Gymnosperms of New Caledonia
New Caledonia is a 19,000 square kilometer island in the equatorial southwest Pacific Ocean, about a thousand kilometers east-northeast of Australia. Due to its warm, wet climate, its long isolation from other large landmasses, and its peculiar geology (about half the island is underlain by ultramafic rocks, which create soils exceptionally low in nutrients and high in toxic metals), the island has a rich flora with a very high degree of endemism. A fine discussion of the island's biogeography and flora, with many maps and photographs, is available at the Diversity, Endemism and Extinction in the Flora of New Caledonia site. Also, species descriptions, photographs and distribution maps are available at the Association Endemia site.
New Caledonia is of special interest to us because it holds 3 endemic conifer genera and 43 endemic conifer species (there are no non-endemic conifers) in, relatively speaking, a very small place. The only other places on earth that even approach this level of conifer diversity and endemism are New Zealand, California and Sichuan, all of which are very much larger but have fewer endemic species. New Caledonia is home to nearly half the world's species of Araucariaceae (18 out of 44 species), and also supports 18 species of Podocarpaceae, 6 species of Cupressaceae, and one of Taxaceae. As you might expect, some of these are among the rarest conifers on Earth. Araucaria nemorosa is known only from a single population of several dozen individuals, Podocarpus decumbens grows only on a single mountaintop, Libocedrus chevalieri grows only on two mountaintops, Podocarpus longefoliolatus is only known from three spots on high ridgecrests, and Dacrydium guillauminii grows only in a popular touist destination on the Plain of Lakes, where it is consequently threatened with extinction. Several other species are also very rare.
Perhaps the most extraordinary aspect of the conifer flora is that 27 species have only been recorded as growing on ultramafic substrates, with another 12 species found on varied substrates including ultramafics. Ultramafic substrates are uncommon on a global scale, but they are widespread in some areas, such as in parts of California, Cuba and Turkey. They produce soils with very low concentrations of mineral nutrients and very high concentrations of metals such as chromium, nickel and manganese, which are more or less toxic to plants. In most areas the plants growing on ultramafic soils are the same as those growing nearby on typical (silicate) soils, but they grow with less vigor and at lower concentrations on ultramafics. Some ultramafic areas develop races of ultramafic-tolerant plants, and some areas have a few species that are so well adapted that they outcompete other species on ultramafic substrates, but it is relatively ununsual to find species that grow only on ultramafics. In New Caledonia such a situation is not unusual, either among conifers or among angiosperms, and consequently the area is also a Mecca for scientists who study ultramafic-adapted vegetation. The above link will also guide you to detailed information and literature about ultramafic soils in New Caledonia. New Caledonia split off from Gondwana prior to the eruption of the ultramafics, so the conifers have adapted since New Calodonia became an island. This is actually a fairly common situation in island biogeography; Darwin's finches on the Galapagos and land snails on Hawaii provide analogues.
The most distinctive New Caledonian habitat is 'maquis,' also called 'maquis miniers', a shrub-dominated habitat underlain by ultramafic substrates (the name means 'mined maquis', because its rock is mined for nickel). The dominant vegetation is evergreen sclerophyll, sometimes with a dense sedge (Carex spp.) substratum, and often with an overstory of Agathis ovata or Araucaria spp. The forest trees are highly shade-intolerant, so the forest is at best very open, and usually has the character of a woodland. In sharp contrast to European maquis habitats, it can be quite moist, with most conifer-rich maquis occurring at elevations over 600 m and receiving rainfall of more than 2000 mm per year.
Rainforest is also a common habitat type, supporting more New Caledonian conifers than any other habitat. It primarily occurs on the flanks of the mountains that stretch down the long northwest-southeast spine of New Caledonia and milk rain from the trade winds and tropical cyclones, and rainfall generally increases with elevation. The rainforest starts at about 300 m elevation and the low altitude to montane forest, from 300-1000 m elevation, receives about 1500-3500 mm of rain annually. Although this forest contains no exceptionally large trees, it does sustain fairly high arboreal species diversity, including most of the conifers that are logged for timber. The 11 conifer species found in this forest are sizable trees, growing in the canopy or emergent above it. Although most conifers occur dispersed amongst the hardwood, various species of the Araucariaceae can form highly conspicuous pure (or nearly so) stands. Above about 1000 m elevation the forest changes to a cloud forest receiving more than 3500 mm precipitation annually. Trees are much shorter, about 3-8 m tall, and angiosperm dominance gives way to a great profusion of mosses, lichens, ferns, and of course conifers, which occur in all strata from the forest floor to canopy emergents. Six species of conifer grow only or largely in this highland forest.
Other habitats include riparian areas, wetlands, low forest (elevation less than 300 m), and coastal habitats. Some conifers occupy these habitats but they are largely dominated by angiosperms.
