Cliff paintbrush (Castilleja rupicola) COSEWIC assessment and status report: chapter 7

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Habitat

• Habitat requirements
• Trends
• Protection/ownership

Habitat requirements

Castilleja rupicola was found between 2030 and 2170 m elevation in the subalpine and alpine zones of the Skagit River drainage in the writers’ 2003 survey (Figure 4). Elevations for collections previously made in British Columbia range from 1830 to 2300 m. Climatic conditions in this region are coastal, characterized by mild or occasionally warm, dry summers, a short growing season and wet winters with abundant snowfall.

The populations of C. rupicola occur in the Alpine Tundra (AT) and Mountain Hemlock Parkland (MHmmp) biogeoclimatic zones (Meidinger and Pojar 1991) or alpine and subalpine zones sensu Krajina (1969), Douglas (1971, 1972), Douglas and Bliss (1977). The subalpine zone is defined as that area above the montane zone and below the upper limit of conifers as an upright tree form (Douglas 1972). The vegetation in this zone consists of a meadow/tree-clump complex (Douglas 1971, 1972). Above the subalpine zone, the alpine zone (commonly referred to as alpine tundra) has been described as an area where trees occur only in krummholz (dwarfed) form and the vegetation is extremely short, less than 1 m (Krajina 1969, Douglas 1972, Douglas and Bliss 1977). Coniferous trees, or krummholz, in the subalpine and alpine zone in the Skagit River drainage include the following species: Abies lasiocarpa, Larix lyallii, Picea engelmannii, Pinus albicaulis and Tsuga mertensiana.

Figure 4. Subalpine/alpine ridges on Marmot Mountain, Skagit River valley.

Photo S.J. Smith 2003.

Castilleja rupicola occurs on gravelly or stony soils, often in crevices on cliffs, rock outcrops and ridges (Figures figure4, figure5, and figure6). Vegetative cover is sparse (usually less than 10% cover) on these habitats. Associated species in these habitats include Antennaria lanata, Castilleja rhexifolia, Erigeron aureus, Penstemon davidsonii var. menziesii, Phlox diffusa, Potentilla villosa,Saxifraga bronchialis, Tonestus lyallii, Salix nivalis, Silene acaulis and Trisetum spicatum. On some subalpine and alpine slopes, C. rupicola occurs in gravelly openings in the Phyllodoce empetriformis/Cassiope mertensiana plant community (see Douglas 1972 and Douglas and Bliss 1977). The sites surveyed in 2003 were moderately steep (20 to 40% slope) with westerly aspects.

Trends

Habitat trends are probably stable at this time. However, if climate change predictions of higher global temperatures develop, it is possible that the subalpine/alpine habitats could be adversely affected. It is not possible at this time to predict what specific changes to the habitat would occur.

Figure 5. Typical rocky alpine habitat of Castilleja rupicola on Mount Brice in the Skagit River valley.

Photo by G.W. Douglas 2003.

Figure 6. Castilleja rupicola, in fruit (centre foreground), on Mount Brice, Skagit River valley.

Photo by G.W. Douglas 2003.

Protection/ownership

All populations of C. rupicola in British Columbia occur on Crown land. Three of the 12 extant sites (Finlayson Peak, Whitworth Peak, and Mount Brice) are located in Skagit Valley Provincial Park and receive protection through the Provincial Parks Act. Two other sites (Silvertip Mountain and Marmot Mountain) are within 500 m and 10 m, respectively, of the park boundary.