Influence of root characteristics and soil variables on the uprooting mechanics of Avena sativa and Medicago sativa seedlings

Abstract

The success of seedlings and rejuvenated woody debris growing on river bedforms depends on the resistance to uprooting by flow provided by their simple root architecture. Avena sativa and Medicago sativa seedlings were used in flume experiments as prototypes for juvenile riparian plants. Very little is known about the magnitude of root anchoring forces and the role of secondary roots of such simple root systems. We performed 1550 vertical uprooting experiments on Avena sativa and Medicago sativa seedlings grown in quartz sand. Seedlings were pulled up by direct traction using a wheel driven by a computer‐controlled motor and the force was recorded. Roots were scanned and architectural parameters (root length and number of roots) determined. Uprooting force and work (the integral of the applied force times the distance over which it is applied) were then related to root architecture and soil variables. Resistance to uprooting increased with decreasing sediment size and sediment moisture content. The initial response of the root–soil system to uprooting showed linear elastic behaviour with modulus increasing with plant age. While the maximum uprooting force was found to increase linearly with total root length and be mainly dependent on the length of the main root, uprooting work followed a power law and has to be related to the whole root system. Thus, for the young plants we considered, secondary roots are responsible for the ability to withstand environmental disturbances in terms of duration rather than magnitude. This distinction between primary and secondary roots can be of crucial importance for seedlings of riparian species germinating on river bars and islands where inundation is a main cause of mortality. Beyond clarifying the biomechanical role of soil and root variables, the uprooting statistics obtained are useful in interpreting and designing ecomorphodynamic flume experiments. Copyright © 2014 John Wiley & Sons, Ltd.

Biomechanics of plant anchorage at early development stage

“…Our modelling efforts are guided by our observations in the experiments by Edmaier et al (2012Edmaier et al ( , 2014. We aim at explaining and reproducing the main features of the stress-strain curves obtained experimentally (see Fig.…”

“…We choose those two indicators since they are both relevant to quantify resistance of the seedling to environmental mechanical constraints (Edmaier et al, 2011(Edmaier et al, , 2014. The uprooting work and the maximal uprooting force are however not able to capture the details of the fluctuations in the force signal.…”

“…We formulate a minimal mechanistic model of friction (with stochasticity in the friction properties) that is able to reproduce experimental observations from previous works (Edmaier et al, , 2014. Uprooting experiments on Avena sativa L. (common oat) seedlings growing in non-cohesive sediment were conducted and allow to test our model on a simple root architecture.…”

Swiftness of biomorphodynamics in Lilliput- to Giant-sized rivers and deltas

“…In van the vegetation died rather quickly; it survived longer in Tal and Paola (2010); and in Braudrick et al (2009) it continued to develop branched root systems that strengthened the bed even further. Indeed, experiments with force measurement at uprooting by Edmaier et al (2014) showed a strong dependence of the necessary work on the development of the species-dependent secondary root system, in addition to moisture content and sediment size. These differences are all because of different lighting and moisture conditions (Van de Lageweg et al, 2010;Clarke, 2014), but we cannot exclude differences between batches of seeds, and fungi in the soil .…”

“…Furthermore, these experiments would benefit from a multiple number of species that are sensitive to the small water depth differences in the experiments to simulate different eco-engineers in contrasting habitats. Also, it remains to be studied what part of the plant population in meandering and braided rivers is uprooted by flow during floods (Edmaier et al, 2014) or uprooted because of bank migration , in the laboratory and in the field.…”