Trial Island Overview: Physical and Biological

Posted July 15, 1998 | Categories : 132,Oil Spill Threat,Rare Species,Reports,Species List |
 ORIGINAL PURPOSE: To protect the most outstanding known assemblage of rare and endangered plant species in British Columbia
Access: Landing on the islands is restricted to protect sensitive plants and ecosystems. A permit is required to access the reserve.
Accessible by boat, but no docking facilities.
See the complete PDF from BC PARKS: Trial Islands ER 132
Physical:  The reserve comprises parts of two elongate rocky islands and associated islets. Marine waters are not included. Shorelines on the southwest side are mostly steep and dissected but the rest of the shoreline is gently sloping with a few small pocket beaches, comprised mostly of gravel. The islands are of considerable interest for the interpretation of local and regional geology, being situated at or adjacent to a major suture between two crustal blocks, the Leach River Complex and Wrangellia Terrane. Soil cover is thin and incomplete on much of the island, consisting mostly of Brunisols lying on bedrock. Small areas of Regosolic soils and considerable exposed bedrock are present. The climatic regime here is the mildest in the province, and characterized by frequent wind and summer drought.
Twenty-eight species of vascular plants listed as rare in British Columbia are
present in the reserve, 15 of which are in the categories of greatest rarity in the
province. The latter are mostly plants of a more southerly distribution, centred in northern California and in Oregon, and are at or near the northern limit of their range in the Victoria area. Many were once scattered along the Victoria waterfront prior to urbanization but are now found in only a few sites outside of the Trial Islands.
Shallow soils, summer drought and strong winds combine to prevent tree growth on these islands. Plant communities consist of herbaceous meadows, shrub thickets and sparse growth of lichens and other plants on bedrock.
Nine plant communities have been described. Two are dominated by lichens growing on bedrock, but contain other dry-site plants like stonecrops and a few species tolerant of salt spray. A community characterized by dune wildrye and  beach pea occurs on gravel beaches and among driftwood. A small area of salt  marsh contains salt-tolerant plants like Pacific glasswort, seashore saltgrass, Nutka alkaligrass and sea plantain. Four meadow communities occur on upland sites having the best soil development. The most important of these, a vernal pool community characterized by Bigelow’s plantain and Scouler’s popcornflower, contains 13 species of rare plants. Other meadow communities support showy stands of spring wildflowers such as common camas, death-camas, chocolate lily, shootingstar, sea blush, Hooker’s onion and blue-eyed Mary. Dense, wind-pruned
shrub thickets are dominated by Garry oak, aspen, snowberry and rose.One glaucous-winged gull nest has been reported, but the island is not a significant seabird site. A turkey vulture nest was found in the early part of the century (mid- 2000s) but it has not been occupied since. Terrestrial birds and mammals have not been surveyed.
Cultural: The reserve encompasses a traditional First Nations and Songhees bulb harvesting site. There are no known archaeological sites on the islands.
The island has been the site for a lighthouse for over a century.
MANAGEMENT CONCERNS See the PDF above for the COSEWIC listed species
SIGNIFICANT SPECIES: The first 13 are red-listed species.
Western Meadowlark (Georgia Depression population)
Common Ringlet, ssp.insulana
Carolina meadow-foxtail
golden paintbrush
Macoun’s meadow-foam
dense-flowered lupine
seaside birds-foot trefoil
snake-root sanicle
purple sanicle
creeping wildrye
rosy owl-clover
Garry oak-California brome association
coastal Scouler’s catchfly
Victoria’s owl-clover
The following  are blue listed species
banded cord-moss
white-top aster
Nuttall’s quillwort
Henderson’s checker-mallow
pigmyweed (Crassula aquatica)
seashore lupine
dwarf montia
chocolate lily
dune bluegrass
Garry oak

Hooker’s Onion

Hooker’s onion
Climate Change:
Raised sea levels may reduce the habitat area protected in the reserve and increased storm intensity and frequency may degrade
the habitat. Other climatic factors such as warmer temperatures and increased annual precipitation may alter the community
composition on the islands.
Non-native species:
Aggressive invasive Scotch broom, English Ivy, and Gorse are
present in reserve.
Trampling of extremely rare plant species and micro habitats occurs.
Presence of marine vessels and kayaks disrupts marine mammal and bird behaviour.

Threat of oil spill due to tanker traffic and cargo ships

alkaligrass, Pacific (Puccinella nutkaensis)
aspen, trembling (Populus tremuloides)
aster, white-top (Aster curtus)
blue-eyed Mary, small-flowered (Collinisia parviflora)
bluegrass, dune (Poa macrantha)
brome, California (Bromus carinatus)
camas, common (Camassia quamash)
catchfly,coastal Scouler’s (Silene scoulerissp.grandis)
chaffweed (Anagallis minima)
checker-mallow, Henderson’s (Sidalcea hendersonii)
cord-moss, banded (Entosthodon fascicularis)
death-camas, meadow (Zigadenus venenosus)
glasswort, American (Sarcocornia pacifica)
lily, chocolate (Fritillaria affinis var.affinis)
lupine, dense-flowered (Lupinus densiflorus)
lupine, seashore (Lupinus littoralis)
meadow-foam, Macoun’s (Limnanthes macounii)
meadow-foxtail, Carolina (Alopecurus carolinianus)
montia, dwarf (Montia dichotoma)
oak, Garry (Quercus garryana)
onion, Hooker’s (Allium acuminatum)
owl-clover, rosy (Orthocarpus bracteosus)
owl-clover, Victoria (Castilleja victoriae)
paintbrush, golden (Castilleja levisecta)
pea, beach (Lathyrus japonicusvar. maritimus)
pigmyweed (Crassula aquatica)
plantain, Bigelow’s (Plantago bigelovii)
plantain, sea (Plantago maritima ssp.juncoides)
popcornflower, Scouler’s (Plagiobothrys scouleri)
quillwort, Nuttall’s (Isoetes nuttallii)
saltgrass, seashore (Distichlis spicata)
sanicle, purple (Sanicula bipinnatifida)
sanicle, snake-root (Sanicula arctopoides)
sea blush (Plectritis congesta)
shootingstar, broad-leaved (Dodecatheon hendersonii ssp.hendersonii)
snowberry, common (Symphoricarpos albus)
trefoil, seaside birds-foot (Lotus formosissimus)
wildrye, creeping (Leymus triticoides)
wildrye, dune (Leymus mollis ssp. mollis)
Gull, Glaucous-winged (Larus glaucescens)
Meadowlark, Western , Georgia Depression population (Stumella neglectapop. 1)
Ringlet, Common, ssp. insulana (Coenonympha tulliassp.insulana)
Vulture, Turkey (Cathartes aura)