Branched phacelia (Phacelia ramosissima) COSEWIC assessment and status report: chapter 5

Habitat

Habitat requirements

Phacelia ramosissima populations in British Columbia are found in the Bunchgrass Biogeoclimatic Zone of southern British Columbia. This area, particularly in the southern Okanagan Valley, has a cold, semi-arid steppe climate.  Summers are hot and dry with mean July temperatures around 20°C. Precipitation is low with mean annual rainfall of about 300 mm. Growing seasons are relatively short with mean monthly temperatures falling below freezing from December to February in the valley bottoms.

In Canada, the speciesis restricted to extremely dry talus slopes at the base of usually, but not always, calcareous cliffs and rock outcrops (Figure 6). These sites, at elevations of 396 to 900 m, receive little moisture after early summer thus this species reaches senescence by mid-summer. Vegetation on these sites is often sparse due to the harsh conditions. Associated species include Achillea millefolium, Bromus tectorum, Eriogonum heracleoides var. angustifolium, Phacelia hastata var. hastata, Thelypodium laciniatum var. laciniatum and Toxicodendron radicans.In California, where the species is more widespread and is present as several varieties, var. ramosissima, the variant that is also found in British Columbia, is found in diverse habitats--slopes, ridges, washes and meadows at elevations between 100 and 2800 m (Hickman 1993).

Trends

The Bunchgrass Zone occupies less that one percent of the total area of British Columbia and is one of the most populated and developed areas in the British Columbia interior (Ministry of Forests 1998). In general, trends for natural habitats in the Okanagan Valley have shown a marked decline during recent years due to various land developments. The South Okanaganis currently experiencing the fastest population increase in the province (Nature Trust 2003). According to Environment Canada (2003), the population of the Regional District of the Okanagan-Similkameen increased by 18% between 1991 and 2002, to almost 81,000 people. In addition, the town of Osoyoos has seen a population increase of over 22% between 1986 and 1996, making it the fastest growing municipality in the South Okanagan -Similkameen Regional District (Town of Osoyoos 2003).

Figure 6. Phacelia ramosissima habitat on the east slopes of Mount Kruger. Mining activity (at top of left image) is within a few metres of Phacelia ramosissima habitat. Phacelia ramosissima plants occur (in the right image) at the base of this rock outcrop. Photos by Shyanne Smith 2003.

Figure 6. Phacelia ramosissima habitat on the east slopes of Mount Kruger. Mining activity (at top of left image) is within a few metres of Phacelia ramosissima habitat. Phacelia ramosissima plants occur (in the right image) at the base of this rock outcrop.

Considerable development in the Osoyoos area is currently occurring on the east slopes of Mount Kruger, above downtown Osoyoos. Natural habitat has been appropriated in favour of mineral exploration and golf course, housing and industrial development. All of these, with the exception of golf course development, have destroyed Phacelia ramosissimasites as well as other potential rare species habitat (Figure 7).

Figure 7. New housing development on east slope of Mount Kruger. Mining exploration activity (reddish and whitish talus, in colour images of the site) is evident on slopes in the background. Two subpopulations, now extirpated, were at the exploration area and on a home site just to the right of the photo. Photo by Shyanne Smith 2003.

Figure 7. New housing development on east slope of MountKruger. Mining exploration activity (reddish and whitish talus, in colour images of the site) is evident on slopes in the background. Two subpopulations, now extirpated, were at the exploration area and on a home site just to the right of the photo.

Protection/ownership

The population on the west slope of Mount Kruger, as well as one of the east slope subpopulations, is located in the South Okanagan Grasslands Protected Area. This area receives protection under the Provincial Parks Act. Three additional sub-populations are located on Crown land on the east slopes of Mount Kruger. Much of this area is covered by active mineral claims. A Wildlife Habitat AreaFootnote2 is currently under consideration for part of the east slope of Mount Kruger (J. Hobbs, pers. comm.). This would provide protection for the latter three subpopulations on the east slope of the mountain. The remaining five extant subpopulations (as well as the two extirpated subpopulations) on the east slope of Mount Kruger and the north slope population are on private land (Figure 4).

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