Plot Name: Reference Stand 18 (HJA)

Plot Size: 0.25 ha

Established: 1973

Remeasurements: 1976, 1981, 1986, 1992, 1998

Site Description

Latitude: 44.25

Longitude: 122.16

Elevation: 1080 m

Aspect: SW

Slope: 20 to 50%

Landform: concave pediment backslope

Soil Parent Material: alluvium-colluvium from andesite and volcanic ash

Soil: Dystrochrepts, Tidbits Series

Plant Association: Pseudotsuga menziesii/Acer circinatum/ Whipplea modesta

Age Class: old-growth

Soils:

The soil profile at one soil pit was described and sampled (see profile no. 94 in the HJA Soils Data Base). It is made up of very dark brown gravelly silt loam over dark brown gravelly loam. The surface soil contains 30% gravels and the subsoil 20-30% gravels. The soil is moderately deep (70 cm to saprolite) and well drained. Bulk density was 0.9 g/cc in the A1 horizon and 1.0 g/cc in the B2. Organic matter content was measured at 7.4% in the A1 and 1.8% in the B2.

General Stand Description:

This stand appears to be seral to the typical TSHE- ABAM/LIBO association as described by Dyrness et al. (1974). The youth of this community is shown by the dense, old Pseudotsuga menziesii overstory and the size-class distribution of all trees. The stand is exemplary of the PSME/ACCI/WHMO community because of the high cover of Acer circinatum and Berberis nervosa and the exclusion of Rhododendron macrophyllum. Most characteristic species of all strata are present and abundant, with the exception of Whipplea modesta.

The tree canopy is dominated by a dense stand of old Pseudotsuga menziesii over immature size classes of dense Tsuga heterophylla.

The tall shrub layer is dominated by Acer circinatum which covers over half of the reference stand. Tsuga heterophylla follows in importance in the tall shrub layer. Low shrubs are dominated by Berberis nervosa. Other shrub species have low cover and low frequency.

The herb layer is well developed. Patches of Linnaea borealis, clumps of Polystichum munitum, and several other species are frequent. Mosses are generally lacking.

Stand Structure and Composition

Live Tree Data at Last Measurement

Basal Area: 92.4 m²/ha
PSME-91.1 m²/ha
Stem Numbers: 332/ha
PSME-228/ha
TSHE-100/ha
Diameter Distribution:
median-51.4 cm
quadratic mean-59.5 cm
maximum-128.5 cm
Age: not available
Height (measurements within the last 20 years): not available
Volume: 1399.5 m³/ha
PSME-1388.6 m³/ha
Biomass: 802.5 Mg/ha
PSME-797.3 Mg/ha

Coarse Woody Debris (measured in 1982):

The total volume and mass of logs is 472 m³/ha and 104 Mg/ha, respectively. The volume and mass of standing dead trees (snags) is 111 m³/ha and 36 Mg/ha, respectively.

Ecosystem and Population Dynamics (measurements for most recent interval, 1992-1998)

Net Bole Production: 7.0 Mg/ha/yr

Annual Mortality: 5.7 Mg/ha/yr

Percent of Trees Dying: 1.3%/yr

PSME-1.7%/yr