Root morphology and effects on soil reinforcement and slope stability of young vetiver (Vetiveria zizanioides) plants grown in semi-arid climate

Abstract

Currently used in many countries in the world, vetiver grass (Vetiveria zizanioides) applications include soil and water conservation systems in agricultural environment, slope stabilization, mine rehabilitation, contaminated soil and saline land remediation, as well as wastewater treatment. The root system morphology of vetiver was investigated in a small plantation growing on abandoned marl terraces in southern Spain. Root distribution with depth, laterally from the plant, as well as root parameters such as root diameter and tensile strength were also investigated. The profile wall method combined with the block excavation showed that the vetiver grass grows numerous positively gravitropic roots of more or less uniform diameter. These were generally distributed in the uppermost soil horizon closer to the culm base. In situ shear test on blocks of soil permeated with vetiver roots were carried out and showed a greater shear strength resistance than the samples of non vegetated soil. The root reinforcement measured in situ was comparable to the one predicted by the perpendicular root reinforcement model. The stability of a modelled terraced slope planted with vetiver was marginally greater than the one of a nonvegetated slope. A local instability on one terrace can have a detrimental effect on the overall stability of the terraced slope.

The Study of Soil-Roots Strength Performance by Using Pennisetum Setaceum Grass

“…From the regression analysis between tensile strength and root diameter, it can be observed that the tensile strength decreased with increasing root diameter which is in line with the previous root studies conducted by [2,4]. According to [5], during soil shearing, the finer and thinner roots that have high tensile strength would slip while the thicker roots with lower tensile strength would break.…”

Shallow landslide initiation on terraced slopes: inferences from a physically based approach

“…Assuming that plant roots provide additional cohesion to the soil as a function of the vegetation type (e.g. Mickovski and van Beek 2009;Burylo et al 2011), the calibration has been iterated until a minimum number of cells resulted as unstable before the beginning of the event. On the basis of the land-use map, the cohesion then varies between 4.5 kPa (in the case of recently abandoned terraces, where the vegetation is sparse) to 6 kPa, in correspondence of forest and scrubland areas (Table 2).…”

New tools and routines for ecotechnological slope stability analysis

“…This is particularly true for small diameter roots which can be considered as flexible reinforcements Mickovski et al, 2007), and which provide ductility for the root-soil continuum , reaching the peak strength at high strains (e.g. Mickovski et al, 2007;Mickovski and van Beek, 2009). …”

“…The study site is located near Almudaina, Spain (X=729275 Y=4293850 and Z=480 m on UTM 30 s) and comprises approximately 2.0 m high slopes with overall slope angles ranging between 45° and 70°. The slope length was approximately 60 m, and long term monitoring recorded potential instability connected to runoff and soil slippage after intense rainfall events (Mickovski and van Beek, 2009). The runoff from the slope contributed to the undermining of the slope toe where the progressive failure initiated before migrating up the slope and resulting in bulging mid-slope and soil mass depositing at the toe ( Figure 5).…”

“…The development and use of plant root reinforcement models to assess the effects of vegetation in slope stability analysis has become a prominent research area all over the world in the last 10 years with research developments in root anchorage models Bourrier et al, 2013) and their application in practical stability problems such as shallow landslides or soil erosion (Coppin and Richards, 2007;Danjon et al, 2007;Comino and Druetta, 2009;Mickovski and van Beek, 2009;Thomas and Pollen-Bankhead, 2010).…”