 Conference
1999
New Zealand Plants and their Story
The
Body Language of New Zealand Trees
David
Muir
Grounds Superintendent
Victoria University of Wellington
Private Bag 600, Wellington
Introduction
In November 1998 Dr.
Claus Mattheck of Germany visited New Zealand as a guest of the
New Zealand Arboricultural Association. He presented a three-day
seminar on "The Body Language of Trees", and the credit for much
of what I present to you today must be given to him.
Claus Mattheck is a physicist
with a deep interest in trees, and in particular the mechanical
engineering aspects of trees — what holds them up, and what
causes them to fail structurally and fall over. The message he brought
us last year opened our eyes and taught us a whole new way of observing
trees.
Over the past two decades
Claus has developed his Visual Tree Assessment (V.T.A.) method.
This teaches that trees show external symptoms of internal characteristics,
and just as doctors do with humans, we need to learn to read and
analyse the body language of a tree to know what is happening inside.
The symptoms show up mostly in the bark, so we learnt to "read the
bark". But they also show in the morphology or general shape or
visible structure of a tree.
A key feature of the
European research was the flow-on benefit of using it to predict,
in advance, structural failures in trees (or the potential risk
of same) and so enable remedial action to be taken before a crisis
occurred. Claus himself has become renowned as an expert witness
in the German Courts, giving evidence on tree matters (usually after
the crisis!).
The New Zealand link
Almost all the slides
Claus Mattheck showed us were of European deciduous trees —
oaks, elms, ash, chestnuts; and European beech, which have a particularly
expressive bark. And a limited range of conifers — pines and
spruces.
I never doubted the veracity
of Claus' findings in Europe; but I did begin to wonder if the range
of symptoms and clues that his trees showed, would automatically
show up in our native species. What about our conifers, for example,
that have excoricating bark that constantly flakes off? Would a
structural fault inside a fork of a miro show up after a few years
of shedding bark?
Indeed, there is an obvious
and understandable gap in Claus Matthecks research, simply because
he had never been to New Zealand before and never been exposed to
our native species. Perhaps someone should attempt to fill in the
gap?
I was interested in recording
on film all the body language I could find amongst our native trees,
so I began to take my camera everywhere.
Horticultural vs. Engineering
approach
Claus Mattheck is not
a horticulturalist; sometimes he was unable to identify the species
of tree he showed us in his slides. He presented his slides as a
mechanical engineer would — grouped according to the mechanical
or structural problem they illustrated. For example, shear fractures
all together; descending branches all together; fibre collapse all
together. He jumped from one species to another.
On the other hand, I
am not a mechanical engineer. I find that the first thing I do on
arrival at a tree site (and I believe most other horticulturalists
or arborists would do likewise) is to identify the species of the
tree I'm dealing with.
This is sometimes easier
said than done, especially in dense bush where foliage is intertwined,
and where one is squinting upwards against the light. So I am teaching
myself to identify from the bark and the trunk morphology, as much
as from the foliage or flowers of our native trees.
As an aside, I now realise
why noted academics such as John Salmon devote so much space in
their books to photographs of bark and tree trunks — knowledge
of them is an integral part of knowing the tree.
My experiences show me
that it is vital to correctly identify the native tree,
before reaching conclusions about its condition. I believe my slides
illustrate this point several times over, today. I am a confirmed
advocate of a horticultural approach to reading the body language
of trees.
I suspect we have a fundamental
flaw, in general terms, in our horticultural industry in this country
— we don't emphasise plant identification skills enough. Subsequently
our management of trees and shrubs is less than what it could be.
Work to Date
I have photographed over
300 native trees, covering some 35 species. Photographing and learning
to read the body language of New Zealand native trees is not as
simple as I imagined. I realise now that it was a little naïve
of myself to begin the task without expecting some complications.
Incidentally, the species
that have proven to be the most expressive and easiest to read have
been tawa, karaka, and puriri. I recommend these to beginners. The
trees that have been most pleasurable are the giant kauri of the
Coromandel.
All the common structural
weaknesses and faults that Claus Mattheck describes in European
trees can be identified in one or more of our native species.
In most cases this body
language is clear and unequivocal. But .
What is "normal"?
