RESUMO As características peculiares dos substratos de remanescentes da mineração (estéril de mina) representam um desafio para a recuperação ambiental. Neste estudo avaliamos o potencial de uso de Paspalum cinerascens para revegetação de estéril de mina na Serra dos Carajás, Pará (Brasil). Paspalum cinerascens é uma gramínea nativa amplamente distribuída nas cangas, vegetação típica dos campos rupestres que cobrem reservas de minério de ferro. As plantas de P. cinerascens foram cultivadas em topsoil de canga (controle) e em estéril de mina com meio e completo regime de fertilização atualmente empregado para revegetação das áreas mineradas na Serra dos Carajás. Foram utilizadas sementes coletadas nas cangas e as plantas foram cultivadas em condições controladas por 90 dias. Independentemente da fertilização, plantas cultivadas em estéril de mina não apresentaram diferenças significativas na assimilação de carbono, perfilhamento ou biomassa radicular, apesar de valores mais elevados de nutrientes foliares e menor razão raiz: parte aérea quando comparadas às plantas em topsoil de canga. A fertilização completa resultou em plantas mais altas, maior biomassa aérea e menor eficiência no uso da água. Metade da fertilização aumentou a densidade estomática, a eficiência de uso da água e de fósforo. Esses resultados confirmaram que P. cinerascens possui características adaptativas para crescer e prosperar em condições ambientais adversas remanescentes da mineração, sendo indicada para uso em processos de recuperação de áreas degradadas na Serra dos Carajás. Além disso, o uso de metade do regime de fertilização otimiza o uso da água pelas plantas sem perdas significativas de crescimento, uma característica desejável para recuperação de áreas com restrições hídricas. ambiental Carajás Brasil. Brasil . (Brasil) ferro P controle (controle 9 dias carbono radicular raiz altas estomática fósforo disso crescimento hídricas (Brasil

ABSTRACT The peculiar characteristics of mining waste substrates represent a significant challenge for environmental rehabilitation. Here, we evaluated the revegetation potential of Paspalum cinerascens on substrates from mining areas of Serra dos Carajás, a region harboring a large mine complex in the eastern Brazilian Amazon. Paspalum cinerascens is a native grass widely distributed in the canga ecosystem, a vegetation type covering iron ore reserves. Seeds of P. cinerascens harvested in canga were germinated in sterilized quartzite sand and the seedlings grown in controlled conditions for 90 days. The seedlings were then cultivated in canga topsoil (control, without fertilization) and mining waste substrate with half and complete fertilization currently applied at the beginning of mineland rehabilitation in Serra dos Carajás. Regardless of fertilization, plants grown in the mining waste substrate did not differ in carbon assimilation, tillering rate and root biomass, despite higher leaf nutrient content and lower root: shoot ratio when compared to plants in canga topsoil. Compared to the control, complete fertilization led to significantly taller plants, higher shoot biomass and reduced water use efficiency. Half fertilization led to higher phosphorus and water use efficiency and stomatal density. Our results confirmed that P. cinerascens has adaptive traits to grow and thrive in the harsh environmental conditions of post iron ore mining, and can be used in rehabilitation processes. Moreover, half fertilization led to plants with optimized water loss in exchange for carbon without significant costs to plant growth, an interesting trait for rehabilitation in areas experiencing water restrictions. Here Carajás Amazon ecosystem reserves P 9 days control (control assimilation density processes Moreover growth restrictions

ABSTRACT. The intergovernmental panel on climate change predicts a progressive increase in atmospheric CO2 concentration and temperature; however, their effects on cereals have been shown for a limited number of species. This study evaluates the effects of increased CO2 concentration and temperature separately and combined on millet growth and grain production in open-top chambers where the microclimate was adjusted to the following conditions: ambient CO2 and temperature; CO2 enriched (~ 800 ppm) and ambient temperature; ambient CO2 and higher temperature (+3ºC); and CO2-enriched and higher temperature. For each treatment, two chambers were used, each containing 15 7 L pots. Each pot received five seeds at the beginning of the experiment and thinning to one plant per pot at 15 days after sowing. Ten plants were harvested from each chamber 65 days after sowing and the plant height, the number of leaves and the longest root length as well as shoot and root biomass were measured. The remaining plants were harvested 130 days after sowing to evaluate grain production. The results indicate that high CO2 levels did not affect plant growth and biomass. On the other hand, plants subjected to high temperature grew 7% taller than those grown under ambient temperature. Contrastingly, plants submitted to both elevated CO2 and temperature were 19% taller and had 22% more shoot biomass than plants under ambient CO2 and temperature. However, grain production did not change in any of the environmental conditions. We provide evidence that millets are tolerant of the predicted climate changes and that grain production potential may not be affected.