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iForest -Biogeosciences and Forestry
IntroductionThe Brazilian Atlantic biome is recognized as one of the hotspots for the conservation of biodiversity (Forzza et al. 2012), though it is severely affected by diverse human interferences, particularly in the State of São Paulo, southeastern Brazil (Domingos et al. 2003). The semideciduous Atlantic Forest is highly fragmented in central-eastern São Paulo because of the expansion of agriculture and urban and industrial growth (Nalon et al. 2008). Besides the reduction of forest cover, human activities bring about a variety of pollutants from combustion of fuels, waste disposal, long-term sewage sludge and fertilizer application and other sources, which may be toxic to the plant community and modify the chemical status of soil, depending on its original chemical and physical conditions (Nriagu 1990, Sharpley 1995, Schaaf et al. 2004, Pouyat et al. 2008, Lucas et al. 2011. Soil nutrients are among the main factors that regulate plant growth and play an important role in the sustainable use of soils; however, their excess due to pollution from human sources may damage the soils and affect the soil-plant relationships. Air pollution may also disrupt other nutrient cycling processes in natural ecosystems, such as the decomposition of litter (Cotrufo et al. 1995).Most anthropogenic pollutants deposited in forest ecosystems accumulate in the soil surface layers (Ruan et al. 2008), where pollutants are typically immobilized for long periods (Hawkins et al. 1995, Verstraeten et al. 2012. However, these accumulations are considered a "chemical time bomb" (Kabala & Szerszen 2002, Hovmand et al. 2008, because pollutants will eventually be leached into waterways (Miller & Friedland 1994).Increased deposition of sulfur and nitrogen compounds (SO2, NOx and NH3) in natural communities induces soil acidification (Falkengren-Grerup & Tyler 1993, Akselsson et al. 2013, Gao et al. 2013. Soil acidification depletes the basic nutrient cations, causes a decrease of pH, lowers the quality of humus, and accelerates the mobilization of aluminum (Boruvka et al. 2005, Miller & Watmough 2009). The depletion of basic cations from the forest floor alters the mineral nutrition of trees, modifies tree growth patterns (Klumpp et al. 2002, Högberg et al. 2006, Sebesta et al. 2011) and affects the distribution of roots (Joslin & Wolfe 1992). As a consequence, biodiversity, vegetation productivity and dynamics of the soil carbon pool are affected (Binkley et al. 2000).Altogether, such negative effects contribute to the forest decline observed in the Atlantic Rain Forest on the coastal mountain range named Serra do Mar (region of Cubatão, São Paulo State, Brazil). This forest is affected by air pollution from an industrial complex that caused destabilization of the land surface, disturbance of soil processes and landslides (Leitão Filho et al. 1993, Mayer et al. 2000a, 2000b. Furthermore, the large metropolitan regions of the São Paulo State (SE Brazil) are responsible for the intense fragmentation of...
