Handheld soil respiration measurements
Growing season soil CO~2~ fluxes are measured at respiration collars using the Li-Cor 6400 and a handheld soil respiration chamber (LiCor 6400-09).
In use at:
PVC collars are inserted in the soil at field sites to make soil respiration measurements with the LI-6400. Collars should be made from ~4 inch (10cm) PVC tubing to accommodate the 9.55cm diameter LiCor-6400-09 chamber. The tubing should be cut at roughly 5cm lengths and then beveled on one edge. These are inserted 1.5-3cm into the soil surface in the location where respiration is to be measured. Because installation of the collars severs roots and upsets the CO~2~ gradient, they should be installed at least 12 hours prior to measurement.
- LiCor 6400 (in carrying case)
- LiCor 6400-09 handheld soil CO~2~ flux chamber (attaches to the IRGA)
- Cables/tubing for connecting items 1 and 2 (in carrying case)
- 2 fully charged LiCor batteries
- 2 full charged spare batteries
- Pack frame for carrying the case (if hiking into the field)
- Soil temperature probe (Omega Type-T thermocouple probe) assuming the LiCor 6400's is broken as usual.
- Bring the probe AND its console
- Span gas tank - optional, see the notes in the measurement procedure.
Making measurements with the LI-6400
The general procedure for operating the LiCor 6400 is on the instrument page.
- This procedure will need to be adapted for each site (see below and notes on the instrument page)
General site considerations
- Number and location of collars
- Depends on the site
- Moving collars
- Collars may remain stationary through the growing season, or they can be moved prior to each measurement.
- This depends on research objectives.
- Allow 12+ hours of recovery after hammering collars in at a new location.
- Measurement frequency:
- Every two weeks during the growing season is excellent
- Less frequently during shoulder seasons?
- Time of measurements:
- Morning might be cold
- Afternoons might be too hot
- Night might exclude autotrophic components
- Timing should probably be similar between measurement periods
- Order of collar measurement:
- If measuring a control and treatment plot, alternate the measurements so that soil temperature changes during the measurement period occur evenly between treatments.
Notes for Hidden Canyon
Aux OP Parameters:
- Extra drawdown = 5ppm
- Flow = 500
- Dead time = 20 sec
- Minimum measurement time = 30 seconds
Deltaof around 5-6 usually works best, more if there are lots of roots.
- May need to modify things to stay within
Target +/- Deltarange.
- Measure the soil temperature at 5cm and 15cm depths using the Omega probe (the Li-Cor one is busted)