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BEN # 111
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No. 111 August 26, 1995
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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THE DECLINE OF PACIFIC MADRONE: SYMPOSIUM SYNOPSIS
From: Clement W. Hamilton and Paul West c/o <pwest@eskimo.com>
[Copyrighted material released with the authors' permission for
posting on BEN.]
The past several years has seen increasing interest, on the part
of the horticultural public as well as landscape professionals,
in the health of the Pacific madrone, Arbutus menziesii. Several
general trends -- such as the desire for more broad-leaved
evergreens in urban landscapes, the growing appreciation of
native plants of ornamental and ecological value, and ever
augmented plant-physiological stress due to urbanization --
converge on the madrone. People are almost unanimous in their
praise of the tree's desirability for urban landscapes, and also
unanimously puzzled about what might be causing its decline in
urban areas of the Pacific Northwest.
The symposium on "The Decline of Pacific Madrone: current
theories and research directions" was held at the University of
Washington Center for Urban Horticulture April 28, 1995. About
200 researchers, professionals, and interested citizens gathered
to share their knowledge and perspectives. They sought to deter-
mine whether any common understandings could be reached and what
future research might be of greatest help to the madrone. Two
questions underlay the twelve presentations and ensuing discus-
sions: 1) What are the nature and causes of the decline of
Arbutus menziesii in urban environments of the Pacific
Northwest? and 2) How can the madrone be propagated, restored,
and managed in urban landscapes?
This symposium was initiated by a group of Seattle community
activists who had been witnessing the gradual demise of many
formerly handsome madrones along Magnolia Bluff. In 1994, they
won special funding to determine how to reverse this decline as
mitigation for the West Point sewage treatment plant at nearby
Discovery Park. Save Magnolia's Madronas, as they called them-
selves, recognized that the madrone's decline was widespread
throughout the Seattle area, and that research was needed to
better under stand the causes of decline.
At the beginning of the symposium, Christopher Chappell and
Gregory Ettl spoke of the natural context of the madrone, Chap-
pell noting the apparent importance of fire in the establishment
and persistence of plant associations in which madrone
predominates. Fairly dry, sunny sites with shallow, well drained
soil seem to be prime madrone habitat.
Richard Hunt considered that a particular growth characteristic
of the madrone actually may accelerate its decline. When the
tree becomes stressed, it flowers more prolifically, an evolu-
tionary strategy to continue its lineage despite its possibly
impending death. That excessive flowering, however, detracts
from the resources to put into new terminal shoot growth, and
the tree produces fewer new leaves. As flowering increases and
leaf production declines, the tree may begin to lack the vigor
necessary t o defend itself against the canker-causing diseases
described by Hunt and by Ralph Byther.
Dana Bressette and Clement Hamilton have been sampling in-
dividual madrone trees west of the Cascades, recording site
conditions and grading tree health. Their preliminary results
suggest that two characteristics correlate with decline: tall,
single-stemmed growth habit and thin bark. This implicates
exposure of the stem as a primary causative factor. Bressette
noted also that she witnessed bark exfoliation more often on
south sides of samples, possibly implicating sun exposure as a
direct cause of decline. Their observations complement a model
of stand decline that A.B. Adams has proposed. He noted that the
trees studied in the landscaped area of Magnolia Bluff exhibited
more dieback and canker than do the trees in the natural setting
of nearby Thorn dyke Park. This led him to posit a positive
feedback process whereby the disturbance and exposure caused by
landscape development causes a stress response in the tree, such
as exfoliation of the bark. This may then predispose the tree to
infection by pathogens, which accelerates the decline. As the
tree canopy dies back and individual trees are lost, the ex-
posure of the stand further increases, thus augmenting the
potential for general decline.
Trees are dying, but these are typically remnant trees of former
forest stands that have not been able to adjust to changes --
usually clearing -- in the environment around them. In contrast,
young, vigorous madrone trees can be seen growing up along
highways, in parking lot medians, and in other stressful urban
situations. It appears, therefore, that madrones can thrive in a
wider variety of conditions than found in its usual habitat, if
they are established as juveniles within those same growing
conditions. Madrones have been witnessed growing at the edges of
wetlands, in irrigated turf, and under closed conifer canopy,
for instance. This perspective holds promise that madrones can
find new niches in many parts of the urban landscape.
