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BEN # 220
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No. 220 April 7, 1999
aceska@freenet.victoria.bc.ca Victoria, B.C.
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Dr. A. Ceska, P.O.Box 8546, Victoria, B.C. Canada V8W 3S2
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PLANT DIVERSITY IN BARKLEY SOUND [Part 1 of 3]
From: Martin L. Cody <mlcody@ucla.edu>
THE TOPOGRAPHICAL AND HISTORICAL SCENE
About one-third of the way up the outer coast of Vancouver
Island, British Columbia, Barkley Sound is a 35 km2 indentation
dotted with hundreds of tiny to moderately-sized islands, with
several of the larger over 1 km2 in area. The most isolated
islands comprise the Broken Group in the center of the Sound,
and are up to about 20 km from "mainland" Vancouver Island. All
are continental or landbridge islands, representing hilltops
isolated with rising late-Pleistocene sea-levels (e.g. Dawson
1992); from marine charts showing channel depths, the oldest of
the present-day islands date from ca. 12,000 yBP, although many
(with shallow channel depths of a few meters) are much younger.
Very low-lying islands will have re-emerged relatively recently,
as continued coastal uplift has dropped relative sea level 3-4m
from maximum rise some 6-7,000 yBP (Friele & Hutchinson 1993).
Island substrates are uniformly rocky, composed of mixed Ter-
tiary volcanics and metamorphics (Muller 1983, Yorath 1995);
their shores generally rocky, often steep, with a few sandy and
many mud/cobble beaches. Most islands are in pristine condition;
those in the Broken Group are part of Pacific Rim National Park
and several support camping beaches; others are variously
private, First Nations, or Crown land. Being exposed and rela-
tively low-lying, the islands are generally dry with shallow
soils, and fresh water seeps reaching the beach only on islands
>105 m2 in area. The climate (at Bamfield, s. edge of the Sound)
is wet maritime, ave. 2950 mm of precipitation/y, but only ca.
10% of the annual total falls in the three summer months Jun-
Aug.
Diversity, distribution, dispersal and population dynamics of
plant species in from forest to shoreline have been the subject
of biogeographic and ecological studies since 1981. Plant sur-
veys on islands in Barkley Sound have continued up to 1997, with
ten summer seasons spent in the area (Cody 1992a,b, 1998; Cody &
Overton 1996). To date, some 210 islands have been surveyed,
many of these repeatedly, often in adjacent or subadjacent
years. Surveyed islands cover a size range of about 6 orders of
magnitude, and the largest samples sizes are in the range 102-
104 m2; nearly 40% of the sample islands are in the center of
the Sound, the remainder closer to the mainland (Vancouver
Island) coast. All surveyed islands have been accurately mapped
by transit at the Fucus line and by elevational contours at 1,
2, 5, 10, 20 and 50 m intervals, with coverage of the major
vegetation types superimposed.
THE FLORA: VEGETATION, DIVERSITY AND DISTRIBUTION
The vegetation of the mainland coastal areas and over much of
the larger islands is Coastal Coniferous Forest (Klinka et al.
1989, Pojar & MacKinnon 1994; for floristics, I follow Hitchcock
& Cronquist 1973). The forests are dominated by Red Cedar (Thuja
plicata), Sitka Spruce (Picea sitchensis), and Western Hemlock
(Tsuga heterophylla), with occasional firs (Abies grandis, A.
amabilis), alders (Alnus rubra), and maples (Acer macrophyllum,
A. douglasii). On the islands (only) Douglas fir (Pseudotsuga
menziesii) is common, coast pines (Pinus contorta) are found on
all shorelines, with Western White pine (P. monticola) on the
edges of bogs. The forest understory is composed of mostly
ericaceous shrubs such as Arctostaphylos, Gaultheria, Menziesia,
and Vaccinium species, ferns, and a few geophytes (Maianthemum,
Goodyera, Listera) and forbs (Tiarella, Boykinia). Around the
interior forests on islands are concentric rings of first woody
shrubs (many Rosaceae, some Caprifoliaceae), second a zone of
largely weedy herbaceous, mostly perennial forbs of a wide
variety of taxonomic affinities (especially Asteraceae, some
Brassicaceae, Onagraceae, Fabaceae), and lastly a shoreline
flora of plants specific to rocky shores or sandy, muddy or
cobble beaches, many of cosmopolitan distribution.
The flora of the islands is essentially that of the adjacent
mainland, since most habitats, even coastal marsh fragments and
tiny island bogs, are represented; it currently totals around
300 plant species. Some adjacent mainland species are absent on
the islands, mostly wetland species typical of shallow inlets
(e.g. Jaumea carnosa, Lilaeopsis occidentalis), extensive sandy
beaches (Franseria chamissonis, Carex macrocephala), larger bogs
(e.g. Vaccinium alaskense, V. uliginosum, Botrychium sp.), many
other freshwater aquatics (e.g. Lysichiton americanum, Carex
spp.), and weedy plants, often aliens, typical of roadsides and
settlements (e.g. Senecio vulgaris, Medicago, Vicia spp. among
others).
