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Abstract. 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 (+0, +2.25, +4.5, +6.75 and +9 °C) in large 115 m2 open-topped enclosures 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 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 situ WEW method 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.

<p><strong>Abstract.</strong> 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 CO<sub>2</sub> was also incorporated to test how temperature responses may be modified by atmospheric CO<sub>2</sub> 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 m<sup>2</sup> open-topped chambers with elevated CO<sub>2</sub> 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<sup>−1</sup> during the warm season to 80102 MJ d<sup>−1</sup> 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<sup>−1</sup> of energy in the warm and cold seasons, respectively. The residual energy was consumed by measurement and communications systems. Sustained temperature and elevated CO<sub>2</sub> 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.</p>

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A direct comparison of treatment uniformity and CO 2 use of pure and prediluted free-air CO 2 enrichment (FACE) systems was conducted in a forest ecosystem. A vertical release pure CO 2 fumigation system was superimposed on an existing prediluted CO 2 fumigation system and operated on alternate days. The FACE system using prediluted CO 2 fumigation technology exhibited less temporal and spatial variability than the pure CO 2 fumigation system. The pure CO 2 fumigation system tended to over-fumigate the upwind portions of the plot and used 25% more CO 2 than the prediluted CO 2 fumigation system. The increased CO 2 use by the pure CO 2 system was exacerbated at low wind speeds. It is not clear if this phenomenon will also be observed in plots with smaller diameters and low-stature vegetation.