Smith (2004) provides the following comments on species occurrence within the principal habitat types: "Where [tropical and subtropical rainforest with coniferous elements] occurs there is often a gradient from a lowland rainforest to an evergreen cloud forest. Overall fourteen species of Araucariaceae, eleven species of Podocarpeaceae, two Cupressaceae and a single species of Taxaceae occupy niches in these forests. The Araucarians (Araucaria and Agathis species) plus Retrophyllum comptonii and Dacrydium araucarioides form both the canopy and emergent layers (however, these latter two form an emergent layer only on 'cuirasse' boulder fields that are largely unvegetated), and Austrotaxus spicatus, Libocedrus austrocaledonica and the majority of the Podocarpaceae are found in the understorey. Angiosperms such as Metrosideros (Mytraceae) and Quintinia (Saxifragaceae), and primitive groups such as Winteraceae are also found in the understorey and canopy. Most species have strong Gondwanan associations. In some areas unusual, almost pure tree layer stands occur, such as Agathis montana on several mountain tops and Neocallitropsis in some wetlands in the south of the main island, and Araucaria columnaris in a pure narrow band on calcareous rocks on the seashore on the main island, the Isle of Pines and the Loyalty Islands."
Jaffre, T., P. Bouchet, and J.-M. Veillon. 1998. Threatened plants of New Caledonia: Is the system of protected areas adequate? Biodiversity and Conservation 7(1): 36.
Papineau, C. 2002. State of Forest and Tree Genetic Resources in New Caledonia. http://www.fao.org/DOCREP/005/AC485E/AC485E00.HTM (accessed 2006.11.19).
Data for this table are from Jaffré 1995, which I strongly recommend you read if you have interest in the conifers of New Caledonia.
|Agathis corbassonii||Rainforest, 300-700 m||S|
|Agathis lanceolata||Rainforest, 200-1000 m||U or S|
|Agathis montana||Rainforest, 1000-1600 m||S|
|Agathis moorei||Rainforest, 250-1000 m||U or S|
|Agathis ovata||Maquis & Rainforest, 150-1150 m||U or S|
|Araucaria bernieri||Rainforest, 100-700 m, very tolerant||U or S|
|Araucaria biramulata||Rainforest, 250-1150 m||U or S|
|Araucaria columnaris||Rainforest, 0-100 m, coastal||U or C|
|Araucaria humboldtensis||Maquis & Rainforest, 800-1550 m||U or S|
|Araucaria laubenfelsii||Maquis & Rainforest, 400-1300 m||U or S|
|Araucaria luxurians||Maquis & Rainforest, 0-200 m, very tolerant||U or S|
|Araucaria montana||Maquis & Rainforest, 300-1350 m||U or S|
|Araucaria muelleri||Maquis & Rainforest, 150-1000 m||U or S|
|Araucaria nemorosa||Rainforest, 0-50 m, <2000 mm annual ppt.||U only|
|Araucaria rulei||Maquis & Rainforest, 150-1200 m||U or S|
|Araucaria schmidii||Rainforest, 1500-1600||S|
|Araucaria scopulorum||Maquis & Rainforest, 0-200 m, <2000 mm annual ppt.||U or S|
|Araucaria subulata||Rainforest, 300-1000 m||U or S|
|Callitris neocaledonica||Maquis & Rainforest, 950-1350 m||U or S|
|Callitris sulcata||Maquis & Rainforest, 50-200 m||U or S|
|Libocedrus austro-caledonica||Rainforest, 700-1300 m||U or S|
|Libocedrus chevalieri||Maquis, 1450-1600 m||U only|
|Libocedrus yateensis||Rainforest, 150-250 m||U or S|
|Neocallitropsis pancheri||Maquis & Rainforest, 850-950 m||U or S|
|Acmopyle pancheri||Rainforest, 100-1300 m||U or S|
|Dacrycarpus viellardii||Rainforest, 100-800 m||U or S|
|Dacrydium araucarioides||Maquis, 200-1000 m||U only|
|Dacrydium balansae||Maquis & Rainforest, 150-900 m, very tolerant||U|
|Dacrydium guillauminii||Riparian, in 4 localities on the Rivière des Lacs and the edge of the Lac en Huit.||U or S|
|Dacrydium lycopodioides||Rainforest, 900-1400 m||U or S|
|Falcatifolium taxoides||Rainforest, 100-1400 m||U or S|
|Parasitaxus ustus||Rainforest, 150-1100 m||U or S|
|Podocarpus decumbens||Maquis, 800-1000 m||U only|
|Podocarpus gnidioides||Maquis, 600-1600 m, on rocky or lateritic crests||U only|
|Podocarpus longifoliolatus||Rainforest, 1100-1200 m||U or S|
|Podocarpus lucienii||Rainforest, 200-1100 m||U or S|
|Podocarpus novae-caledoniae||Maquis, 50-750 m||U only|
|Podocarpus polyspermus||Rainforest, 650-950 m||U or S|
|Podocarpus sylvestris||Rainforest, 150-1200 m||U or S|
|Prumnopitys ferruginoides||Rainforest, 150-1400 m||U or S|
|Retrophyllum comptonii||Rainforest, 750-1450 m||U or S|
|Retrophyllum minus||Riparian||U or S|
|Austrotaxus spicatus||Rainforest, 500-1350 m||S|
(1) Substrate types: U = Ultramafic; S = Silica; C = Carbonate.
Last Modified 2010-12-12