Mechanics of root-pullout from soil: a novel image and stress analysis procedure

When plants are loaded by external forces, whether they be above ground e.g. wind or canopy weight, or from within the soil e.g. soil displacement on slopes, the roots will be mechanically loaded. Exactly how the plant roots carry loads during these events is unknown because of their complex morphology and the heterogeneity of the root properties. To gain greater insight into plant root-soil mechanical interactions, a series of tests have been carried out to investigate the mechanical behaviour of roots and rubber root-analogues under tension during pull-out from soil. The results of the mechanical tests are augmented by a novel use of image analysis (specifically Particle Image Velocimetry) of sequential digital photographs taken during loading. This allows root and soil movements to be measured during the tests so that more can be learned about the effects of root morphology on the load distribution and deformation behaviour. The testing methodology and philosophy are presented here together with preliminary results.