A study of crown development mechanisms using a shoot-based tree model and segmented terrestrial laser scanning data

Background and Aims: Functional-structural plant models (FSPMs) allow simulation of tree crown development as the sum of modular (e.g. shoot-level) responses triggered by the local environmental conditions. The actual process of space filling by the crowns can be studied. Although the FSPM simulations are at organ scale, the data for their validation have usually been at more aggregated levels (whole-crown or whole-tree). Measurements made by terrestrial laser scanning (TLS) that have been segmented into elementary units (internodes) offer a phenotyping tool to validate the FSPM predictions at levels comparable with their detail. We demonstrate the testing of different formulations of crown development of Scots pine trees in the LIGNUM model using segmented TLS data. Methods: We made TLS measurements from four sample trees growing in a forest on a relatively poor soil from sapling size to mature stage. The TLS data were segmented into intenodes. The segmentation also produced information on whether needles were present in the internode. We applied different formulations of crown development (flushing of buds and length of growth of new internodes) in LIGNUM. We optimized the parameter values of each formulation using genetic algorithms to observe the best fit of LIGNUM simulations to the measured trees. The fitness function in the estimation combined both tree-level characteristics (e.g. tree height and crown length) and measures of crown shape (e.g. spatial distribution of needle area). Key Results: Comparison of different formulations against the data indicates that the Extended Borchert- Honda model for shoot elongation works best within LIGNUM. Control of growth by local density in the crown was important for all shoot elongation formulations. Modifying the number of lateral buds as a function of local density in the crown was the best way to accomplish density control. Conclusions: It was demonstrated how segmented TLS data can be used in the context of a shoot-based model to select model components.Peer reviewe

Calibration of topological development in the procedure of parametric identification: application to the stochastic GreenLab model for Pinus Sylvestris var. Mongolica

International audienceArid climate, biophysical conditions and human activities all contribute to the occurrences of ecosystem and environment problems, i.e. water scarcity, desertification, salinization, in arid and semiarid zone of North China. Mongolian Scots pine tree (Pinus sylvestris var. mongolica) is one of the principal species of the windbreak and sand-fixing forest in this area. In this paper, we present the calibration process of stochastic GreenLab model based on experiment data. Specific plant topology and sink–source parameters were estimated for Mongolian Scots pine trees through optimizing procedure. The fitting results showed that the calibration was reasonable and acceptable. The model produces several three-dimensional visual representations of Mongolian Scots pine trees with different topological structures simulated by Monte Carlo methods. This model can be used to describe the plant development and growth in a stand level, taking into accounts the variations in plant topology and biomass

Development of methods for characterizing plant and stand architectures and for model comparisons

Diese Arbeit steht im Kontext der individuenbasierten Baumbestandesmodellierung mit vereinfachten Kronenarchitekturen. Die klassische Forstwirtschaft hat in der Vergangenheit sehr einfach strukturierte Bestände erzeugt, die man mit einfachen Modellen wie Ertragstafeln sehr präzise abbilden kann. Individuenbasierte Modelle mit vereinfachten Architekturen haben dagegen zum Ziel, die klassischen statistischen Ansätze zu ersetzen, da diese das Wachstum von heterogenen Beständen, die teilweise einer sich ver andernden Umgebung ausgesetzt sind, nicht mehr präzise vorhersagen k onnen. Ziel dieser Arbeit ist es, in diesem Bereich der Bestandesmodellierung regelbasierte Sprachen f ur ihre Umsetzung einzuführen. Hierdurch wird die Transparenz bei der Umsetzung und Publikation verbessert. Eine weitere Zielsetzung betrifft die Modellierung bzw. Simulation von Naturverjüngung. Die Problematik bei der Modellierung von Naturverjüngung im Allgemeinen ist die Parametrisierung mit Realdaten: Die Datenaufnahme ist sehr aufwändig. Diese Arbeit zeigt auf, dass es möglich ist, derartige Modelle unter Zuhilfenahme von komplexeren Struktur-Funktions-Modellen (hier das finnische Modell LIGNUM) am Beispiel von jungen Kiefern (Pinus sylvstris L.) zu parametrisieren. Das Beispiel umfasst ein einfaches Modell für das Wachstum von Jungkiefern unter lichtreduzierendem Einfluss einer Schirmlücke. Die Parametrisierung geschieht über einen Aggregationsprozess der LIGNUM-Ergebnisse, der die Grundlage für das vereinfachte, regelbasierte Modell liefert

