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Dacrydium x suprinii NIMSCH
Characterization

II. Introduction [C]

C 1  Taxonomy of the species Dacrydium guillauminii BUCHHOLZ

The species Dacrydium guillauminii was first described in the Bull. Mus. Nat. Hist. Nat. Paris, sér. 2, 21.:282 in 1949, later on by SARLIN in Bois et Forêts de la Nouvelle-Calédonie:  92 et pl. 21 in 1954, and by HARRISON in DALLIMORE & JACKSON, Handbook Conif. Ed 4: 223 in 1966.

Last revisions on the genus were made by D.J. DE LAUBENFELS in 1969 and by C.J. QUINN in 1982.

C 2  Distribution

According to the map after B. SUPRIN, Nouméa, Nouvelle-Calédonie, 1990, about the distribution area of Dacrydium guillauminii, that is published herein for the first time, all of the nine small and micro-scale habitats are located at Rivière des Lacs and Plaine des Lacs. The importance of this map is stressed by the fact that the natural habitats of Dacrydium x suprinii are exclusively located within the distribution area of Dacrydium guillauminii.

Dacrydium II
Pfeil nach oben Dacrydium x suprinii
Branches compared
left: Dacrydium guillauminii
middle: Dacrydium araucarioides
right: Dacrydium x suprinii
Plaine des Lacs, Nouvelle-Caledonie
Foto:© H. Nimsch

Census of  Dacrydium guillauminii habitats in New Caledonia

Location 1:
Lac de Yate, former estuary  of the Rivière des Lacs. This habitat was recorded by Dr. HUERLIMANN, Switzerland (in 1957) and is extinguished now by damming the Yaté Lake.

Location 2:
A larger habitat of Neocallitropsis pancheri had existed once at the eastern side of the Rivière des Lacs and was destroyed due to the construction of the “Ligne de transport d’ énergie électrique” in the south of the main street (route principale). A smaller habitat of  Neocallitropsis pancheri remained at the western side of the Rivière des Lacs. There is no habitat of D. guillauminii.

Location 3:
Rivière des Lacs, a micro-scale habitat of several D. guillauminii together with some Neocallitropsis is located about 5 km upstream and close to the river.

Location 4:
Rivière des Lacs, a micro-scale habitat of eight D. guillauminii and two Neocallitropsis is located about 7 km upstream of the main street, likewise close to the river.

Location 5:
Rivière des Lacs, a habitat of a single specimen of D. guillauminii close to the river bank, without Neocallitropsis.

Location 6:
Rivière des Lacs, a micro-scale habitat of two D. guillauminii and a few Neocallitropsis is located about 12 km upstream of the main street.

Location 7:
Rivière des Lacs, at a site 13 km upstream of the main street the richest population of D. guillauminii can be found, mingled with numerous Retrophyllum minor. The small trees are reaching heights of 2-4 m. As all specimens of Retrophyllum are growing in the water, D. guillauminii is partly growing inside the water and partly close to the water. Dacrydium araucarioides sprouts a few meters off the river banks, 2-3 m above the water level of the river. At 4 m above water level the first Neocallitropsis can be found, loosely mingling with Dacrydium araucarioides. In spite of the fact that their habitats are situated 3-4 m above water level both last mentioned conifers may sometimes be reached by floods (December 2005/January 2006). Adjacently in the south extends a larger area to the Rivière des Lacs containing wet habitats with Retrophyllum and dry habitats with Neocallitropsis and a single D. guillauminii  growing directly at the bank.
B. SUPRIN, Nouméa, estimated that the age of all specimens of Dacrydium guillauminii, whose trunks reach diameters of 20-30 cm, amount to more than 300 years.

Location 8:
“Lac en Huit”, two micro-scale habitats exist at the most plane bank of the lake. The first site is located at the western bank of the lake, merely meters 20 x 15 m size, and contains very few D. guillauminii. The second site is situated at the southern bank of the Lac en Huit, a limited occurrence as well. Only a few D. guillauminii are growing there, all of them scarcely topping heights of 1 m. Their trunks only reach few centimeters in diameter, but the trees nevertheless appear to be very old. (B. SUPRIN, Nouméa, estimated more than 100 years.)

