Biological and chemical attributes of soils under forest species in Northeast Brazil

Timber forests contribute to the sustainable development of the biomes in tropical regions.The aim of this study was to evaluate the biological and chemical properties of the soil as a consequence of the cover with native and non-native species in the Acarau basin,a transition area from the coast to the Brazilian semi-arid region.Areas planted with four native species(Anadenanthera colubrina,Astronium fraxinifolium,Handroanthus impetiginosus,Colubrina glandulosa)and three exotic species(Acacia mangium,Casuarina equisetifolia,Eucalyptus urophylla)plus a non-forested agricultural area were evaluated for organic carbon contents,and microbial and chemical soil properties.The levels of soil organic carbon were highest in A.colubrina and C.equisetifolia plantations.Low basal soil respiration was observed but the microbial biomass was particularly low in the non-forested area.In the C.equisetifolia,E.urophylla,and H.impetiginosus plantations,elevated soil metabolic quotients were found.The A.colubrina and H.impetiginosus plantations had the highest levels of easily extracted-glomalin related soil protein.Tree species affect concentrations of essential nutrients and the biological quality of the soil in different ways.They can also improve the biological and chemical properties of the soil in the coastal plains of tropical regions.

Diversity of mycorrhizal fungi and soil indicative species in coastal plantations of northeast Brazil

The aim of this work was to evaluate arbuscular mycorrhizal(AM)fungi as soil indicators and the mycorrhization of native and exotic tree species planted in the Acaraúbasin,a transition area from the coast to the Brazilian semiarid region.Plots with 6-year-old trees of four native and three non-native species as well as one non-forested area were evaluated in terms of the diversity of AM fungi in the mycorrhizosphere and the root colonization by AM and ectomycorrhizal(EcM)fungi.Twenty-four AM fungi were identified;Claroideoglomus etunicatum,Glomus sinuosum,Paraglomus albidum,Acaulospora laevis,and Acaulospora brasiliensis were abundant in the forest soil.Diversity,dominance,evenness and richness indices of AM fungi were higher in plots with native trees.All root samples were colonized by AM fungi and only A nadenanthera colubrina,Acacia mangium,Casuarina equisetifolia and Eucalyptus urophylla formed associations with EcM fungi.Acaulospora morphotypes served as soil indicators for coverings with the native species Astronium fraxinifolium and Colubrina glandulosa.Exotic species may favor the proliferation of rarer AM fungi.These fungi–plant relationships may be important in the management of forest systems,and the evidence with mycorrhizal associations allows the inclusion of Brazilian species in tropical reforestation.