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.