Land use changes and soil attributes of a Brazilian Cerrado-Amazon Rainforest ecotone landscape

Abstract

Historically, Amazon rainforest and Cerrado in Maranhão state, Brazil, have been subjected to deforestation. The long-term conversion from natural vegetation to mismanaged pasture may induce soil carbon depletion and compaction. Sustainable land management could be an alternative for recovering degraded land in tropical regions. The objective of this study was to evaluate some soil chemical and physical attributes associated with land use change in a Cerrado-Amazon rainforest ecotone. The study was carried out in Maranhão state, in Northeastern Brazil. Plots were selected from three main land uses in the southwestern part of the state: successional forest (SF), conventional pasture (CP) and agroforestry system (AFS). The experimental design was completely randomized, with three treatments (CP, SF, and AFS) and five replications. To evaluate the chemical attributes, a principal component analysis (PCA) was applied. For the chemical and physical attributes, a factorial scheme (land uses and depths) was used. The PCA separated the AFS land use from the other uses, due to the greater influence of pH, organic matter, available P, Ca, Mg, and K, sum of bases, soil cation exchange capacity and base saturation. The CP was mainly influenced by the acidity components. Long-term conversion from extensive pastures to SF and AFS showed a trend of bulk density reduction and led to lower soil resistance to penetration. The improvement of these two physical indicators in the AFS was associated with soil organic matter and carbon stocks and confirmed the improvement of edaphic conditions after adopting a well-managed system, in this small-scale study, in a tropical region.