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Carbon dioxide concentration in atmosphere is actively increasing since industrial revolution (1800) from 285 ppmv to 378 ppmv in 2005. Carbon dioxide efflux from soil due to floral and faunal respiration in soil, called soil respiration, is the second largest source of increasing concentration of CO2 in atmosphere. Soil respiration produces almost 11 times more carbon dioxide in atmosphere than that produced due to fossil fuel burning [18]. Microorganisms are the most abundant biotic group in soil and huge amount of v CO2 is evolved from soil due to bacterial and fungal respiration. The present study investigated soil respiration and distribution of bacteria and fungi in the soil. The study was conducted in semi arid (subtropical) climate around New Delhi in India. Two different sites (Aravali Biodiversity Park and Yamuna Biodiversity Park) with ecologically different soil and vegetation conditions were studied. Three different locations were selected at each site and at each location CO2 efflux and microbial population were measured at three depths, topsoil (0-5 cm depth), midsoil (15-20 cm depth) and Deep soil (40-45 cm depth). Higher soil activity was found at Yamuna Biodiversity Park (YBP) having profuse ground vegetation, sandy soil with high organic matter and moisture content than Aravali Biodiversity Park (ABP) having scares vegetation, rocky area and dry soil with low organic matter content. Higher soil respiration is recorded in the surface and mid soil at YBP than ABP. However the soil respiration rate was slightly more in deep soil at ABP. In most of the cases soil respiration was found increasing from surface soil to deeper soil till 50 cm depth. Rate of soil respiration is highly correlated (R-2 = 0.7) to fungal population. Our study suggests that soil respiration process is a function of bacterial and fungal abundance in the soil. However, fungal population is more responsible for CO2 evolution in atmosphere from soil than bacterial population. Better understanding of soil respiration process can help in reducing CO2 emission and carbon sequestration process.