Attaining whole-ecosystem warming using air and deep-soil heating methods with an elevated CO<sub>2</sub> atmosphere

Abstract

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.

Temporal and Spatial Variation in Peatland Carbon Cycling and Implications for Interpreting Responses of an Ecosystem‐Scale Warming Experiment

“…The earliest pretreatment measurements began in 2010 but several other measurements were initiated in later years. In 2014, a deep peat heating experiment (heating targeted at 2-m peat depth) was initiated (Wilson et al, 2016;Hanson et al, 2017), and thus pretreatment measurements of depth-specific peat characteristics were collected only until 2013. However, pretreatment measurements for shallow peat or aboveground processes were collected throughout the deep peat heating period and until whole-ecosystem warming commenced in August 2015.…”

“…The Spruce and Peatland Responses Under Changing Environments (SPRUCE) project is addressing an important gap in the understanding of peatland ecosystem responses to climate change Wilson et al, 2016;Hanson et al, 2017). The overall objective of SPRUCE is to examine the responses of various ecosystem processes to a range of future temperatures under ambient and elevated CO 2 concentrations.…”

A zero-power warming chamber for investigating plant responses to rising temperature

“…However, the volume of potable water required for such an endeavour is enormous and the artefacts associated with maintaining VPD can be considerable (Hanson et al, 2017). As a result, warming experiments rarely attempt to control VPD (Bronson et al, 2009).…”

“…4072 K. F. Lewin et al: A zero-power warming chamber for investigating plant responses bers (Bronson et al, 2009;Hanson et al, 2017;Barton et al, 2010). These different approaches for manipulating temperature have clear trade-offs (Amthor et al, 2010;Aronson and McNulty, 2009;Elmendorf et al, 2015).…”

Near real time environmental monitoring and large volume data collection over slow communication links

“…The seven remaining non-enclosure plots are also instrumented and monitored to provide information on undisturbed, background ambient conditions. More details about warming manipulation studies of ecosystems can be found in Hanson et al, 2017.…”