EVALUATION OF VEGETATIVE PROPAGATION OF SPECIES EMPLOYED IN EARTHWORK STABILIZATION WITH SOIL BIOENGINEERING TECHNIQUE

Abstract

Soil bioengineering techniques use live construction materials like plants and live cuttings as well as inert materials as structural elements in simple constructions, with the purpose of ecological restoration and soil stabilization. The inert materials used depend on the aims and the local availability, are essentially metal structures, geotextiles, timber, stones or even concrete. These, in addition to provide immediate soil stabilization also supply protection and support for the further development of the vegetation. The vegetative part complements, gradually or entirely, replaces the functions of stabilizing inert components. However, construction works, can only be performed successfully when the vegetation technical characteristics are known and, thus, properly exploited. This research is the result of a sequence of experiments performed with the goal of identifying, among riparian inhabit species, those with vegetative propagation capacity and development. A large part of soil bioengineering models use exclusively that way of propagation. Among the many potentially influential factors in vegetative development, such as survival, rooting and sprouting rate, growth roots and shoots velocity, should be also highlighted, the importance of collecting and planting time for vegetation. Therefore, this study, using experimental plots built in different times of the year, seeks to obtain this information by assessing the survival rate, shoots and roots development using cuttings of six potential species easily found along stream banks in southern Brazil rivers. The tested species are: Calliandra brevipes, Phyllanthus sellowianus, Pouteria salicifolia, Salix humboldtiana, Salix x rubens and Sebastiania schottiana. The experimental results indicate the possibility of using some of these species. Calliandra brevipes, Sebastiania schottiana and Pouteria salicifolia presented lower development than Phyllanthus sellowianus, Salix humboldtiana and Salix x rubens. It was evidenced that the planting season, is less important in species with fast rooting, as Phyllanthus sellowianus, Salix humboldtiana and Salix x rubens, but can be decisive in species with slower rooting, such as Sebastiania schottiana, and can even have an effect on the survival rate of these species.