. The Canadian field-naturalist. Natural history; Sciences naturelles. 166 The Canadian Field-Naturalist Vol. 120. '\; â -- '«t,. J«rjE' â¢^Jl Figure 3. Calcareous vernal pool habitat of Psilocarphus brevissimus van brevissimus south of Princeton, British Columbia. Colorado Rush (Juncus confusus), another rare species in British Columbia, is conspicuous on both sides of the dried- up vernal pool. The several large plants in the habitat are the introduced grass, American Sloughgrass {Beckmannia syzigachne). cultural Land Commission 2003*). On these lands, development pressures do not appear t
. The Canadian field-naturalist. Natural history; Sciences naturelles. 166 The Canadian Field-Naturalist Vol. 120. '\; â -- '«t,. J«rjE' â¢^Jl Figure 3. Calcareous vernal pool habitat of Psilocarphus brevissimus van brevissimus south of Princeton, British Columbia. Colorado Rush (Juncus confusus), another rare species in British Columbia, is conspicuous on both sides of the dried- up vernal pool. The several large plants in the habitat are the introduced grass, American Sloughgrass {Beckmannia syzigachne). cultural Land Commission 2003*). On these lands, development pressures do not appear to be an imme- diate issue at this time. The Agricultural Land Reserve status may prevent subdivision development, but does allow other activities that could also potentially threaten the populations. In recent years many tracts of Agri- cultural Land Reserve land in southern British Colum- bia has been converted to housing developments, shop- ping malls and golf courses, either by decisions of the Agricultural Land Commission or very rarely by an "order in council" by the sitting provincial legislature. Another threat likely to have a negative impact is recreational off-road vehicle use. The authors observed evidence of all-terrain vehicles and dirt bike use in the area of the sites in 2004. The vernal pools and ephemer- al pond edges are wet in spring and are susceptible to permanent changes if disturbed at this. An additional threat to the population of P. brevis- simus var. brevissimus is its vulnerability to extirpation due to the extremely small occupied area and popula- tion size. Such small populations are at risk of inbreed- ing depression (Primack 1998). Due to lack of genetic variation, these small populations are vulnerable to demographic and environmental variation. Further- more, suitable habitats for P. brevissimus var. brevis- simus in the southern interior of British Columbia are extremely limited and thus opportunities for coloni- sation are al
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