Soil respiration in three soil types in agricultural ecosystems in Finland

Seasonal changes in soil respiration (SR), soil temperature (ST) and soil water content (SWC) were monitored in three different soil types (peat, sand and clay soils) in Finnish agricultural ecosystems. Rates of CO₂ emission were measured by the closed chamber method using an infrared gas analyser (IRGA) at intervals of 2 - 3 weeks from May to October. The seasonal changes in SR were different among the soil types: peat soil, maximum rate (650 mg CO₂ m^-2 h^-1) in summer, positive significant relation between SR and ST and negative relation between SR and SWC; sandy soil, stable SR (300 mg CO₂ m^-2 h^-1) without seasonal changes, positive relation between SR and SWC and no significant relation between SR and ST; clay soil, maximum rate (500 mg CO₂ m^-2 h^-1) in summer, highly positive significant relation between SR and ST and negative relation between SR and SWC. A statistical model was developed to predict the amount of CO₂ evolved from the cultivated soils based on the relationships between SR and certain abiotic environmental factors. The model calculation indicated that the amount of CO₂ evolved from Finnish agricultural soils during the cultivation period was comparable to the values obtained from different locations around the world. These suggest that soils in northern crop fields release a relatively large amount of CO₂, equivalent to that in regions with warm - temperate and temperate climates.