A morphological and mechanical study of the root systems of suppressed crown Scots pine Pinus sylvestris (original) (raw)
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The development of symmetry, rigidity and anchorage in the structural root system of conifers
1999
The stability of shallowly rooted trees can be strongly influenced by the symmetry of the 'structural' system of woody roots. Root systems of forest trees are often markedly asymmetric, and many of the factors affecting symmetry, including root initiation and the growth of primary and woody roots, are poorly understood. The internal and environmental factors that control the development, with respect to symmetry and rigidity, of shallow structural root systems are reviewed and discussed with particular reference to Sitka spruce (Picea sitchensis Bong. Carr.). Areas where there is insufficient knowledge are highlighted. A scheme is proposed that represents the root system as a set of spokes that are variable in number, size and radial distribution. Rigidity can vary between and along each of the spokes. The root system is presented as a zone of competition for assimilates, where allocation to individual roots depends upon their position and local variations in conditions. Factors considered include the production of root primordia of different sizes, effects of soil conditions such as the supply of mineral nutrients and water on growth of primary and woody roots, and the effect of forces caused by wind action on growth of the cambium, giving rise to roots which, in cross section, resemble I-or T-beams, and efficiently resist bending.
Trees, 2004
Static winching tests were carried out in order to determine the mechanical resistance of Maritime pine to overturning. The tested stands were selected according to podzolic soil conditions: "wet Lande", characterised by a shallow ground water table and a hard pan horizon, and "dry Lande", with a deeper ground water table and a hard pan absent or broken up. As this soil horizon limits the vertical growth of tree roots, anchorage resistance was investigated with regards to the presence or absence of a hard pan underneath each tree. To determine if mechanical behaviour differed within a stand, trees from inside the stand and edge trees at the border exposed to prevailing winds were also tested. The critical turning moment (TM crit,total ) at the base of the stem was positively related to the variable (H × DBH 2 ) (H, total tree height; DBH, tree diameter). Linear regression analyses between TM crit,total and (H × DBH 2 ) showed that the presence of a hard pan had no significant effect on anchorage resistance in uprooted trees. Stem failure occurred for 82% of trees on dry Lande when (H × DBH 2 ) < 1 m 3 . Moreover, stem failure type on dry Lande indicated that trees were better anchored. On soil with a hard pan, edge trees were found to be 20% more resistant to overturning than inner trees. Edge trees differed from inner trees in that the soil-root plate was two times larger and also possessed a larger surface area on the windward side.
Numerical analysis of the anchorage of Maritime pine trees in connection with root structure
2003
The mechanical structure of 24 root systems was studied in 50 year old Maritime pine (Pinus pinaster Ait) trees after the 1999 storm, which resulted in the loss of >4 million hectares of forest in southwest France. Half of the study trees had been uprooted during the storm and the other study trees were left standing. Topology and geometry of the root systems were measured using a 3D digitising device. The spatial distribution of roots was then analysed. The 3D representation of each root system was used to calculate the mechanical behaviour of the structure in different compass directions, using a finite element model. Results show that resistance to windthrow can be provided by four different structural adaptations of root systems, and that root architecture may explain half of the sensitivity to uprooting. There was no significant difference in uprooting resistance between trees that were damaged by the storm, and those which remained upright. However, all root systems were found to be highly asymmetric with regard to morphology. This asymmetry influenced strongly the mechanical behaviour of anchorage, depending on the direction of loading.
Root architecture and wind-firmness of mature Pinus pinaster
New Phytologist, 2005
This study aims to link three-dimensional coarse root architecture to tree stability in mature timber trees with an average of 1-m rooting depth. • Undamaged and uprooted trees were sampled in a stand damaged by a storm. Root architecture was measured by three-dimensional (3-D) digitizing. The distribution of root volume by root type and in wind-oriented sectors was analysed.
