BEN # 245

Adolf Ceska aceska at
Thu Mar 23 06:12:11 EST 2000

BBBBB    EEEEEE   NN   N             ISSN 1188-603X
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BBBBB    EEEEE    NN N N             BOTANICAL
BB   B   EE       NN  NN             ELECTRONIC
BBBBB    EEEEEE   NN   N             NEWS

No. 245                              March 23, 2000

aceska at                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]

From: Frank Lang <flang at>

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
of Washington."

"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.

From: "Robert G.Coleman" <coleman at>

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
"serpentine syndrome."

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
surface serpentinization.

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.

From: Nishanta Rajakaruna <nishanta at>

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
Californian serpentine.

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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