Assessment of Phytolith-Occluded Carbon Sequestration Potential in Uncultivated Grasses of Coimbatore, India
L. Arul Pragasan *
Department of Environmental Sciences, Bharathiar University, Coimbatore – 641 046, Tamil Nadu, India.
R. Vidhya
Department of Environmental Sciences, Bharathiar University, Coimbatore – 641 046, Tamil Nadu, India.
T. Gnanambal
Department of Environmental Sciences, Bharathiar University, Coimbatore – 641 046, Tamil Nadu, India.
*Author to whom correspondence should be addressed.
Abstract
Terrestrial biogeochemical carbon sequestration is recognised as a promising strategy to slow the rapid rise of atmospheric CO₂ levels and mitigate associated climate impacts. Recent studies highlight the occlusion of carbon within phytoliths as a stable and long-term carbon sequestration mechanism. The present study evaluates the carbon sequestration potential of five uncultivated grass species, Cenchrus ciliaris (L.), Setaria verticillata (L.) P. Beauv., Paspalum sumatrense Roth., Panicum maximum Jacq., and Hackelochloa granularis (L.) Kuntze through an analysis of carbon stock, phytolith content, phytolith morphotypes, and Phytolith-occluded carbon (PhytOC) in both above-ground biomass (AGB) and below-ground biomass (BGB). The study was conducted in Coimbatore, Tamil Nadu, India. Phytoliths were extracted from plant material using a dry ashing and acid digestion method. Data were analysed using one-way analysis of variance (ANOVA) to test for significant differences among means, with the Least Significant Difference (LSD) test applied at P < 0.05. Correlation analysis between carbon stock and PhytOC was performed using SPSS software (version 21, IBM Corp., Chicago, USA). Biomass quantification revealed values ranging from 1.208 ± 0.010 kg/m² to 2.007 ± 0.005 kg/m² across the species. Phytoliths were extracted using the dry ashing method in a muffle furnace, followed by acid digestion. Results indicated that phytolith content was consistently higher in BGB compared to AGB in all species, with significant variation ranging from 0.1984 ± 0.0013 mg/g to 0.3384 ± 0.0044 mg/g. Notably, Setaria verticillata exhibited the highest PhytOC content in AGB, while Panicum maximum showed the highest PhytOC in BGB. The average PhytOC content in BGB ranged from 0.08% to 0.340%, highlighting its role in long-term carbon storage. Among all species, Cenchrus ciliaris displayed the greatest diversity of phytolith morphotypes, suggesting a higher capacity for silicon and carbon interaction. This study underscores the significant role of uncultivated grasses in carbon sequestration through phytolith formation and organic carbon occlusion. Given the stability and longevity of PhytOC in soils, these grasses represent a promising, nature-based solution for mitigating climate change. Promoting the conservation and restoration of such grasslands could enhance terrestrial carbon sinks and support sustainable land management practices.
Keywords: Phytolith-occluded carbon, carbon sequestration, uncultivated grasses, below-ground biomass, phytolith morphotypes