Balanço de energia e fluxo de carbono em uma área de cerrado que sofreu queima acidental

Tese (doutorado)—Universidade de Brasília, Instituto de Ciências Biológicas, Programa de Pós-Graduação em Ecologia, 2003.A vegetação do Cerrado é conhecida com um potencial sorvedouro de CO2 no período de chuvas e uma fonte de CO2 para atmosfera na estação seca, foi pouco estudado, liste estudo foi desenvolvido na Reserva Ecológica do IBGE, próxima a Brasília, DF, com o objetivo de medir a recuperação da fitomassa e das taxas de evapotranspiração e fluxos de CO2 em uma área de 37,3 ha de cerrado que sofreu queima acidental em agosto de 1999. Foi feito o acompanhamento da fitomassa aérea, da cobertura vegetal e o dos fluxos dc CO2, vapor de água, pela técnica de ‘'eddy covariance”, c radiação no período de agosto dc 2000 a outubro de 2002. O índice de cobertura arbórea foi de 11% nos períodos de seca e 18% nos períodos de chuva. A composição da biomassa do estrato rasteiro apresentou leve redução nas folhas vivas, de 234 gm"2 em abril de 2000 para 52% deste valor (122 gm"2) no mesmo período de 2002. Entretanto, os ramos vivos e as gramíneas mantiveram-se com valores próximos a 120 gm"2 ao longo do período. A sazonalidade foi marcante em todos os anos, onde houve uma redução dc até 73% na biomassa da camada herbácea na estação seca. Ocorreu um gradual aumento na necromassa do estrato herbáceo de todos os componentes, com aumento de até 400% dos valores iniciais. A exceção é para os ramos mortos que se mantiveram na média de 100 gm'2. O total de biomassa aérea baseada no levantamento florístico de 2001 apresentou um total de 5,33 tha'1 para estrato herbáceo, 9,16 tha"' para indivíduos lenhoso com diâmetro > 2,0 cm e 0,02 tha'1 para indivíduos lenhosos com diâmetro 2.0 cm and 0.02 tluf1 for tree individuals with diameter < 2.0 cm with a total basal area of 121.6 n rh a'1 and total volume of 2,443.7 m3ha'1. 'Hie slope of the energy balance equation during the three years for the area was not significantly different. The variation in the components of the energy balance equation for the rainy season was: 451 Wnf2 to 716 Win'2 for solar radiation (St); 240 Wm'2 to 433 Wm"2 for liquid radiation (Rn); 111 W nf2 to 216 Wnf2 for sensible heat (H) and 120 W n f2 to 189 W in'2 for latent heat (À.H). In the dry season (June - September) the values varied from 394 Wm'2 to 742 Win'2 for St; 187 Wnf2 to 433 W nf2 to Rn; 119 Wm"2 to 262 Wm'2 tor H and 74 Win'2 to 111 Wm'2 (br À.K. About 45% of the radiation balance was used in the evapotranspiration process during the rainy season (XE/Rn = 0,45). The values of fluxes in the ground (g) varied from 17 Wm 2 in the rainy season to 14 wm‘~ in the dry season. The slope of the energy balance, plot (Rn-G) versus (1I-Â.E), for the three years, was 0,93. The sensible heat represented 46% of Rn during this period. The stomata resistance (rs) varied from 158 sm"1 to 278 snT1 in the wet season and 391 sm'1 to 259 sm'1 in the diy season. The values of maximum photosyntheses (Pmax) had varied from 5,9 pmolm'V1 in the dry season to 10,7 pmol.m^.s'1 in the wet season. The maximum values of carbon absorption was around of 11:00 AM and 02:00 PM, with a gradual reduction in maximums absorption to 3,87 pmolm'V1 and 6,12 pmolm'V1 in the rainy and beginning and middle of the dry season, when the area functioned as a carbon sink, with the maximum of assimilation (-484.2 pmolm'V1) and emission (304,8 mmolm'V’) in December. During August and September, when the area functioned as carbon source for the atmosphere, the maximum value of absorption was -3,46 pmolm'V1 and -3,33 pmoIm'V1, respectively. It was not possible to calculate with precision the total or emission of carton to 2000, but the estimate for 2001 were 1,746 kg Cha'1 and 214,8 kg Cha*1 and for 2002 was 238,4 kg Cha'1 and 1,419.7 kg Cha'1 of emission and accumulation respectively

