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International Dendrological Research Institute

Vegetation Profile of a Douglas Fir

Douglas fir (Pseudotsuga menziesii, 1) - Grand fir (Abies grandis, 2) - Western hemlock (Tsuga heterophylla) - Western red-cedar (Thuja plicata, 3) forest in the Pacific Northwest of North America.

LOCATION (Map p. 23; Climate diagrams p. 52): Olympic National Park, Mt. Olympus (highest point 2428m =7965'), Washington State, USA with a transitional Mediterranean-oceanic type climate (tempered by the warm North-Pacific- and the cool California currents) which here varies from the coast to the rain-shadow of the mountain, from very humid (Aberdeen: 9ºC, 2600mm*) to less humid (Vancouver: l0ºC, 1000mm. Seattle: l0ºC, 864mm). with a short or distinct dry period in the summer in the lower altitudes, to the most humid regions of the continent with almost 3700mm (12') on the higher western slopes of Mt. Olympus**.

Acer circinatum

Acer macrophyllum

Alnus rhombifolia

Sample area: near. Rt. 101 and Port Angeles; alt. 150m (study date: Aug 25, 1997); cool temperate rain forest often profuse in epiphytic lichens (Usnea) and mosses*** associated with the long pendent Selaginella oregano and S. girgensohnii.

Gaultheria shallon

Linnea borealis

Mahonia nervosa

Description of the sample area: The forest is dominated here by 3-4 coniferous species (as above) or, with Sitka spruce (Picea Sitchensis), up to 5, with trunks l.5-2m or more across (rarely to 4m) and a canopy typically reaching 50-60m (A1/a layer). Only the Oregon or Bigleaf maple (Acer macrophyllum) competes here with the conifers, still restricted to a lower layer (A1/b). The low, decumbent Vine maple (Acer circinaturn), the only "Japanese maple" (sect. Palmatum) of America dominates the lower tree (A2) layer to such an extent that it largely replaces the shrub (B1) level; other Asian ties in these forests includes Devils-club (Oplopanax horridus), a close relative of O. japonicus.

Oplopanax

Polystichum munitum

Rhamnus purshiana

The lower shrub layer is poor with scattered patches of the "polycormon"-developing Salal (Gaultheria shallon) a western "Wintergreen" or Partridgeberry and the "Asian spirited" Oregon-grape (Mahonia nervosa) with long, pinnate leaves, terminal, fascicled racemes and creeping stem. The herbaceous layer is ruled by the woody-stemmed evergreen, Western Swordfern (Polystichum munitum), more bulky than the Eastern Swordfern (P. acrostichoides). In raised mossy patches near the trunks, the small creeping circumpolar subshrub, Twinflower (Linnaea borealis), forms a carpet. The moss (D) layer is rich and completely covers the forest floor and fallen "nurse" trunks with the abundant conspicuous lichens Lobaria oregano and L. pulmonaria.

Vaccinium parviflorum

Plant list with percentage of coverage:

A/la (upper tree layer; 100%( ****):

Pseudotsuga menziesii 25-37.5%,
Abies grandis 25-37.5%,
Tsuga heterophylla 25-37.5%,
Thuja plicata 12.5-25%;

A/1b (upper tree layer l0%):

Acer macrophyllum l5-12.5%,
Alnus rhombifolia 0.25%;

A2(lower tree layer; 70%):

Acer circinatum 62.5-75%,
Rhamnus purshiana 0.25%;

B1 (upper shrub layer; 15%):

Taxus brevifolia 0.25%,
Oplopanax horridus 5-12.5%,
Oemleria =Osmaronia cerasiformis 0.25%;

B2 (lower shrub layer; 20%):

Mahonia nervosa 1-5%,
Gaultheria shallon 5-12.5%,
Vaccinium parviflorum 1-5%,
Rubus idaeus 0.25-1%;

C (herbaceous and subshrub layer; 90%):

Polystichum munitum 75-87.5%,
Linnaea borealis 1-5% (up to 37.5-50%),
Blechnum spicant 1-5%,
Pteridium aquilinum 0.25-1%,
Dryopteris filix-femina 1-5%,
Oenanthe sarmentosa 0.25 1%,
Adenocaulon bicolor 0.25-1%,
Galium bifolium 0.25%,
Tiarella trifoliata 0.25%,
Asarum sp. 0.25%,
Oxalis oregana 0.25-1%,
Maianthemum dilatatum 0.25-l%,
Luzula sp. 0.25%,
Disporum hookeri 0.25%,
Achlys triphylla 0.25-1%,
etc., a total of 28 higher plant species;

D (Moss layer; 100%).