BEN # 245
aceska at victoria.tc.ca
Thu Mar 23 06:12:11 EST 2000
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No. 245 March 23, 2000
aceska at victoria.tc.ca Victoria, B.C.
Dr. A. Ceska, P.O.Box 8546, Victoria, B.C. Canada V8W 3S2
BEN issues 244, 245, and 246 are dedicated
to botanist and plant ecologist
DR. ARTHUR R. KRUCKEBERG,
Professor Emeritus of the University of Washington in Seattle,
on the occasion of his 80th birthday, March 21, 2000. His name
does epitomize the Pacific Northwest botany. All the best, Art!
[APOLOGIES: I am sorry I mispelled Dr. Richard Walker's name in
his article "Arthur R. Kruckeberg -- Active octogenarian" in the
last BEN. Dr. Walker is Professor Emeritus at the University of
Washington and a close colleague of Dr. Art Kruckeberg. I apolo-
gise to him and to the readers. - Adolf Ceska]
NATURE NOTES: A.R. KRUCKEBERG
From: Frank Lang <flang at cdsnet.net>
I spend a certain amount of time bring natural history to the
hoi poli via a weekly 3-4 minute radio spot on southern Oregon's
National Public Radio Station, Jefferson Public Radio. Subjects
vary from dust mites to Darlingtonia, and often include
vignettes of notable botanists. In 1990 I helped Art Kruckeberg
celebrate his retirement from the University of Washington. Ten
years later, Art is still very active and about to celebrate his
80th birthday. What follows is the script of that radio spot
broadcast 10 years ago.
"May 18, 1990, students, friends, and colleagues met at the
University of Washington to pay homage to one of the Pacific
Northwest's great outdoor botanists, Arthur R. Kruckeberg. The
event? His retirement, at the age of 70, from the University of
Washington after a distinguished career as an outstanding scien-
tist and teacher."
"Professor Kruckeberg is known to many of you as the author of
Gardening with Native Plants of the Pacific Northwest. Others of
you may know him as one of the world's leading authorities on
serpentine vegetation and flora. I knew him as my major profes-
sor while I was working on my Masters degree at the University
"His gardening book is a must for anyone interested in cultivat-
ing our native flora. The book is beautifully illustrated with
both color and black and white photographs and line drawings.
The introduction includes discussions of plant names, the his-
tory of gardening with Northwest plants, natural environments
including plant hardiness zones, and propagation techniques.
With few exceptions, transplanting whole plants from the wild is
discouraged. Grow from seeds, propagate from cuttings, or pur-
chase from a reputable native plant nursery, but don't plough up
the native habitat."
"For each species there is a discussion of ecology and distribu-
tion, distinguishing features and propagation methods with many
interesting facts woven into the very readable text. Professor
Kruckeberg's superb knowledge of the flora of the Pacific
Northwest and his love for plants shines throughout the book."
"Serpentine, to botanists, has nothing to do with snakes. It has
to do with a special soil type, that has an unusual mineral
composition, high in magnesium and heavy metals like iron and
sometimes chromium and cobalt and low in calcium. These unusual
conditions account for many of the unusual plant species of
southwest Oregon. For the past forty years, Art Kruckeberg's
continuing scientific investigations have done much to explain
the relationship between serpentine soils and their native
floras. I have my plant ecology students read his early paper on
the response of plants to serpentine as much for the simple,
elegant, experimental methods as the answers they provide."
"I pay homage to him for the privilege of having been his stu-
dent. What we are, as we progress through life, is the final
distillation of those who influence us in various ways. I am
grateful to the good professor for putting up with me through
good moments and bad, and for being largely responsible, draft
after thesis draft, for what meager writing skills I now pos-
sess. So I wish, for Arthur Kruckeberg, a long and fruitful
retirement. I don't know why I was surprised to learn that Art
was retiring at seventy. It was only 29 years ago that I was his
"For Nature Notes this is your host Frank Lang."
Now it has been 39 years since I was his student. I continue to
learn. Thanks, Art.
ART'S ROMANCE WITH SERPENTINES
From: "Robert G.Coleman" <coleman at pangea.stanford.edu>
Professor Art Kruckeberg's romance with serpentine has made
geologists realize that vegetation supported by this unique
substrate has a unique evolutionary history of survival in a
very hostile environment. Art has been a leader among a group of
botanists-biologists-chemists-geologists-pedologists that are
enhancing our knowledge of the strange flora found growing on
"serpentines". This short note will show why these serpentine
soils are so different and why they attracted Art's curiosity.