But the islands support additional plant species that are rarely
or never seen on the immediately adjacent mainland, such as
Douglas-fir, manzanita (Arctostaphylos columbianum) and other
plants more typical of the inner and drier (NE) coast of Van-
couver Island, and additionally various shoreline, rock and
cliff plants (e.g. Baeria maritima, Cochlearia officinalis,
Carex pansa). Other notable island records include Carex
gmelinii, present on a single cluster of islands at the outer
edge of the Sound.
The largest islands support around 125 plant species, with
species numbers declining with area in the classical manner. The
larger islands in Barkley Sound (logA[rea] > 4.25) fit the same
regression line:
logSPP = 0.661 + 0.241*logA (r**2 = 0.764, p <.001),
regardless of isolation. This would indicate that their species
numbers (and composition) reflect a pre-isolation state typical
of supersaturated non-equilibrial landbridge islands, largely
uninfluenced by colonization. Variation in species composition
among these islands suggests two lines of enquiry:
1. some species persist only on less isolated islands, where
they may be retained by a rescue effect via ongoing
colonization;
2. some species occur on island groups by dint of historical
legacy. For example, two plant species, Carex gmelinii and
Streptopus amplexifolius, have been found on just three
islands, mutual neighbors in the Deer Group which (from
channel depths) have shared a common branch of the island
"phylogeny" for ca. 10,000 y.
Joint occurrence of species on islands for reasons independent
of similar area (incidence) have been systematically evaluated
for rescue and historical legacy influences.
On the other hand, small-island groups have species-area curves
that differ as a function of isolation distance, with lower
species numbers on more distant islands; their differences in
diversity, per area, are attributable therefore to differences
in the rates of on-going colonization.
[Continuation in BEN # 221]
RE: PROMINENT BOTANIST-BRYOLOGIST COURT-MARTIALED
[Benito Tan, a BEN subscriber, posted my note about Archibald
Menzies on the bryological discussion list BRYONET-L. This
posting triggered an interesting discussion on the role of Dr.
Archibald Menzies as a bryologist. I am using two replies
originally posted on BRYONET-L. - AC]
From: David Long <D.Long@rbge.org.uk>
In Edinburgh we have Menzies' own cryptogamic herbarium which is
one of the most meticulously prepared collections I have seen.
He was clearly an extremely eagle-eyed and careful collector and
searched hard for sporophytes in the field, and most of his
liverworts bear sporophytes. Of course he sent duplicates to
William Hooker in Glasgow who published most of the novelties;
these holotypes are now in BM (ex K), but the isotypes he kept
in his own herbarium are in pristine condition and one of our
most prized assets in Edinburgh. The specimens are mounted on
small sheets with the data (scanty but usually with place, year
and 'AM') on the reverse. Menzies also received many duplicates
from James Dickson, Swartz, Schleicher, Schwaegrichen and other
contemporaries and was not just a good collector but a serious
student of cryptogams.
Further information on Archibald Menzies is to be found in:
Balfour, F.R.S. 1945. Archibald Menzies 1754-1842. Proc. Linn.
Soc. London 156: 170-183.
Haber, E. 1985. The type locality for Menzies' collection of
Pyrola picta, P. dentata, and P. aphylla from the northwest
coast of North America. Taxon 34: 462-463.
Galloway, D.J. & E.W. Groves. 1987. Archibald Menzies MD, FLS
(1754-1842), aspects of his life, travels and collections.
Archives of Nat. Hist 14: 3-43.
Naish, J. 1989. Archibald Menzies: Surgeon and Botanist. Int.
Dendrol. Soc. Year Book 1988: 123-128.
From: Allan Fife <FifeA@landcare.cri.nz>
There are two other references that those with an interest in
Menzies might wish to consult:
Galloway, D.J. 1995. The extra-European lichen collections of
Archibald Menzies, M.D. FLS (1754-1842). Edinb. J. Bot. 52
(2): 95-139.
Godley, E.J. 1960. A note on Archibald Menzies. Trans. Roy Soc.
New Zealand 88: 63-64.
CORRECTION: SPRING GATHERING TO REMEMBER CHESS LYONS
The spring gathering to remember Chess Lyons (see BEN # 212)
will take place on Sunday, April 11, 1999 at Freeman King Nature
House, in GOLDSTREAM PROVINCIAL PARK from 2:00 to 4:00 p.m., NOT
in "Freeman-King Park," as previously stated.
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