Nicolau Priante Filho

ECOLOGICAL RESEARCH IN THE LARGE-SCALE BIOSPHERE– ATMOSPHERE EXPERIMENT IN AMAZONIA: EARLY RESULTS

The Large-scale Biosphere-Atmosphere Experiment in Amazonia (LBA) is a multinational, interdisciplinary research program led by Brazil. Ecological studies in LBA focus on how tropical forest conversion, regrowth, and selective logging influence carbon storage, nutrient dynamics, trace gas fluxes, and the prospect for sustainable land use in the Amazon region. Early results from ecological studies within LBA emphasize the var- iability within the vast Amazon region and the profound effects that land-use and land- cover changes are having on that landscape. The predominant land cover of the Amazon region is evergreen forest; nonetheless, LBA studies have observed strong seasonal patterns in gross primary production, ecosystem respiration, and net ecosystem exchange, as well as phenology and tree growth. The seasonal patterns vary spatially and interannually and evidence suggests that these patterns are driven not only by variations in weather but also by innate biological rhythms of the forest species. Rapid rates of deforestation have marked the forests of the Amazon region over the past three decades. Evidence from ground-based surveys and remote sensing show that substantial areas of forest are being degraded by logging activities and through the collapse of forest edges. Because forest edges and logged forests are susceptible to fire, positive feedback cycles of forest degradation may be initiated by land-use-change events. LBA studies indicate that cleared lands in the Amazon, once released from cultivation or pasture usage, regenerate biomass rapidly. However, the pace of biomass accumulation is dependent upon past land use and the depletion of nutrients by unsustainable land-management practices. The challenge for ongoing research within LBA is to integrate the recognition of diverse patterns and processes into general models for prediction of regional ecosystem function.

EFFECTS OF METEOROLOGICAL VARIATIONS ON THE CO2 EXCHANGE OF A BRAZILIAN TRANSITIONAL TROPICAL FOREST

The net ecosystem CO2 exchange (NEE) of a 28-30 m tall transitional (eco- tonal) tropical forest of the Brazilian Amazon was quantified using tower-based eddy co- variance. Measurements were made between August 1999 and July 2001 and were used to develop nonlinear statistical models to assess daily variations in ecophysiological param- eters and provide annual estimates of NEE, gross ecosystem CO2 exchange (GEE), and respiration (Re). Diurnal trends in NEE were correlated with variations in photosynthetic photon flux density ( Q), vapor pressure deficit (V ), and temperature. Seasonal trends in the CO2-flux components estimated from nonlinear regression ( Amax and R0) were highly cor- related with soil water availability and canopy structural properties (LAI and litter pro- duction). These results suggest that variations in soil water content can affect rates of canopy photosynthesis and whole forest respiration by altering both physiological processes and canopy structural properties. Estimates of the annual NEE suggest that the forest was in balance with respect to CO2 during the study period, which, in terms of rainfall, was a relatively typical period compared to the 30-yr average rainfall regime. Our results also suggest that the warmer and dryer microclimate and decline in LAI that accompany land- cover change will cause transitional forests to be sources of CO 2 to the atmosphere.

Seasonal variation in the leaf gas exchange of tropical forest trees in the rain forest-savanna transition of the southern Amazon Basin

The photosynthetic light response of Amazonian semi-deciduous forest trees of the rain forest-savanna transition near Sinop Mato Grosso, Brazil was measured between July 2000 and September 2003 to test the hypothesis that the photosynthetic capacity of trees acclimated to different growth light environments will decline during the dry season. Maximum photosynthesis (A max ) and stomatal conductance (g max ) were significantly higher during the wet season; however, the physiological response to drought was not a clear function of growth light environment. For some species, such as Psychotria sp. growing in the mid-canopy, internal leaf CO 2 concentration (C i ) was > 30% lower during the dry season suggesting that declines in A max were caused in part by stomatal limitations to CO 2 diffusion. For other species, such as Brosimum lactescens growing at the top of the canopy. Tovornita schomburgkii growing in the mid-canopy, and Dinizia excelsa growing in the understorey, dry season C i declined by < 20% suggesting that factors independent of CO 2 diffusion were more important in limiting A max . Dry-season declines in g max appeared to be important for maintaining a more consistent leaf water potential for some species (T. schomburgkii and D. excelsa) but not others (Psychotria sp.). These results indicate that while seasonal drought exerts an important limitation on the physiological capacity of semi-deciduous Amazonian forest trees, the mechanism of this limitation may differ between species.

