Introduction
In 1996, a survey was conducted on the entire 5-ha Pothole Creek Study Area to describe the coarse woody debris (CWD) present.
The initial survey also provided background (e.g., aspect, slope) and
an estimate of the regeneration present on the site.
Methods
Twenty-six points were randomly located within the 5 ha study area. Two 24-m line transects radiated perpendicularly from these points. Coarse woody debris pieces larger than 7.5 cm diameter intersecting the transects were counted and the
diameter at intersection, large end diameter, a simple decay class, slope orientation, and an ocular estimate of length of the piece were recorded.
The decay classes used were: Solid - the log was firm throughout; Intermediate - log contained visible rot but was partly firm; Rotten - log could be kicked to pieces. Slope orientation was recorded as: Down - log was aligned down slope plus or
minus 30 degrees; Across - log was aligned perpendicular to slope direction plus or minus 30 degrees; Intermediate - log did not fall in the Down or Across class. The random points from which the line transects radiated were marked with a metal tent
peg and a write-on aluminum tag for future location. These points were also the centre of the regeneration survey.
Results
The 1996 survey data suggest that there are 136 m3/ha (s.e., 35) of coarse woody debris present.
The number of pieces estimated is 1212/ha (s.e., 207).
Table 1. Coarse woody debris large end diameter classes present on the Pothole Creek Study Area. The survey is based on twenty-six randomly located 5-m2 sample plots on two 24-m line transects.
| Large End Diameter
Class (cm) |
Number of Pieces |
Volume (m3/ha) |
| Mean |
Std. Err. |
Mean |
Std. Err. |
| 7.5 - 10 |
288 |
71 |
3.1 |
0.8 |
| 11-20 |
667 |
103 |
57.5 |
29.5 |
| 21-30 |
180 |
49 |
26.1 |
6.1 |
| 31-40 |
30 |
11 |
9.1 |
2.8 |
| 41-50 |
26 |
16 |
12.9 |
5.0 |
| 51+ |
21 |
13 |
26.9 |
11.8 |
| Total |
1212 |
|
135.6 |
|
Discussion
This survey provides baseline information about the coarse woody debris present at the Pothole Creek Study Area. There are more smaller (< 20 cm diameter and < 3 m length) pieces present on the site than large pieces, which may reflect
the site's past partial harvesting history. However, whether the logs had fallen naturally or by cutting was not recorded. Most logs were fairly solid (i.e., bark had fallen off and log was weathered but
firm),
indicating that the decay dynamics on this dry sight might be fairly slow if many of these logs did originate with partial harvesting
40 years ago.
The orientation of the logs will have some impact on the role that the log plays on the site. A log oriented across-slope presumably would slow the movement of such materials as water, snow, and organic matter down a gradient more than would a
log oriented down-slope. On the 5-ha study site, only 17% of the logs were oriented across-slope.
If the fall pattern were completely random, we might expect this figure to be
closer to 33%
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