GNSS precipitable water vapor from an Amazonian rain forest flux tower

Understanding the complex interactions between water vapor fields and deep convection on the mesoscale requires observational networks with high spatial (kilometers) and temporal (minutes) resolution. In the equatorial tropics, where deep convection dominates the vertical distribution of the most important greenhouse substance-water-these mesoscale networks are nonexistent. Global Navigational Satellite System (GNSS) meteorological networks offer high temporal/spatial resolution precipitable water vapor, but infrastructure exigencies are great. The authors report here on very accurate precipitable water vapor (PWV) values calculated from a GNSS receiver installed on a highly nonideal Amazon rain forest flux tower. Further experiments with a mechanically oscillating platform demonstrate that errors and biases of approximately 1 mm (2%-3% of PWV) can be expected when compared with a stable reference GNSS receiver for two different geodetic grade receivers/antennas and processing methods [GPS-Inferred Positioning System (GIPSY) andGAMIT]. The implication is that stable fixed antennas are unnecessary for accurate calculation of precipitable water vapor regardless of processing techniques or geodetic grade receiver. © 2011 American Meteorological Society

Fechamento do Balanço de Energia em uma Floresta Tropical: Contribuições da troca Turbulenta e Armazenamento de Calor Ecossistema

The surface energy balance is rarely closed using the common half-hourly averaging period for turbulent fluxes as eddies of greater characteristic time scales often provide a non-trivial contribution to energy exchange. Here, we briefly discuss previous efforts to improve surfasse energy balance closure of a tropical rainforest ecosystem – the K34 site - and describe how measurements from the GoAmazon campaign can be used to improve our understanding of energy flux and storage in tropical canopies.O balanço de energia da superfície raramente é fechado usando o período médio a cada meia hora comum para fluxos turbulentos como turbilhões de maior tempo característico escalas costumam oferecer uma contribuição não-trivial para troca de energia. Aqui, discutimos brevemente os esforços anteriores para melhorar o fechamento do balanço de energia da superfície de uma floresta tropical ecossistema tropical - o site K34 - e descrever como mediçõesda campanha GoAmazon pode ser usado para melhorar a nossa compreensão do fluxo de energia e armazenamento em copas tropicais

COMPOSIÇÃO E ABUNDÂNCIA DE ORQUÍDEAS EPIFÍTICAS EM UMA CAMPINARANA PRESERVADA E OUTRA ANTROPIZADA NA AMAZÔNIA CENTRAL

Orchidaceae Juss. possui distribuição cosmopolita e é considerada uma das maiores famílias de Angiospermas, sendo composta por 800 gêneros e cerca de 24.000 espécies, um número que tende a aumentar conforme as contínuas descrições de espécies novas para a Ciência. As orquídeas, como são popularmente conhecidas, destacam-se por suas flores que apresentam uma diversidade de cores, formas e adaptações aos diferentes ambientes e ocupação de praticamente todos os substratos disponíveis (p. ex. epifíticas, terrestres ou rupícolas). Neste contexto, este estudo teve como objetivo determinar os parâmetros florísticos para comunidade de orquídeas epífitas a partir de dez forófitos de Aldina heterophylla, em duas florestas de Campinarana (alterada e não alterada) próximo a região de Manaus-AM, Amazônia Central, Brasil. Identificou-se um total de 17 espécies para as duas áreas estudadas, sendo que as que apresentaram maior abundância foram Prosthechea aemula e Heterotaxis superflua, enquanto as menos abundantes foram Epidendrum compressum, Maxillaria kegelii, Maxillaria pauciflora, Ornithidium pendens (Pabst) Senghas. Christensonella uncata. Foi interessante observar que a Campinarana alterada apresentou maior diversidade comparada à Campinarana não alterada. Isso alerta para o fato de que uma área tão diversa está sendo devastada e muito do conhecimento sobre a flora orquídica desse local pode se perder.Palavras-chave: Amazônia brasileira, lista anotada de espécies, macucu Orchidaceae, vegetação de areia branca

Photochemical Efficiency and Oxidative Metabolism of Tree Species during Acclimation to High and Low Irradiance

The balance between efficiency of absorption and use of light energy is fundamental for plant metabolism and to avoid photoinhibition. Here, we investigated the effects of light environments on the photosynthetic apparatus of tropical tree species of three successional groups (pioneer, mid-, and late successional) subjected to different light conditions: full sunlight (FS), moderate shade (MS), and deep shade (DS). Twenty-nine ecophysiological parameters were correlated with each other. The pioneer species exhibited better photochemical performance and a more efficient antioxidant enzymatic system in comparison with the other successional groups. Plants in FS showed higher intensity of lipid peroxidation, with superoxide dismutase having a prominent role in the antioxidant system. At lower irradiance the enzymatic activity was reduced, and the photochemical efficiency was the preferred way to reduce oxidative damages. P was highly related to photochemical yield, and the N modulation amplified the light harvesting complex in DS to the detriment of the antioxidant system. Despite evidence of cell damage, most species exhibited the ability to adjust to high irradiance. Contrary to expectations, Hymenea courbaril (late-successional) exhibited higher plasticity to fluorescence, nutritional, and antioxidant parameters. Only Carapa guianensis (late-successional) displayed photoinhibitory damage in FS, and Ochroma pyramidale (pioneer) did not survive in DS, suggesting that acclimation to shade is more challenging than to high irradiance

Fertilization and seasonality influence on the photochemical performance of tree legumes in forest plantation for area recovery in the Amazon.

