2002 Banks Memorial Lecture
The flora of Mt Taranaki/Egmont: Understanding natural and garden
Reproduced from an article by Bruce D. Clarkson
Centre for Biodiversity
and Ecology Research, Department of Biological Sciences, University
of Waikato, Private Bag 3105, Hamilton
From the New Zealand
Garden Journal (Journal of the Royal New Zealand Institute of Horticulture),
Volume 5, Number 2, December 2002, pp. 2-5.
In this, the 2002 Banks
Memorial Lecture, I have two main aims. First, I will trace what
has been discovered by botanists about the Mt Taranaki/Egmont flora
since Joseph Banks scanned the mountain from the deck of Cook's
Endeavour in 1770. Second, I will discuss some of the results of
my own garden and natural experiments, conducted in more recent
The landscape that has
been the setting for this work is the sequence of linear (NNW to
SSE) volcanic activity known as The Taranaki Volcanic Succession.
Volcanic activity began at Paritutu and the Sugar Loaf Islands near
New Plymouth 1.75 million years ago and was followed by the genesis
of Kaitake, Pouakai and Mt Taranaki/Egmont, 575,000, 250,000 and
70,000 years ago, respectively. My research has focused on the plants
growing on these three, progressively younger volcanoes. Each has
its own distinctive features: each is in effect a small but distinct
botanical district. Nearly all of the landscape covered with indigenous
vegetation is within Egmont National Park (Figure 1).
|Figure 1. Mt Taranaki/Egmont, the most recent
volcano of the Taranaki Volcanic Succession.
It is fitting that my
topic for the Banks Memorial Lecture has a direct link to Joseph
Banks. As a botanist I can easily imagine how frustrating it would
have been for Banks to see the mountain from the deck of the Endeavour
and yet not be able to go ashore and investigate its botanical treasures.
Banks did observe "many white lumps in companies of fifty or sixty
together, which probably were stones or tufts of grass, but bore
much resemblance to flocks of sheep". It is most likely those were
hummocks or patches of the Racomitrium mosses that are
still a feature of the debris flows on the upper western slopes
of the mountain. But unfortunately Banks never had the opportunity
to botanise on the ground.
The first European to
describe plants on the mountain was Ernst Dieffenbach, naturalist
to the New Zealand Company. His contribution is still commemorated
in the name of Kelleria [Drapetes] dieffenbachii,
the dwarf native daphne found in the alpine zone. James Buchanan,
a surveyor and botanist, followed in 1869 and recorded 180 vascular
species on a journey from New Plymouth over the Pouakai Range to
the northern slopes of Mt Taranaki. Leonard Cockayne, the internationally
renowned plant ecologist, made several trips to Mt Taranaki and
listed some 220 vascular species. Oliver (1931) was the first to
publish evidence of the recent eruptions, describing the presence
of scoria lodged in large trees near Stratford, and Maori ovens
(umu) beneath recent ash layers. However, the most significant contribution
to understanding the flora of the Egmont National Park was made
by the late Anthony (Tony) Druce in a series of publications between
1953 and 1976. Tony more than doubled the number of vascular species
known within the park (to 440), quantified the extent of "missing"
taxa (460) and clearly established the significance of recent eruptions
in determining vegetation composition.
natural and garden experiments
My interests in the native
flora began as a child growing up "under the mountain". Between
1961 and 1973, I established and maintained a small native plant
garden in the front lawn of our homestead. My mother's exotic bedding
plants and shrubs were removed and replaced by a native plant collection,
including many species collected from the higher slopes of the mountain.
These first garden experiments helped me to identify plants and
observe their phenology and behaviour at close hand. This was the
foundation for much of my later research.
Between 1975 and 1977,
for my Master of Science thesis I focused more on natural experiments
following the approach advocated by Pielou (1977): "Because natural
zonation (which can be thought of as a natural experiment) is so
ecologically informative, it is worthwhile to seek it out even in
places where it would not automatically be expected". Such places
include the margins of wetlands, sites of major disturbance or change
in topography. I documented and explained changes in vegetation
structure and composition with increasing altitude, and changes
in species interactions relating to slope.
