In the last few decades, both ecological indices-based biometric method and flux-based eddy covariance technique have been used extensively for quantification of the ecosystem productivity and carbon sequestration potential. This study presents a narrative review of past and current methods used for the quantification of ecosystem productivity and carbon sequestration, and provides distinction in terminologies used by the field and index-based method and flux-based methods. In addition, efforts are also made to compare the seasonal variation of net ecosystem carbon exchanges, gross primary productivity, and ecosystem respiration between three forest types of Himalayas, i.e., a needle leaf Pine forest, a broad leaf Oak forest of central Himalaya, and a mixed deciduous forest of eastern Himalaya. This comparative assessment is made based on data obtained from the flux-based eddy covariance technique which simultaneously measures selected micrometeorological parameters. One of the major findings of this study indicates that the accelerated carbon uptake in the needle leaf Pine forest compared to broad leaf Oak and deciduous forest of eastern Himalaya is linked to lesser ecosystem respiration, particularly during the monsoon season. Moreover, it is noted that the needle leaf Pine forest has higher responses to changes in the environmental conditions compared to Oak and deciduous forests of Himalaya.