N-fixing leguminous species can reach atmospheric dinitrogen gas (N2), having an advantage under N-limited degraded environments. These N-fixers are constantly used as facilitative species. Chlorophyll a fluorescence (ChF) acknowledges how different species take up and use light energy during photosynthesis. These techniques assess stress and performance responses to photosynthesis and are used for the selection of species with potential for reforestation. Six Fabaceae species were selected for this study: three nonfixing species (Cenostigma tocantinum, Senna reticulata and Dipteryx odorata) and three N-fixing species (Clitoria fairchildiana, Inga edulis and Acacia spp.). Variations in chlorophyll fluorescence under high vs. low water and nutrient conditions were studied. Multivariate analysis was performed to detect the effects of seasonality and fertilization on dark-adapted ChF two years after the experiment was established. The correlation among ChF variables and growth, photosynthesis and foliar nutrient concentrations was evaluated. Under high water- and nutrient-availability conditions, plants exhibited an enhanced performance index on absorption basis values correlated with electron transport fluxes. Under drought and nutrient-poor conditions, most species exhibit increased energy dissipation as photoprotection. High interspecific variation was found; therefore, species-specific responses should be considered in future ChF studies. Corroborating the ability to colonize high-light environments, N-fixers showed an increased performance index correlated with electron transport and Zn and N foliar concentrations. Negative correlations were found between photosynthesis and trapped fluxes. Diameter growth was positively correlated with electron transport fluxes. Given the different responses among species, ChF is an effective technique to screen for seasonality, fertilization and species effects and should be considered for use during forest restoration. Finally, the addition of fertilization treatments may facilitate tropical forest restoration due to the importance of nutrients in physiological processes. N-fixers showed high photochemical performance and tolerance to abiotic stress in degraded areas and therefore should be included to support ecosystem biomass restoration

Investigating the mechanisms responsible for the lack of surface energy balance closure in a central Amazonian tropical rainforest

This work investigates the diurnal and seasonal behavior of the energy balance residual (E) that results from the observed difference between available energy and the turbulent fluxes of sensible heat (H) and latent heat (LE) at the FLUXNET BR-Ma2 site located in the Brazilian central Amazon rainforest. The behavior of E is analyzed by extending the eddy covariance averaging length from 30 min to 4 h and by applying an Information Flow Dynamical Process Network to diagnose processes and conditions affecting E across different seasons. Results show that the seasonal turbulent flux dynamics and the Bowen ratio are primarily driven by net radiation (Rn), with substantial sub-seasonal variability. The Bowen ratio increased from 0.25 in April to 0.4 at the end of September. Extension of the averaging length from 0.5 (94.6% closure) to 4 h and thus inclusion of longer timescale eddies and mesoscale processes closes the energy balance and lead to an increase in the Bowen ratio, thus highlighting the importance of additional H to E. Information flow analysis reveals that the components of the energy balance explain between 25 and 40% of the total Shannon entropy with higher values during the wet season than the dry season. Dry season information flow from the buoyancy flux to E are 30–50% larger than that from H, indicating the potential importance of buoyancy fluxes to closing E. While the low closure highlights additional sources not captured in the flux data and random measurement errors contributing to E, the findings of the information flow and averaging length analysis are consistent with the impact of mesoscale circulations, which tend to transport more H than LE, on the lack of closure. © 2017 Elsevier B.V

A dense GNSS meteorological network for observing deep convection in the Amazon

A dense Global Navigation Satellite System (GNSS) meteorological network (∼20 stations) in the central Amazon Basin in Brazil is being developed for long-term studies of deep convection/water vapor interactions and feedback. In this article, the network is described and preliminary results are presented: GNSS-derived precipitable water vapor is useful for tracking water vapor advection and in identifying convective events and water vapor convergence timescales. Upon network completion (early 2011), 3D water vapor field analyses and participation in the intensive field campaign GPM-CHUVA will provide unique data sets for initializing, constraining or validating high-resolution models or refining convective parameterizations. © 2011 Royal Meteorological Society

Linking meteorology, turbulence, and air chemistry in the amazon rain forest

A field campaign reveals that the Amazon rain forest produces enough chemical species to undergo oxidation and generate aerosols, which can activate into cloud condensation nuclei and potentially influence cloud formation. © 2016 American Meteorological Society