Preliminary assessment of soil and tree-ring δ 13C variability in mangrove system in the Shastri River estuary

Abstract

Mangroves in India represent a significant contributor to carbon storage potential, yet there have been limited studies conducted on both the east and west coasts of India, with west coast being less explored. This exploratory study explores the soil organic carbon content (SOC) and the stable carbon isotopes assessment within a one-meter depth profile in the mangrove ecosystem of Jambhari, Ratnagiri, Maharashtra. It also examines the δ13C values of leaves and the variations in δ13C found in tree rings throughout the year. The results revealed a decline in both SOC content and δ13C values with increasing depth. The SOC values range from 1.5% to 4.8%, which were consistent with other Indian and global mangroves. The patterns are linked to microbial activity, burrowing in the upper soil layers by benthic fauna, organic carbon mineralization due to iron reduction and input of autochthonous and allochthonous terrestrial organic matter delivered by the riverine system of Western Ghats. Leaf δ13C values were consistently more depleted than bulk soil δ13C, reflecting physiological discrimination under stress conditions while intra-annual measurement of δ13C in mangrove tree rings revealed uniform patterns attribute to seasonal variation in relative humidity, salinity, post-photosynthetic processes. These findings provide us with a preliminary assessment of δ13C variability in the mangrove systems present along the west coast of India, underscoring their importance in carbon storage and ecological functioning.