Many travelers to Northeast Siberia return with fond memories
of the young chosenia groves they have seen. These riverside
communities that harbor many showy
flowering herbs stand out brightly against the otherwise monotonous
background of the Siberian taiga. But even more impressive are groves
of mature chosenias
with their colossal trees, whose size is unusual not only for Yakutia, the coldest place
on the continent of Eurasia, but even for lushly productive regions, such as Manchuria.
The floodplain groves miraculously emerge on lifeless river pebbles in just some
10–12 years; the entire transformation from tiny chosenia seedlings on bare
pebbles to majestic sixty-feet trees on fertile soil normally takes place in just
60–70 years! By then, the organic mass accumulation in chosenia stands reaches
record amounts, which any other most productive kinds of the taiga forest may yield only in
150–200 years.
Chosenia arbutifolia (Pall.) A. Skv., one of the
fastest-growing trees
of Northeast Asia, is closely related to the willows. It has often been
mistaken for a large willow even by experienced botanists.
However, a close look at its catkins and flowers reveals clear differences
from the willows. The nectaries or glands (structures
that are found in any willow flower) are missing in the chosenia
flowers; the stamens,
pistils, and bracts look different from both the willow and poplar
flower structures.
The chosenia staminate flower has five stamens hiding under the bract and
connate with it in the lower filaments; the pistillate flower
has two styles, each with
a two-cleft stigma. Like poplars, chosenia is wind pollinated,
whereas all of the willows are insect pollinated.
These peculiarities alone provided enough grounds
for botanists to
place chosenia in its own, monotypic (single-species) genus.
But the list of this tree's interesting traits is not yet exhausted. Chosenia also
surprises us with very distinctive root system featuring the taproot (none of
the willows possess this kind of a "carrot") along with unique
anchoring structures. Its
wood has a very unusual anatomic character:
the so-called homogeneous rays.
Chosenia's leaves are also quite special.
Like the xeromorphic (water-saving) leaves of the primitive
Turanga poplars
and the primitive willows of the Section
Longifoliae, they are somewhat fleshy and
covered with bluish
bloom, especially on young trees. This pruinose bloom also covers
the tender young
twigs, which gives chosenias their peculiar habit
(Fig.
1). The twigs remain barkless
for a few years and
contribute to the photosynthesis along with the leaves.
Later they develop brownish
bark, which darkens with age. Old chosenias attain a
captivating habit with their bark
(Fig.
2)
exfoliating much like
that of shagbark hickory (
Carya ovata),
but unlike any of the
willows (the bark of
Salix triandra also exfoliates,
but in a different pattern.)
Being strictly confined to a certain kind of habitat,
the sandy-pebbly deposits on banks of
mountain rivers, this tree, at the same time, has a huge geographic area ranging from
the subtropical broadleaf forests of Honshu to the ascetic tundras in Siberia (the
Anadyr River basin) and reaching along rivers beyond the Arctic Circle where no
other tree of such a magnitude can grow. The vast area of chosenia comprises a major
part of Siberian Russia east of Lake Baikal and the Lena River, the Russian Far East
including Sakhalin Island and the Kamchatka Peninsula, northeastern China,
northeastern North Korea; and
the Islands Hokkaido and Honshu of the Japanese archipelago.
(Fig.
3)
From sandals to telegraph poles
The peoples of Northeast Asia have long known, loved, and utilized
chosenia for all kinds of industries from sandal-, clog-, and rope-making to
fanza- and bridge-building. Chosenias have been used for making
dugout boats with displacement capacity of up to one ton. This fact alone gives
a sense of the impressive dimensions these trees can attain.
Among the northern reindeer breeders, chosenia is particularly valued as
forage. In the wintertime, the reindeer dig diligently under the snow
for fallen chosenia
leaves, which contain unusually high amounts of ash and therefore
serve as a calcium
supplement for the animals in winter.
The most ambitious commercial venture in which chosenia played a role
was a bold attempt in the 1860's by
the Western Union Telegraph Company
to build a telegraph
line connecting North America with Europe via the Bering Strait and Siberia.
However, when a competing
company succeded in dragging a telegraph cable across the Atlantic,
the Western Union gave up the
entire project, and after several years of hard work
the indefatigable leader of the Siberian expedition, George Kennan,
had to abandon thousands of telegraph poles already prepared with
great difficulty along the proposed telegraph line.
Many of those poles were trunks of
chosenia, which Kennan apparently considered to be a kind of
large willow or poplar. At the Lower Anadyr he indeed
could hardly find any material suitable for the poles other
than chosenia trees. By
the time the construction was canceled, this remarkable man had
bravely surveyed the
wildest and most remote regions of Northeast Siberia, notorious for
their extremely harsh
climate and very sparsely inhabited by nomadic tribes.