I continued with the
natural experiment approach for my Doctor of Philosophy research
between 1978 and 1981. This time I focused on variation in vegetation
structure and composition around the cones, and understanding eruption
effects on vegetation, especially at the treeline. Results showed
how the treeline composition related to the direction and depth
of recent ash showers, especially the Burrell eruption of 1655 AD.
A small suite of tree species, kamahi (Weinmannia racemosa),
kaikawaka (Libocedrus bidwillii), broadleaf (Griselinia
littoralis) and Hall's totara (Podocarpus hallii),
are found in various different combinations at different treeline
sites depending on past eruption effects. The distinctive goblin
forest (kamahi-Hall's totara forest) of the main Egmont cone at
Dawson Falls, Stratford Mountain House and near the North Egmont
Visitor Centre also owes much of its character to the impacts of
recent eruptions (Figure 2).
|Figure 2. Kamahi (Weinmannia
racemosa) dominated goblin forest at North Egmont.
From 1981 to 1992, while
working for the Department of Scientific and Industrial Research
in Rotorua, the main emphasis of my research turned back to common
garden experiments. This included growing a wide range of North
Island natives to test hypotheses about species status particularly
in Hebe, Coprosma, Melicytus and Olearia.
of the flora
Turning to the current
statistics on the flora of the Egmont National Park, we now know
that at least 550 indigenous vascular species occur here. The magnitude
of the vascular flora of the park is now very well known. I am aware
of only four new listings to the park flora since the 1980s. A recent
exciting discovery was the threatened native milfoil (Myriophyllum
robustum). Progress has been made in understanding the status
of many of the species in the park, but several problems remain.
I will discuss some examples that I have worked on, recognising
that this is not a comprehensive discussion.
a continuing problem, especially the taxa belonging to the C.
gracilenta/graminifolia complex. Celmisia major var.
brevis may or may not be part of a widespread species complex,
and perhaps could be distinct only at a subspecies level. However,
more DNA sequencing research will be required to test this hypothesis.
Similarly, the status of the rhizomatous bog Celmisia on
the Pouakai Range requires resolution. The largest Celmisia
recorded in the park, C. semicordata (= C. coriacea),
is doubtfully native. It occurs on the main cone at one isolated
site and was probably planted there.
Hebe also remains
problematic although its resolution seems more imminent than in
Celmisia. The common subalpine scrub species is named Hebe
stricta var. egmontiana in the Flora Volume 1, but
it is clearly a different species to H. stricta, having
double the chromosome number (2n = 80). At present it should
be referred to as Hebe sp. unnamed (H. "egmontiana").
Hebe subsimilis var. astonii which occurs only
on Pouakai could possibly be a variety of the more widespread Hebe
tetragona complex, but in cultivation it retains its more delicate
growth form and is not as drought tolerant as true H. tetragona.
Hebe odora has
two distinct forms in the park. The common form occurs mainly in
tussock grassland and subalpine shrublands on both the Egmont and
Pouakai cones, but on the Pouakai tops there is a prostrate form
that retains this character in cultivation. Other variants occur
elsewhere, on North Island mountains at least, and resolution will
require more detailed comparison before a decision about its status
can be made.
One taxon previously
considered an Egmont endemic, Ourisia macrophylla subsp.
macrophylla, has lost this status, having been found on
the Herangi Range some 120km to the north. The everlasting daisy
(Anaphalioides alpina) of the alpine zone of Egmont and
many other mountains has at last been recognised as distinct from
the more widespread A. bellidioides.
Of the five or six species
still considered to be Egmont endemics,
only one has been fully resolved. This is the unusual divaricating
shrub of the Ahukawakawa Swamp, Melicytus drucei, named
in honour of Tony Druce (Figures 3 and 4). The story behind this
species has to be one of the most interesting and intriguing of
all the plants in Taranaki. Melicytus drucei is a permanent
odd polyploidy (triploid) with a chromosome number of 2n =
48. Its putative parents are M. flexuosus (a diploid; 2n
= 32) and M. aff. alpinus (a tetraploid;
2n = 64). Neither putative parent occurs in the park or
nearby. It is necessary to speculate on a comparatively recent origin,
perhaps during a period when harsh climatic conditions prevailed
in the region, and when the two putative parents were more widespread.
|Figure 3. Melicytus
drucei shrubs on the margins of Ahukawakawa Swamp (Dr Brian
Molloy as scale).
