Rayless goldfields (Lasthenia glaberrima) COSEWIC assessment and status report 2000: chapter 8

Limiting Factors and Threats

Trampling

Trampling and related activities present a major threat to Lasthenia glaberrima. The sole Canadian occurrence is adjacent to a hiking trail and footprints have been observed among the plants during the critical growing season in April and May and in 2005, six of the twenty plants were crushed by trampling. The Capital Regional Parks Department established a fence around the vernal pool in September 2005 which will probably reduce casual damage but may attract undesirable attention of some hikers.

Threats associated with invasive alien plants

A number of alien plant species have invaded existing and potential habitat for Lasthenia glaberrima. These include several invasive grasses: creeping bentgrass (Agrostis stolonifera), water meadow-foxtail (Alopecurus geniculatus), sweet vernalgrass (Anthoxanthum odoratum), annual bluegrass (Poa annua), forbs hairy cat’s-ear (Hypochaeris radicata), and sheep sorrel (Rumex acetosella). Invasive shrubs such as Scotch broom (Cytisus scoparius) are unable to establish on the microsite occupied by Lasthenia glaberrima but can root in adjacent pockets of deep soil and shade out the small patches.

Grazing

There are no long-term data on grazing damage but grazing removed some or all of the heads from eight of twenty plants in 2005 and two of twenty-one plants in 2006.

Habitat loss

Habitat loss has been the leading factor in the disappearance of suitable habitat. Much of the suitable shoreline in the Victoria Metropolitan Area was developed and most of this development (primarily residential and industrial) occurred before 2003, when Lasthenia glaberrima was first discovered in Canada.

Demographic collapse

The single Canadian population of Lasthenia glaberrima is threatened simply by its small size and very small area of occurrence. This predisposes it to extirpation through chance events that would not pose a risk to larger or more extensive populations.

Threat associated with altered hydrological regimes

Lasthenia glaberrima is dependant upon winter and spring seepage. Any actions that disrupt the hydrological regime may eliminate this essential process.

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