...

Keyword(s):

National Parks ◽

Fagus Sylvatica ◽

Laser Scanning ◽

Three Dimensional ◽

European Beech ◽

Point Clouds ◽

Tree Regeneration ◽

Understory Vegetation ◽

Fagus Sylvatica L ◽

Primary Forests

Understory vegetation influences several ecosystem services and functions of European beech (Fagus sylvatica L.) forests. Despite this knowledge on the importance of understory vegetation, it is still difficult to measure its three-dimensional characteristics in a quantitative manner. With the recent advancements in terrestrial laser scanning (TLS), we now have the means to analyze detailed spatial patterns of forests. Here, we present a new measure to quantify understory complexity. We tested the approach for different management types, ranging from traditionally and alternatively managed forests and national parks in Germany to primary forests of Eastern Europe and the Ukraine, as well as on an inventory site with more detailed understory reference data. The understory complexity index (UCI) was derived from point clouds from single scans and tested for its relationship with forest management and conventional inventory data. Our results show that advanced tree regeneration is a strong driver of the UCI. Furthermore, the newly developed index successfully measured understory complexity of differently managed beech stands and was able to distinguish scanning positions located on and away from skid-trails in managed stands. The approach enables a deeper understanding of the complexity of understory structures of forests and their drivers and dependents.

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A Novel Approach for the Detection of Standing Tree Stems from Plot-Level Terrestrial Laser Scanning Data

Remote Sensing ◽

10.3390/rs11020211 ◽

2019 ◽

Vol 11 (2) ◽

pp. 211 ◽

Cited By ~ 26

Author(s):

Wuming Zhang ◽

Peng Wan ◽

Tiejun Wang ◽

Shangshu Cai ◽

Yiming Chen ◽

...

Keyword(s):

Laser Scanning ◽

Terrestrial Laser Scanning ◽

Natural Forests ◽

Individual Tree ◽

Urban Scenes ◽

Novel Approach ◽

Wide Range ◽

Standing Trees ◽

The Mean ◽

Point Cloud Classification

Tree stem detection is a key step toward retrieving detailed stem attributes from terrestrial laser scanning (TLS) data. Various point-based methods have been proposed for the stem point extraction at both individual tree and plot levels. The main limitation of the point-based methods is their high computing demand when dealing with plot-level TLS data. Although segment-based methods can reduce the computational burden and uncertainties of point cloud classification, its application is largely limited to urban scenes due to the complexity of the algorithm, as well as the conditions of natural forests. Here we propose a novel and simple segment-based method for efficient stem detection at the plot level, which is based on the curvature feature of the points and connected component segmentation. We tested our method using a public TLS dataset with six forest plots that were collected for the international TLS benchmarking project in Evo, Finland. Results showed that the mean accuracies of the stem point extraction were comparable to the state-of-art methods (>95%). The accuracies of the stem mappings were also comparable to the methods tested in the international TLS benchmarking project. Additionally, our method was applicable to a wide range of stem forms. In short, the proposed method is accurate and simple; it is a sensible solution for the stem detection of standing trees using TLS data.

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La pousse courte, un indicateur du degré de maturation chez le hêtre (Fagus sylvatica L.)

Canadian Journal of Botany ◽

10.1139/b99-103 ◽

2000 ◽

Vol 77 (11) ◽

pp. 1539-1550 ◽

Cited By ~ 1

Author(s):

Eric Nicolini ◽

Bernard Chanson

Keyword(s):

Fagus Sylvatica ◽

Adult Stage ◽

Morphological Characters ◽

Juvenile Stage ◽

The State ◽

Tree Architecture ◽

Vegetative Stage ◽

Flowering Stage ◽

Fagus Sylvatica L

In beech, no external morphological characters that allow an understanding of how an individual stem gradually and continuously evolves from a juvenile vegetative stage toward a mature flowering stage, has ever been demonstrated. The only known traits are marcescence, indicating a juvenile stage, and flowering, indicating passage to adult stage. However, in young trees growing under a forest shadow, these markers are not visible since marcescence is not expressed and the trees are too young to flower. This study was conducted to find one or more external morphological characters that indicate the state of differentiation in beech. For that purpose, a simultaneous description of tree architecture and the short, 1-year-old, foliated growth units (u.c.) of the trees was completed. Analysis showed that the morphology of short u.c.'s evolved according to their localization in the plant, the age of the plant, and the environment where in which it is developping. Analysis also revealed that this evolution was directly related to growth in height of trees, but also and above all, to the degree of complexity reached during the trees' development. Thus, evolution of short u.c.'s is a scale on which some traits expressing internal plant potentialities (marcescence, flowering) can be localized.