As already noted, approximately
460 species found elsewhere in the North Island, and which might
be expected to occur in Egmont National Park, are "missing". The
well known species include the beeches (Nothofagus), but
others include tawheowheo (Quintinia serrata), a tree which
has seeds well adapted for wind dispersal, and which is abundant
on other west coast volcanic cones such as Pirongia. The long history
of disturbance and isolation of the Taranaki mountains from other
high ground are probably major reasons for the depauperate flora,
as well as the exceptional abundance of kamahi and leatherwood (Brachyglottis
elaeagnifolia) over large areas of the park.
Five taxa common in the
South Island have their only North Island occurrence in the park.
These vary considerably in abundance, the extremes illustrated by
the alpine shield fern (Polystichum cystostegia) and mountain
lacebark (Hoheria glabrata). Alpine shield fern can be
found in the alpine zone on Egmont, but the mountain lacebark has
so far completely eluded me. This tree was found in the 1960s by
Tony Druce and Geoff Kelly while measuring the forest composition
on a transect line near the old North Egmont Chalet. Despite intensive
searching by colleagues and myself it has not been seen for more
than 40 years.
|Figure 4. Close up of Melicytus drucei
showing divaricating growth form and diminutive flowers.
Approximately 30 taxa
have very localised distributions in the park, being found in only
one or two places, usually in low numbers, and therefore particularly
vulnerable to local extinction. The bog mingimingi (Androstoma
[Cyathodes] empetrifolia) is a classic example,
a clump of plants occurring at only one place on the crest of Pouakai.
Conservation and protection
of the park's flora remain significant challenges for the future.
Possums will require ongoing control to ensure the forests remain
in good health, especially since the kamahi dominated stands are
probably predisposed to mass dieback, having extensive even-aged
cohorts relating to volcanic disturbance events. At present there
is apparently no effective alternative to aerial poisoning using
1080, especially in the difficult terrain of the montane, subalpine
and alpine zones. The conservation benefits by far outweigh the
risks. Goats are now under control since reaching plague proportions
in the 1960s, and thankfully deer and pigs have never been a significant
problem. Most of the weeds that have invaded the park to date are
rather benign by national and international standards. However,
ongoing surveillance will be required to ensure the forests especially
are protected from invasive shade tolerant shrubs, trees and lianes
cultivated in lowland gardens, which have not yet naturalised.
The indigenous vegetation
protected within the park is not representative of the full range
of diversity once characteristic of the Egmont Ecological District.
There are still some prospects for developing lowland corridors
of forest especially by protecting the riparian margins of some
of the larger rivers and streams such as the Manganui, Hangatahua
and Oakura. But even in these supposedly environmentally enlightened
times, there have been notable, albeit rare, examples of ecological
vandalism such as the clearance of the regionally important swamp
forests of waiwaka or swamp maire (Syzygium maire) on Norfolk
In parts of the North
Island, community groups are contributing to the gathering "Green
Renaissance" by adopting reserves and supporting the management
agencies in their restoration efforts, for example the Maungatautari
Ecological Island predator proof fence project. In Hamilton City,
where almost all the indigenous vegetation and habitat was destroyed
in the last 100 years, an innovative project to reconstruct from
scratch examples of the Hamilton basin ecosystems at Waiwhakareke
(Horseshoe Lake) seems likely to proceed. Again, a predator proof
fence will enable not just the plants to flourish, but the return
of many threatened birds and other fauna. New Plymouth City is much
better endowed with bush remnants and reserves. It has the National
Park close at hand and a comparatively long tradition of incorporating
indigenous plants into gardens and parks.
But the challenge for
the people of Taranaki in the future will be to adopt a broader
vision that reconstructs some of the missing elements of the original
diversity linking the mountains to the sea, and by riparian planting
and protection to the city. Consideration will also need to be given
to predator proof islands, which will enable restoration of at least
some portions of ecosystems to their original status. This approach
surely would have met with the approval of the renowned patron of
science and botany, Sir Joseph Banks.
and further reading
Bayfield, M.A. and Benson,
M.A. (1986). Egmont Ecological Region. Survey report for
the New Zealand Protected Natural Areas Programme. New Zealand Protected
Natural Areas Programme. No. 2. Wellington, Department of Lands
Buchanan, J. (1869).