The Earth's mantle consists of peridotite (ultramafic rock) a
dense brownish to black rock consisting of ferromagnesian sili-
cate minerals. Continuous plate tectonic movements at the
Earth's surface incorporated small masses of peridotite into
continental margin sedimentary wedges. Peridotite instability in
the presence of water at low temperatures leads to its transfor-
mation into serpentine minerals producing a green, light, and
weak rock within the Earth's Crust. Serpentine rock has nearly
the same chemical composition as peridotite except that it
contains 13% H2O and is less dense. Serpentinization is usually
not complete and highly variable leading to a great range in its
physical appearance. Where there has been shearing, serpentine
rock displays highly polished greenish-black surfaces.
On the surface of the Earth's Crust, peridotite and serpentine
soils create a hostile environment for plants because of their
inherent lack of nutrients required for plant life and a chemi-
cal composition rarely found for the Earth's soils. Chemically,
serpentine soils developed in temperate climatic zones from
serpentinized mantle peridotites have a Ca/Mg less than 0.7 and
are extremely low in the essential nutrients Ca, K and P. Ni,
Cr, and Co are concentrated during soil and laterite formation
producing a toxic environment for certain plant species. Profes-
sor Hans Jenny referred to the strange soil composition as the
These high concentrations of chromium and nickel combined with
very low Ca/Mg ratio in serpentine soils gives rise to the
sparse vegetation having a unique floristic population. The
abiotic aspects of peridotite-serpentine evolution are unique.
Deep weathering of peridotite in tropical climates produces
nickel laterite, our main source of nickel. Economic chromite
concentrations are present in some peridotite and most of the
commercial asbestos fibers are extracted from serpentine-
peridotite rock. Ground water within peridotite-serpentine
assumes unique compositions high in magnesium bi-carbonate and
in some arid and semi-arid climates these waters exceed pH 11.5
as they become saturated with calcium hydroxide during near
Minor and trace elements in serpentine soils are concentrated in
some plants that have adapted to the toxic chemical elements.
Plants with concentrations of heavy metals greater than 1000 ppm
are referred to as hyper-accumulator plants. These hyper-
accumulator plants are of great interest to scientists trying to
understand environmental pollution or fundamental plant evolu-
tion. Serpentinized peridotites contain about 0.3% of NiO con-
centrated mainly in the olivine and less so in the pyroxene.
Nickel becomes available to plants by weathering of these sili-
cates in the soil horizons especially in humid tropical
climates. Many plants known to be hyperaccumulators of nickel
occur on serpentinized peridotites. The high concentration of Ni
in these hyperaccumulators is ideal for phytochemical studies
involving mineral exploration, agronomy, and biochemistry. Other
transition metals such as Co, Cr, Mn, and Cu are found in ser-
pentine endemic plants but do not reach the elevated concentra-
tions found for nickel. The phytoextraction of toxic metals in
contaminated areas has become an important new tool for environ-
mental remediation as a direct result of scientific studies on
Ni-hyper-accumulators found in serpentine areas.
Recognition of the biotic and abiotic uniqueness of peridotite-
serpentine tracts has prompted a worldwide agenda to preserve
them as ecological islands of great scientific value. Future
studies could well focus on the microbiotic populations to learn
of their adaptation to serpentine soils. Genetic studies on the
serpentine endemic plants may provide answers to plant adapta-
tion in hostile environments.
GOLDFIELDS IN THE WORLD OF SERPENTINE
From: Nishanta Rajakaruna <nishanta at interchange.ubc.ca>
I first became aware of plant life on serpentine soils in my
second year as an undergraduate at College of the Atlantic,
Maine when I wrote a term paper on the evolutionary ecology of
plants on serpentine soils. That was when I first heard of Dr.