A new name for the old friend
No wonder that Kennan mistook chosenias for willows: Russian settlers
of the Kamchatka
Peninsula, where chosenia grows abundantly, have always called the tree
vetla (a tree willow). Topol
(poplar), its
other Russian name, is used in Northeast Siberia (whereas real poplars are called
'aspens' there.) The Yakuts have called it tiryakh, which is also
their name for a poplar (Populus suaveolens) that often
grows in mixed groves with chosenia; for willows they have a different word,
talakh. Chosenia's colloquial names also include:
seiakhta and sikhta (respectively, in Nanayan
and Udegeyan—languages of some of the small nations in the Far East);
leo-mo and zhuantianliu—Chinese
names; kesho-yanagi (the beautiful willow) and
karafuto-kuroyanagi (Sakhalin black willow)—the names
used in Japan. The confusion about this tree's identity lasted well
beyond the time of the
telegraph project. By the beginning of the 20th century chosenia had
been observed by botanists multiple times. However,
some mistakenly took it for a willow
species familiar to them, others described it as yet another, new willow. No one
realized that the proliferating names all referred to a single species.
The Japanese botanist Takenoshin Nakai once again "discovered" a strange new willow in
Korea in 1918 (at the very beginning of his encounter with the tree, from 1911 to 1918,
he also had taken it for another willow familiar to him). By 1920, he gradually came to
the conclusion that he was dealing with something that wasn't quite a willow. He proudly
introduced the tree to the scientific world as a new genus of the
Salicaceae Family:
Chosenia. The discovery of a
new genus in such a well-known family produced a sensation in the botanical field!
Educated Russians started to call the tree
koreyanka, a Russian
translation of the name
Chosenia, which literally means
'an inhabitant of Korea' (however, this name didn't take
and was gradually supplanted by the
international 'chosenia'). Nakai did not identify his finding with many of the
scientific names
(Fig.
4) previously given to the tree. It
took nearly forty years to completely clear up the lasting confusion: identify chosenia
with its existing synonym names and choose the correct species epithet according to
priority considerations.
The start: The first three hurdles
Let's now take a closer look at the tiny chosenia seedlings
and the intricate path they must follow to
survive and develop into majestic trees. At the very beginning of its life this
remarkable plant depends completely upon the water flow and sediment accumulation that
occurs in river floodplains. The Far East is famous for its unusual
floods—severe, abrupt, and overwhelming, sometimes even catastrophic. They
occur in summer rather than in spring, usually two or three times during the
season. As the snow melts on the hills and mountains
(
sopka's), it adds to the pouring rains brought by the summer
monsoon. These rains turn each river into a powerful stream that soon leaves its bed
and fills the entire floodplain. Near the bottom of the riverbed, the wate is filled
with great number of drifting pebbles that originate in the upper reaches.
The amount of pebbles
dragged by the water is enormous: the noise they produce sometimes becomes so loud
that a person talking at the streamside can't hear his own voice. Each
flood forms fresh pebble deposits
(Fig.
5) along river banks and may cause
the river to meander, that is, change its direction.
During late July–early August (often
immediately following a summer flood) chosenia trees disseminate their abundant
minute seeds, each as light as 0.25 mg, bearing a crown of white hair.
The seeds cover the entire surface of the water,
crowd the banks, and accumulate along the water edge. It is mostly on
newly deposited pebbles, that they succeed to develop into seedlings. The seeds
germinate right away, and multitudes of seedlings appear on bare moist
pebbles at the edge of the
flowing water. Due to the favorable conditions for germination along the water edge,
entire stripes of chosenia seedlings of different generations are formed along banks of
meandering rivers—and the older the plants, the more faraway from the water
they are located. The young chosenia seedling is tiny: only one centimeter tall.
The root,
however, extends down as deep as 3–4 cm between the pebbles.
(Fig.
6) Most of these little plants do not
survive the next following flood. However, those that manage to hang on at least for a
month become so firmly anchored amidst the pebbles that you cannot pull or even dig them out
without breaking the root.
During the second year, the primary shoot dies back, and another shoot,
larger than the first, starts
growing. By the end of the second growing season, this new shoot becomes prostrate, with
just the very tip ascending from the pebbles. Finally it also dies off
giving way to
three or four virgate (long and flexible) shoots during the third summer.
These new shoots
still hide from severe floods by lying flat on the pebbles,
and the entire plant now
attains a habit of a prostrate rosette.
(Fig.
7,
8,
9)
Self-serving a nice layer cake
Juvenile chosenia leaves are somewhat different from those of the adult tree: they
appear to be even more succulent, that is, fleshy, juicy, and covered with pruinose
bloom, as if they were leaves of some desert species. There is nothing
strange about this resemblance, since during
the periods of drought between floods the bare pebbles around the young plants
may become as hot as 50° C
(120° F).
