1 September 2018 Meet the SRS

Journal

The Woods Hole Research Center (WHRC) NASA ABoVE (Arctic Boreal Vulnerability Experiment) team has set up their unique Soil Respiration Stations (SRS) at several different sites across Northern Alaska. Sites vary in vegetation density (forested area or open tundra) and some compare areas that are close together but have/have not experienced a recent burning event. These stations are collecting all sorts of information year-round to give the team insights into winter respiration (how much CO2 is being released into the atmosphere from the soil). Previously scientists where only measuring summer respiration during the active growing season – and winter respiration was assumed to be null since it is during the non-active/"frozen" season. Some initial studies suggest this may not be the case, and this is a longer-term project looking more deeply into the question. The SRS consist of several different elements:

Forced Diffusion Chambers: These chambers sit on the ground around the site. They have a membrane on their bottom with a large cap over them, creating a chamber to collect gas. These chambers are measuring the amount of carbon gas that emits from the soil. The carbon gas comes out of the soil (more on why in a later post), goes through the membrane where it is collected in the chamber. The data loggers are programmed to open specific valves leading to the chambers at certain intervals/times of day. A pump then turns on to suck the gas out the chamber, through a hose, to the CO2 Sensor. The data logger records the time of measurement and the level of CO2. It also has a second hose with a valve that is measuring gas levels in the atmosphere. The comparison of the CO2 levels in the atmosphere with that in the soil gives the team the rate (or flux) of carbon from the soil to the atmosphere. This is the core and unique measurement the project is taking. But to support this data, you need several other types of equipment and monitoring devices.

Additional Chambers: These however, are placed below the surface, at 5cm, 15 cm, and 25 cm. They also have thermalcouple wire to measure soil temperature. The chambers are measuring CO2 (same as the ones above), but below the ground. This gives the team a whole profile of the carbon release through the soil – is there more carbon deep down? More at the surface? How much carbon is being released vs. being stored in the soil?

Forced Diffusion Chamber — The forced diffusion chamber helps measure the CO2 flux between the soil and atmosphere.

Solar Panel and Batteries: (Challenge #3 – power) The solar panel recharges the 12 volt batteries that power the data logging devices.
Each SRS is powered by 12 volt batteries recharged by a solar panel.
Trail Camera: The trail camera is mounted to a tree facing a snow pole which takes pictures at 9AM, noon, and 3PM. The snow pole has alternating black and white lines at regular (pre-measured) intervals. These photos can be used for many different purposes – it of course shows snow depth, but can also give information on the micro-weather of the station – vegetation changes (greening/browning) and snow accumulation (is the snow that is falling sticking or blowing away?). It is just a good idea to have a camera on the station so you can look back on what was happening when you have questions about your data.
The trail camera looks directly at the SRS and snow stick.

If you haven't already seen it, here is an example of trail cam data from Atqasuk:
Soil Temperature: Measuring soil temperature will help give insight and provide context for the carbon flux data. Probes are placed at 100 cm and 50cm below the ground. Measurements are taken every ~6hrs.
The data logger is above ground but two probes go down to measure soil temperature at 50 and 100cm.
Additional Soil Temperature and Soil Moisture: These are placed at 15 cm below the surface in two different locations. Data is taken every hour.
Additional Soil Temperature Monitoring on SRS.
Light Intensity/Surface Temperature: This is measured by a little pendant placed on the ground.
Close-up view of a forced diffusion chamber and surface temperature/light intensity monitor.
Thaw Depth: Measured through human power! Three 30m lines (transects) measured at the beginning (minimum levels – in theory) and end (maximum) of the summer.
Thaw depth is measured at transects 30 m long.
Soil Samples: Soil "brownies" need to be taken at each site, and taken back to the lab to help calibrate sensors to improve data quality.
My first soil brownie!