Art Kruckeberg. In a short period of time I became completely
fascinated with life on serpentine soils and the abundant oppor-
tunities these habitats may provide to study plant ecology,
evolution, and physiology. Five years after writing the term
paper on serpentine ecology I came in contact with Dr. Bruce
Bohm at the University of British Columbia in Vancouver, B.C.,
who promised me an opportunity to get my hands dirty in the
My research, which began about five years ago, has been directed
towards using goldfields, Lasthenia californica Lindley (As-
teraceae) as a model system to understand the process of specia-
tion under edaphic influence (Rajakaruna & Bohm, 1999). Las-
thenia californica is the most widely distributed of the 17
species of this mostly Californian genus. Studies of L. califor-
nica have indicated the existence of two distinct races. I have
documented strong edaphic preferences by the two races (A and
C); they are physiologically differentiated, notably in their
sodium physiology and root growth. Race A plants have the
capacity to accumulate sodium to levels found in halophytes and
have much larger root:shoot ratios than race C plants.
The physiological adaptations of race A plants possibly play a
key role in the initial ecological isolation of the races.
Greenhouse studies have shown that race C is unable to survive
to reproductive maturity in the soils of race A plants. Although
the races are generally found in allopatry they occasionally
occur in sympatry. The largest known sympatric population is
found on a serpentine outcrop at the Jasper Ridge Biological
Preserve of Stanford University. Here, the races are restricted
to the upper and lower reaches of the outcrop and maintain a
sharp boundary that correlates well with changes in soil
chemistry. Surprisingly, the boundary has not changed con-
siderably in over 15 years.
Since Lasthenia plants are obligatory outcrossers and are pol-
linated by a variety of insects, there is opportunity for gene
exchange. However, field observations and greenhouse studies
showed that the races have reduced crossability. At Jasper
Ridge, the flowering times between the races differ by seven to
ten days. This phenology has been repeatedly confirmed in both
field observations and greenhouse studies. Apart from this
seemingly effective flowering time difference the races have a
limited capacity to cross. A breeding study, using seven popula-
tions from the species' range, revealed that races can in-
terbreed, but often with low seed production.
The sympatric races from Jasper Ridge have a very limited
capacity to cross (4-7% seed set in an inter-racial cross com-
pared to over 79% in an intra-racial cross). The level of cros-
sability between allopatric populations of the two races was
always higher than in the sympatric location. There are two
possible explanations for this result: 1) Jasper Ridge repre-
sents the point of most extreme divergence between the races.
Alternatively, 2) strength of reproductive isolation between
races may indicate that reinforcement of reproductive barriers
has occurred in this locality. Recent studies are showing that
the barrier to inter-racial crossability at Jasper Ridge may be
prezygotic where the pollen grains from one race are aborted on
the stigmas of the other race.
The research conducted so far has revealed some interesting
findings. The long-term study at Jasper Ridge is the first case
where population differentiation has been documented within a
serpentine outcrop. Our studies have also clearly documented
that serpentine soil within the same outcrop can be very
heterogeneous and that chemical and physical features can change
drastically along an elevational gradient. The finding of sodium
accumulation by a race growing on serpentine soils is also a new
finding. Our hypothesis that the sodium is used as an osmoticum
by race A, which dominates soils of extreme ion content will be
tested in the near future. If proven correct this will be one of
few studies to document a mechanism of adaptation to these harsh
Besides my studies of Lasthenia californica, I have had the
opportunity to visit four of the five serpentine outcrops in my
native Sri Lanka. I have compiled a list of 54 species for these
sites and have analyzed both the soils and the tissues of plants
growing there. This is the first study of the serpentine sites
in Sri Lanka. I have discovered three (possibly five) hyperac-
cumulators of nickel from these sites along with many other
plants of taxonomic and physiological interest.
The more I become involved in serpentine research the more I
understand why botanists like Art are so dedicated to the study
of serpentines. Serpentine outcrops offer so many puzzles and to
a keen botanist there will always be so many unanswered ques-
tions. I am sure Art has never got bored trekking the serpen-
tines of the Pacific Northwest and the rest of the world. It is
amazing to think of the wealth of knowledge he has accumulated
in his years of research, teaching, and keen observations.
I wish Art a very happy eightieth birthday and many more years
of good health. I feel extremely privileged to have been able to
write this very personal account in his honor. May his dedica-
tion and love for the world of serpentine inspire many others
like myself, now and for many more years to come.
Rajakaruna, N. & B.A. Bohm. 1999. The edaphic factor and pat-
terns of variation in Lasthenia californica (Asteraceae).
Amer. J. Bot. 86: 1576-1596.
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