Papuan Vegetation

Plant Formations in the Papuan BioProvince

Peter Martin Rhind

Papuan Lowland Rain Forest These tall floristically rich and structurally diverse forests are the most luxuriant of the Papuan forests. The canopy can reach heights of 35 m with scattered trees emerging to 50 m or more. Many of the larger trees have wide buttresses, some attaining girths of well over 2.5 m. Their vertical structure may include up to three tree layers, a shrub layer, and tall and low herb layers, although each of these may be very irregular. The most constantly present trees of the upper stories are Alstonia scholaris species Ficus, including strangling figs, Pometia pinnata and Terminalia. Some of the larger endemic trees include Agathis labillardieri (Araucariaceae), Canarium macadamii (Burseraceae), Dillenia quercifolia (Dilleniaceae), Elaeocarpus prafiensis (Elaeocarpaceae) Myristica archboldiana (Myristicaeae), and Terminalia papuana (Combretaceae). Typical lower story trees are represented by genera such as Diospyros, Myristica, Maniltoa and Microcos but include a multitude of endemic species such as Atalaya papuana (Sapindaceae), Carallia papuana (Rhizophoraceae), Dillenia papuana (Dilleniaceae), Gjellerupia papuana (Opiliaceae), Gomphandra papuana (Icacinaceae), Leea papuana (Leeaceae), Mammea papuana (Hypericaceae), Maniltoa browneoides (Caesalpiniaceae), Myristica cornutiflora (Myristicaeae) and Vavaea papuana (Meliaceae).

In the shrub layer, palms are a conspicuous including small tree palms, true shrub palms, young rattan palms, together with members of the genus Licucula with their conspicuous fan-shaped leaves. Members of the Marantaceae and tall gingers are locally common, but tree ferns and bamboos are generally scarce. Endemic shrub species are legion including Agapetes carrii (Ericaceae), Archidendron hooglandii (Fabaceae), Arytera miniata (Sapindaceae), Casearia papuana (Flacourtiaceae), Celastrus novoguineensis, Xylonymus versteeghii (Celastraceae), Cupaniopsis curvidens (Sapindaceae), Elaeocarpus whartonensis (Elaeocarpaceae), Fagraea umbelliflora (Loganiaceae), Gyrinops ledermannii (Thymelaeaceae), Helicia hypoglauca (Proteaceae), Kibara nitens (Monimiaceae), Leea gonioptera (Leeaceae), Polyscias sleumeri (Araliaceae), Rhus lenticellosa (Anacardiaceae), Rhyticaryum fasciculatum (Icacinaceae), Securidaca ecristata (Polygalaceae), Semecarpus nitificans (Anacardiaceae) and Sericolea micans (Elaeocarpaceae).

The low herb layer tends to be patchy and may be absent where there are abundant shrubs, but in other areas it can be quite dense especially where it is dominated by species of Elatostema or Selaginella or species of the families Commelinaceae or Marantaceae. Generally, though, it is composed of ferns, tree seedlings, forest grasses, sedges and a variety of other herbacous species. Examples of some of the endemic herbs include Phyllocharis oblongifolia (Campanulaceae) and Sciaphila quadribullifera (Triuridaceae). As you would expect there are also many lianas and climber including a variety of endemic species such as Aristolochia dielsiana (Aristolochiaceae), Bauhinia williamsii (Caesalpiniaceae), Carronia thyrsiflora (Menispermaceae), Dichapetalum tenerum (Dichapetalaceae), Erycibe brassii (Convolvulaceae), Dimorphanthera tridens (Ericaceae), Illigera novoguineensis (Hernandiaceae), Legnephora microcarpa, Macrococculus pomiferus (Menispermaceae), Neosepicaea leptophylla (Bignoniaceae), Palmeria brassii (Monimiaceae), Phytocrene interrupta (Icacinaceae), Polygala papuana (Polygalaceae), Salacia subalternifolia (Celastraceae), Strychnos ledermannii (Loganiaceae), Tetracera lanuginosa (Dilleniaceae) and Vaccinium viridiflorum (Ericaceae). Among the many epiphytic species, ferns and orchids predominate, but in Copyright © 2010 Peter Martin Rhind contrast to the orchids of high mountain forests, most have fairly inconspicuous flowers. Members of the endemic orchid genera Dryadorchis, Kerigomnia and Sepalosiphon and the near endemic orchid genera Epiblastus, Microtatorchis and Pedilochilus are all epiphytic. Others endemics epiphytes include Lindsaea versteegii (Lindsaeaceae), Microsorum cinctum, Pyrrosia novo-guineae and Selliguea archboldii (Polypodiaceae). There are also numbers semi-parasitic aerial shrubs of the Loranthaceae endemic to these forests such as Decaisnina djamuense.