I have discovered that
there are certain patterns of body language that are a feature of
New Zealand trees, found repeatedly enough, and across a wide enough
range of species, that they could be described as "normal". That's
"normal" in the dictionary sense of the word, i.e., standard / usual
/ typical / natural / conforming.
These patterns cut across
genus and family lines. Some of them confirm Claus Mattheck's teachings;
but others, at first glance, appear to defy or even discredit some
of his ideas.
The questions that arise
are:
- Are these patterns
a result of something peculiar to New Zealand? Our windy climate?
A deficiency in our soils? The fact that our position on the Earth's
geomagnetic grid is different to Europe?
- Why do the patterns
show up in so many unrelated species? And why, within any one
species, are there always at least a few trees that don't conform
to the pattern and so suggest that it is not "normal"?
- If this body language
is normal in a New Zealand species, does it signify anything wrong
or faulty with the tree? Is there really a potential risk of structural
failure in such a tree?
- If this body language
is normal and natural, and the tree is structurally sound, how
can the tree manager distinguish between these characteristics
and those that Claus Mattheck teaches us are indicators of potential
biomechanical faults? Can both show up on a tree at the same time?
I shall be honest with
you and tell you that I do not know any of the answers. All I seem
to have done is uncovered the need for more research and scientific
analysis of our native trees.
Pattern One: Vertical
fluting
These are ridges, more-or-less
vertical, non-spiralling, running up and down the trunk.
They are not "branch
shadows" which are generally faint depressions found running vertically
below a major side branch. Sometimes the vertical fluting is literally
connected to a buttress root; but as yet I have not found a consistent
relationship in any species, between a buttress rooting habit and
a vertical fluting habit.
Species this pattern
is observed on:
Tawa
Pseudopanax
Karaka
Rewarewa
Puriri
Kohekohe
Pittosporum
tenuifolium/P. crassifolium
Hoheria
Pattern Two: Spiral
fluting
The crown of the tree
appears to be turning clockwise or anticlockwise, which results
in ridges of raised wood spirally around the trunk. Claus Mattheck
prescribed this sort of pattern to the effects of wind on a lop-sided
tree canopy. This is a remarkably frequent characteristic amongst
New Zealand trees.
In the vast majority
of all the species I have observed, the spiralling indicates the
crown is turning clockwise, when viewed from below and
looking up at the crown of the tree. So much so, that one could
speculate that clockwise is normal, and possibly caused by the Southern
Hemisphere gravitational pull. Thus, if an anticlockwise
turn is observed, the alarm bells should ring because it is not
normal and could indicate spiralling growth caused by wind pressure.
The complication with
this idea is that I have seen and photographed, within a 100 metre
diameter in Totara Reserve, Pohangina, a large Totara with a clockwise
spiral; one with an anticlockwise spiral; and one that is perfectly
vertical with no spiral! All in dense valley-bottom bush with a
consistent wind direction.
If spiral fluting is
normal in a species, it may be necessary to dissect a tree or two
to determine how the spiralling affects the structure and strength
of the tree. Remember that Claus Mattheck teaches that spiralling
indicates fractures caused by twisting or tearing by wind or some
other cause.
I have not yet seen both
clockwise and anticlockwise spiralling on the one tree — but
I'm keeping an open mind on the possibility.
Spiral fluting should
not be confused with distortions or bark patterns caused by constricting
vines: once again, these are always clockwise! All vines seem to
twine clockwise around themselves, too.
Species this pattern
is observed on:
| Clockwise:
|
Anticlockwise: |
| |
|
| Totara |
Totara |
| Pohutukawa |
Pohutukawa |
| Pseudopanax |
|
| Rimu |
|
| Melicytus |
|
| Ngaio |
|
| Kauri |
|
| Pittosporum
crassifolium |
|
Pattern Three: Horizontal
girdling wrinkles and/or colour bands
Horizontal wrinkling
is common; and varies a lot in severity and size between species.
I do not think it signifies fibre collapse, or if it does, it is
on such a small scale that it may not be structurally faulty. It
gives the impression that it is wrinkles in the bark alone, not
in the underlying wood.
I have only ever seen
three native trees in which I suspected fibre collapse of the type
Claus Mattheck illustrated: one tree each of karaka, Myrsine
australis, and Cordyline australis.
Colour banding is equally
common, but appears to be more frequent where a stem is shaded.
Some colourations are probably algae or similar, but possibly not
all. Why they are horizontally-aligned is not known.
