Soil Respiration of Native Saskatchewan Grassland Calculated from Carbon Dioxide Concentration Profiles

Abstract

A study was conducted to monitor soil respiration by measuring CO2 concentrations in soil throughout the growing season. The technique of gas chromatography was used to obtain CO2 concentration profiles on native grassland and cultivated soils. The CO2 concentration gradients were then used to calculate CO2 flux through successive soil layers. Production of CO2 by these layers was calculated from the flux through the upper and lower plans of a soil layer. Field and growth chamber data, collected over a three year period, is presented. Evolution and production of CO2 was highly correlated with soil moisture in both the field and growth chamber studies. Significant correlations were also obtained between CO2 evolution or production and soil temperature on summer-fallow fields. In the growth chamber, an increase in soil temperature form 5C to 15Cr resulted in an increase in CO2 evolution of more than 2 times. On an irrigated native grassland soil, a maximum CO2 evolution rate of 28 kg ha-1 hr-1 was obtained. Over a period of three summer seasons, an average rate of CO2 production by dry-land native grassland soils was 2.5 kg ha-1 hr -1. A carbon balance showed that an average annual carbon fixation of 240 g carbon per m2 compared with an annual CO2-carbon release of 220 g m-2. An equation is derived to predict CO2 evolution from the native grassland soil from soil moisture and soil temperature.