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We designed, constructed, and tested an automated chamber system for continuously monitoring soil respiration. Our objective was to design a chamber that would permit monitoring of C[O.sub.2] efflux rates over long time periods without altering the natural microclimate within the chamber. Furthermore, the design would permit accurate measurements even in a highly fluctuating C[O.sub.2] environment. We built a chamber that operates by closing over the soil in response to a control signal and remains dosed for a 14-min period before opening again. Thus, the chamber allows normal drying and wetting of the soil between measurements. An automated switching system was programmed to sequentially open and close chambers in concert with an infrared gas analysis system (IRGA). The IRGA was operated in a differential mode, and equivalent flow rates of reference gas (ambient air) and sample gas (air exiting chamber) were maintained with mass flow controllers. A flexible neoprene lid, stretched tightly over each chamber when closed, provided an airtight seal. This feature and the use of a large mixing bottle (for buffering frequent changes in ambient C[O.sub.2] concentration) permitted us to measure soil C[O.sub.2] efflux rates even in an environment with highly variable atmospheric C[O.sub.2] concentration. Soil respiration rates, measured over a period of several weeks with the automated chambers, were in agreement with traditional point-in-time measurements, and the soil microclimate was not affected by the chambers. However, when extrapolated over a period of several weeks the point-in-time measurements overestimated C[O.sub.2] efflux rates based on continuous measurements with the automated system.

This paper describes the operational methods to achieve and measure both deep-soil heating (0-3 m) and whole-ecosystem warming (WEW) appropriate to the scale of tall-stature, high-carbon, boreal forest peatlands. The methods were developed to allow scientists to provide a plausible set of ecosystem-warming scenarios within which immediate and longer-term (1 decade) responses of organisms (microbes to trees) and ecosystem functions (carbon, water and nutrient cycles) could be measured. Elevated CO2 was also incorporated to test how temperature responses may be modified by atmospheric CO2 effects on carbon cycle processes. The WEW approach was successful in sustaining a wide range of aboveground and belowground temperature treatments (C0, C2.25, C4.5, C6.75 and C9 °C) in large 115m2 open-topped enclosures with elevated CO2 treatments (C0 to C500 ppm). Air warming across the entire 10 enclosure study required ~90% of the total energy for WEW ranging from 64 283 mega Joules (MJ) d-1 during the warm season to 80 102 MJ d-1 during cold months. Soil warming across the study required only 1.3 to 1.9% of the energy used ranging from 954 to 1782 MJ d-1 of energy in the warm and cold seasons, respectively. The residual energy was consumed by measurement and communication systems. Sustained temperature and elevated CO2 treatments were only constrained by occasional high external winds. This paper contrasts the in situWEWmethod with closely related field-warming approaches using both aboveground (air or infrared heating) and belowground-warming methods. It also includes a full discussion of confounding factors that need to be considered carefully in the interpretation of experimental results. The WEW method combining aboveground and deep-soil heating approaches enables observations of future temperature conditions not available in the current observational record, and therefore provides a plausible glimpse of future environmental conditions. [ABSTRACT FROM AUTHOR]

This paper describes the operational methods to achieve and measure both deep soil heating (0-3 m) and whole-ecosystem warming (WEW) appropriate to the scale of tall-stature, high-carbon, boreal forest peatlands. The methods were developed to allow scientists to provide a plausible set of ecosystem warming scenarios within which immediate and longer term (one decade) responses of organisms (microbes to trees) and ecosystem functions (carbon, water and nutrient cycles) could be measured. Elevated CO2 was also incorporated to test how temperature responses may be modified by atmospheric CO2 effects on carbon cycle processes. The WEW approach was successful in sustaining a wide range of above and belowground temperature treatments (+0, +2.25, +4.5, +6.75 and +9 °C) in large 115 m² open-topped chambers with elevated CO2 treatments (+0 to +500 ppm). Air warming across the entire 10 enclosure study required ~ 90 % of the total energy for WEW ranging from 64283 MJ d-1 during the warm season to 80102 MJ d-1 during cold months. Soil warming across the study required only 1.3 to 1.9 % of the energy used ranging from 954 to 1782 MJ d-1 of energy in the warm and cold seasons, respectively. The residual energy was consumed by measurement and communications systems. Sustained temperature and elevated CO2 treatments were only constrained by occasional high external winds. This paper contrasts the in situ WEW method with closely related field warming approaches using both above (air or infrared heating) and belowground warming methods. It also includes a full discussion of confounding factors that need to be considered carefully in the interpretation of experimental results. The WEW method combining aboveground and deep soil heating approaches enables observations of future temperature conditions not available in the current observational record, and therefore provides a plausible glimpse of future environmental conditions. [ABSTRACT FROM AUTHOR]