Attaining Whole-Ecosystem Warming Using Air and Deep Soil Heating Methods with an Elevated CO2 Atmosphere.

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]