Papuan Swamp Forest The forests of permanent swamps are generally open and have a varied range of heights. Much of them are composed of a mixture of trees such as Alstonia scholaris, Bischofia javanica and the endemic Terminalia canaliculata (Combretaceae). Other areas can be described as pandan swamp, in which Pandanus species predominate; sago palm (Metroxylon sagu) swamp, which may include the endemic Aceratium sinuatum (Elaeocarpaceae); Campnopermum swamp, in which Campnospermum brevipetiolata often dominates; Terminalia swamp, in which Terminalia brassii is the main species and finally Melaleuca swamp usually dominated by Melaleuca cajuputi. Other endemic trees of these forests include Aglaia lepidopetalum (Meliaceae), Calophyllum suberosum (Hypericaceae), Cupaniopsis bilocularis (Sapindaceae), Dacrydium cornwalliana (Podocarpaceae), Dysoxylum brevipaniculum (Meliaceae), Elaeocarpus branderhorstii (Elaeocarpaceae), Gomphandra pallida, Pseudobotrys dorae, Rhyticaryum macrocarpum (Icacinaceae), Horsfieldia pulverulenta, Myristica inundata, Paramyristica sepicana (Myristicaceae), Lepidopetalum micans (Sapindaceae), Maniltoa brassii (Caesalpiniaceae) and Terminalia sogerensis (Combretaceae). Smaller palms, pandans, and shrubs often fill in much of the spaces below the canopy. Among the endemic shrubs and small tree are Harpullia rhachiptera (Sapindaceae), Neuburgia rumphiana (Loganiaceae) and Rhododendron angulatum (Ericaceae), while the ground layer typically includes tall sedges such as the endemic Capitularina involucrata (Cyperaceae) and ferns. There are also a great variety of climbing plants such as the endemic Chlaenandra ovata (Menispermaceae) and a number of epiphytic shrubs like the endemic Vaccinium kostermansii (Ericaceae).

Papuan Dipterocarp Forests In Papua New Guinea, dipterocarps (Dipterocarpaceae) are represented by the genera Anisoptera, Hopea and Vatica with just seven species in total including the endemic Hopea papuana and Vatica papuana. This is in marked contrast to Malaya where there are some 200 dipterocarp species. In Papuan BioProvince these forests also have a patchy distribution being mainly confined to foothills below 1000 m. Certain genera may dominate large areas, and only rarely, such as in parts of the southwest, do all of the above mentioned genera occur together.

Papuan Casuarina Forest These are mainly broad-leaved forests with an upper story dominated by the near endemic Casuarina papuana (Casuarinaceae). They commonly occur on limestone or ultrabasic rocks from almost sea-level well into the lower montane zones, but Casuarina papuana has a wide ecological tolerance and is not confined to any particular rock type. It also tends to be a pioneer species often colonizing areas destroyed by fire. On the other hand, it does not live for very long, and more mixed forests eventually take over. This is also supported by the fact the Casuarina papuana does not regenerate under dense shade.

Papuan Castanopsis Forest Forests dominated by almost pure stands of Castanopsis acuminatissima occur on ridge crests and slopes at altitudes ranging from about 500 to 2300 m. Their dense canopies limit the development of lower layers, which are usually limited to an open shrub and a sparse ground layer of herbs. The few associated trees include a number of endemic species such as Chisocheton pohlianus (Melicaceae), Elaeocarpus tariensis (Elaeocarpaceae), Helicia olivacea (Proteaceae), Hopea similis (Dipterocarpaceae), Kibara sleumeri (Monimiaceae), Myristica laevifolia (Myristicaeae), Podocarpus pseudobracteatus (Podocarpaceae), while the many endemic shrub layer species include Dimorphanthera elegantissima (Ericaceae).

Papuan Nothofagus Forest Altogether there are some 19 species of Nothofagus (southern beech) in Papua New Guinea and several of these, including N. brassii, N. carrii, N. crenata, N. flavirama, N. grandis, N. nuda, N. perryi, N. pseudoresinosa, N. pullei, N. resinosa, N. rubra and N. womersleyi are endemic to this BioProvince. Nothofagus is the only genus of the Fagaceae found in the southern hemisphere and its presence in Papua New Guinea is still a mystery. Members of the genus start to appear at an altitude of about 600 m but only assume dominance between 1500 and 3000 m. However, the species have a very patchy distribution tending to be most frequent on ridge crests and upper slopes, and may be very frequent in one locality but absent from an adjacent one with apparently similar conditions. Associated trees include many endemics such as Clethra papuana (Clethraceae), Dryadodaphne crassa (Monimiaceae), Dryadodaphne novoguineensis (Monimiaceae), Dubouzetia novoguineensis and Elaeocarpus trachophyllus (Elaeocarpaceae), Fagraea amabilis (Loganiaceae), Helicia calocoma (Proteaceae), Kibara streimannii (Monimiaceae), Myristica fusiformis (Myristicaceae), Sarcopteryx caudata (Sapindaceae), Symplocos composiracemosa (Symplocaceae) and Vaccinium crassistylum (Ericaceae). These forests are also well endowed with endemic tree ferns such as Cyathea hooglandii, C. nigropaleata and C. womersley (Cyatheaceae). A shrub layer can usually be distinguished supporting endemic species such as Dimorphanthera alpina (Ericaceae), Elaeocarpus sayeri (Elaeocarpaceae), Kibara versteeghii (Monimiaceae), Rhododendron asperum (Ericaceae), Steganthera cyclopensis (Monimiaceae), Trochocarpa arfakensis (Epacridaceae) and Vaccinium angiense (Ericaceae). Many of the endemic shrubs, especially ericoids such as Diplycosia muscicola and Rhododendron warianum (Ericaceae), are epiphytic, but ferns, such as the endemic Elaphoglossum thamnopteris, probably constitute the main epiphytic species. Among the liana species is the endemic Vaccinium fissiflorum (Ericaceae), and an interesting endemic parasite of these forests is Langsdorffia papuana (Balanophoraceae).

