BEN # 105
Adolf Ceska
aceska at CUE.BC.CA
Fri Jul 7 09:26:18 EST 1995
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No. 105 July 7, 1995
aceska at 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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IDENTITY CRISIS: DO WE REALLY KNOW WHAT WE WANT TO REHABILITATE?
From: Dr. Hans Roemer <hroemer at galaxy.gov.bc.ca>
This article is based on an illustrated presentation given at
the Garry Oak Grassland Rehabilitation Symposium, June 10, 1995.
When we speak about rehabilitating Garry oak grassland most of
us will automatically equate this with restoring this ecosystem
to its original, natural state. The assumption is made that we
know with some accuracy what this original state was. Unfor-
tunately this is not the case for much of this ecosystem.
Another assumption is, as the word "restore" implies, that it is
possible to return to this original state. Indications are that
this, too, is unrealistic.
A more appropriate title for this contribution would therefore
be "Where are we coming from and where are we going?", both in
terms of species combination for the Garry oak grasslands.
Garry oak communities may be grouped into two broad complexes,
one associated with the dry core area, and another with the less
dry periphery of their occurrence (compare p. 21/22, Proceed-
ings, Garry Oak Meadow Colloquium, 1993). While we know
reasonably well what the original species combination of the
peripheral complex was, the same cannot be said about the core
area complex. The latter communities coincide with the urbanized
area of southern Vancouver Island and their present herb/grass
layers are now occupied by so many alien species that we don't
know of which species the matrix was composed from which taller
plants such as camas emerged. There are now no mass-forming
native grasses and herbs in the meadow component of these com-
munities, especially among the smaller, annual species. A pos-
sible exception is Festuca megalura (Vulpia myurus ssp. hirsuta)
which, however, is not a constant component. James Douglas
reported in 1842 that "several varieties of red clover grow in
the rich, moist bottoms...". If we ignore the "moist bottoms" of
this quote, these could be interpreted to be the native Tri-
folium tridentatum, T. oliganthum and T. variegatum, all annuals
which may well have formed continuous stands, although they are
now absent or only scattered in communities of the Garry oak
core area.
Another open question with significance for both the past and
the future composition of Garry oak communities pertains to the
presence or absence of shrub layers. It is quite possible that
high ungulate populations and the native peoples' practice of
setting grass fires combined to gradually eliminate shrub
layers. Will these shrub layers, presumably dominated by Sym-
phoricarpos albus, gradually re-invade the grassy areas, now
that both fires and ungulate browsing have ceased?
Table 1 addresses the problem of non-native species in the
herb/grass layers. It is arranged to show native species above,
and non- native species below the horizontal dividing line.
Higher constancies of both native and non-native species are
shown closer to the line than lower constancies. The herb/grass
layers of eighteen plots from Roemer (1972) are shown averaged
in the first column (bold). The other columns represent in-
dividual releves, recorded in May, 1995. Locations for these
releves were chosen subjectively to represent the highest den-
sities of camas. All plots are representative of the core area
which is increasingly influenced by the urban environment of
greater Victoria. One great camas (Camassia leichtlinii) meadow
and one common camas (Camassia quamash) meadow is described by a
releve in each of three localities.
While the average number of native species in the 1972 plots
still exceeded the number of non-natives (13:11), the total
number of native species in the entire table is now smaller than
that of the non-native species (30:35). Table 2 summarizes
native/non-native counts for table 1. The proportion of native
species ranges from a disconcerting low of 24% to a high of 60%
(for the only sample outside of the urbanized area). When cover
values are used for the calculation, the proportion of native to
non-native species is even lower. Taking into account that the
18 samples of 1972 already represented the most "urbanized" part
of that data set, it is of even more concern that the percent-
ages in comparable 1995 samples (#3 t o #8) are still lower. In
addition, the sampled stands are likely among the least dis-
turbed of the remaining communities as they were selected on the
basis of showing optimal Camassia displays. With other words,
most parts of these remaining Garry oak communities may have
considerably fewer native plants.
There appear to be no significant differences in the native/non-
native proportions between common camas and great camas meadows,
although more extensive sampling would be desirable to confirm
this. However, there are different kinds of grasses and herbs
that tend to invade the two types of meadows. The shallow,
exposed soils of common camas meadows are more conducive to
annuals, while the deeper, often sheltered and shaded sites of
great camas meadows are increasingly occupied by perennial and
taller European meadow species.
Some non-native grasses, notably the small annuals, are rela-
tively benign and allow most native plants to co-exist with
them. Others, such as orchard grass (Dactylis glomerata), are in
the long run capable of smothering much of the native flora,
including camas and white fawn lily (Erythronium).
Concluding, it may be said that -
--- Introduced species are now dominating the herb/grass layer
of the Garry oak ecosystem in its dry and urbanized core
area. The proportion of non-native species appears to have
increased over the last two decades and appears to be
highest in the most fragmented and "urbanized" remnants of
the ecosystem.
--- There is considerable uncertainty which species formed the
bulk of the herb/grass layer in the Garry oak communities of
what is now the urban and suburban area of Victoria.
