Soil attributes along an agricultural-forested gradient in a riparian zone

This study was carried out from January 2008 to December 2008 and aimed to evaluate modifications caused by the recovery of riparian vegetation on soil attributes. Transactions were defined in two margins of a dam, in order to represent continuous types of occupation (sugarcane-recent forest-old forest). Topsoil (0-0.2 m) and subsoil (0.2-0.4 m) samples were collected for evaluation of soil quality through chemical [pH, cation exchange capacity (CEC), and organic matter (OM), P, Ca and Al contents], physical (total porosity and apparent density) and microbiologic (basal respiration rate) attributes. Physical attributes were not affected for the soil use type and for vegetation cover. Significant differences (p<0.05) were observed for CEC, OM content and microorganisms activity according to soil use. CEC and OM content increased from the sugarcane plantation to the old forest, suggesting that the input of vegetal biomass through the recovered forest contributed to the improvement of chemical soil quality. Microbiological activity also indicated that the period of replacement of sugarcane plantation for recent forest was not still enough to cause changes in biological soil attributes. There was increase of the soil quality with the decrease of the use intensity and with the recovery of the natural vegetation.