Soil chemical and physical status in semideciduous Atlantic Forest fragments affected by atmospheric deposition in central-eastern Sao Paulo State, Brazil

The expansion of agricultural, urban and industrial areas in the Sao Paulo State (SE Brazil) led to the fragmentation of the original semideciduous Atlantic Forest into small, patchy forest remnants. Anthropogenic activities produce a variety of pollutants affecting many ecological processes in these remaining forest fragments through soil acidification and fertilization. In this study, we investigated the soil chemical and physical status of six forest remnants (Paullnia, Holambra, Americana, Jaguariuna, Campinas and Cosmopolis) differently affected by industrial, rural and urban pollution in central-eastern Sao Paulo in order to determine the soil potential to buffer the inputs of pollutants. Soil samples from 0-10, 10-20 and 20-40 cm depths were collected in the dry and the wet season and the following variables were analyzed: soil texture, pH in CaCl2 solution, exchangeable cations and exchange capacity, organic carbon, total nitrogen, extractable sulfur, phosphorus and heavy metals. Distinct buffering capacities were observed in industrial and in rural and urban areas, primarily due to the natural characteristics of the soils, such as soil texture, acidification and organic matter. The forest soils affected by atmospheric deposition from the industrial complex (Paulinia and Americana) were more sandy and acidic (pH = 3.6) than those near rural and urban sources (pH = 4.5). The optimal chemical conditions (high contents of organic matter, exchangeable bases, nitrogen, phosphorus and sulfur) were found in the clay soils of forest remnants located in Campinas and Jaguariuna, which were more affected by rural or urban pollution than by industrial emissions. Such clay soils provide the highest buffering capacity against environmental impacts in the study region.