Journal of Theoretical Biology, 2005
The arrangement of a plant's roots in the soil determines the ability of the plant to resist uprooting. We have investigated the influence of root morphology on anchorage using simple patterns of root systems and numerical simulation. The form and mechanical properties of roots were derived from results found in the literature. Major parameters determining soil characteristics, root patterns and strength were varied so that their influence could be evaluated. The design of the experimental method we used generated an optimal number of configurations of different root systems, the tensile resistances of which were calculated by two-dimensional finite element analysis. We could quantify the influence of specific parameters, e.g. branching angle, number of lateral roots and soil cohesion, as well as global parameters such as total contact area, basal diameter and volume of the whole root system. We found that the number of roots and the diameter of roots were major components affecting the resistance to uprooting. The combination of topology and biomass explained 70% of the variation of tensile resistance.
Root System Architecture of Quercus pubescens Trees Growing on Different Sloping Conditions
Annals of Botany, 2004
Background and Aims Plant roots' growth direction has important implications for plant development and survival; moreover it plays an effective and vital role in stabilizing weathered soil on a steep slope. The aim of this work was to assess the influence of slope on the architecture of woody root systems. Methods Five mature, single-stemmed Quercus pubescens trees growing on a steep slope and five on a shallow slope were excavated to a root diameter of 1 cm. A very precise numeric representation of the geometry and topology of structural root architecture was gained using a low-magnetic-field digitizing device (Fastrak, Polhemus). Several characteristics of root architecture were extracted by macros, including root volume, diameter, length, number, spatial position and branching order. Key Results The diameter at breast height (dbh) was the best predictor of the root volume but had no correlation with length and number of roots. The slope affected the root volume for each branching order, and the basal crosssectional area (CSA), number and length of the first-order roots. Number and length of the second-and third-order laterals were closely related in both conditions, although this relationship was closer in the shallow trees, suggesting the influence of a genetic control. Sloping trees showed a clustering tendency of the first-and second-order lateral roots in the up-slope direction, suggesting that the laterals rather than the taproots provide much of the anchorage. In a steep-slope condition, the taproot tapering was positively correlated with the asymmetry magnitude of first-order roots, indicating compensation between taproot and main lateral roots' clustering tendency. Conclusions These results suggest that on a slope, on clayey soils, root asymmetry appears to be a consequence of several environmental factors such as inclination, shallow-slides and soil compactness. In addition, this adaptive growth seems to counteract the turning moment induced by the self-loading forces acting in slope conditions, and as a consequence improves the tree stability.
Dendrochronologia, 2019
Our knowledge of the root system architecture of trees is still incomplete, especially concerning how biomass partitioning is regulated to achieve an optimal, but often unequal, distribution of resources. In addition, our comprehension of root system architecture development as a result of the adaptation process is limited because most studies lack a temporal approach. To add to our understanding, we excavated 32-year-old Pinus ponderosa trees from a steep, forested site in northern Idaho USA. The root systems were discretized by a low magnetic field digitizer and along with AMAPmod software we examined their root traits (i.e. order category, topology, growth direction length, and volume) in four quadrants: downslope, upslope, windward, and leeward. On one tree, we analyzed tree rings to compare the ages of lateral roots relative to their parental root, and to assess the occurrence of compression wood. We found that, from their onset, first-order lateral roots have similar patterns of ring eccentricity suggesting an innate ability to respond to different mechanical forces; more root system was allocated downslope and to the windward quadrant. In addition, we noted that shallow roots, which all presented compression wood, appear to be the most important component of anchorage. Finally, we observed that lateral roots can change growth direction in response to mechanical forces, as well as produce new lateral roots at any development stage and wherever along their axis. These findings suggest that trees adjust their root spatial deployment in response to environmental conditions, these roots form compression wood to dissipate mechanical forces, and new lateral roots can arise anywhere and at any time on the existing system in apparent response to mechanical forces.
Modelling the influence of morphological and mechanical properties on the anchorage of root systems
2003
A sensitivity analysis based on numerical simulation is presented, in order to investigate the anchorage resistance of root systems. The form and mechanical characteristics of roots used in the models were derived from experimental results found by previous authors. Finite element models were developed to analyse the mechanical process of uprooting. The analysis of local phenomena occurring during uprooting was performed using 2D models, whereas the anchorage of complete tree root systems used 3D models. The principal parameters which determined root shape and material properties were varied so that their influence could be evaluated. The design of experiments method (DOE) was used to generate an optimal number of root / soil configurations. It was possible to determine the influence of each of these parameters, therefore the modelling carried out provided a broad overview of the interacting mechanisms taking place during uprooting.