The Sensitivity of Diel CO2 and H2O Vapor Exchange of a Tropical Transitional Forest to Seasonal Variation in Meteorology and Water Availability

Abstract Measurements of ecosystem gas exchange, meteorology, and hydrology (rainfall and soil moisture) were used to assess the seasonal patterns of, and controls on, average diel (24 h) net ecosystem CO2 exchange (NEE), evapotranspiration (E), and bulk canopy water vapor conductance (Gc) of a tropical transitional (ecotonal) forest in the Brazilian Amazon. Diel trends in E and NEE were almost completely explained by the diel variation in photosynthetic photon flux density (QPPFD), and while the QPPFD response of E varied little over the annual cycle, the QPPFD response of NEE declined substantially during the dry season, and the magnitude of hysteresis in the NEE–QPPFD response increased as well. The magnitude of the residuals for the QPPFD versus NEE response was significantly negatively correlated with total monthly rainfall and surface soil moisture and positively correlated with the maximum daily temperature and atmospheric vapor pressure deficit (V). Average daily Gc was also significantly correlat...

A molecular dynamic study of the starch obtained from the Mangifera indica Cv. Bourbon and Espada seeds by 13C solid state NMR

Abstract The molecular mobility of the starch obtained from Mangifera indica Cv. Bourboun and Espada , has been characterised by 13 C solid state nuclear magnetic resonance, using techniques, such as magic angle spinning (MAS) and cross polarisation magic angle spinning (CPMAS) NMR and by proton spin-lattice relaxation time in the rotating frame ( T 1 H ρ ). The CPMAS 13 C NMR spectra of these seeds showed three signals for Bourboun and two very broad signals for Espada . The seeds of the Mangifera indica Cv. Bourboun and Espada are heterogeneous amorphous polysaccharides that present, at least, two domains with distinct molecular mobility. These domains differ in size and chain packing. The variable contact time decay confirms that these starches are amorphous and present one predominant rigid domain. Mango fruits were also analysed by delayed contact time experiments, and the 13 C decays showed that the polysaccharides are heterogeneous and contain one rigid domain that controls the relaxation parameter.

GPR para a verificação do nível d'água subterrânea em transição floresta amazônica e cerrado

A Ground Penetratin Radar (GPR) water level monitoring study of a mature transitional tropical forest is presented. Three water tables monitoring wells were installed during 2001/2002 at three different sites: under permanent forest, under managed forest and pasture. The GPR profiles show that the water table appears as a strong horizontal reflector in March and August, 2002,and as a weak, discontinuous reflector during measurements in May and October 2001. Due to several laterite lenses in the soil, the water table can easily be mistaken in place of such lenses. Soil moisture had an influence on these reflection signals, changing the dielectric constant of soil. The depth of the water table varied 1.8 m under permanent forest, 0.9 m under management forest and 3.7 m under pasture.

Impregnação com resina natural na Figueira Branca como forma alternativa de impermeabilização

Investigou-se, neste trabalho, a capacidade de impregnacao da Figueira Branca (Ficus monckii) com a resina natural da arvore de Jatoba (Hymenaea courbaril); trata-se de uma especie de madeira de baixa densidade, originaria do Estado do Mato Grosso, Brasil. Foram determinados os coeficientes de retracao da madeira, preparando-se posteriormente, a resina, para impregnacao, e depois se fez o ensaio inverso do inchamento da madeira impregnada. Compararam-se os dois coeficientes para a madeira nao impregnada com o da madeira impregnada, a partir de testes estatisticos com amostras pareadas. O coeficiente de inchamento da madeira impregnada foi significativamente menor que o de retracao da nao impregnada, em todas as direcoes dos corpos de prova. Com isto, foi possivel se constatar que a impregnacao da Figueira Branca com a resina natural do Jatoba tornou-a mais impermeavel aumentando, assim, a possibilidade dessa madeira ser empregada na construcao civil ou na industria moveleira.

