Contents

Coarse Woody Debris Form

Field Procedure

Getting Started

1. The materials required for sampling coarse woody debris (CWD) are:

• a compass, graduated in degrees;
• a clinometer, in percent and degrees (the latter read through the side window);
• slope correction tables or trigonometry formulas;
• two measuring tapes (minimum of 30 m each);
• a diameter tape and/or calipers;
• notebook with forms, pencil.

2. Establish the first sampling line by following a random azimuth for that plot.

• Measure out a 24-m line from the plot centre, correcting the slope distance to horizontal by using slope tables or trigonometry.
• Anchor the tape at both ends of the line.

3. Establish the second sampling line at plus 90^o from the first line by following the same procedures in (2) above.

4. Record the azimuth of each line.

Measure and Record

Definition of Coarse Woody Debris

Coarse woody debris (CWD) is dead woody material, in various stages of decomposition, located above the soil, larger than 7.5 cm in diameter (or equivalent cross-section) at the crossing point, which is not self-supporting. Trees and stumps (intact in ground) are considered self-supporting.

Pieces of coarse woody debris may be suspended on nearby live or dead trees, other pieces of coarse woody debris, stumps or other terrain features.

Coarse woody debris includes:

• downed horizontal or suspended (not self-supporting) dead tree boles with or without roots attached;
• fallen trees which still have green foliage if they no longer have roots attached (no living cambium) to the ground to keep them alive;
• woody pieces greater than 7.5 cm at the point where the sampling line crosses the piece;
• uprooted (not self-supporting) stumps greater than 7.5 cm in diameter at the crossing point and any of their exposed dead roots greater than 7.5 cm in diameter at the crossing point;
• fallen broken tree tops which may be horizontal or leaning, or large fallen branches; and,
• recently cut logs.

Coarse woody debris does not include:

• dead branches still connected to standing trees;
• self-supporting (not overturned) stumps;
• exposed roots of self-supporting trees or stumps;
• material that is buried beneath organic or mineral soil layers or has decomposed enough to be part of the forest floor; and,
• live or dead trees (still rooted) which are self supporting.

Sampling Methods

Sample coarse woody debris along two 24 m (horizontal distance) lines. These should run from the plot centre, the first following a random azimuth and the second at plus 90∫ to the azimuth. Take the slope of each line and determine the slope distance required to produce a horizontal line of 24 m length. If for any reason all of the line cannot be sampled, note the distance which was actually sampled out of the total distance (record in comments section why the portion was not measured).

If the line falls on heavy accumulations such as windthrow, felled and bucked timber, or logging debris and the random azimuth is odd, sample only the first and third quarters of the line (from 0 to 6 m and from 12 to 18 m). If the random azimuth is even, sample the second and fourth quarters of the line (from 6 to 12 m and from 18 to 24 m).

If the line falls on very heavy accumulations of windthrown, felled and bucked timber, or a debris pile, sample only the second quarter of the line (from 6 to 12 m) for even random azimuths and the third quarter (12 to 18 m) for odd random azimuths. An estimate should be made of the number of pieces and their diameters in heavy accumulations which can not be safely or accurately measured.

Coarse woody debris in the form of felled and bucked logs, or cold decks, is sampled even though this material will likely be removed.

When non-linear pieces are encountered, an equivalent diameter is recorded. This applies to chunks with odd configurations.

Rules for Sampling

If the transect crosses coarse woody debris, measure the amount above the soil at the crossing point. Some of the CWD may be suspended above the transect line. In such cases it might be necessary to estimate diameter and length measurements.

FIGURE 7.1. Rules for sampling coarse woody debris.

• Coarse woody debris must be greater than 7.5 cm in diameter (or equivalent) at the line intersect point (see 7.1a).

FIGURE 7.1a

• The transect must cross the central axis of the piece (see 7.1b).

FIGURE 7.1b

• If the transect coincides closely with the centreline, make the best decision as to whether the line crosses the centreline, and where (see 7.1c).

FIGURE 7.1c

• If the transect intersects a curved or angular piece more than once, measure each intersection as a separate observation (see 7.1d).

FIGURE 7.1d

• If a log has split open, but is still partially held together, record the diameter as if the piece were whole. If a stem has shattered into a number of distinct, unconnected pieces, record each piece that is greater than 7.5 cm in diameter at the point of sampling.
• Do not tally undisturbed stumps. Tally uprooted stumps and their exposed dead roots if they meet the other criteria.
• Tally only the CWD that lies above the soil (see 7.2). A piece is no longer above the soil when it is entirely buried beneath a layer of surface organic matter (forest floor) and/or mineral soil. Estimate an "equivalent" diameter for the remaining portion of logs where part of the wood has decayed and become part of the soil layer.

FIGURE 7.2. Tally only coarse woody debris that lies above the soil.

[Back to TOC] [Previous] [Next]

We hope you find this service useful and welcome your comments at: Habitat Data Manager Information Disclaimer and Copyright Notice