António Costa

Seasonality in CO2 and H2O flux at an Eastern Amazonian Rain Forest

[1]xa0Previous studies of CO2 fluxes in Amazonia have suggested seasonal variation in net ecosystem exchange. We find little evidence of this seasonality at a new site in eastern Amazonia, despite the expectation that this site would be particularly sensitive to seasonal fluctuation of rainfall. The average rate of peak net ecosystem exchange was −19 ± 0.9 (1 S.E.) μmol CO2 m−2 s−1. Canopy conductance, evaporation, and vapour pressure deficit were all increased during the dry season, consistent with an increase in bulk temperature and solar radiation. The lack of a dry season decrease in photosynthesis was thought to be due to the observed increase in leaf area following dry season flushing. This was accompanied by an increase in solar radiation, and we suggest that the effect of “dryness” was merely to preclude optimality of photosynthetic response to this increase in radiation. The gross primary productivity of this site was estimated to be 36 t C ha−1 yr−1. This is similar to that reported for other Amazon forest stands. The year may have been a particularly productive one due to the lack of an El Nino event.

Transpiração em espécie de grande porte na Floresta Nacional de Caxiuanã, Pará

During the Long-term impact of drought on water and carbon dioxide fluxes in Amazonian Tropical Rainforest Experiment (ESECAFLOR), this study was carried out, which is a subproject of Large Scale Biosphere Atmosphere Experiment in Amazonia (LBA), located in the Ferreira Penna Scientific Station (FPSS) in the Caxiuana National Forest (CNF) in Para State (1o 42- 30-- S; 51o 31-45-- W; 62 m altitude). The region has a well-preserved forest, with canopy of 35 m. The predominate tree species in the landscape are Eschweilera coriacea (White Mata-mata), Voucapoua americana (Acapu) and Protium pallidum (White Pitch). Sap flow measurements were made in the wet season (03-16 December 2000 and 12-25 January 2003), to evidence the effect of long term induced drought, aiming to determinate the transpiration of Eschweilera coriacea. The ESECAFLOR site consists of two different areas with 1 ha each. Plot A (control) and Plot B (rainfall exclusion). The Trunk Heat Balance (THB) method was applied to sap flow measurements, by Sap Flow Meter P4.1 system. Between analysed periods, the mean transpiration of E. Coriacea increased 56% in the tree A237 (control plot) and decreased 68% in B381 (drought plot).

Fluxos de calor no dossel vegetativo e infiltração de água no solo, em floresta tropical

Este estudo analisou as variacoes sazonais e anuais dos fluxos de calor sensivel e latente, armazenados pelo dossel vegetativo de floresta tropical umida, bem como a taxa de infiltracao de agua no solo em duas parcelas experimentais, uma com exclusao de chuva e outra submetida as condicoes reais de precipitacao pluvial. Os dados aqui usados foram obtidos do projeto Estudo da Seca da Floresta (ESECAFLOR), subprojeto do Experimento de Grande Escala da Biosfera-Atmosfera na Amazonia (LBA), conduzido na reserva florestal de terra firme em Caxiuana, PA. Os dados de temperatura e umidade relativa do ar foram coletados no perfil da floresta amazonica, em intervalos de 8 m, deSde a superficie ate 32 m, durante o ano de 2008, em intervalos horarios, para se determinar os fluxos de calor sensivel e latente armazenados nos periodo chuvoso (fevereiro, marco e abril) e menos chuvoso (setembro, outubro e novembro). Os resultados indicaram que o fluxo de calor sensivel armazenado no dossel da floresta no ano de 2008, foi 167,93 W m-2 e o fluxo de calor latente armazenado foi de 5184,38 W m-2. A taxa de infiltracao de agua do solo na floresta foi reduzida drasticamente nos primeiros minutos do inicio do experimento, independentemente das condicoes de umidade do solo e, em seguida, ela apresentou comportamento quase constante ao longo do tempo.

Impactos da redução da pluviometria na biomassa aérea da Floresta Amazônica

Este estudo foi desenvolvido na Floresta Nacional de Caxiuana, Para, Brasil, com o objetivo de se analisar os efeitos da reducao da precipitacao pluvial na biomassa aerea e a mortalidade das arvores na area basal de uma floresta tropical, dentro do Projeto ESECAFLOR (LBA). Utilizaram-se duas parcelas experimentais, cada uma medindo um hectare de floresta tropical, sendo a parcela A submetida as condicoes normais do clima e a parcela B com exclusao de aproximadamente 90% das chuvas. As analises dos parâmetros de crescimento da floresta apresentadas neste estudo, se referem aos dados mensais obtidos durante o periodo experimental de 2005 a 2009, nas duas parcelas experimentais. Os resultados desta pesquisa permitem concluir que a reducao da precipitacao pluvial sobre a floresta afeta significativamente todos os parâmetros de crescimento das arvores, cuja principal evidencia e de que o efeito da exclusao de chuva provoca reducao da area basal florestal, em especial daquelas com diâmetro a altura de peito maior que 10 cm. Os resultados tambem indicam que o aumento na taxa de mortalidade das arvores e a consequente perda de biomassa vegetal, sao maiores na area com exclusao de chuva que nas florestas submetidas as condicoes naturais do clima.

