Seasonal and Diurnal Variations of Carbon Dioxide and Energy Fluxes over Three Land Cover Types of Nepal

This study examines the seasonal and diurnal variations of carbon dioxide and energy fluxes over three land cover types of Nepal by using the eddy covariance method from March to November 2016. The surface energy balance closures were moderate with the values of about 56%, 61%, and 64% closure at Kirtipur, Simara, and Tarahara sites respectively. The monthly average values of net radiation flux and latent heat flux peaked in August at Kirtipur and Tarahara sites whereas in June at Simara site respectively. The maximum monthly average measured sensible heat flux was 37 W m^-2, 43.6 W m^-2, and 36.3 W m^-2 in April for all the sites whereas soil heat flux was 5.1 W m^-2 and 2.9 W m^-2 in April for Kirtipur and Simara sites and 6.2 W m^-2 in June for Tarahara site. The magnitude of diurnal peak of net ecosystem CO₂ exchange (NEE) reached up to 11.04 µmol m^-2 s^-1 at Kirtipur, 15.04 µmol m^-2 s^-1 at Simara, and 10.44 µmol m^-2 s^-1 at Tarahara sites respectively. Among the three study sites, the ecosystem at the Kirtipur site was a good carbon source; the ecosystems at Simara and Tarahara sites were low and good carbon sink in the growing season. In addition, all three different land cover ecosystems were carbon sources when accounted for the measurement period.