Palmyrah (Borassus flabellifer) palm land-use system: A potential key tool for enhancing carbon stock and floristic diversity in a dry zone tropical landscape

The threat of global warming, biodiversity loss, and land degradation highlight the urgency of identifying sustainable land use systems that serve as climate-adaptive solutions. This study assessed the carbon stock and floristic diversity of the Borassus flabellifer (Palmyrah palm) land uses under 14 different soil series in the Jaffna district of Sri Lanka. A total of 75 sampling quadrats (10 m × 10 m) were surveyed, collecting data on the number of Palmyrah palms and other flora species and, the height. Soil samples were collected at three depths (0–10 cm, 10–20 cm, and 20–30 cm) for organic carbon analysis. Carbon stock in biomass was estimated using standard allometric equations, and total carbon stock was calculated by summing biomass (above-ground and below-ground) and soil carbon. The study found that soil organic carbon percentage of surface layer (0 – 30 cm) in different soil series ranged from 0.31 to 1.61 %. The topmost layer (0 – 10 cm) had higher average soil organic carbon stock (12.25 Mg C ha^-1) than sub surface layers (10 – 20 cm – 11.57 Mg C ha^-1), 20 – 30 cm – 10.11 Mg C ha^-1). A total of 22 floral species belonging to 13 families were identified in the surveyed quadrats. Shannan Weaver index (SWI) and the evenness were 1.2 and 0.74, respectively indicating moderate biodiversity levels. The average values of Palmyrah palm density, biomass carbon stock, soil carbon stock, and total carbon stock were 914 ± 179 stems ha^-1, 72.48 ± 15.11 Mg C ha^-1, 36.05 ± 15.81 Mg C ha^-1, and 108.53 ± 21.47 Mg C ha^-1, respectively. These findings highlight Palmyrah palm land use as a significant carbon sink with substantial potential for biodiversity conservation. Promoting this land use system could contribute to sustainable climate mitigation and adaptation strategies in regions facing similar ecological challenges.