Assessment of the Carbon dioxide sequestration potential of selected tree species using controlled growth chambers.

Abstract

The present study attempted to assess the CO 2 assimilation efficiencies of six tree species (Terminalia arjuna, Swietenia macrophylla, Pongamia pinnata, Simarouba glauca, Mimusops elengi, and Syzygium cumini) under controlled growth conditions. The experiment was carried out in two growth chambers, each with a volume of 6.32 m 3 , constructed with PVC frames and covered with transparent polyvinyl chloride sheets. The control chamber (CC) was equipped with the facility for the supply of ambient air, whereas the treatment chamber (TC) with the facility for the supply of CO 2- air mixture in specific doses using an air compressor and a nebulizer. Both chambers were fitted with the facility for the analysis of CO 2 (NDIR type Infrared Gas Analyzer), temperature ( 0 C), and humidity (%) using a Billion Bag digital wireless electronic hygro-thermometer. Both chambers were also equipped with an exhaust facility at the top along with a semi-automated facility for the irrigation of plantlets during experimentation. For treatment studies, ca. 11⁄2-year-old saplings of T. arjuna, S. macrophylla, P. Pinnata, S. glauca, M. elengi, and S. cumini were employed separately. For each study, one set of saplings was retained in the CC and the other in the TC and were then closed and sealed from the outside. The CC was supplied daily twice (9 am and 6 pm) with ambient air, maintaining a CO 2 concentration of 475±42 ppm, and the TC with a CO 2 -air mixture, maintaining a resultant CO 2 concentration of 979.83±30.93 ppm. The magnitude of CO 2 concentration (ppm) along with temperature and humidity within the chambers was monitored twice a day at 9 a.m. and 6 p.m. The experiment was continued for 15 days. The resultant day and night flux in CO 2 was estimated from these results of CO 2 . A standardization study was also undertaken in the same way in empty chambers (without plants) and the results were used for the estimation of gross and net flux in CO 2 associated with the respective tree species. During experimentation the growth (plant height, stem diameter, leaf length, leaf breadth, leaf number, and leaf area and biomass) and biochemical changes (pigments such as chlorophyll a, b, total chlorophyll, carotenoids; plant metabolites such as carbohydrates, protein, and phenol; minerals such as calcium, magnesium, sodium and xviipotassium and carbon and nitrogen) owing to varying levels of CO 2 supply at specific stages of growth were assessed. The results are statistically validated. The study revealed that the CO 2 assimilation potentials of Swietenia macrophylla are higher, followed by Terminalia arjuna, Pongamia pinnata, Simarouba glauca, Syzygium cumini, and Mimusops elengi. The species Swietenia macrophylla is found to be more efficient in carbon sequestration, due to its increased CO 2 assimilation, lower respiratory release, increased biomass content, increased growth characteristics, metabolites, and nutrients. The species can be considered by policymakers and urban planners for its inclusion in various carbon offset planting initiatives. However, the present outcomes are based on a laboratory-based analysis and hence field-level or site-specific validation of the species is required for further confirmation of their Carbon sequestration potentials.