Components of functional-structural tree models

Peer reviewe

Soft set theory based decision support system for mining electronic government dataset

Electronic government (e-gov) is applied to support performance and create more efficient and effective public services. Grouping data in soft-set theory can be considered as a decision-making technique for determining the maturity level of e-government use. So far, the uncertainty of the data obtained through the questionnaire has not been maximally used as an appropriate reference for the government in determining the direction of future e-gov development policy. This study presents the maximum attribute relative (MAR) based on soft set theory to classify attribute options. The results show that facilitation conditions (FC) are the highest variable in influencing people to use e-government, followed by performance expectancy (PE) and system quality (SQ). The results provide useful information for decision makers to make policies about their citizens and potentially provide recommendations on how to design and develop e-government systems in improving public services

Effect of branch position and light availability on shoot growth of understory sugar maple and yellow birch saplings

Phenotypic plasticity enables tree saplings to change their morphology according to their environment to grow toward a better light micro-habitat. Therefore, processes of crown development could be expected to vary as a function of light. The objectives of this study were to (i) evaluate the effects of position and light availability on shoot growth within the crowns of understory saplings of sugar maple (Acer saccharum Marsh.) and yellow birch (Betula alleghaniensis Britton.); (ii) develop a new vigour index for shoots; and (iii) evaluate the possible factors relating to branch mortality in the crown of sugar maple saplings. The results revealed that there is a clear branch position effect on shoot growth in the crown for yellow birch saplings and that it is partly related to the presence of two types of shoots. Dead branches were located at the bottom of the crown of sugar maple saplings; they were smaller in size, had wider angles and had lower indexes of vigour than live branches found nearby. Preliminary results obtained on the vigour index indicate that it is a potentially useful tool for predicting the growth and vigour status of a branch

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

International audienceFunctional-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

Adaptation of the GreenLab model for analyzing sink-source relationships in Chinese Pine saplings

International audienceSince the 1990s, a new generation of models has emerged to simulate tree growth with consideration of both tree structure and functional processes. However, calibration of these functional-structural models (FSMs) often remains an open problem due to the topological complexity of trees and to the heavy measurements required. In this paper, we explore a possible way for dealing with the fitting problem, based on the GreenLab model approach. Detailed organ-level data including topological and geometrical measurements were collected on eight Chinese Pine saplings (Pinus tabulaeformis carr.) grown near Beijing. Adaptation of GreenLab to introduce a flexible modeling for biomass allocation to ring growth is presented. The main assumptions, such as allometry rules and sink relationships, were investigated. The problem of calibration of a complex branching structure was solved by defining an average tree. The results were interpreted with particular focus on the ones concerning the hidden mechanisms of secondary growth

Latvusarkkitehtuuri ja sen rooli lajien välisessä vuorovaikutuksessa boreaalisissa sekametsissä

