Tropical forests and savanna account for nearly 65% of the total global terrestrial net primary production (NPP); however, there are still large uncertainties in tropical forest NPP because of limited field measurements, especially in the structurally diverse Brazilian savanna (cerrado). To address this uncertainty, we measured patterns of aboveground wood C stocks (C w ) and rates of wood C storage (ΔC w ) over a 7-year period for cerrado forests and woodlands of southern Mato Grosso, Brazil, arrayed across hydrological and soil fertility gradients. We focused on ΔC w because it is an important component of NPP, and wood is a stable, long-term, C storage reservoir. Annual rates of ΔC w were significantly affected by estimates of P and cation (K and Ca) availability, and analysis of covariance indicated that relationships between ΔC w and nutrient availability were independent of stand hydrology. Both upland and hyperseasonal stands exhibited a decline in ΔC w during the 2015-16 El Niño event, which was exceptionally warm and dry. A limited analysis of the uncertainty associated with the field measurements ranged from 7% for wood density to 24% for tree density, while the uncertainty associated with derived quantities ranged from 10% for tree height to 41% for C w . Overall, these results suggest that soil fertility and annual precipitation are important drivers of ΔC w and that warming and drying associated with climate change will cause a decline in aboveground woody C storage for these, and similar, tropical forests and woodlands.Plain Language Summary Tropical forests and savannas are important reservoirs for global carbon (C) storage, but there are still uncertainties in how much C is stored in these ecosystems, especially for savanna. We measured the amount and rate of C stored in aboveground wood for forests and woodlands of the Brazilian savanna in the southern part of the Amazon Basin. Rates of wood C storage increased as nutrient availability increased, and C storage declined during drought years for both seasonally flooded and non-flooded forests and woodlands. These results have implications for how climate and land-use change alter wood C storage in these globally important ecosystems.

The savanna vegetation of Brazil (Cerrado) accounts for 20–25% of the land cover of Brazil and is the second largest ecosystem following Amazonian forest; however, Cerrado mass and energy exchange is still highly uncertain. We used eddy covariance to measure the net ecosystem CO2 exchange (NEE) of grass‐dominated Cerrado (campo sujo) over 3 years. We hypothesized that soil water availability would be a key control over the seasonal and interannual variations in NEE. Multiple regression indicated that gross primary production (GPP) was positively correlated (Pearson's r = 0.69; p < 0.001) with soil water content, radiation, and the Moderate Resolution Imaging Spectroradiometer (MODIS)‐derived enhanced vegetation index (EVI) but negatively correlated with the vapor pressure deficit (VPD), indicating that drier conditions increased water limitations on GPP. Similarly, ecosystem respiration (Reco) was positively correlated (Pearson's r = 0.78; p < 0.001) with the EVI, radiation, soil water content, and temperature but slightly negatively correlated with rainfall and the VPD. While the NEE responded rapidly to temporal variations in soil water availability, the grass‐dominated Cerrado stand was a net source of CO2 to the atmosphere during the study period, which was drier compared to the long‐term average rainfall. Cumulative NEE was approximately 842 gC m−2, varying from 357 gC m−2 in 2011 to 242 gC m−2 in 2012. Our results indicate that grass‐dominated Cerrado may be an important regional CO2 source in response to the warming and drying that is expected to occur in the southern Amazon Basin under climate change.

Temporal variations in land-atmosphere water vapor exchange are more pronounced in seasonal environments, especially grass-dominated savannas (known as campo sujo Cerrado) of the southern and eastern Amazon Basin. Recent work in campo sujo indicates that rates of canopy conductance (g c) were directly and indirectly affected by a variety of meteorological variables, which limited our understanding of how seasonal variation in meteorology affected rates of g c. 22 Thus, our overall objective here is to determine how individual meteorological variables affect 23

publicado na web em 26/08/2016Brazil plays an important role with regard to the emission of aerosols into the atmosphere. Ecosystems such as the Amazonian tropical forest and Brazilian Cerrado are undergoing sweeping changes. These human activities promote an increase in the levels of gases and particles emitted into the atmosphere. To determine how these activities have affected the emission of coarse and fine particulate matter (PM 10 and PM 2.5 ), atmospheric aerosol samples were collected continuously from June 2004 to April 2005 in the Cuiaba Basin of south-central Mato Grosso, Brazil. Aerosols were sampled using stacked filter units. Filters were analysed for particulate mass, black carbon and for concentrations of seventeen elements by Particle Induced X-Ray Emission. The results revealed that Mg, Al, Si, S, K, Ca, Ti and Fe were the major components detected in PM 2.5 and PM 10 . The high enrichment factors observed in PM 2.5 and PM 10 suggest that anthropogenic activities were the predominant source for elements such as Cu, Zn and Pb. These data indicate that most of the aerosols measured in the Cuiaba Basin originate from land conversion and biomass burning. These patterns are similar to those observed in other Cerrado and Amazonian forest areas that are undergoing rapid and spatially extensive land-cover change.

Resumo:As ações antrópicas, em especial a queima de biomassa, são as principais responsáveis pelo envio de aerossóis para a atmosfera, e esse particulado exerce influência sobre o balanço de energia e os ciclos hidrológicos, fazendo com que o seu estudo seja inerente à compreensão desses processos. Cientes disso, o objetivo deste estudo foi obter uma relação entre a profundidade ótica dos aerossóis (POA) e a radiação solar incidente em área de Cerrado em MT. Utilizou-se dados de POA coletados de jan/2010 a dez/2012, obtidos pela rede AERONET (Aerosol Robotic Network -NASA). Esses dados foram analisados em conjunto com dados de focos de queimadas, sendo possível encontrar altos valores de POA nas estações secas, chegando a uma média de 3,8 em 2010. Tanto a radiação global (R g ) quanto a radiação fotossinteticamente ativa (RFA) tem correlação significativa (p < 0.01 para 2011 e 2013, p < 0.05 para 2011) com POA, e altos valores de POA correspondem a uma quantidade significativa de particulados na atmosfera, diminuindo a intensidade da radiação solar e provocando alterações de sua distribuição no sistema superfície-atmosfera.Palavras-chave: Radiação solar. AERONET. Balanço de radiação. Queimadas. RELATIONSHIP BETWEEN AEROSOLS OPTICAL DEPTH AND PHOTOSYNTHETICALLY AND GLOBAL RADIATION IN A SAVANNA OF MATO GROSSO, BRAZILAbstract: The anthropic activities, particularly the biomass burning, are the main responsible source of aerosols to the atmosphere, and this particulate matter influences the regional energy balance and hydrological cycle, studying this is inherent to the understanding of these processes. The goal of this study is obtain a relationship