This hope is fueled by great evidence that madrones can be
readily propagated from seed. The work of Ray Maleike, Rita
Hummel, Diana Privett, and Rico Gonzclez indicates that con-
tainer production is within reach using standard nursery prac-
tices. Another challenge is transferring the plants from the
nursery into the landscape. Thus far, the work of Hummel,
Privett, Gonzclez, and Tony Shoffner has focused on establishing
1- to 3-gallon sized material. Because madrone exhibits sen-
sitivity to transplanting, smaller material offers more im-
mediate potential. Working with small material presents special
challenges to the landscape manager, however, requiring extra
protection in environments with heavy traffic, careful monitor-
ing for pests (notably slugs and root weevil), and allowing the
juvenile bushy habit and low branching to prevail in order to
protect the trunk. The challenge does not end with establishment
of the trees, as Phil Coker points out; proper arboricultural
treatment depends on understanding the physiology of mature
trees.
At the close of the symposium, participants discussed over
twenty areas of research that could benefit madrones in the
future, among them the following: 1) systematic study of the
canker-causing organisms; 2) genetic study of disease resis-
tance, coupled with a program of selecting, propagating, and
introducing desirable plants; 3) exploring the possible sig-
nificance of mycorrhizal associations; 4) trial plantings in
different types of urban site; 5) determining the size and area
of minimum viable populations in urban greenbelts; and 6) com-
parative study of different approaches to pruning and other
arboricultural practices.
Seldom does one plant species, outside of agriculture or produc-
tion forestry, arouse such a high degree of concern as has
Arbutus menziesii. The contributors to this volume hope that
their work has helped lay a significant foundation for a heal-
thier future for the Pacific madrone.
Proceedings from the symposium will be published this fall and
will be available from the Center for Urban Horticulture,
University of Washington GF-15, Seattle WA 98195, for $15 US.
CAREX PRAIREA IN MONTANA
From: Toby Spribille
</S=T.SPRIBILLE/OU1=R01F14D03A@mhs-fswa.attmail.com>
The recent exploration of the calcareous wetlands in the Tobacco
Valley in northwest Montana has resulted in numerous new records
for the region and an interesting overview of bryophyte diver-
sity in an otherwise poorly-known area. One of the most sig-
nificant finds to date is the discovery of Carex prairea Dewey
in two marl fens near the village of Trego in the northern
Salish Mountains. This species is very rare in the west, and is
present in British Columbia only in the Fraser Plateau region.
Phytogeographically, it can be regarded as a northeast North
American element at its western periphery; its discovery in
northwest Montana represents a range extension south from
central B.C. and west from the northern Great Plains.
The plant was first brought to my attention by Jack Triepke, a
botanist on the Fortine Ranger District, who collected it in a
large marl fen/Betula glandulosa carr. It was subsequently
collected in another fen in the vicinity. At the latter site it
was the dominant cover, forming extensive hummocks with Carex
gynocrates. The seeping water had a pH of 7.2.
In addition to the Carex, many other rare or infrequent species
were discovered in the second fen. These include the mosses
Scorpidium cossoni, Meesia triquetra and Catascopium nigritum
and the rare lichen Cetraria sepincola, known from only a hand-
ful of collections south of the Canadian border. It was found to
be locally common on twigs of Betula glandulosa.
Voucher specimens of Carex prairea: MONTANA; FLATHEAD CO.:
Collins Fen, Lime Creek, 25. July 1995, J. Triepke FJT025;
Magnesia Creek, abundant in rich fen, 21. June 1995,
Spribille 3355; same location, 1. Aug. 1995, Spribille
3902; specimens to be deposited at COLO, MICH, MONTU.
ALIEN SPECIES IN HAWAII - DATABASE OF DATA SOURCES
From: Philip A. Thomas - National Biological Service
Haleakala Field Station <halesci@hawaii.edu>
I am working on a project sponsored by the Research Corporation
of the University of Hawaii to compile a database of sources of
information RE: alien species in Hawaii. I would be very inter-
ested to hear from anyone who has any kind of data on alien
species (plants, animals, etc.) which occur in Hawaii. Data can
be field notes, electronic databases, incidental or spatial
observations, etc. I would appreciate any information.
Please respond to me directly with a brief description of the
data that you have/know about, or if you would like further
details about this project.
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