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Exploring the Variability of Tropical Savanna Tree Structural Allometry with Terrestrial Laser Scanning

Remote Sensing ◽

10.3390/rs12233893 ◽

2020 ◽

Vol 12 (23) ◽

pp. 3893

Author(s):

Linda Luck ◽

Lindsay B. Hutley ◽

Kim Calders ◽

Shaun R. Levick

Keyword(s):

Laser Scanning ◽

3D Structure ◽

Terrestrial Laser Scanning ◽

Tree Height ◽

Tree Architecture ◽

Allometric Equations ◽

Environmental Research ◽

Tree Level ◽

Individual Tree ◽

Monitoring Programs

Individual tree carbon stock estimates typically rely on allometric scaling relationships established between field-measured stem diameter (DBH) and destructively harvested biomass. The use of DBH-based allometric equations to estimate the carbon stored over larger areas therefore, assumes that tree architecture, including branching and crown structures, are consistent for a given DBH, and that minor variations cancel out at the plot scale. We aimed to explore the degree of structural variation present at the individual tree level across a range of size-classes. We used terrestrial laser scanning (TLS) to measure the 3D structure of each tree in a 1 ha savanna plot, with coincident field-inventory. We found that stem reconstructions from TLS captured both the spatial distribution pattern and the DBH of individual trees with high confidence when compared with manual measurements (R2 = 0.98, RMSE = 0.0102 m). Our exploration of the relationship between DBH, crown size and tree height revealed significant variability in savanna tree crown structure (measured as crown area). These findings question the reliability of DBH-based allometric equations for adequately representing diversity in tree architecture, and therefore carbon storage, in tropical savannas. However, adoption of TLS outside environmental research has been slow due to considerable capital cost and monitoring programs often continue to rely on sub-plot monitoring and traditional allometric equations. A central aspect of our study explores the utility of a lower-cost TLS system not generally used for vegetation surveys. We discuss the potential benefits of alternative TLS-based approaches, such as explicit modelling of tree structure or voxel-based analyses, to capture the diverse 3D structures of savanna trees. Our research highlights structural heterogeneity as a source of uncertainty in savanna tree carbon estimates and demonstrates the potential for greater inclusion of cost-effective TLS technology in national monitoring programs.

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Modelling individual tree height to crown base of Norway spruce (Picea abies (L.) Karst.) and European beech (Fagus sylvatica L.)

PLoS ONE ◽

10.1371/journal.pone.0186394 ◽

2017 ◽

Vol 12 (10) ◽

pp. e0186394 ◽

Cited By ~ 12

Author(s):

Ram P. Sharma ◽

Zdeněk Vacek ◽

Stanislav Vacek ◽

Vilém Podrázský ◽

Václav Jansa

Keyword(s):

Picea Abies ◽

Norway Spruce ◽

Fagus Sylvatica ◽

Tree Height ◽

European Beech ◽

Individual Tree ◽

Fagus Sylvatica L

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

Trees ◽

10.1007/s00468-021-02124-9 ◽

2021 ◽

Author(s):

Yonten Dorji ◽

Bernhard Schuldt ◽

Liane Neudam ◽

Rinzin Dorji ◽

Kali Middleby ◽

...

Keyword(s):

Seed Dispersal ◽

Growth Performance ◽

Fractal Analysis ◽

Tree Species ◽

Laser Scanning ◽

Three Dimensional ◽

Growth Patterns ◽

Tree Architecture ◽

Geometrical Analysis ◽

Crown Shape

Abstract Key message Mobile laser scanning and geometrical analysis revealed relationships between tree geometry and seed dispersal mechanism, latitude of origin, as well as growth. Abstract 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.

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Parametric identification of a functional - structural tree growth model and application to beech trees (Fagus sylvatica)

Functional Plant Biology ◽

10.1071/fp08065 ◽

2008 ◽

Vol 35 (10) ◽

pp. 951 ◽

Cited By ~ 51

Author(s):

Véronique Letort ◽

Paul-Henry Cournède ◽

Amélie Mathieu ◽

Philippe de Reffye ◽

Thiéry Constant

Keyword(s):

Fagus Sylvatica ◽

Tree Growth ◽

Parametric Identification ◽

Critical Issue ◽

Tree Architecture ◽

Specific Description ◽

Fagus Sylvatica L ◽

Species Specific ◽

Tree Growth Model ◽

Source Sink

Functional–structural models provide detailed representations of tree growth and their application to forestry seems full of prospects. However, owing to the complexity of tree architecture, parametric identification of such models remains a critical issue. We present the GreenLab approach for modelling tree growth. It simulates tree growth plasticity in response to changes of their internal level of trophic competition, especially topological development and cambial growth. The model includes a simplified representation of tree architecture, based on a species-specific description of branching patterns. We study whether those simplifications allow enough flexibility to reproduce with the same set of parameters the growth of two observed understorey beech trees (Fagus sylvatica L.) of different ages in different environmental conditions. The parametric identification of the model is global, i.e. all parameters are estimated simultaneously, potentially providing a better description of interactions between sub-processes. As a result, the source–sink dynamics throughout tree development is retrieved. Simulated and measured trees were compared for their trunk profiles (fresh masses and dimensions of every growth units, ring diameters at different heights) and compartment masses of their order 2 branches. Possible improvements of this method by including topological criteria are discussed.

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