Native grass sod and plug production as an alternative technique to restore neotropical rupestrian grassland after mining.

Abstract

Despite the importance of grasses in the structure and functioning of tropical grasslands, there is still a lack of efficient and economically viable techniques to produce and introduce grasses in restoration projects. Here, we evaluated the sod and plug-plant production and planting of a native grass from Brazilian rupestrian grasslands, Sporobolus metallicolus, in a post-bauxite mining. To produce the sod, we used post-mining substrate and its mixture with commercial substrate. Then, we sowed 270 seeds of S. metallicolus on a 4-cm layer of substrate in 144-cm2 trays. Eighty days after sowing, we subdivided the contents of each tray (substrate + plant) into 4 × 3–cm plug-plants. Plug-plants were planted in the degraded area with and without the incorporation of litter from an adjacent conserved rupestrian grassland. We also evaluated the cost of production of each plug-plant. The mixture of substrates provided greater plant growth and rooting, obtaining plug-plants with an average of 13 individuals, dry mass of 270 mg, and estimated cost of US$ 0.0045. In the degraded area, the addition of litter increased shoot biomass gain. Plant survival was 100% with and without litter addition and the plants started seed dispersal at 7 months after planting. The production of S. metallicolus plugs with the mixed substrate and the growth of plants in the post-mined area showed promising results and reduced costs, indicating technical and financial feasibility. The presented techniques can be an option for introducing grasses in degraded areas and optimize the use of seeds.