Biosphere Atmosphere Exchange of CO2, H2O Vapour and Energy during Spring over a High Altitude Himalayan Forest in Eastern India

For the first time, the exchange of greenhouse gases, such as CO 2 and H 2 O vapour, between the biosphere and the atmosphere at an eastern Himalayan site in India has been investigated. This study was carried out over a high altitude (2286 m asl) evergreen coniferous forest (27.04°N, 88.08°E), where we measured the fluxes of CO 2 and H 2 O vapour along with the sensible and latent energy using the eddy covariance method both above (38 m) and within (8 m) the canopy, the soil-CO 2 flux and the vertical profile of CO 2 during spring (March–April) in 2015. The mean eddy flux of CO 2 above the canopy was –2.8 ± 6.5 µmol m −2 s −1 , whereas it was 0.6 ± 0.4 µmol m −2 s −1 within the canopy. The mean flux of H 2 O vapour above the canopy (1.5 ± 1.8 mmol m −2 s −1 ) was three times higher than within the canopy (0.5 ± 0.6 mmol m −2 s −1 ). The mean flux of CO 2 emitted from the soil surface was 1.6 ± 0.1 µmol m −2 s −1 . The diurnal variation showed high sequestration of CO 2 during daytime, when the negative flux increased beyond –10 µmol m −2 s −1 . We observed that precipitation significantly enhanced CO 2 sequestration (by approximately fourfold) as well as H 2 O vapour emissions (by approximately threefold) by the tall canopies. Overall, during the entire study period, the net ecosystem exchange (NEE) was –656.5 g CO 2 m −2 , suggesting that the evergreen coniferous forest in the eastern Himalaya acts as a net sink of CO 2 during spring. Therefore, we can estimate the sequestration of anthropogenic carbon emission by the eastern Himalayan forest ecosystem, improving the national greenhouse gas inventory.