# Lab processing of SNOTEL site samples

3 circular plots (10m diameter) are sampled in each forest. 6 soil sampling locations are randomly selected in each plot. Note that in 2008 soil sampling happened at only 5 locations per plot and there were no bulk density measurements.

See the SNOTEL field sampling page for more on sampling methods

**Samples returned**

- 3 litter bags --- 1 per plot, aggregates of 6 sampled locations per plot (15x15cm quads - 225cm^2^).
- 3 O-horizon samples --- 1 per plot, aggregate of 6 sampled locations per plot. These may be in multiple bags. Area sampled varies but is known.
- 3 Mineral soil (0-10cm depth) --- 1 per plot, aggregate of 6 sample locations per plot.
- 3 bulk density tins (0-10cm depth) --- 1 per plot, absent at extremely rocky locations.
- 3 bulk density tins (10-20cm depth) --- 1 per plot, absent at extremely rocky locations.
- 9 tree increment cores --- 3 per plot, including 1 from largest tree in plot.

**Data returned**

- Depth of organic horizon for each plot --- average of 4 measurements at each of 6 sampling locations in the plot
- Coarse woody debris (> 5cm) volume --- length and center diameter of all CWD within plot
- Diameter at breast height of each tree in all three plot
- Estimate of percent cover of the understory in each plot (this is a
**rough**estimate) - Slope and aspect of each plot

## Litter

- Oven dry sample bags until dry. This may take multiple days.
- Empty the bag into a tared weigh tray (a tupperware most likely).
- Remove any rocks and weigh them.
- Weigh the bulk litter remaining in the tared weigh tray.
- Sort out CWD (> 0.5cm) and weigh remaining fine litter and leaves.
- Homogenize the remaining sample and take a representative subsample for grinding
- Grind this well-mixed subsample of litter and archive in a labeled sample cup

## O horizon

- Oven dry sample bags
- Empty the bag into a tared weigh tray.
- Remove rocks & weigh them.
- Weigh the bulk organic soil remaining in the tared weigh tray.
- Sort out CWD (>0.5cm) & weigh the remaining organic soil sample.
- Sample fine roots if available and put in coin envelope (1 per site) for later analysis.
- Homogenize the remaining sample and take 2 representative subsamples:
- One sample sifted through 2mm mesh to remove fine roots, then save ~20g of each (>2mm & <2mm fractions) for density fractionation.
- A larger bulk sample ground in coffee grinder and archived in a sample cup for further SOM analysis.

The first sample will be separated with density fractionation and fractions then undergo prep for EA-IRMS analysis. The second sample can be subsampled for immediate prep for EA-IRMS analysis.

## Mineral 0-10

- Oven dry sample bags
- Weigh bulk sample in a tared weigh tray.
- Sift sample through 2mm screen.
- Weigh any rocks (>2mm) remaining on the screen.
- If there are roots left on the screen, sample them and place in a coin envelope for later analysis (1 envelope per site/per depth)
- Homogenize the remaining (<2mm) sample and take a representative subsample for archiving in labeled sample cup.
- Weigh or archive all remaining >2mm material (roots and wood).

Note that for 2008 samples half of the oven-dried bulk samples were immediately archived for rock, sand, silt, clay fraction analysis.

The archived soil sample can be further subsampled for density fractionation (with fractions then undergoing prep for EA-IRMS), or for immediate prep and EA-IRMS analysis.

## Fine roots

- While sifting organic and mineral samples above, sample intact fine roots and place in a coin envelope.

## Bulk Density Tins

- Oven dry tins
- Record tin weight written on bottom of tin
- Weigh dry sample tins (without lids)
- Sift to 2mm - wet sifting may be necessary for this.
- Measure volume of rocks remaining in screen (>2mm sample) by volume displacement.
- Archive any roots, wood, or charcoal remaining in the screen (>2mm sample).
- Weigh sifted sample (<2mm)

## Intact cores

- Remove end caps and place cores (still in liners) on a tray or tin in the drying oven.
- Once dry, cores should slide out of the liners into a tared weigh tray. Be careful not to lose any soil.
- Weigh the cores.
- Sift to 2mm - wet sifting may be necessary for this.
- Measure volume of rocks remaining in screen (>2mm sample) by volume displacement.
- Archive any roots, charcoal, or wood remaining in the screen (>2mm sample).
- Weigh sifted sample (<2mm) and archive for later analysis.