It is only during its third and fourth years that chosenia gradually abandons the
prostrate habit and starts to grow as an upright shrub.
(Fig.
10) By this time,
the young chosenia already finds itself
a few feet away from the flowing water edge. Of course, this happens due to the
river meandering rather than any movement of the plant. Yet another important process
contributes to "moving" the young chosenia plants away from the running water: their
vigorous long shoots, particularly the lower ones, become damaged during floods, but do
not fall off when dead, forming a thick brush-like network.
This brush functions very
much like whalebone catching efficiently alluvial material and
forming large sediment deposits around the tree.
The nourishing soil layer self-produced by chosenia for its own benefit may
grow as much as 30 cm or more during a single flood. The older the plant, the higher is
its position and the larger the distance from the edge of the open water, where it once
started its life. If you dig into the soil in an old chosenia grove,
you will find it to be layered
like a cake with each layer representing a single flood, its lower portion
consisting of coarse material and the upper parts containing fine particles.
The champion of the neighborhood
Every year the chosenia plants loose a large share of their branches. Young branches
are rather brittle and break off easily (which is not unusual in the Family
Salicaceae). During the summer floods,
many branches are scratched by moving
pebbles, but even more of them (up to half of all the branches) do not survive the
harsh winters. Anything that protrudes from the snow dies back,
if it is not consumed by moose
or reindeer. However, this huge die-back doesn't hinder the growth.
During its early
years, this amazing tree performs rather like a semi-shrub producing one
generation of branches after another. Every year the new growth becomes more
and more vigorous, and
the growth rate accelerates accordingly.
(Fig.
11) By the age of five, a young
chosenia may be adding up to a full meter to its height in a single season.
Around this time, the
sapling finally "realizes" that it is destined to develop into a majestic tree and
produces a leader with a crown of powerful virgate shoots around it, all densely
covered with thin and slender pruinose leaves. At this age the plant attains a habit
intermediate between a tree and a shrub.
A few years later, when the crowns of the young chosenias merge,
the trees start to thin out and
develop into a grove typically consisting of some 30 to 100 trees. The grove still
endures floods, but since the trees are now farther from the river,
the water flows much more slowly and deposits fine particles rather than heavy
pebbles. By the
age of eight to ten, the trees become 7–8 m tall, their stems 10–15
cm in diameter. The leader starts to dominate; the only traces of virgate branches,
which used to give the trees their shrub appearance, are dense brushes of dead wood at
the bottoms of stems.
(Fig.
12) These remnants continue to play their role
as alluvium traps during floods.
A grove of young chosenias with its open canopy and fertile alluvial soil produces a
quite showy plant community is brightened by abundant grasses,
flowering legumes, and other herbs. However, herbaceous species found in the chosenia
groves aren't specific for chosenia. These plants as well occur in willow, poplar or
any other riverine woods. Some of them have a much wider distribution than chosenia
and can be found even
outside the river valleys. In northern Yakutia, for example, the legumes found in
chosenia groves (species of
Astragalus,
Oxytropis, and
Hedysarum) are also widely distributed in sparse larch forests and mountain tundras.
Chosenia's period of intensive growth lasts until the trees become about 30 years old. By
then they normally attain heights of 25 to 30 m and trunk diameters
of almost half a meter. There
are records of chosenias as tall as 40 m and as thick as 1.5 m! The root system of an
adult tree consists of a central carrot-like taproot that extends as far as 3 m and
reaches the underground water table underneath the river bed. The entire
surface of the central root bears scars left by moving pebbles. Plenty
of thick and thin thread-like roots grow in all directions downward from the
"carrot." At the depth of 30–40 cm, adult trees develop special anchoring
structures: three to five horizontal appendages, each shaped like an anchor.
This system
stabililizes the tree in the most unstable environment. Adult chosenias
successfully stand up against the wind and the majority of severe floods.
The crown of a young adult tree growing in open space is pyramidal: the lower branches
grow at an angle of 60–70°
from the trunk
(Fig.
13), whereas the upper
branches grow at a much smaller angle. Crowns of adult chosenia growing in dense groups are
umbrella-shaped
(Fig.
14). During the wintertime, chosenia trees
drop the top tender portions of their branches. This may add to their ability to
conserve water in extreme winter conditions of Siberia. The deadwood brush at the
lower trunks persists for a long time, though it gradually looses its importance.
Mature chosenia groves are found as far as 50 to 100 m away from the riverbed and
occupy the central parts of the floodplain, which means they are situated
as high as 1.5 m above the water level.
Floods occur there only once or twice a year. It is dark and damp
underneath the canopy of a mature chosenia grove.
Only shade-loving grasses and herbs survive here.
