Carbon dioxide, water vapour and energy fluxes over a semi-evergreen forest in Assam, Northeast India

• Published in: Journal of Earth System Science 2018-10, Vol.127 (7), p.1-13, Article 94
• Main Authors: Sarma, Dipankar, Baruah, Kushal Kumar, Baruah, Rulee, Gogoi, Nirmali, Bora, Abhijit, Chakraborty, Supriyo, Karipot, Anand
• Format: Article
• Language: English
• Subjects: Biosphere; Canopies; Canopy; Carbon dioxide; Carbon dioxide exchange; Carbon dioxide flux; Coniferous forests; Covariance; Data processing; Diurnal variations; Earth and Environmental Science; Earth Sciences; Ecosystems; Eddy covariance; Energy; Energy balance; Enthalpy; Evapotranspiration; Evapotranspiration estimates; Fluctuations; Forest canopy; Forest ecosystems; Forests; Heat; Heat exchange; Heat flux; Heat transfer; Instability; Latent heat; Leaf area; Leaf area index; Measurement techniques; Meteorological parameters; Monsoons; National parks; Photosynthesis; Photosynthetically active radiation; Plant cover; Radiation; Rain; Seasonal variation; Seasonal variations; Sensible heat; Sensors; Software; Space Exploration and Astronautics; Space Sciences (including Extraterrestrial Physics; Stability; Terrestrial ecosystems; Water vapor; Water vapour
• ISSN: 0253-4126; 0973-774X
• DOI: 10.1007/s12040-018-0993-5

The eddy covariance method is a powerful technique for quantification of CO 2 , H 2 O and energy fluxes in natural ecosystems. Leaf area index (LAI) and its changes are significant drivers of CO 2 and H 2 O exchange in a forest ecosystem due to their role in photosynthesis. The present study reports the seasonal variation of CO 2 and energy fluxes and their relationship with other meteorological parameters of a semi-evergreen primary forest of Kaziranga National Park, Assam, India during February 2016–January 2017. The diurnal pattern of half hourly average CO 2  fluxes over the forest was found to be mostly dominated by the incident photosynthetically active radiation. During the period of study, diurnal variations of CO 2 flux showed a maximum value of - 9.97 μ mol m - 2 s - 1 in the month of June during summer which is also the beginning of the monsoon season. The monthly averaged diurnal CO 2 flux and variation in LAI of the forest canopy closely followed each other. The annual net ecosystem exchange of the forest estimated from the CO 2 flux data above the canopy is 84.21 g C m - 2 yr - 1 . Further studies are in progress to confirm these findings. The estimated average annual evapotranspiration of the semi-evergreen forest is 2.8 ± 0.19 mm day - 1 . The study of partitioning of energy fluxes showed the dominance of latent heat fluxes over sensible heat fluxes. The energy balance closure was found to increase with an increase in instability and the highest closure of around 83% was noted under neutral conditions.