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Trees as simple vertical rods might be an overly simplistic approach

29 septembre 2016 ( maj : 5 octobre 2016 ), par Administrateur

Finally, considering the trees as simple vertical rods might be an overly simplistic approach, even though the seismic wavelength for Rayleigh waves (between 10 and 20 m) will probably not be sensitive to (i) the decomposed subsurface soil (the width of organic deposits and humus should be <0.3 m) or the roots system architecture in the case of maritime pine tree (Fig. 1a), or (ii) the effects of lateral branches on the compressional/ flexural resonance in the trees (Fig. 1b). As a matter of fact, the vertical taproot of the maritime pine tree is the first order root ; the maximum taproot depth averaged only 45 cm. The second order roots expand horizontally over several meters and ensure the stability and anchorage of the tree. Half of the root volume is located in the 10 upper centimeter of soil. This means that a 25 m high tree (height 15m) will be anchored by the root structure established in the very first years of growth, and only modified later by diameter growth (see more information about the Maritime pine tree root system architecture with Danjon et al, 1999a, 1999b, 2005).

Figure 1.
(a) Detailed root system architecture for the maritime pine tree. The roots coordinates were measured with a 3D digitizer using low frequency electromagnetic fields sensing (from Danjon et al., 2013). (b) Picture of maritime pine tree forest in the Landes department showing trees without lateral branches until 10-m height