Soil respiration in a tropical grassland

Abstract

Soil respiration throughout an annual cycle was measured at three different stands in a tropical grassland situated at Kurukshetra at 29° 58' N lat. and 76° 51' E long. Rates of CO₂ evolution were measured by alkali absorption using 13 cm dia × 23 cm aluminium cylinders inserted 10 cm into the ground. Both movable and permanently-fixed cylinders were used. The CO₂ evolution rates for the three stands were: Stand I (dominated by Sesbania bispinosa) 49-358 mg CO₂ m⁻² h⁻¹; Stand II (mixed grasses) 55-378 mg CO₂m⁻² h⁻¹; and Stand III (dominated by Desmostachya bipinnata) 55-448 mg CO₂ m⁻² h⁻¹. A positive significant relation existed between rate of CO₂ evolution and soil water content (r = 0.59-0.740), and between soil respiration and temperature (r = 0.58-0.69). A statistical model developed on the basis of the relationship between CO₂ evolution rates and certain abiotic environmental factors showed 69% comparability between the calculated and observed values of soil respiration. The contribution of root and root-associated microorganisms to total soil respiration was estimated at 42% using the relationship between root biomass and CO₂ output from movable cylinders.