Development of an automatic chamber system for long-term measurements of CO2 flux from roots

To separate CO 2 efflux from roots ( R r ) and soil ( R s ), we developed a system to measure R r continuously. Using this system, seasonal variation in R r was obtained in a temperate forest in Japan. We measured R s , CO 2 efflux from mineral soil ( R m ) and environmental factors simultaneously, and the characteristic and seasonality of R r were analysed in comparison with R s . R r and R s showed different responses to soil water content: R s decreased with decreasing soil water content, whereas R r peaked at relatively low soil water content. R r / R s decreased from 64.8% to 27.3% as soil water content increased from 0.075 to 0.225 cm cm −3 . The relationship between respiration and temperature appears to change seasonally in response to phenological and biological factors. R r showed clear seasonal variation as a function of soil temperature. During the growing period, R r exhibited a higher rate at the same soil temperature than during other periods, which may be due to phenological influences such as fine root dynamics. R s decreased during the summer despite high soil temperatures. The seasonal peak for R s occurred earlier than that for soil temperature. R r / R s ranged between 25% and 60% over the course of the year. DOI: 10.1111/j.1600-0889.2006.00216.x