STAND DESCRIPTION

Plot Name: Reference Stand 17 (HJA)
Plot Size: 0.25 ha
Established: 1973
Remeasurements: 1976, 1981, 1986, 1992, 1998
Site Description
Latitude: 44.22
Longitude: 122.24
Elevation: 500 m
Aspect: NW
Slope: 20 to 40%
Landform: concave pediment footslope
Soil Parent Material: alluvium and colluvium from red breccia and andesite
Soil: Dystrochrepts, Frissell Series
Plant Association: Tsuga heterophylla/Rhododendron macrophyllum-Berberis nervosa
Age Class: Old-growth

Soils:

The soil profile at one pit was described and sampled (see profile no. 93 in the HJA Soils Data Base). The soil has a dark brown gravelly silt loam A1 horizon overlying a brown silty clay loam B2. The surface soil has about 45% gravel and shot content, while the subsoil layers range from 15 to 30% gravels and cobbles. Depth to a saprolitic C horizon averages 1 m. Bulk density averages 0.8 g/cc in the surface and 0.9 g/cc in the subsoil. Organic matter content was about 11% in the A and 2% in the B horizon.

General Stand Description:

RS 17 is a good representation of the TSHE/RHMA-BENE habitat type as described by Dyrness et al. (1974). However, it does appear to be slightly more moist and earlier in succession than average. Indicating a more mesic site is the deversity and abundance of herb species (Linnaea borealis cover is 26% and Oxalis oregana cover is >3%). Seral shrub species such as Acer circinatum, Cornus nuttallii, and Rhododendron macrophyllum indicate at least a slightly earlier successional stage.
The tree canopy is mature and dominated by several old- growth Pseudotsuga menziesii and abundant large Tsuga heterophylla and Thuja plicata. Tsuga heterophylla is the only abundant immature conifer in the understory of this mesic habitat type.
Tsuga heterophylla, Taxus brevifolia, and Acer circinatum dominat the well-developed tall shub layer. Rhododendron macrophyllum and Cornus nuttallii are also important. The low shrub layer is sparse, with Berberis nervosa being most important.
The herbaceous layer, dominated be Linnaea borealis, is unusually well-developed for this habitat type. Coptis laciniata and Oxalis oregana are also common. Mosses are abundant is RS 17 and are dominated by Eurhynchium oreganum; Hylocomium splendens is also common.
Stand Structure and Composition
Live Tree Data at Last Measurement
Coarse Woody Debris (measured in 1982):
Ecosystem and Population Dynamics (measurements for most recent interval, 1992-1998)
Net Bole Production: 1.8 Mg/ha/yr
Annual Mortality: 0.8 Mg/ha/yr
Percent of Trees Dying: total-1.0%/yr (42.9% were uprooted)