The effect of root architecture and root loss through trenching on the anchorage of tropical urban trees (Eugenia grandis Wight).

Eugenia grandis (Wight) is grown in urban environments throughout Malaysia and root systems are often damaged through trenching for the laying down of roads and utilities. We investigated the effect of root cutting through trenching on the biomechanics of mature E. grandis. The force necessary to winch trees 0.2 m from the vertical was measured. Trenches were then dug at different distances (1.5, 1.0 and 0.5 m) from the trunk on the tension side of groups of trees. Each tree was winched sideways again and the uprooting force recorded. No trenches were made in a control group of trees which were winched until failure occurred. Critical turning moment (TMcrit) and tree anchorage rotational stiffness (TARS) before and after trenching were calculated. Root systems were extracted for architectural analysis and relationships between architectural parameters and TMcrit and TARS were investigated. No differences were found between TMcrit and trenching distance. However, in control trees and trees with roots cut at 1.5 m, significant relationships did exist between both TMcrit and TARS with stem dimensions, rooting depth and root plate size. TARS was significantly decreased when roots were cut at 0.5 m only. Surprisingly, no relationships existed between TMcrit and TARS with any root system parameter when trenching was carried out at 0.5 or 1.0 m. Our study showed that in terms of TARS and TMcrit, mechanical stability was not greatly affected by trenching, probably because rooting depth close to the trunk was a major component of anchorage

Plant Growth Modelling and Applications: The Increasing Importance of Plant Architecture in Growth Models

Background Modelling plant growth allows us to test hypotheses and carry out virtual experiments concerning plant growth processes that could otherwise take years in field conditions. The visualization of growth simulations allows us to see directly and vividly the outcome of a given model and provides us with an instructive tool useful for agronomists and foresters, as well as for teaching. Functional-structural (FS) plant growth models are nowadays particularly important for integrating biological processes with environmental conditions in 3-D virtual plants, and provide the basis for more advanced research in plant sciences. Scope In this viewpoint paper, we ask the following questions. Are we modelling the correct processes that drive plant growth, and is growth driven mostly by sink or source activity? In current models, is the importance of soil resources (nutrients, water, temperature and their interaction with meristematic activity) considered adequately? Do classic models account for architectural adjustment as well as integrating the fundamental principles of development? Whilst answering these questions with the available data in the literature, we put forward the opinion that plant architecture and sink activity must be pushed to the centre of plant growth models. In natural conditions, sinks will more often drive growth than source activity, because sink activity is often controlled by finite soil resources or developmental constraints. PMA06 This viewpoint paper also serves as an introduction to this Special Issue devoted to plant growth modelling, which includes new research covering areas stretching from cell growth to biomechanics. All papers were presented at the Second International Symposium on Plant Growth Modeling, Simulation, Visualization and Applications (PMA06), held in Beijing, China, from 13-17 November, 2006. Although a large number of papers are devoted to FS models of agricultural and forest crop species, physiological and genetic processes have recently been included and point the way to a new direction in plant modelling researc

Resistenza a trazione di un terreno con vegetazione parzialmente saturo

Il rinforzo delle radici nel terreno è stato valutato in letteratura, a livello di sperimentazione di laboratorio, principalmente tramite percorsi di sollecitazione di compressione per carico o tramite prove di taglio diretto. Il loro effetto durante altri percorsi di sollecitazione e il comportamento all'interfaccia suolo-radice risultano ancora poco esplorati. A questo proposito, in questo studio viene presentata un'apparato che consente di testare congiuntamente il terreno e le radici in estensione uniassiale. Campioni di terreno, compattati sempre allo stesso stato idro-meccanico, sono stati poi seminati con Cynodon dactilon e testati dopo tre mesi di crescita radicale. Dalle prove di trazione realizzate, si è osservata una risposta duttile nei campioni di terreno in prossimità della saturazione ed una fragile in condizioni più secche. In ogni caso, la vegetazione ha contribuito ad aumentare la resistenza dei provini. Le misure del grado di saturazione e di suzione matriciale nonchè l’assegnazione delle direzioni principali di sollecitazione hanno permesso di interpretare i risultati tramite un criterio di resistenza al taglio per terreni parzialmente saturi. Le caratteristiche meccaniche e morfologiche delle radici all’interno di ogni provino di terreno sono state caratterizzate dopo le prove, in maniera tale da assicurare la comparabilità dei risultati in termini di rinforzo meccanico delle radici.Postprint (published version

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