Notes on the botany of Mount Egmont and neighbourhood, New Zealand,
February 1867. Journal of the Proceedings of the Linnean Society
of Botany 10: 57-62.
Clarkson, B.D. (1977).
Vegetation change along an altitudinal gradient, Mount Egmont, New
Zealand. MSc thesis, University of Waikato, Hamilton.
Clarkson, B.D. (1980).
Present day vegetation. In: Tullett, J.S. ed. Egmont
National Park Handbook. 4th edition. New Plymouth, Egmont National
Park Board. Pp. 68-77.
Clarkson, B.D. (1981).
Vegetation studies in the Taranaki Land District, New Zealand. Unpubl.
DPhil thesis, University of Waikato, Hamilton.
Clarkson, B.D. (1985).
The vegetation of the Kaitake Range, Egmont National Park, New
Zealand. New Zealand Journal of Botany 23: 15-31.
Cockayne, L. (1917).
Egmont botanical field notes. Unpublished notes, Ms. 74, Auckland
Institute and Museum Library, Auckland.
Cockayne, L. (1922).
The plant life of Mount Egmont. In: Mount Egmont. Issued
by the Egmont Mountain Club. Hawera, Ekdahl Print. Pp. 6-12.
Cockayne, L. (1928).
The vegetation of New Zealand. 2nd edition. Leipzig, Englemann.
Dieffenbach, E. (1843).
Travels in New Zealand. Two vols. London, John Murray.
Druce, A.P. (1953). Plant
distribution records (1). Wellington Botanical Society Bulletin
Druce, A.P. (1956). Plant
distribution records (3). Wellington Botanical Society Bulletin
Druce, A.P. (1961). Mountain
vegetation of the North Island. New Zealand Soil News 3: 95-107.
Druce, A.P. (1964). The
vegetation. In: Scanlan, A.B. ed. Egmont National Park
Handbook. 1st edition. New Plymouth, Egmont National Park Board.
Druce, A.P. (1966). Tree-ring
dating of recent volcanic ash and lapilli, Mount Egmont. New
Zealand Journal of Botany 4: 3-41.
Druce, A.P. (1970). The
vegetation. In: Scanlan, A.B. ed. Egmont National Park
Handbook. 2nd edition. New Plymouth, Egmont National Park Board.
Druce, A.P. (1973). Checklist
of the higher plants of Mount Egmont including Pouakai and Kaitake
ranges (from sea-level to the summit). Third approximation November
1973. Unpublished checklist, Botany Division, DSIR, Lower Hutt.
Druce, A.P. (1974). Some
notes on the flora of Mount Egmont. Auckland Botanical Society
Newsletter 31(2): 1-4.
Druce, A.P. (1976). The
vegetation. In: Fullarton, J.H. ed. Egmont National
Park Handbook. 3rd edition. New Plymouth, Egmont National Park
Board. Pp. 39-50.
Druce, A.P. (1976). Egmont
botanical studies. In: National Parks Series 6. Wellington,
National Parks Authority. Pp. 53-57.
Glenny, D. (1997). A
revision of the genus Anaphalioides (Asteraceae:Gnaphalieae).
New Zealand Journal of Botany 35: 451-478.
Molloy, B.P.J. and Clarkson,
B.D. (1996). A new, rare species of Melicytus (Violaceae)
from New Zealand. New Zealand Journal of Botany 34: 431-440.
Oliver, W.R.B. (1931).
An ancient Maori oven on Mount Egmont. Journal of the Polynesian
Society 40: 73-80. Pielou, E.C. (1977). Mathematical Ecology.
New York, Wiley.
Dr Bruce Clarkson
is Associate Professor and Director of the Centre for Biodiversity
and Ecology at the University of Waikato. Bruce has had a
lifelong interest in growing and researching native plants
and has published more than 40 papers on various aspects of
the systematics and ecology of native plants and vegetation.
He has also written or co-authored several books including
Vegetation of Egmont National Park, Botany of
Rotorua, Gully Restoration Guide and Botany
of the Waikato.