VARIABILITY OF CO2 FLOW IN THE SOIL IN TWO EXPERIMENTAL PLANS OF THE ESECAFLOR PROJECT / CAXIUANÁ- PA

The present work was carried out in the National Forest of Caxiuana, located in the municipality of Melgaco / PA, at the experimental site of the Forest Drought Study Project (ESECAFLOR), which has been developed since 2000 at the Ferreira Penna Scientific Station. The experiment consists of the artificially created creation of a drought period in the tropical rainforest, aiming to evaluate the impacts of drought on the water and CO2 flows in this ecosystem. The physical structure of ESECAFLOR consists of two plots of one hectare. The data used refer to the period from August 2009 to December 2011. The main objective was to study the monthly variability of soil carbon flux in the two experimental plots of the project with different soil water contents. The results indicated significant variability between the flows observed in the two treatments, and in both plots, the highest values were always observed in the places with the highest amount of organic material.

Índices de Conforto Térmico e suas Variações Sazonais em Cidades de Diferentes Dimensões na Região Amazônica (Thermal comfort indices and their seasonal variations in cities of different sizes in the Amazon Region)

O objetivo desta investigacao foi quantificar a variabilidade media horaria do conforto termico em quatro cidades de diferentes dimensoes e localizacoes na Amazonia Brasileira (Belem-PA, Manaus-AM, Macapa-AP e Santarem-PA). Na quantificacao do conforto termico foi utilizado o Indice de Calor (IC) que considera somente a temperatura e a umidade relativa do ar. A metodologia de investigacao consistiu na coleta da dados medios horarios de temperatura e umidade relativa do ar, respectivamente para os meses de marco (chuvoso) e setembro (seco) para os anos de 2009 a 2012. Estacoes meteorologicas automaticas foram instaladas nos centros urbanos destas cidades. As series mensais obtidas das variaveis foram comparadas com o objetivo verificar suas variacoes medias no tempo (Kruskal-Wallis, p Normal 0 false false false PT-BR X-NONE X-NONE /* Style Definitions */ table.MsoNormalTable {mso-style-name:Table Normal; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-priority:99; mso-style-parent:; mso-padding-alt:0in 5.4pt 0in 5.4pt; mso-para-margin-top:0in; mso-para-margin-right:0in; mso-para-margin-bottom:10.0pt; mso-para-margin-left:0in; line-height:115%; mso-pagination:widow-orphan; font-size:11.0pt; font-family:Calibri,sans-serif; mso-ascii-font-family:Calibri; mso-ascii-theme-font:minor-latin; mso-hansi-font-family:Calibri; mso-hansi-theme-font:minor-latin; mso-ansi-language:PT-BR; mso-fareast-language:PT-BR;} A B S T R A C T The aim of this study was to quantify the variability in mean hourly thermal comfort in four cities of different sizes and locations in the Brazilian Amazon (Belem - PA, Manaus - AM, Macapa - AP and Santarem - PA). The Heat Index (HI) which considers only the temperature and relative humidity was used to quantify thermal comfort. The research methodology consisted of collecting hourly average temperature and relative humidity data for the months of March (wet season) and September (dry season) for the years 2009-2012. Automatic weather stations have been installed in the urban centers of these cities. The monthly time series of weather variables were compared in order to verify their mean changes over time (Kruskal-Wallis test, p Keywords: thermal comfort, Amazon, urban climate.

Sensible and Latent Heat Storage Fluxes within the Canopy Air-Space in the Amazon Rainforest

Ecosystem–atmosphere exchanges of energy display considerable variability over a range of temporal and spatial scales. This study evaluated the seasonal and annual variations in sensible and latent heat storage fluxes within the canopy air-space in the Amazon rainforest. The data for this study were obtained from the “Long-term drought impact on water and carbon dioxide fluxes in Amazonian Tropical Rainforest Experiment (ESECAFLOR)” which is a subproject of Large Scale Biosphere Atmosphere Experiment in Amazon forest (LBA), carried out in terra firma rainforest in Caxiuana National Forest, Para, Brazil. The data sets also included observations to obtain the sensible and latent heat storage fluxes within forest collected throughout the 1-year period. The vapor pressure and air temperatures were obtained for each 8 m interval from the surface to 32 m. Results indicated that the cumulative sensible heat storage flux in the Amazon rainforest canopy was 167.9 Wm-2 in 2008 and the average daily magnitude was always low for the same period. The latent heat storage flux (ranging from -32.7 to -10 Wm-2) was more influenced by rainfall producing high humidity.