A mechanical analysis of the relationship between free oscillations of Pinus pinaster Ait. saplings and their aerial architecture

Abstract

The aim of this study was to investigate the influence of aerial architecture on the dynamic characteristics of young maritime pines (Pinus pinaster Ait.) using a mechanistic approach. For this purpose, three 4-year-old saplings with prominent differences in their branching patterns were submitted to free oscillation tests. The tests were carried out with different methods and directions of mechanical loading in order to initiate the movement of each sapling. The oscillations of the different architectural elements, i.e. stem and branches of different topological order, were measured with inclinometers and strain gauges fixed to saplings. Successive pruning of the architectural elements was carried out to evaluate their relative influence on the dynamic characteristics of the trees. The aerial systems were digitized before the mechanical tests in order to use 3D visualization techniques and to make architectural analyses of the crown structure. Two distinct modes of deformation were detected during free oscillations. The natural swaying frequency ranged from 0.6-0.8 Hz for the saplings tested at the same period of the year. The frequency variations were partly explained by the morphological differences of the experimental subjects. The motions of the axes were found to depend on their topology, i.e. the movement of the axes of a given branching order was forced by the movement of their respective bearing axis. The axes of third branching order had a significant and negative effect on the damping of the natural deformation mode. Results point out the major role played by foliage, qualitatively and quantitatively, on the damping of tree motions and on coupling the motions of the crown components.

Dynamic analysis of olive trees in intensive orchards under forced vibration

“…This could be explained by the existence of a scale function with proportion to mass and geometry, providing similar morphology to the trees, and therefore producing similar dynamic behaviors (Sellier and Fourcaud 2005). The main mode of vibration in the range of excitation frequencies was identified at a frequency of 20.2 Hz.…”

“…Its usual values range from 0.2 Hz for P. sylvestris in 11.1-m trees (Hacinen et al 1998) to 0.6 Hz in 4-year-old Pinus pinaster (Sellier et al 2006). However, in open center trees, the main mode of vibration is more influenced by the branches, with the natural frequency becoming less important (Sellier and Fourcaud 2005;James et al 2006). …”

“…Tree stability has been studied according to free or forced vibrations. In a free oscillation of the tree, the trunk immediately appears to govern the oscillation of the complete system in a way in which the heaviest element is also the most predominant element in the response (Sellier and Fourcaud 2005). Thus, when the proportion of branch mass increases with respect to the trunk mass, the natural frequencies of the trunk become less dominant.…”

Comparison of Pruning Regimes for Stone Pine (Pinus pinea L.) Using a Functional Structural Plant Model

“…Thus, it is difficult to couple these models with others that include variables for plant growth. It is possible to estimate, for example, stand structure and biodiversity (Pretzsch et al, 2002), but calculation of tree-stability (Sellier and Fourcaud, 2005), stand aesthetics (Surová and Pinto-Correia, 2008), light conditions (Dauzat et al, 2008), or other architectural characteristics is difficult or impossible using these models.…”

Wind effects on trees

“…Their results demonstrate the impact of edge shape and stand density on quantities of the flow field near the canopy top, the region most relevant for tree failure in strong wind conditions. The aerial parts of trees start to vibrate in response to wind excitation (Sellier and Fourcaud 2005;Rodriguez et al 2008). In forests, dynamic tree responses are not only observed at the single tree level (Mayer 1987;Gardiner 1995;Peltola 1996;Flesch and Wilson 1999;Rudnicki et al 2008;Schindler et al 2010) but also at the tree group level (Rudnicki et al 2001(Rudnicki et al , 2003Schindler et al 2011, this issue).…”