This thesis concerns crown architecture and its role in species interactions in mixed forests. The species specific growth patterns make plastic tree architecture respond in different manner to different environments modifying their influence to neighbours. The main aims were to separate the effect of neighbour species identity from the abundance, size and proximity of the neighbours in between-tree competition and to link crown architecture with hydraulic architecture by identifying the associated within-tree variation of crown traits. The empirical part of the work was based on digitising three-dimensional (3D) crown architecture and measuring xylem anatomy. Digitising allowed the development of crown architecture models for Betula pendula (Roth.) and Pinus sylvestris (L.). The models were further applied to simulate light transmission in mixed stands. Crown architecture of the studied species responded to increased competition intensity primarily by reducing branch number and size. Proportional biomass distribution to foliage and main branches over the stem increased in young B. pendula with increasing competition intensity, whereas Pinus sylvestris used the opposite strategy. In addition to competition intensity, crown architecture of the studied species showed plastic responses to the species identity of neighbouring trees. Lower overall growth but added height growth indicating stronger competition was found in mixtures of B. pendula and Pinus sylvestris compared to monocultures. Both species-specific effects on resource gradients and non-resource signals remain plausible explanations for this result: B. pendula transmitted more light than Pinus sylvestris at simulated dense stands. Hydraulic architecture was shown to be interlinked with crown architecture as the conduit diameter varied as a function of tree compartment, branching hierarchy, leaf area and distance from the apex. The results suggest that the use of detailed tree structure models and species-specific competition analysis is useful in predicting and understanding growth in mixed boreal stands.Tutkin väitöskirjassani puiden latvuksen rakennetta ja sen roolia lajien välisessä vuorovaikutuksessa sekametsässä. Aiheesta tekee kiehtovan latvusrakenteen joustavuus eli puut vastaavat herkästi kasvuympäristössään tapahtuviin muutoksiin muokkaamalla rakennettaan. Kiinnostus puulajiston monimuotoisuutta suosivaa metsänkasvatusta kohtaan on kasvussa, mutta silti tiedämme melko vähän siitä, miten pääpuulajiemme latvusrakenne toimii kilpailtaessa elintilasta ja resursseista metsiköiden sisällä. Väitöskirjassani keskityin selvittämään miten puiden rungon, oksien ja versojen muodostama latvusrakenne muuttuu naapuripuista johtuvan kilpailun vaikutuksesta, ja onko muutoksissa naapuripuulajista johtuvia eroja. Halusin myös ymmärtää paremmin minkälainen suhde on latvuksen ulkoisella ja puuaineen sisäisellä rakenteella. Väitöskirjani tulokset osoittavat, että mänty ja koivu vastaavat molemmat latvuskilpailuun mm. kasvattamalla vähemmän ja pienempiä oksia, joissa lehdetön osuus oksan pituudesta kasvaa. Lajien välillä näyttää kuitenkin olevan eroa biomassan suhteellisessa jakautumisessa, sillä nuorilla koivuilla pääoksien osuus kokonaisbiomassasta kasvoi kilpailun lisääntyessä rungon kustannuksella, kun taas nuorilla männyillä rungon biomassaosuus kasvoi. Männyn ja koivun latvusrakenne muuttuu paitsi naapuripuiden koon, lukumäärän ja etäisyyden suhteen myös naapuruston pääpuulajin suhteen. Sekä mänty että koivu kasvoivat toistensa ympäröimänä enemmän pituutta, mutta niiden kokonaiskasvu oli alhaisempi verrattuna lajitovereiden ympäröimiin yksilöihin. Selvitimme tuloksen taustoja metsiköiden valaistussimulaatioiden avulla ja havaitsimme, että koivikko päästi tiheissä metsiköissä valoa latvuston läpi samanpituista männikköä enemmän, mutta harvemmissa metsiköissä tätä eroa ei ollut. Tulosten mukaan ennustettaessa latvusrakennetta ja kasvua, naapuripuiden lajityypillinen rakenne on otettava huomioon niiden kilpailuvaikutusta arvioitaessa. Tulokseni osoittavat myös, että puun solukoiden rakenne on yhteydessä ulkoiseen latvusrakenteeseen. Vesi kulkee puun sisällä juurista ylös haihduttaviin lehtiin vedenkuljetussoluista muodostuneissa putkimaisissa rakenteissa. Vedenkuljetussolujen läpimitta leveni odotetusti ylhäältä alaspäin etäisyyden funktiona. Tämän lisäksi solukoko pieneni ja solutiheys kasvoi hyppäyksenomaisesti siirryttäessä rungosta oksiin, pääoksista sivuhaaroihin ja koivun tapauksessa oksista lehtiruoteihin. Myös lehtiruodeissa solukoko vaihteli lehden pinta-alan funktiona. Näyttääkin siltä, että myös vedenkuljetussolukon rakenne heijastaa joustavan latvusrakenteen välityksellä kasvuympäristön tilaa kuten latvuskilpailua