Seasonal Variations of Carbon Dioxide, Water Vapor and Energy Fluxes in Tropical Indian Mangroves

We present annual estimates of the net ecosystem exchange ( NEE) of carbon dioxide ( CO2) accumulated over one annual cycle ( April 2012 to March 2013) in the world's largest mangrove ecosystem, Sundarbans ( India), using the eddy covariance method. An eddy covariance flux tower was established in April 2012 to study the seasonal variations of carbon dioxide fluxes due to soil and vegetation- atmosphere interactions. The half- hourly maximum of the net ecosystem exchange ( NEE) varied from - 6 mu mol m(-2) s(-1) during the summer ( April to June 2012) to -10 mu mol m(-2) s(-1) during the winter ( October to December 2012), whereas the half- hourly maximum of H2O flux varied from 5.5 to 2.5 mmol m(-2) s(-1) during October 2013 and July 2013, respectively. During the study period, the study area was a carbon dioxide sink with an annual net ecosystem productivity (NEP =-NEE) of 249 +/- 20 g Cm-2 year(-1). The mean annual evapotranspiration ( ET) was estimated to be 1.96 +/- 0.33 mm day(-1). The gap- filled NEE was also partitioned into Gross Primary Productivity ( GPP) and Ecosystem Respiration ( Re). The total GPP and Re over the study area for the annual cycle were estimated to be 1271 g C m(-2) year(-1) and 1022 g C m-2 year-1, respectively. The closure of the surface energy balance accounted for of about 78% of the available energy during the study period. Our findings suggest that the Sundarbans mangroves are currently a substantial carbon sink, indicating that the protection and management of these forests would lead as a strategy towards reduction in carbon dioxide emissions.