Propagation and establishment of rupestrian grassland grasses for restoration of degraded areas by mining.

Abstract

Investigations on the propagation and establishment of native grasses of rupestrian grassland on degraded substrates are essential to enable their use in the restoration of degraded areas, thus reducing the use of exotic species. This study aimed to evaluate the sexual and asexual propagation, establishment and growth of Axonopus laxiflorus (Trin.) Chase and Sporobolus metallicolus Longhi-Wagner & Boechat, two native grasses from rupestrian grassland developed on laterite substrate of an area degraded by bauxite mining. In greenhouse experiments, A. laxiflorus was propagated by tillers and S. metallicolus by seeds and tillers. Both species were also evaluated for germination in a germination chamber on the treatments: control, addition of potassium nitrate and heating at 80 °C for 2 min. In these evaluations, success of S. metallicolus germination was between 77 and 90%, without significative difference among treatments, whereas A. laxiflorus did not germinate. In the laterite substrate, S. metallicolous, propagated by seeds, showed 29% of survival, whereas in the vegetative propagation all plants of the two species survived. Eight months after starting the tiller experiment, S. metallicolus and A. laxiflorus presented a biomass increase of 239 and 75%, respectively. Although A. laxiflorus showed root biomass approximately seven times higher than S. metallicolus, the two species presented similar root length, that is, S. metallicolus contained more fine roots. The results show that the species can efficiently propagate vegetatively and, in the case of S. metallicolus, sexually. The success of the species in a substrate poor in nutrients and rich in Al, Fe and Mn indicates that they can be used in the restoration of areas degraded by bauxite and iron mining, which are important mining activities in Brazil.