This paper describes the operational methods to achieve and measure both deep-soil heating (0-3m) 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 115m2 open-topped enclosures with elevated CO2 treatments (+0 to +500ppm). Air warming across the entire 10 enclosure study required ∼ 90% of the total energy for WEW ranging from 64283 mega Joules (MJ)d-1 during the warm season to 80102MJd-1 during cold months. Soil warming across the study required only 1.3 to 1.9% of the energy used ranging from 954 to 1782MJd-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.
Climate change is reducing the amount, duration, and extent of snow across high‐latitude ecosystems. But, in landscapes where persistent winter snow cover develops, experimental platforms to ...specifically investigate interactions between warming and changes in snowpack, and impacts on ecosystem processes, have been lacking. We leveraged a whole‐ecosystem warming experiment in a boreal peatland forest to quantify how snow duration, depth, and fractional cover vary with warming of up to +9°C. We found that every snow‐related quantity we examined declined precipitously as the amount of warming increased. The importance of deep, continuous snow cover for moderating shallow soil temperature is highlighted by an increase in soil temperature variance and the frequency of short‐duration freeze‐thaw cycles in the warmer plots. We used a paired‐plot approach to estimate the magnitude of the snow‐albedo feedback effect, and demonstrate that albedo‐driven warming linked to reduced snow cover varies between December (+0.4°C increase in maximum air temperature) and March (+1.2°C increase) because of differences in insolation. Overall, results show that even modest future warming will have profound impacts on northern winters and cold‐season ecosystem processes. Plot‐level data from this warming experiment, and emergent relationships between warming and quantities related to snow cover and duration, could be of enormous value for testing and improving the representation of snow processes in simulation models, especially under future climate scenarios that are outside of the range of historically observed variability.
Plain Language Summary
Climate change is reducing the winter snowpack in many northern ecosystems, but disentangling changes in winter precipitation from concurrent winter warming is challenging. We used data from an already‐established ecosystem warming experiment to look at relationships between warming (up to +9°C) and changes in snow duration, depth, and fractional cover. Even modest levels of warming had severe negative impacts on each snow‐related quantity we investigated. For example, warming of just +2°C was sufficient to reduce the number of winter days with a 5 cm snowpack by about 50%. Reductions in snow cover will have feedback effects on local winter climate because more shrub‐covered ground reflects less solar energy than snow‐covered ground. We estimate that because of this so‐called “snow‐albedo feedback,” maximum daytime air temperature will be elevated by up to about 1°C above snow‐free ground, compared to snow‐covered ground. Our results show how future warming, at levels consistent with IPCC projections, will result in transformative changes to the winter season in boreal peatlands, with impacts on how these ecosystems function, and how they impact the climate system.
Key Points
Winter snow duration, depth, and fractional cover in a boreal peatland is extremely sensitive to warming, especially above +4.5°C
Warming‐driven reductions in winter snowpack result in more frequent soil freeze‐thaw cycles
The snow‐albedo feedback effect is estimated to increase maximum daily air temperature by 0.077 ± 0.010°C per MJ m−2 d−1
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.
This paper describes the operational methods to achieve and measure both deep-soil heating (0-3â¯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 CO.sub.2 was also incorporated to test how temperature responses may be modified by atmospheric CO.sub.2 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 115â¯m.sup.2 open-topped enclosures with elevated CO.sub.2 treatments (+0 to +500â¯ppm). Air warming across the entire 10 enclosure study required ââ¼ââ¯90â¯% of the total energy for WEW ranging from 64â¯283 mega Joules (MJ)â¯d.sup.-1 during the warm season to 80â¯102â¯MJâ¯d.sup.-1 during cold months. Soil warming across the study required only 1.3 to 1.9â¯% of the energy used ranging from 954 to 1782â¯MJâ¯d.sup.-1 of energy in the warm and cold seasons, respectively. The residual energy was consumed by measurement and communication systems. Sustained temperature and elevated CO.sub.2 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.
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