Seasonal dynamics and impact factors of atmospheric CO2 concentration over subtropical forest canopies: observation from eddy covariance tower and OCO-2 satellite in Northwest Himalaya, India

• Published in: Environmental monitoring and assessment 2021-02, Vol.193 (2), Article 106
• Main Authors: Watham, T., Padalia, Hitendra, Srinet, Ritika, Nandy, Subrata, Verma, P. A., Chauhan, P.
• Format: Article
• Language: English
• Subjects: Atmospheric Protection/Air Quality Control/Air Pollution; Canopies; Carbon dioxide; Carbon dioxide atmospheric concentrations; Carbon dioxide concentration; Carbon dioxide flux; Climatic conditions; Covariance; Dynamics; Earth and Environmental Science; Ecology; Ecosystems; Ecotoxicology; Eddy covariance; Environment; Environmental Management; Environmental monitoring; Environmental science; Foothills; Forest canopy; Forest ecosystems; Forests; Greenhouse effect; Indian spacecraft; Microorganisms; Monitoring/Environmental Analysis; Monsoons; Monthly; Photosynthesis; Plant cover; Rain; Rainfall; Satellite observation; Satellites; Seasonal variability; Seasonal variation; Seasonal variations; Terrestrial ecosystems; Towers; Tropical climate; Tropical forests; Vortices
• ISSN: 0167-6369; 1573-2959
• DOI: 10.1007/s10661-021-08896-4

Carbon dioxide (CO 2 ) is the key atmospheric gas that controls the earth’s greenhouse effect, and forests play a major role in abating the atmospheric CO 2 by storing carbon as biomass. Therefore, it is vital to understand the role of different forests in regulating the spatiotemporal dynamics of atmospheric CO 2 concentration. In this study, we have used eddy covariance (EC) tower-based atmospheric CO 2 concentration measurements and satellite-retrieved column average CO 2 concentration of 2018 to understand the diurnal and seasonal dynamics of atmospheric CO 2 concentration over the sub-tropical forest in the foothills of northwest Himalaya, Uttarakhand, India. EC study revealed that the CO 2 concentration over the forest canopy peaks during mid-night to early morning and drop to a minimum during the afternoon. On a monthly scale, peak atmospheric CO 2 concentration was observed during July in both the sites, which was a result of more release of CO 2 by the forest ecosystem through ecosystem respiration and microbial decomposition. Enhanced photosynthetic activities during the late monsoon and post-monsoon resulted in the decrease of atmospheric CO 2 concentration over the forest ecosystem. Among the meteorological variables, rainfall was found to have the highest control over the seasonal variability of the atmospheric CO 2 concentration. Orbiting Carbon Observatory-2 (OCO-2) satellite-retrieved column average CO 2 (XCO 2 ) was also examined to comprehend its reliability on an ecosystem scale. The OCO-2 retrieved XCO 2 value was higher than the EC carbon flux tower-measured atmospheric CO 2 concentration, which might be due to differences in the vertical resolution of the CO 2 column and scale difference. However, the monthly atmospheric XCO 2 retrieved from OCO-2 strongly adheres with the ground-measured monthly pattern. Our study highlights that forests with varying functional traits within the same climatic conditions show variability in the regulation of atmospheric CO 2 concentration.