Understanding the Impact of Root Morphology on Overturning Mechanisms: A Modelling Approach

Abstract

Aims The Finite Element Method (FEM) has been used in recent years to simulate overturning processes in trees. This study aimed at using FEM to determine the role of individual roots in tree anchorage with regard to different rooting patterns, and to estimate stress distribution in the soil and roots during overturning. † Methods The FEM was used to carry out 2-D simulations of tree uprooting in saturated soft clay and loamy sandlike soil. The anchorage model consisted of a root system embedded in a soil block. Two root patterns were used and individual roots removed to determine their contribution to anchorage. † Key Results In clay-like soil the size of the root-soil plate formed during overturning was defined by the longest roots. Consequently, all other roots localized within this plate had no influence on anchorage strength. In sand-like soil, removing individual root elements altered anchorage resistance. This result was due to a modification of the shape and size of the root-soil plate, as well as the location of the rotation axis. The tap root and deeper roots had more influence on overturning resistance in sand-like soil compared with clay-like soil. Mechanical stresses were higher in the most superficial roots and also in leeward roots in sand-like soil. The relative difference in stresses between the upper and lower sides of lateral roots was sensitive to root insertion angle. Assuming that root eccentricity is a response to mechanical stresses, these results explain why eccentricity differs depending on root architecture. † Conclusions A simple 2-D Finite Element model was developed to better understand the mechanisms involved during tree overturning. It has been shown how root system morphology and soil mechanical properties can modify the shape of the root plate slip surface as well as the position of the rotation axis, which are major components of tree anchorage.

Mechanical vulnerability and resistance to snapping and uprooting for Central Amazon tree species

“…In some cases, uprooting one tree can additionally uproot four surrounding trees when roots are interlocked (Coutts, 1983). Despite recent advances in the understanding of the relative roles of root components (lateral, superficial or tap roots) in tree anchorage strength (Fourcaud et al, 2008), general knowledge about roots architecture in tropical species is still scarce. Although this is the first study to describe M crit for Amazonian tree species, our results (Tables S2-S4) are in accord with previous studies (Peterson and Claassen, 2013;Cannon et al, 2015) for similar-sized hardwood and coniferous species of the United States.…”

Modeling root growth in granular soils: effects of root stiffness and packing fraction

“…In particular, the inhomogeneous structure of soil at the particle scale and broad distributions of contact forces can significantly affect root growth trajectories [7][8][9][10][11]. Continuum representation of soils and roots has been used for describing soil stability [12][13][14][15]. In such models, the effect of soil is incorporated mainly through its average resistance to the root ingrowth and the interactions between soil grains and roots are not considered.…”

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

“…However, the root system is much more problematic to manage, largely due to the difficulty in investigating it in situ and carrying out experimental studies on this hidden part of trees. To our knowledge, there is little published research on how much root loss a tree can withstand without seriously compromising mechanical stability (Coutts 1983(Coutts , 1986Fourcaud et al 2008), nor at what distance from the trunk digging or trenching can be carried out without increasing the risk of failure. Arborists often use above-ground tree features to specify the dimensions within which root systems should not be damaged.…”

“…Arborists often use above-ground tree features to specify the dimensions within which root systems should not be damaged. Simple calculations involving branch spread (Bernatzky 1978;Olson and Ray 1979;Schoeneweiss 1982;Tartar 1989;Fazio 1992;Miller and Neely 1993), trunk diameter (Morel 1984, Mattheck andBreloer 1995) and tree height ) are commonly used. Current recommendations as proposed by the British Standard Institute (1989) and Watson (1990) suggest a minimum distance for trenching along one side of the tree of 0.15 m for each 0.025 m diameter at breast height (DBH), whereas Harris et al (2004) and the American Society of Consulting Arborists (1989) recommend 0.30 m for each 0.025 m DBH (Miller and Neely 1993).…”