--- The status of shrub layers, principally of snowberry, is
equally uncertain and it appears possible in the absence of
fire and grazing that shrubs may gradually invade the meadow
component of Garry oak communities.
--- Scotch broom invasions are not our only alien-plant problem,
though it is one of the worst. By introducing additional
nitrogen, Scotch broom may allow secondary invasion of
nitrophilous species such as orchard grass.
--- A return to the original species combination is highly
unlikely. We must therefore be prepared to accept com-
promises and manage for near-natural and/or attractive
combinations such as oak-camas or oak-fawnlily-shootingstar,
combined with the non-native element. Examples of such
combinations maintained over long periods are available in
the region.
--- Experimentation with different management and restoration
methods including reintroductions must be encouraged.
--- We must strive to maintain Garry oak reserves as large as
possible and as distant as possible from the urbanized areas
which are the ultimate sources of disturbance and non-native
species.
--- Systematic monitoring of further shifts in native/non-native
species combinations should be established.
References:
Douglas, J. 1842. Report to McLaughlin, July 12, 1842. Cited in
Founding of Victoria, The Beaver, Outfit 273. March 1943,
p.4-9.
Hebda, R.J. and Fran Aitkens (eds.) 1993. Garry Oak Meadow
Colloquium, Victoria, 1993.
Roemer, H.L. 1972. Forest Vegetation and Environments on the
Saanich Peninsula,Vancouver Island. Unpublished PhD dis-
sertation, University of Victoria.
Table 1.
SPECIES COMBINATION OF CAMAS MEADOWS IN THE VICTORIA AREA
1970-sample (18 plots)
: Woodsend
: : Knockan Hill -great
: : : Christmas Hill -common
: : : : Christmas Hill -great
: : : : : Beacon Hill -great
: : : : : : Knockan Hill
: : : : : : : -common
: : : : : : : Beacon Hill
: : : : : : : : -common
v v v v v v v v
1 2 3 4 5 6 7 8
---------------------------------------------------
Orthocarpus pusillus 1
Vicia americana 1
Orobanche uniflora r
Cerastium arvense +
Delphinium menziesii +
Lotus micranthus 1
Triteleia hyacinthina +
Perideridia gairdneri r
Collinsia parviflora +
Poa canbyi +
Fritillaria lanceolata +
Lomatium nudicaule r
Nemophila parviflora +
Erythronium oregonum +
Lupinus bicolor 2
Luzula campestris +
Sisyrichium douglasii r
Trifolium oliganthum +
Agrostis exarata 3
Brodiaea coronaria + +
Montia perfoliata 1 r
Dodecatheon henders. 1 r
Achillea millefolium + +
Elymus glaucus 1 r 1
Lomatium utriculatum 2 1 2 +
Ranunculus occidentalis + 1 + +
Bromus carinatus 1 + 2 2
Sanicula crassicaulis + + 1 2 r
Camassia leichtlinii 3 + 3 3 5
Camassia quamash 4 1 3 + 4 4
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Festuca bromoides 1 4 5 1 3 1 5
Vicia sativa + 3 3 2 + 1 1
Bromus hordeaceus + 2 1 2 4 4 2
Bromus sterilis 3 2 5 4 1
Geranium molle 1 1 1 2 +
Galium aparine 2 1 3 +
Vicia hirsuta + + + 2
Bromus rigidus 2 1 + 2
Anthoxanthum odoratum 2 3 3 3
Hypochaeris radicata 2 1 1 2
Cytisus scoparius 3 1 3 +
Poa pratensis 2 3 3
Stellaria media + + 2
Rumex acetosella 3 1 +
Veronica arvensis r 1
Dactylis glomerata 2 4
Cynosurus echinatus + +
Holcus lanatus + +
Lolium perenne 2 2
Medicago lupulina 3 1
Plantago lanceolata 2 1
Poa bulbosa 1 2
Festuca megalura 2 2
Cynosurus cristatus 3
Bromus tectorum 3
Teesdalia nudicaulis 2
Agropyron repens 3
Aira praecox 2
Aira caryophyllea 2
Moenchia erecta +
Bellis perennis +
Agrostis gigantea 1
Trifolium pratense 1
Lathyrus latifolius r
Daucus carota +
Table 2.
REMAINING NATIVE SPECIES IN CAMAS MEADOWS OF THE VICTORIA AREA
Meadow samples total no. of % no. % cover
no. of native native native
species species species species
-------------------------------------------------------------
1970 sample (18 plots)/1 24 (avg.) 13 54% 36%
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Woodsend Drive 20 12 60% 41%
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Knockan Hill - great c. 14 6 43% 25%
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Christmas Hill - common c. 9 4 44% 18%
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Beacon Hill - great c. 21 8 38% 27%
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Christmas Hill - great c. 16 5 31% 31%
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Knockan Hill - common c. 20 6 30% 30%
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Beacon Hill - common c. 17 4 24% 27%
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/1 averages representing releve set #1 in Roemer, H.L. (1972)
Forest Vegetation of the Saanich Peninsula; tree cover
omitted.
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