The majestic trees aren't long-lived. They start to decline at the age of
70–80: first, the top dies back
(Fig.
15,
16) and then pieces of the trunk
start to break off from the top downward. Ugly outgrowths caused by bacterial attacks
replace the brush at the bottom of the trunk. On average, if a thirty-year-old grove
contains some 30 to 50 trees, then by the age of about one hundred there normally remain only
some three or five of them. These patriarchs stand as far as 150–200 m away
from the river and almost never experience floods. Poplar and larch trees tend to take
over and succeed the chosenia groves.
Cultivated chosenia: A different story
If we now glance at the entire chosenia life cycle in nature, we will notice that this
tree belongs to the type of plants that yield nice chunks of the environment to their
more competitive neighbors, thus restricting themselves to unfavorable, difficult
situations, where they, however, don't have to address competition. To be able to
survive in the harsh conditions of the bare pebble deposits, chosenia has developed
its very peculiar traits: a unique root system featuring a strong taproot along with
anchoring structures; a prostrate habit at the very tender age followed by semi-shrub
behavior for a few years; the succulent, water-saving foliage; the ability to collect
and reserve nutritious material for itself by means of
brush-like network of dead and broken lower branches.
Yet another distinctive character of chosenia is its plasticity, that is, the
ability to suppress many of the adaptations in case they are not needed. You don't have
to provide bare pebbles, Siberian winter temperatures, or harsh floods in order to grow
a chosenia. With adequate moisture, light, and good drainage, it will do well in an
average garden. When it does not have to meet the challenges of the life in
the wild, it demonstrates its unique abilities in a very subtle manner. In
cultivation it would start its life as a "normal" tree seedling. Though chosenia
seedlings easily become distorted, they never develop a truly prostrate habit and tend
to produce a few weak roots rather than one tap root. Their juvenile leaves don't look
much different from the leaves of adult trees. The tendency to cast branches is
rather pronounced even in cultivation; new generations of more and more vigorous
branches are produced yearly, though this ability never develops to such extremes that
the plant would perform as a semi-shrub. The shrub appearance isn't that much
characteristic of cultivated young chosenias, either: they tend to develop leaders and
start to grow as trees earlier than in the wild. Indeed, the most challenging part of
growing a chosenia in the garden is the propagation itself. Unlike most willows,
chosenias are difficult to be grown from cuttings. At the same time, the seeds loose
viability very quickly, thus leaving little hope for the propagation success when
the seed source is remote.
This narrative is based on the following literature:
Golysheva, M. D. 1973. [On the structure and formation of
the leaf in Chosenia arbutifolia (Pall.) A.
Skvorts.] — Bot. zhurn. 58 (12):
1764–1774.
Kennan, G. 1910.
Tent life in Siberia. A new account of
an old undertaking. Adventures among the Koraks and other tribes in Kamchatka
and northern Asia. Gutenberg eBook
Project. Release date: 12 May 2004.
Kolesnikov, B. P. 1937. [Chosenia and its communities in the
Far East.] — USSR Acad. Sci. Far East Branch Proc., ser. bot. 2: 704–800.
Makryi, T. V. and L. V. Bardunov 1977. [A finding of Chosenia
arbutifolia (Pall.) A. Skv. (Salicaceae) west of
the Baikalsky Mountain Range (Cis-Baikal Region.)]— Bot. zhurn. 62 (11)
1669–1671.
Mazurenko, M. T. and T.
A. Moskalyuk 1989. Ontogeny of Chosenia arbutifolia
(Salicaceae) in the Magadan Region.
— Bot. zhurn. 74 (5):
601–613.
Moskalyuk T. A. and
M. T. Mazurenko1992. [An
amazing northerner—chosenia.]—
Priroda 12: 52–59.
Norin, B. N. 1958. [Some characters of chosenia
communities (Chosenia macrolepis Ass.) at the extreme
northwest of their area.]— Bot. zhurn. 43 (6):
847–850.
Sheludyakova, V. A. 1943. [Chosenia in the Republic of
Yakutia.]— Bot. zhurn. 28 (1):
30–33.
Skvortsov, A. K. 1957. Commentationes de morphologia et
systematica salicarum. IV. [On the correct species epithet
for Chosenia.]
— Bot. mat. Gerb. Bot. in-ta AN SSSR 18: 42–47.
Trofimov, T. T. 1964. [Some interesting Far East plants in
the Moscow University Botanic Garden.]—
Bot. zhurn. 49 (11): 1563.
Yegorov, A. D. and V. B. Kuvayev 1958. [Chosenia
and broad-leaved fireweed—promising forage plants for the
reindeer.]— USSR Acad. Sci. Yakut Branch Reports 1: 92–95.
Irina Kadis
6 Feb 2005
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