Ross Lake ER #22 Overview: Biological and Physical

Posted February 8, 2000 | Categories : 22,Reports,Species List |


To preserve an isolated population of ponderosa pines and other vegetation in a location transitional between coastal and interior climates

Physical: The reserve is situated on the lower slopes of Mount Hozameen, Cascade Mountains, on the east side of the Skagit River valley. Adjacent peaks rise to about 2000 m. The reserve has a westerly aspect and average slope of 25 to 30%. Surficial materials are largely colluvial, and several areas of bedrock outcrop occur. Annual precipitation is intermediate between that of the coast and the interior due to a partial rain-shadow caused by the Skagit River which lies to the west.

See the full PDF at Ross Lake ER 22

Biological: Of major interest here is the occurrence of ponderosa pine trees and associated dry-site plants in a semi-coastal environment. Southwestern exposure and rocky, well-drained soils, together with the reduced precipitation regime allow these species, which may be remnants of formerly more widespread dry forest in this area, to persist in a marginal environment. Ponderosa pine trees occupy a small central part of the reserve, and have an understory dominated by kinnikinnick and bluebunch wheatgrass. Douglas-fir forests cover most of the reserve, and associations having affinities with both coastal and interior zones have been noted. On dry sites a Douglas-fir-kinnikinnick-pinegrass association is present, while in mesic locations a Douglas-fir-Oregon-grape-moss association has developed. This contains typically coastal species such as vine maple, and interior ones like soopolallie. A typically coastal forest type, the western redcedar-devil’s club-foamflower-moss association occurs in moist gullies and seepage areas. Coastal trees like bigleaf maple and grand fir occur sporadically in this forest community.

The Skagit Valley also has a diverse bird and mammal fauna containing both coastal and interior species.

Significant Species:

silvery lupine
lace fern
steers head

Erynnis_propertius,Propertius duskywing photo by Ryan Batten.


devil’s club (Oplopanax horridus)
Douglas-fir (Pseudotsuga menziesii)
fir, grand (Abies grandis)
foamflower, three-leaved (Tiarella trifoliate var. trifoliata)
kinnikinnick (Arctostaphylos uva-ursi)

lupine, silvery (Lupinus argenteus var. laxiflorus)
maple, bigleaf (Acer macrophyllum)
maple, vine (Acer circinatum)
Oregon-grape, dull (Mahonia nervosa)

pine, ponderosa (Pinus ponderosa)
pinegrass (Calamagrostis rubescens)
redcedar, western (Thuja plicata)
soopolallie (Shepherdia canadensis)
steer’s head (Dicentra uniflora)
wheatgrass, bluebunch (Pseudoroegneria spicata)


Duskywing, Propertius (Erynnis propertius)