Species the horizontal
wrinkles are observed on:
Tawa
Hebe
Kauri
Rewarewa
Totara —
usually seen just above the buttress roots, but sometimes in between
Hinau —
slight only
Myrsine australis
— slight only, except for one tree at Otari
Pseudopanax
Nothofagus
menziesii
Whau
Hoheria —
slight only, and always in conjunction with colour banding
Nikau
Pittosporum
tenuifolium
Phyllocladus
Weinmannia
Miro
Pattern Four: Warts
or lumps
Warts and lumps by their
nature vary tremendously, but I place them into two groups according
to what I suspect causes them: man-made, or natural.
Man-made warts and lumps
are common on trees near paths, or wherever population densities
are high. They are probably more scar tissue than anything.
Species:
Ngaio
Melicytus
Rewarewa
Cordyline
Natural warts and lumps,
usually seen high up on trunks and on trees in less populated bush
areas. These would need dissection to determine their significance.
Species:
Kauri
Pseudopanax
Totara —
gives the famous Totara Burr or Totara Knot wood
Karaka
Myrsine australis
Pittosporum
crassifolium
Pattern Five: Close
vertical stems
Close vertical multiple
stem structure tends to be a frequent juvenile habit amongst native
trees, and often leads to weak crotches as trees get larger. It
is less frequent in trees in dense stands of bush, more frequent
in trees in exposed sites; leading to speculation that wind damage
(or other damage) to growing tips of tiny seedlings may be a contributing
factor.
In some cases some stems
die out, or are even pushed out, which may or may not leave inherent
weaknesses in the root crown. In other cases a significant structural
flaw can be seen persisting for many decades in what is perceived
to be a single main stem. Characteristic symptoms include both bull-nose
and elephant-ear swellings just below crotches.
This pattern observed
in:
Totara
Miro
Tawa
Myrsine
Pohutukawa
Kohekohe
Pennantia
Karaka
Phyllocladus
Kauri
Hebe
Pattern Six: Other distortions
or oddities
Keen observation has
revealed occasional irregularities in New Zealand native species,
as follows:
Sophora microphylla
— large side boughs, tending to the horizontal rather than
the upright, are distinctly flattened in cross-section. They lack
the expected deep keel-like structure one would expect the tree
to develop to carry their weight. Otari, March 1999.
Ngaio — Myoporum
laetum — a species capable of the most extraordinary gravity-defying
distortions, spiralling, warts and lumps. Best seen in very old
trees. Kelburn, Wellington, 1999.
Whiteywood — Melicytus
ramiflorus — sometimes seen with girdling branches and
what appear to be aerial roots -- although these latter may be as
a result of soil erosion from around an established plant.
Where to from here?
I am uncomfortably aware
that my research is somewhat amateurish to date, and that I have
raised more questions than I have answered.
I believe there are significant
gaps in our knowledge of the structural characteristics, and hence
the body language, of our native trees, and it is unlikely that
any one person will be able to fill the gaps. I imagine that a team
effort will need to be mounted, between horticulturalists, arborists,
physicists like Claus Mattheck, and maybe others; and almost certainly
the team effort will be based in or near a tertiary institution
with research facilities. Funding will be critical, for any true
research program will stretch over several years.
The research will need
to involve the careful dissection and examination of dozens of native
trees, just as both Claus Mattheck in Germany, and Alex Shigo in
the United States have done. The supply of trees will probably come
from the public, from contributing institutions, and local authorities.
Perhaps ironically, some trees may come from the often-maligned
"developers" who would otherwise turn native trees into firewood.
I have not done justice
to the whole subject of Body Language and VTA today — time
is against me. Those who wish to learn more about it are advised
to read:
Mattheck, Claus, and
Breloer, Helge, 1994
The Body Language of
Trees; a handbook for failure analysis.
Strouts, Robert, (Transl.)
and Lonsdale, David, (Ed.), 1994, Her Majesty's Stationery Office,
London.
And quoting from this
book:
"The tale of the
tree warrior is not silenced with the giant's fall.
E'en
when hostile life has long feasted on his bole and bough,
His
lifeless frame yet tells of battles past with storm and tribulation
.
And
to the understanding eye,
Tells
silently where bold Achilles' heel lay waiting,
till
death's arrow met its mark"
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