Ecological Research in the Large-Scale Biosphere-Atmosphere Experiment in Amazonia: Early Results, 2004 - eScholarship

The Large-scale Biosphere-Atmosphere Experiment in Amazonia (LBA) is a multinational, interdisciplinary research program led by Brazil. Ecological studies in LBA focus on how tropical forest conversion, regrowth, and selective logging influence carbon storage, nutrient dynamics, trace gas fluxes, and the prospect for sustainable land use in the Amazon region. Early results from ecological studies within LBA emphasize the var- iability within the vast Amazon region and the profound effects that land-use and land- cover changes are having on that landscape. The predominant land cover of the Amazon region is evergreen forest; nonetheless, LBA studies have observed strong seasonal patterns in gross primary production, ecosystem respiration, and net ecosystem exchange, as well as phenology and tree growth. The seasonal patterns vary spatially and interannually and evidence suggests that these patterns are driven not only by variations in weather but also by innate biological rhythms of the forest species. Rapid rates of deforestation have marked the forests of the Amazon region over the past three decades. Evidence from ground-based surveys and remote sensing show that substantial areas of forest are being degraded by logging activities and through the collapse of forest edges. Because forest edges and logged forests are susceptible to fire, positive feedback cycles of forest degradation may be initiated by land-use-change events. LBA studies indicate that cleared lands in the Amazon, once released from cultivation or pasture usage, regenerate biomass rapidly. However, the pace of biomass accumulation is dependent upon past land use and the depletion of nutrients by unsustainable land-management practices. The challenge for ongoing research within LBA is to integrate the recognition of diverse patterns and processes into general models for prediction of regional ecosystem function.

Ecological Research in the Large-Scale Biosphere-Atmosphere Experiment in Amazonia: Early Results, 2004

The Large-scale Biosphere-Atmosphere Experiment in Amazonia (LBA) is a multinational, interdisciplinary research program led by Brazil. Ecological studies in LBA focus on how tropical forest conversion, regrowth, and selective logging influence carbon storage, nutrient dynamics, trace gas fluxes, and the prospect for sustainable land use in the Amazon region. Early results from ecological studies within LBA emphasize the var- iability within the vast Amazon region and the profound effects that land-use and land- cover changes are having on that landscape. The predominant land cover of the Amazon region is evergreen forest; nonetheless, LBA studies have observed strong seasonal patterns in gross primary production, ecosystem respiration, and net ecosystem exchange, as well as phenology and tree growth. The seasonal patterns vary spatially and interannually and evidence suggests that these patterns are driven not only by variations in weather but also by innate biological rhythms of the forest species. Rapid rates of deforestation have marked the forests of the Amazon region over the past three decades. Evidence from ground-based surveys and remote sensing show that substantial areas of forest are being degraded by logging activities and through the collapse of forest edges. Because forest edges and logged forests are susceptible to fire, positive feedback cycles of forest degradation may be initiated by land-use-change events. LBA studies indicate that cleared lands in the Amazon, once released from cultivation or pasture usage, regenerate biomass rapidly. However, the pace of biomass accumulation is dependent upon past land use and the depletion of nutrients by unsustainable land-management practices. The challenge for ongoing research within LBA is to integrate the recognition of diverse patterns and processes into general models for prediction of regional ecosystem function.

Ecological research in the Large Scale Biosphere Atmosphere Experiment in Amazonia: A discussion of early results

The Large-scale Biosphere-Atmosphere Experiment in Amazonia (LBA) is a multinational, interdisciplinary research program led by Brazil. Ecological studies in LBA focus on how tropical forest conversion, regrowth, and selective logging influence carbon storage, nutrient dynamics, trace gas fluxes, and the prospect for sustainable land use in the Amazon region. Early results from ecological studies within LBA emphasize the var- iability within the vast Amazon region and the profound effects that land-use and land- cover changes are having on that landscape. The predominant land cover of the Amazon region is evergreen forest; nonetheless, LBA studies have observed strong seasonal patterns in gross primary production, ecosystem respiration, and net ecosystem exchange, as well as phenology and tree growth. The seasonal patterns vary spatially and interannually and evidence suggests that these patterns are driven not only by variations in weather but also by innate biological rhythms of the forest species. Rapid rates of deforestation have marked the forests of the Amazon region over the past three decades. Evidence from ground-based surveys and remote sensing show that substantial areas of forest are being degraded by logging activities and through the collapse of forest edges. Because forest edges and logged forests are susceptible to fire, positive feedback cycles of forest degradation may be initiated by land-use-change events. LBA studies indicate that cleared lands in the Amazon, once released from cultivation or pasture usage, regenerate biomass rapidly. However, the pace of biomass accumulation is dependent upon past land use and the depletion of nutrients by unsustainable land-management practices. The challenge for ongoing research within LBA is to integrate the recognition of diverse patterns and processes into general models for prediction of regional ecosystem function.