Balanço de radiação, energia e fluxo de CO2 em ecossistema de manguezal na Amazônia / Radiation and energy balance and fluxes of CO2 in a Amazon mangrove ecosystem

AUTOR(ES)
DATA DE PUBLICAÇÃO

2006

RESUMO

This work use the longest series of continuous meteorological data and fluxes measurements of CO2, sensible heat and latent heat made in Amazon mangrove ecosystem. The series used in this study corresponds to the period of November, 2002 to August, 2003. The meteorological data were collected using an EDISOL system based on the hedí covariance technique. The main objectives of the work were to evaluate the performance of empirical models in estimating the components of radiation and energy balance; quantify the magnitudes of daily and seasonal fluxes of CO2 and its dependence to meteorological variables to evaluate the seasonal variations; to estimate and analyze the temporal variation of stomatal conductance and establish dependence relationships with the micrometeorology of mangrove and to evaluate micrometeorological changes due to the mangrove degradation. In order to estimate the global solar radiation (Rg) models proposed by Hargreaves-Samani and Bristow-Campbell were used based an variations on daily extreme temperatures. Bristow-Campbells model showed a satisfactory performance while the Hargreaves-Samanis model didnt work well when it rains, although showed good performance in the estimates of Rg under cloudless conditions. The best results for the longwave radiation (BOL) balance estimates were presented by Brutsaert and Bruins model that account for 70% to 80% of the BOL daily variation. Brunts model was the one that showed the greatest differences between measured and simulated values, always underestimating the longwave radiation balance. In order to estimate the sensible heat (H) and latent heat (LE) fluxes in the mangroves the models proposed by Shuttleworth, Bruin- Holtslag and Penman-Monteith were applied. The results for sensible heat estimates showed that Shuttleworthmodel and Bruin-Holtslagmodel were the best in comparison with measurements data, although it was evident some overestimation and underestimation respectively. Penman-Monteith model showed an overestimation of about 10% to 15% and its best results were obtained in the rainy season. A lower performance was presented by the models in the estimation of latent heat flux, in comparison with the sensible heat flux estimates. However, the Penman-Monteith model was the one that showed a lower difference between measured and simulated values and thus in considered the more appropriate in estimating the latent heat flux in mangrove. In regard to the partition of net radiation, it was found that the main Exchange of energy in latent heat flux, with 56% of the available energy used in the process of evapotranspiration in the rainy period and 43% in the less rainy period. The energy used for heating the atmosphere by sensible heat did not change much between both periods, corresponding to 27% of the net radiation. The hourly pattern of the stomatal conductance was evaluated, presenting a mean value of 0,015 m.s-1 in the rainy period and 0,027 m.s-1 in the less rainy period it was found that the vapor pressure deficit was the variable that showed the best dependence relationship with the stomatal conductance in both seasonal periods of the year. The pattern of stomatal conductance was also influenced by the net radiation. The daily cycles of CO2 fluxes showed an mean diurnal assimilation of 7 to 15 μmol.m-2,s-1, and a mean nocturnal emission that corresponds to the ecossystem respiration of 5 μmol.m-2,s-1, suggesting that the mangrove is a sink of CO2. In regard to the changes due to the mangrove degradation, the results showed that the deforestation caused an increase in air and soil temperature. The mangrove degradation caused an increase in surface albedo and a decrease in the air humidity, due to reduction in evapotranspiration because of vegetation renoval. The amplitude of soil heat flux in the degraded mangrove was six times higher than in the natural mangrove due to the high rates of heating in the degraded area.

ASSUNTO(S)

medidas de fluxos measurements of flow manguezal mangrove micrometeorologia modelos empíricos empirical models

ACESSO AO ARTIGO

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