EFFECTS OF ABIOTIC VARIABLES AND ROOT BIOMASS ON CO² EVOLUTION AND CARBON BALANCE AFTER BURNING IN A SEMI-ARID GRASSLAND ECOSYSTEM

Abstract

Soil respiration rates and carbon balance were estimated in a semi-arid grassland ecosystem at Madurai, India. The alkali absorption method was used to measure carbon dioxide evolution rates from the soil. Annual carbon balance was estimated on the basis of litter production, litter disappearance and CO₂- C output. Maximum soil respiration rates were 120 mg CO₂ m^-2 h^-1 in the burned and 183 mg CO2 m^-2 h^-1 in the unburned grasslands. Positive correlations were observed between CO2 rates and soil temperature, litter moisture and soil moisture. Among the three variables, significant positive correlation (p< 0.001, n=12) was observed between soil moisture and soil respiration rates in both the grasslands. Multiple regression analysis revealed that 73 to 85 % variability in soil respiration rates was due to the combined effect of soil moisture, litter moisture and soil temperature. Mean annual carbon output from the soil was 252 and 310 g cm²y¹ in the burned and unburned grasslands respectively. CO₂ - C output by soil respiration exceeded the input of carbon through litter production by 2.76 to 8.27 % and was 3.09 to 9.49 % higher than the estimated loss of carbon through litter disappearance.