Plant growth and metabolism of exotic and native Crotalaria species for mine land rehabilitation in the Amazon

Despite its enormous benefits,mining is respon-sible for intense changes to vegetation and soil properties.Thus,after extraction,it is necessary to rehabilitate the mined areas,creating better conditions for the establishment of plant species which is challenging.This study evaluated mineral and organic fertilization on the growth,and carbon and nitrogen(N)metabolism of two Crotalaria species[Cro-talaria spectabilis(exotic species)and Crotalaria maypu-rensis(native species from Carajás Mineral Province(CMP)]established on a waste pile from an iron mine in CMP.A control(without fertilizer application)and six fertilization mixtures were tested(i=NPK;ii=NPK+micronutrients;iii=NPK+micronutrients+organic compost;iv=PK;v=PK+micronutrients;vi=PK+micronutrients+organic compost).Fertilization contributed to increased growth of both species,and treatments with NPK and micronutrients had the best results(up to 257%cf.controls),while organic fertilization did not show differences.Exotic Crotalaria had a greater number of nodules,higher nodule dry mass,chlorophyll a and b contents and showed free ammonium as the predominant N form,reflecting greater increments in biomass compared to native species.Although having lower growth,the use of this native species in the rehabilitation of mining areas should be considered,mainly because it has good development and meets current government legislation as an opportunity to restore local biodiversity.

How do altitude and soil properties influence the taxonomic and phylogenetic structure and diversity of Brazilian páramo vegetation?

Altitude and environmental variables such as edaphic properties are considered determinants of species distribution and community composition in mountain ecosystems.Here,we aimed to outline the effects of distinct mountain peaks,altitude and soil properties on community composition,species density,phylogenetic structure and diversity of angiosperm páramo communities from the Serra do Brigadeiro State Park,Minas Gerais,southeastern Brazil.For that,we identified all angiosperm species found in 300 plots(1 m×1 m)from three mountain peaks,measured soil depth and analyzed soil fertility and texture in each plot.To reduce the number of soil variables and species composition,we computed principal coordinates based on soil properties and principal coordinates based on species-plot matrix for each plot.Furthermore,we computed the standard effect sizes of the mean phylogenetic pairwise distance and the mean nearest phylogenetic taxon distance for each plot to investigate differences in the degree of relatedness among coexisting species.We compared differences in response variables between peaks and modelled them in function of altitude and principle components of soil properties using mixed effect models.Species density and phylogenetic diversity differed between peaks,but,contrary to the previous findings,no relationships between species richness or phylogenetic diversity and altitude or soil properties were found,indicating that further investigations are necessary to understand the altitude-biodiversity relationship in Brazilian páramo vegetation.Community composition differed between peaks and depended on altitude,soil properties and interactions between them,indicating that upward shifting of bioclimatic conditions due to climate changes may alter communities of this ecosystem.Phylogenetic structure differed between peaks and was influenced by altitude and soil properties.As phylogenetic clustering increased with altitude,eventual upward movements of species in Brazilian páramo vegetation due to climate change may alter community composition and the degree of relatedness among coexisting species,increasing the risk of species from higher altitudes to disappear.Therefore,conservation priorities arise for higher landscape portions,where these high altitude species may find refuges.

Plant growth and nutrient use efficiency of two native Fabaceae species for mineland revegetation in the eastern Amazon

The primary challenge of mineland revegetation is the establishment of species able to cope with low availability of nutrients,especially in steep slopes such as of mine pits.We evaluated plant growth response and nutrient use efficiency(NUE)of two promising native Fabaceae species(Dioclea apurensis—liana from metalliferous savannas;Bauhinia longipedicellata—tree from Amazon rainforest)from the Caraja´s Mineral Province,eastern Amazon-Brazil.Plants were grown separately in 2-kg pots filled with mining waste.Substrates were fertilized with nitrogen,phosphorus,potassium(NPK),lime,and micronutrients.The results showed increments on growth of both species when nutrients were applied to the mining waste.D.apurensis showed increases in leaf area,plant height,stem diameter,and shoot dry mass production when NPK or NPK?micronutrients were applied,while B.longipedicelata was responsive to application of NPK?lime or NPK?lime?micronutrients.Further,D.apurensis showed higher NUE than B.longipedicelata,especially at the lowest doses of N,P and K.These findings may indicate a substantial advantage of D.apurensis for mineland revegetation,as this species may require lower nutrient inputs,being,therefore,a more sustainable way to revegetate degraded areas.