Edmar Mazzi

Can land use changes alter carbon, nitrogen and major ion transport in subtropical brazilian streams?

Several studies in tropical watersheds have evaluated the impact of urbanization and agricultural practices on water quality. In Brazil, savannas (known regionally as Cerrados) represent 23% of the countrys surface, representing an important share to the national primary growth product, especially due to intense agriculture. The purpose of this study is to present a comprehensive evaluation, on a yearly basis, of carbon, nitrogen and major ion fluxes in streams crossing areas under different land use (natural vegetation, sugar cane and eucalyptus) in a savanna region of SE Brazil. Eucalyptus and sugar cane alter the transport of the investigated elements in small watersheds. The highest concentration of all parameters (abiotic parameters, ions, dissolved organic carbon DOC - and dissolved inorganic carbon - DIC) were found in Sugar Cane Watersheds (SCW). The observed concentrations of major cations in Eucalyptus Watersheds (EW) (Mg, Ca, K, Na), as well as DIN and DOC, were found frequently to be intermediate values between those of Savanna Watersheds (SW) and SCW, suggesting a moderate impact of eucalyptus plantations on the streamwater. Same trends were found in relation to ion and nutrient fluxes, where the higher values corresponded to SCW. It is suggested that sugar cane plantations might be playing an important role in altering the chemistry of water bodies.

Factors influencing the food transition in riverine communities in the Brazilian Amazon

The objective of this study was to determine the main patterns and factors influencing food transition in riverine people in the Brazilian Amazon. Through interviews with a semi-structured questionnaire, we inferred their food habits and provide information about general demographic, socioeconomic, resource use and environmental context. Data from the questionnaires were categorized and analyzed using a logistic regression model to assess the relative influence of socioeconomic and environment factors on the local diet. Based on a logistic regression data analysis, it was found a greater consumption of processed food significantly associated with multiple factors such as market participation, sex (female and male), government aid to forest conservation and environment context (upland and wetland). Although the local diet is composed mainly of local resources such as fish and cassava flour, increasing incomes due to direct government subsidy programs and marketing of cassava flour have influenced these local practices and habits. Through the analysis of factors influencing food transition, it was possible to evaluate those having the greatest effect on this Amazon region and propose an alternative method to subsidy food policy grounded in local opinion surveys.

Biogeochemical diversity, O2-supersaturation and hot moments of GHG emissions from shallow alkaline lakes in the Pantanal of Nhecolândia, Brazil

Nhecolândia is a vast sub-region of the Pantanal wetland in Brazil with great diversity in surface water chemistry evolving in a sodic alkaline pathway under the influence of evaporation. In this region, >15,000 shallow lakes are likely to contribute an enormous quantity of greenhouse gas to the atmosphere, but the diversity of the biogeochemical scenarios and their variability in time and space is a major challenge to estimate the regional contribution. From 4 selected alkaline lakes, we compiled measurements of the physico-chemical characteristics of water and sediments, gas fluxes in floating chambers, and sedimentation rates to illustrate this diversity. Although these lakes have a similar chemical composition, the results confirm a difference between the black-water and green-water alkaline lakes, corresponding to distinct biogeochemical functioning. This difference does not appear to affect lake sedimentation rates, but is reflected in gas emissions. Black-water lakes are CO2 and CH4 sources, with fairly constant emissions throughout the seasons. Annual carbon dioxide and methane emissions approach 0.86molm-2y-1 and 0.07molm-2y-1, respectively, and no clear trend towards N2O capture or emission was observed. By contrast, green-water lakes are CO2 and N2O sinks but important CH4 sources with fluxes varying significantly throughout the seasons, depending on the magnitude of the phytoplankton bloom. The results highlight important daily and seasonal variations in gas fluxes, and in particular a hot moments for methane emissions, when the O2-supersaturation is reached during the afternoon under extreme bloom and sunny weather conditions, provoking an abrupt O2 purging of the lakes. Taking into account the seasonal variability, annual methane emissions are around 10.2molm-2y-1, i.e., much higher than reported in previous studies for alkaline lakes in Nhecolândia. Carbon dioxide and nitrous oxide consumption is estimated about 1.9molm-2y-1 and 0.73mmolm-2y-1, respectively. However, these balances must be better constrained with systematic and targeted measurements throughout the seasons.

Litterfall mass and nutrient fluxes over an altitudinal gradient in the coastal Atlantic Forest, Brazil

Litterfall is one of the most important pathways through which nutrients are recycled in the terrestrial biosphere. In tropical soils, which are generally low in essential nutrients such as phosphorus and cations, the flux of nutrients through litterfall is particularly important to sustaining CO 2 -uptake capacity; however, questions remain over the role of altitude in altering litter nutrient cycling rates among tropical forest ecosystems. Here we examine litterfall, carbon (C), nitrogen (N) and phosphorus (P) fluxes through litterfall over an altitudinal gradient in the coastal Atlantic Forest located on the northern coast of the State of Sao Paulo, Brazil. Litterfall was collected twice a month for 1 y (April 2007–March 2008) using 30 litter traps placed in four different forest types arrayed by altitude – coastal forest (sea level), lowland forest (50–200 m asl), submontane forest (300–500 m asl) and montane forest (1000 m asl). Litterfall mass-fluxes decreased with increasing altitude, from ~9 Mg ha −1 in lowland forests to 7 Mg ha −1 in higher-altitude ecosystems. Contribution of reproductive organs to litterfall was significantly greater in lower than in higher altitudes. Litterfall N and P fluxes were higher in the lowland forest vs. other forest types, pointing to strong altitudinal controls over nutrient cycling. Furthermore, nitrogen-use efficiency (NUE) was lower and litter δ 15 N was higher in the lowland site providing additional evidence for lack of N constraints to productivity in lowland of the south-eastern Atlantic Forest.

Sunlight effects on diel CO2 and CH4 emissions from a tropical reservoir

eurrent studies show that reservoirs are responsible for emissions of greenhouse gases (ST. Loms et al. 2000, DucHEMIN et al. 2002, SouMIS et al. 2004, ABRIL et al. 2005, LIMA et al. 2008). Surface waters of aquatic ecosystems exhibit supersaturated dissolved e02 (CüLE 1999, RICHEY et al. 2002) because respiration based on both autochthonous and allocthonous organic carbon usually exceeds primary production (DEL GIORGIO et al. 1997, CoLE 1999, JoNssoN et al. 2003). Dissolved organic carbon transported to the aquatic ecosystem from the drainage basin usually remains bio1ogically refractory. Upon exposure to sunlight in a relatively well-lit aquatic environment, however, terrigenous organic carbon might undergo photolytic degradation and become more labile (CoLE 1999). In spite ofphotominemlization, carbon dioxide effiuxes may also result from methanotrophic activities (FRENZEL et al. 1990, ABE et al. 2005, LIMA 2005) associated with diel oxygen production via photosynthesis (KING 1990, LIMA et al. 2005a). Moreover, diel changes in sunlight may also affect dissolved gas solubility and, in particular, surface water density, leading to convection during cooling events (MAclNTYRE et al. 2001). We evaluated possible ro les of sunlight on the daily variability of eH4 and eo2 diffusive fluxes from eorumbá reservoir in Brazíl. Our results support that eo2 and eH4 emissions in eorumbá are substantially influenced by sunlightinduced processes, although we cannot precisely identify the primary variables inducing diel changes.