Atmospheric deposition and storage of nitrogen on Atlantic Forest remnants exposed to gradients of environmental stress

Abstract

Human actions have provided a considerable input of N to natural ecosystems, as NOx, NO3-, NH4+ and NH3-. In Sao Paulo, the Atlantic forest has been threatened by urban, industrial and agricultural pollution sources, which results in nitrogen enrichments, through wet and dry deposition, and storage in larger proportions in the soil, litter and plant community than expected under natural conditions. Thus, this project was proposed aiming at assessing whether the nitrogen concentrations in leaves of native tree species from three Atlantic Forest remnants, located on growing distances from the edge of the Atlantic plateau in São Paulo, are conditioned by natural climatic/edaphic gradients, by their intrinsic physiological characteristics and/or by atmospheric deposition of nitrogen compounds, originated from different anthropogenic sources. The samplings will be carried out in three conservation units, with Atlantic forest remnants that developed on different soils and climatic in function of their locations in relation to the edge of the Atlantic plateau. The leaf N concentrations (total N, NO3-, NH4+) and P will be quantified in the summer and in winter/2015 in tree species (3 pioneer species and 3 non-pioneers), litter and soil. Atmospheric deposition will be monitored for 1 year, through the weekly monitoring of NO2 in the atmosphere and of NO3-, NH4+ and PO43- on dry (fortnightly collections) and wet deposition (rain collections by events). The N/P ratio will be calculated for all matrices sampled. Analysis of variance and multiple comparisons tests will identify spatial and temporal trends. Multivariate analyses will be applied to find nutritional associations among plants, soil, litter and atmospheric deposition, in order to reach the overall aim proposed. (AU)