Location 9:
“Lac Intermédiare”, a single occurrence of D. guillauminii about 400 m in the northeast of the lake. The tree reaches a height of 1,80 m.

Location 10:
“Lac Intermédiaire”, a micro-scale habitat of D. guillauminii at the north - western bank of the lake. The plants do not exceed 1 m in height.

Location 11:
“Grand Lac”, at the western bank of the Grand Lac a habitat of Dacrydium guillauminii is situated, reaching the dimensions of 60 x 15 m along the very plain bank of the lake. Several up to 1 m high D. guillauminii are mingled there with a large number of Retrophyllum minor which are up to 1 m as well. Not far, i.e. about 15 m away from the lake bank and about 1 m above the water level of the lake, specimens of Dacrydium araucarioides and Neocallitropsis pancheri are growing among others.

  Area measurement

All habitats of D. guillauminii were added up in square metres in order to estimate the dimension of the over-all habitat. By using stretched dimensioning the whole habitat area accounted for 8900 square metres.

06 neukaledonien verbreitung dacrydium guillauminii und dacrydium x suprinii 250
pfNachOben New Caledonia: Distribution of Dacrydium guillauminii and Dacrydium x suprinii
After Bernard Suprin, Noumea, Nouvelle Caledonie, 1990

Conclusions

The over-all stock of D. guillauminii spans distinctly less than 1 hectare!
Therefore the extinction hazard for the species may be assessed as follows:

  • The nine small habitats, three of them micro-scale ones, that forms the over-all habitat of D. guillauminii, are spread out in the landscape with mostly great distances from each other.
  • Consequently, the narrowing of the genetic potential can be ascertained.
  • Due to biotic and abiotic damage of the fragmented over-all habitat, there may be serious concern about the future of the species.


Fortunately there are some positive approaches to conserve the species:

  • one-site protection measures made by the IRD Nouméa (Research Institute for Development)  are appreciated.
  • Natural protection of the habitats against fire is given by the location of D. guillauminii habitats in or alongside flowing waters or lake banks.
  • First success is brought about to create public awareness regarding the problem via public relations.
  • The problems are internationally realized resulting in the classification of Dacrydium guillauminii in the IUCN Red Data Book categories.

It may be stated here that the over-all habitat of Dacrydium guillauminii in the southeast of the Grande Terre was surely not large even before appropriation during colonisation, due to specific requirements regarding the habitat. Further studies about this issue are regarded as desirable.

C 3  Description

Dacrydium guillauminii is a downright rare tree.
Even in New Caledonia it can be found merely at a few and specific sites.
The tree grows very slowly up to 3 m, at most 4 m.
The oldest specismen are estimated to be more than 300 years old.
For approximately the first 20 years or more, young plants are growing tautly straight, without considerable collateral ramification.
Over the course of growth, a conical and regular crown develops that changes furthermore into a more turbid and abstract form.
Due to the closely arranged branches with dense foliation, the small trees appear more like shrubs.

Adult needles reach a length of 13-17 mm and a breadth of 1 mm.
It is difficult to detect the seed cone that always grows at twig tips.
It contains up to 5 seeds that are 4 mm long, and is enclosed by needles.
The occurrence of the species is limited to habitats along the banks of rivers and lakes.

Obviously, the tree roots are able to tolerate constant or lasting inundation. As the trunks of old trees are thickened up to the height of  80 cm, this can not be found for  young plants at the same site.
Retrophyllum minor specimen, also growing there and likewise occasionally or continuously under flood conditions, reveal much more thickened trunks than the former. Retrophyllum has markedly light wood of an almost sponge like consistence.

10 dacrydium guillauminii branchlet and seed
pfNachOben Dacrydium guillauminii: Branchlet (x 3) and seed scale (x 3)
H. NIMSCH and D-J- DE LAUBENFELS

07 dacrydium guillauminii young tree
pfNachOben Dacrydium guillauminii
Young Tree

08 dacrydium guillauminii branchlets
pfNachOben Dacrydium guillauminii
Branchlets
  09 dacrydium guillauminii old tree
pfNachOben Dacrydium guillauminii
Old Tree
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