Potential of tea plants in carbon sequestration in North-East India

The potential of carbon (C) sequestration through photosynthesis depends on the nature of different plant species. Tea (Camellia sinensis L.) is an evergreen perennial plant and cultivated over a wide region in the world, and its potential to sequestrate atmospheric carbon dioxide (CO₂) in plant biomass is already evaluated. However, proportions of assimilated CO₂ which tea plant can sequestrate in their biomass and in soil are not evaluated before. In this experiment, ten (10) 6-month old tea plants of four different cultivars (TV1, TV20, S3A/3, and TV23) were transplanted in the field and CO₂ assimilation flux of tea plants was periodically measured under in situ condition using close-chamber method at 15 days interval throughout the year. The cumulative CO₂ assimilation flux of young tea plants varied within 31.82-249.22 g CO₂ plant^-1 year^-1; however, it was estimated that tea bushes also emitted 5.2-70.8 g CO₂ plant^-1 year^-1 due to aerobic respiration. After 1 year, tea plants were uprooted and the changes in their biomass were compared as the measure of their C-sequestration within the study duration. The weight gain in the whole plant biomass was proportional to the CO₂ assimilation potential of tea cultivars. Overall, tea plants sequestrated 50.8% of the assimilated atmospheric CO₂ in their biomass. The study revealed that tea bushes release organic C through the root exudates, the amount of which was equivalent to 5.9-8.6% of the assimilated CO₂. Those secreted root exudates have potential to increase organic C up to 44-48 kg ha^-1 year^-1 in tea-growing soil.