Rayless goldfields (Lasthenia glaberrima) COSEWIC assessment and status report 2000: chapter 5

Habitat

Habitat requirements

Lasthenia glaberrima generally occurs in wet open places, often in muddy vernal pools or on muddy ground on perched water tables (Hitchcock et al. 1955, Peck 1941, Segotta pers. comm. 2004, Ornduff 1993). The single British Columbia site is a rock-bound vernal pool on a shoreline rocky bluff about 15 m above sea level. The vernal pool has a thin layer of medium-textured soil above gneissic bedrock. It begins to moisten with the first rains in late summer or early fall and remains saturated or inundated for long periods throughout the winter and early spring. The soil gradually dries out with the onset of summer drought and is quite dry from mid-June to late August or early September. Annual herbaceous species including water meadow-foxtail (Alopecurus geniculatus), large water-starwort (Callitriche heterophylla), rayless goldfields (Lasthenia glaberrima) and annual coastal plantain (Plantago bigelovii) dominate the site.

Habitat trends

The amount of potential habitat has declined greatly over the past century as coastal areas in southeast Vancouver Island have been developed for residential and recreational use.

Lasthenia glaberrima occurs in a rare type of vernal pool generally associated with Garry oak ecosystems, so the decline of these ecosystems provides an indirect measure of the loss of habitat for L. glaberrima. Overall, Garry oak systems have, over the past century, been reduced to less than 5% of their original extent in the Victoria area (Lea 2002). Garry oak ecosystems persist largely as isolated communities that are heavily fragmented and lack connections that would allow substantial genetic interchange. Lasthenia glaberrima appears to prefer shoreline sites, which are also sought for residential development, while Garry oak ecosystems are more broadly distributed, so the actual decline in suitable habitat is probably even higher.

Much of the remaining habitat suitable for Lasthenia glaberrima has been heavily altered due to invasion by alien weeds including several grasses and forbs.

The location of Lasthenia glaberrima in Canada lies at the heart of one of North America’s fastest growing regions. The population of metropolitan Victoria has increased from approximately 180,000 in 1966 to 318,000 in 1996 and is projected to increase to more than 400,000 by 2026. The Capital Regional Plan adopted in 1959 led to expansion into rural areas surrounding Victoria over the past 44 years and this pattern of expansion may continue in order to accommodate population increases (Capital Regional District 2003a). During past the 18 years, average prices for single family residences in Metropolitan Victoria have increased 330% from $94,000 to $313,000 in 2003, reflecting the pent-up demand for property (Capital Regional District 2003b). Since then, the average price has accelerated, climbing by about 50% to approximately $470,000 (Victoria Real Estate Board 2005). The most expensive and sought-after properties are ocean frontage, apparently the favoured habitat of Lasthenia glaberrima.

Habitat protection/ownership

The sole Canadian population occurs within East Sooke Regional Park. The Capital Regional District (CRD) has recently given the conservation and management of rare threatened and endangered plants and wildlife, and their supporting habitats, precedence over all other park uses (Capital Regional District Parks 2000). Despite its occurrence within a park, the population was subject to heavy trampling damage, at least until recently. In September 2005 Capital Regional District Parks established a fence around the population to protect it from visitor traffic.

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