Soil respiration in three soil types in agricultural ecosystems in Finland

Seasonal changes in soil respiration (SR), soil temperature (ST) and soil w ater 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 i n SR were different among the soil types: peat soil, maximum rate (650 mg C O2 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 SW C and no significant relation between SR and ST; clay soil, maximum rate (5 00 mg CO2 m(-1) h(-1)) in summer, highly positive significant relation betw een 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 soi ls based on the relationships between SR and certain abiotic environmental factors. The model calculation indicated that the amount of CO2 evolved fro m Finnish agricultural soils during the cultivation period was comparable t o the values obtained from different locations around the world. These sugg est that soils in northern crop fields release a relatively large amount of CO2, equivalent to that in regions with warm-temperate and temperate clima tes.