Efficiency of vegetation roots for protection against surface erosion in mountainous areas: the case of Mahonia aquifolium

Topsoil is a valuable resource for agricultural production. Any destructive changes in the quantity and quality of topsoil can deteriorate the on-site and off-site environment and be detrimental to agricultural production. Small scale mountain agro-ecosystems are particularly sensitive to soil degradation and their productivity is heavily influenced by soil quality. The appropriate plant selection, cultivation and soil conservation techniques can help provide income in the long term as well as prevent or reduce land degradation. This research provides information and possible solutions to farmers and soil conservationists on the sustained utilization and maintenance of small-scale mountain agro-ecosystems in Hungary and France with the view to prevent or reduce soil erosion damage for long term sustainability. Vegetation cover is of major importance for soil protection, especially on slopes. The role of vegetation in improving soil stability is widely recognized. And while vegetation is able to improve soil stability through both its above-ground and below-ground biomass, few studies have focussed on the significance of the root system. The root system is particularly important when above-ground vegetation is absent for some time. Therefore, this study investigated root characteristics and how root systems contribute to reducing topsoil erosion in mountainous agro-ecosystems. The morphological and functional traits of roots of various plant species (tree, shrub and herbaceous) and their efficiency in erosion control were first determined. In particular, the root system of Mahonia aquifolium was studied. The Mahonia aquifolium shrub has been cultivated in Hungary for decades. Due to its wide marketability as well as its high adaptability to soil and site conditions it is of interest to determine its potential for soil erosion control. Laboratory, field and modelling studies were carried out to evaluate the suitability of Mahonia aquifolium for soil erosion reduction. An existing reinforcement model was applied to evaluate and compare the root system of Mahonia aquifolium with tree, herbaceous and shrub species for soil reinforcement. The results show that the root system of Mahonia aquifolium is comparable in terms of slope stabilization with other plant species that are used or could potentially be used for slope stabilization. Plot based field studies on soil loss and runoff with different ages of Mahonia aquifolium shrubs were carried out and confirmed the plant’s suitability as effective erosion control. Such soil conservation techniques are significant factors in the stabilisation of the soil and for long-term sustainable use of small-scale mountainous agro-ecosystems. The use of permanent vegetation strips between crops on cultivated slopes is a common and effective way to trap runoff and sediment. Therefore the effectiveness of Mahonia aquifolium strips on soil erosion control under various bio-physical conditions was investigated by model simulations. The outcome of the empirical soil erosion model simulations confirmed that contour strips of Mahonia aquifolium on sloping agricultural fields can reduce soil loss up to 73% and runoff up to 13% on the selected crop fields. The results also show that steeper slopes can be used for agricultural plant production both on small-scale and large-scale if Mahonia aquifolium strips are applied.