Effects of Forest Restoration Techniques on Community Diversity and Aboveground Biomass on Area Affected by Mining Tailings in Mariana,Southeastern Brazil

Currently there is an urgent and special attention in actions to restore tropical forests.In this study,we evaluated the effect of different restoration methods on aboveground biomass(AGB)stock,tree community diversity and structure,in areas affected by the Fundão tailings dam collapse in Mariana,Minas Gerais state,Brazil.We measured and compiled data of the AGB,community diversity and structure attributes in 36 plots distributed in six restoration treatments and six replicas:planting of native tree seedlings with fertilization and pH correction(PSf)and without fertilization and pH correction(PS);seeding of native trees with fertilization and pH correction(SDf)and without fertilization and pH correction(SD);natural regeneration with fertilization and pH correction(NRf)and without fertilization and pH correction(NR).No significant differences in substrate properties and AGB between treatments.Although biomass storage between treatments was not statistically different,there is a clear pattern showing higher values active restoration method.The Pielou index ranged from 0.520(SDf)to 0.943(NR),except for SDf all the others treatments had values higher than 0.76.This result suggests floristic heterogeneity,without ecological dominance in the plant community.Overall,active restoration had important implications for the forest restoration where natural regeneration is limited.

Influence of Environmental Variables on the Natural Regeneration of a Forest under Restoration after Bauxite Mining and in a Reference Ecosystem in Southeastern Brazil

The shrub-tree floristic composition of the natural regeneration stratum of a bauxite mine in the process of restoration and in a reference ecosystem(remnant of a preserved secondary Seasonal Semi-Deciduous Forest)were analysed to evaluate forest restoration conditions after five years of planting.The influence of canopy openness,accumulated leaf litter and soil attributes in the regeneration stratum were also investigated in both the forests.The floristic composition of the regeneration stratum in the forest under restoration(16 species and 5,083 individuals ha-1)and in the reference ecosystem(58 species and 26,250 individuals ha-1)are distinct due to the difference in the environmental variables.Results showed that the reference ecosystem favours the presence of species that tolerate environments with greater shading and higher aluminium and organic matter content in the soil like Psychotria carthagenensis Jacq.,while the forest under restoration favours the presence of species adapted to fertile soils and those that tolerate greater luminosity like Vernonanthura phosphorica(Vell.)H.Rob.

Study on Site Preparation and Restoration Techniques for Forest Restoration in Mining Tailings of Mariana,Brazil

Ecological restoration in forest ecosystem is a priority in Mariana,Brazil.Thus,we evaluated the effects of passive and active restoration methods through different site preparation techniques by manipulating physical-chemical properties of substrates on tree community coverage in Mariana,Brazil.A total of 48 plots(12×12 m each)were established in two areas along the flood plains with accumulation of tailings.The following treatments were established:(1)planting of native tree seedlings with fertilization(PSf)and(2)without fertilization(PS);(3)direct seeding of native trees with fertilization(SDf)and(4)without fertilization(SD);(5)natural regeneration with fertilization(NRf)and(6)without fertilization(NR).Differences in substrate properties and tree community coverage were evaluated between treatments,the substrate properties and tree community coverage relationship,and main effects of substrate fertility and texture on tree community coverage.There were marked differences in substrate and plant coverage between treatments.On average,the highest plant coverage was found in treatment with fertilization,such as NRf(59,5%)and SDf(48%).However,the treatment with seedling planting(PSf and PS)and NR did not show differences(~37%),while the lowest values were observed in SD(23%).There is a strong relationship between substrate fertility and plant community coverage,with significant positive effects.We observed that the passive and active restoration methods can be complementary in the soil and plant community coverage recovery.

Soil Seed Banks in Two Environments of Forest Restoration Post Bauxite Mining:Native Tree Plantation and Natural Regeneration

The objective of this study was to compare the soil seed bank in an area under natural regeneration(F1)and another reforested through seedling planting(F2),seven years after bauxite mining,in Southeast,Brazil.In each area,10 sampling points were randomly distributed,using three samples of topsoil to represent each point.The samples were transported to a shade house and evaluated for six months,where emerging individuals were identified every two weeks.Floristic similarity was evaluated with cluster analysis based on the Jaccard index(SJ).Species richness and abundance of individuals were compared using Student's t test.In F1,2,114.94 propagules m-2 were registered,belonging to 51 species and 24 botanical families,Shannon-Wiener diversity index H’=2.770 and Pielou evenness index J’=0.705.In F2,1,168.62 propagules m-2 were registered,belonging to 42 species and 22 families,H’=2.618 and J’=0.700.The(SJ)between F1 and F2 was 0.61,indicating a high similarity.The results showed high density of propagules,good diversity and absence of ecological dominance.The high number of individuals and diversity of tree species with zoochoric dispersion found in the areas indicates that both natural regeneration and reforestation were efficient in the ecological restoration of bauxite mined areas.

Attributes of stand-age-dependent forest determine technosol fertility of Atlantic forest re-growing on mining tailings in Mariana,Brazil

Understanding how soil fertility changes due to environmental conditions and stand-age-dependent forest attributes is important for local-scale forest restoration.We evaluated the effects of stand-age-dependent forest attributes(plant community composition and litter stock)on soil and technosol fertility across two second-growth Atlantic forests(SGF)after the deposition of mining tailings in Mariana,southeastern Brazil.We hypothesized that technosol fertility in the SGF tailings is positively affected by plant community composition variability,stand age,and litter stock.We used total exchangeable bases and organic matter as fertility indicators for technosol and soil,and species composition and litter stock as stand-age-dependent forest attributes.Our results showed significant differences in the stand-age-dependent forest attributes and soil chemical properties between the two forest patches(SGF tailing and SGF non-tailing)evaluated.Thus,there was a marked gradient of litter storage and fertility between soil and technosol that can be important forest recovery indicators for the affected plant communities.Furthermore,according to the tested models,we corroborated the hypothesis that technosol fertility is positively affected by stand age,plant community composition variability,and litter stock,which may contribute considerably to forest recovery on tailings.Our results demonstrate that the fertility predictors analyzed to explain the forest recovery on tailings can also be considered as ecological indicators for assessing forest restoration in areas impacted by mining tailings in Mariana.