Crescimento inicial de espécies florestais na recomposição da mata ciliar em taludes submetidos à técnica da bioengenharia de solos

Abstract

The São Francisco River Basin has been submitted to strong environmental impacts through changes in the hydrologic and sedimentological regime, and also the ongoing destruction of its riparian vegetation. The riparian vegetation has an important role on the riverbank’s protection, through the roots system and the plant cover, improving the soil particles aggregation in a low cohesion situation, reducing the runoff and resulting in a lower erosion rate and sedimentation of the river channel. The objective of study was to evaluate the initial development of forest species at riverbank under soil bioengineering technique in São Francisco River. The soil bioengineering technique was composed of longitudinal slope covered with the biotextile (Fibrax 400 BF) and sediment retainers (Bemalonga® D40), to reduce the impact of wave water at the slope botton, avoiding the bank undercutting, due to daily variations of water level. Before the biotextile installation the specie, Brachiaria decumbens was sown to promote rapid cover vegetation. Six forest native species such as aroeira vermelha (Schinus terebinthifolius Raddi.), pau pombo (Tapirira guianensis Aubl.) mulungu (Erythrina velutina Willd.) tamboril (Enterolobium contortisiliquum (Vellozo) Morong), canafístula (Cassia grandis Lf) and pau-ferro (Caesalpinia leiostachya (Bentham) Ducke) were planted. The species developments were analyzed through the Relative Growth Rate (RGR) of the shoot height and crown diameter. After 6 (six) months, by the end of evaluations, the bigger number of live individuals was identified in the soil bioengineering treatment. The high density and strong growth of Brachiaria decumbens in the area with biotextile, have contributed to the lower initial tree seedlings development.