SOIL ORGANIC CARBON DYNAMICS IN TROPICAL INDIAN FORESTS: INVESTIGATION USING RADIOCARBON AND STABLE ISOTOPE RATIOS

Abstract

The study here analyses the distribution of soil organic carbon and stable carbon isotopic ratio with depth and among particle size fractions in two forests from Dehradun, Uttarakhand, and Muzaffaranagar, Uttar Pradesh. The sand has low organic content and less variation in 13C along with the depth. On the other hand clay associated soil particles are enriched in 13C and have more significant organic carbon content. Microbes decompose the organic matter and utilize the lighter isotope preferentially; The classical Rayleighs model is applied to the system where the material is continuously removed along with the isotopic fractionation. This can be modified by adding the source term, where the addition of input material is happening from the top surface with the assumption of any isotopic fractionation in input material; this is used to estimate the input of fresh organic matter from the surface. The radiocarbon age of bulk soil from Dehradun and Muzaffarnagar is estimated reaching to the value of ~500 yrs and ~2700 in the deeper soil layers, increasing almost linearly with the depth. The radiocarbon age of soil mostly depends on the clay content. However, the Radiocarbon ages of segregated soil particles are under process. The radiocarbon age of soil CO2 is observed to be modern. 13C in soil and soil CO2 from Ratanmahal Sloth Bear Sanctuary, a reserved forest in Gujarat, is analyzed, showing no systematic trend in change in 13C along with the depth.