Soil attributes under agroecosystems and forest vegetation in the coastal tablelands of northestern Brazil

This study evaluated the changes occurred in a set of soil attributes, particularly those related to the dynamics of soil organic carbon (SOC), as a function of the replacement of native forest for agricultural ecosystems of regional importance in the coastal tablelands of Northeastern Brazil (orange, coconut, eucalyptus and sugarcane). Six commercial sites under these agroecosystems were compared to neighboring areas of native forest in five areas along this region (Coruripe, Umbaúba, Acajutiba, Cruz das Almas and Nova Viçosa). Soil samples were taken from 0-5 and 5-20 cm depth and analyzed for particle size distribution, bulk density, organic C (OC), particulate organic matter, C in soil solution, microbial biomass C, total cation exchange capacity and water stable aggregates. Linear correlation and multivariate techniques were used for data analysis. The values of base saturation and Al saturation for the 0-20 cm depth layer were also calculated. In all the studied areas, soils under native forest presented better status of physical and chemical attributes than their agroecosystem counterparts, especially in the 0-5 cm layer. For both layers, OC content was the attribute most strongly correlated with the overall changes in all attributes. Unexpectedly, the OC content showed no significant correlation with the sum of silt and clay contents. The set of variables investigated in this study is sensitive to differentiate the quality of soils under perennial and semi-perennial land uses from their counterparts under natural vegetation in the landscapes of the coastal tablelands of Northeastern Brazil. Este trabalho avaliou as alterações de um conjunto de atributos de solos dos tabuleiros costeiros do Nordeste do Brasil, em especial os relacionados à dinâmica do C orgânico (CO), em função da substituição da vegetação florestal nativa por agroecossistemas de importância regional (laranja, coco, eucalipto e cana-de-açúcar). Seis sítios comerciais sob esses agroecossistemas foram comparados a áreas vizinhas de mata nativa, em cinco locais de amostragem ao longo dos tabuleiros costeiros (Coruripe, Umbaúba, Acajutiba, Cruz das Almas e Nova Viçosa) Foram coletadas amostras de solo de 0-5 e de 5-20 cm de profundidade para determinar granulometria, densidade do solo, C orgânico (CO), matéria orgânica particulada, C da solução do solo, C da biomassa microbiana, capacidade de troca catiônica e agregados estáveis em água. Para análise dos dados foram realizadas correlaçõ