Papuan Araucaria Forest In Papua New Guinea these forests are characterized by the presence of two endemic taxa – Araucaria cunninghamii var. papuana and A. hunsteini (Araucariaceae). The latter is a massive tree reaching heights of 89 m and girths of well over 3 m, and often towers up to 30 m above the associated mixed broad-leaved forest. Araucaria cunninghamii is not quiet as large but has a wider altitudinal and geographical distribution, although both species often occur together on a variety of landforms and soils. These are ancient conifers and some authors believe that they are relicts slowly being ousted by the more recently evolved components of the mixed broad-leaved forest. On the other hand, both still regenerate well and continue to be viable components of these forests. Among the associated trees are many endemic species such as Hopea papuana (Dipterocarpaceae) and Myristica crassipes (Myristicaceae).

Papuan Coniferous Forest Forests in which conifer genera such as Araucaria, Dacrycarpus, Papuacedrus, Phyllocladus and Podocarpus dominate occur in many upland areas above altitudes of about 2400 m. The pyramidal crowns of emergent trees of the endemic Papuacedrus papuana (Cupressaceae) can be seen from a great distance. However, near the upper limit of tree growth at about 3900 m many of the trees become stunted and shrub like, although certain conifers such as the endemic Dacrycarpus compactus, Podocarpus brassii (Podocarpaceae) retain their true tree structure even within the alpine shrub forests. Other endemic conifers found in these mountain forests include Falcatifolium papuanum and Podocarpus archboldii (Podocarpaceae), while the few endemic broad- leaved trees are Harmsiopanax ingens (Araliaceae) and Pittosporum berberidioides. In the lower stories there are tree ferns such as the endemic Cyathea muelleri (Cyatheaceae) and a multitude of endemic shrubs especially of the Ericaceae family such as Dimorphanthera callinsii, Rhododendron correoides and Vaccinium densifolium, while other endemic shrubs include Trochocarpa dispersa (Epacridaceae). Many of the Rhododendron shrubs are epiphytic such as the endemic R. microphyllum and there are also a number of endemic aerial semi-parasitic shrubs such as Amyema dilatipes (Loranthaceae).

Papuan Mossy Forest Moving into the region of prolonged cloud cover at about 9000 ft there is often an abrupt change in forest formation. Above this height is the realm of the so-called ‘mossy’ forest or ‘cloud’ forest, which are extremely damp and characterized by constantly dripping water. They normally have a singletree layer commonly dominated by the angiosperm family Myrtaceae (with genera such as Decaspermum, Eugenia, Syzygium and Xanthomyrtus), and the coniferous family Podocarpaceae. The canopy never reaches more than about 40 ft in height, and is typically made up of close, slender often gnarled and crocked trees, with leaves that are usually small, coriaceous and dark green giving the forest a gloomy appearance. But the most distinctive feature of these forests is the predominance of mosses and liverworts, which festoon all of the trees and carpet the forest floor. Filmy ferns and tree ferns also reach their pinnicle of diversity here. The many endemic trees include Casearia archboldiana (Flacourtiaceae), Dacrydium spathoides (Podocarpaceae), Dysoxylum enantiophyllum (Meliaceae), Elaeocarpus latescens (Elaeocarpaceae), Fagraea salticola (Loganiaceae), Geniostoma randianum (Loganiaceae), Guioa pseudoamabilis (Sapindaceae), Harmsiopanax ingens (Araliaceae), Hartleya inopinata (Icacinaceae), Helicia archboldiana (Proteaceae), Horsfieldia schechteri (Myristicaceae), Kibara karengana (Monimiaceae), Levieria nitens (Monimiaceae), Libocedrus papuana (Cupressaceae), Parasponia rigida (Ulmaceae), Pittosporum sinuatum (Pittosporaceae), Podocarpus brassii, P. crassigemmis (Podocarpaceae), Prunus brassii (Rosaceae), Rhododendron agathodaemonis (Ericaceae), Rhyticaryum lucidum (Icacinaceae), Sarcopteryx rubiginosa (Sapindaceae) and Steganthera myrtifolia (Monimiaceae). Endemic shrubs include Agapetes stenantha (Ericaceae), Casearia ledermannii (Flacourtiaceae), Dimorphanthera denticulifera (Ericaceae), Fagraea dodenii (Loganiaceae), Gaultheria pullei (Ericaceae), Helicia microphylla (Proteaceae), Mackinlaya radiata (Araliaceae), Polyscias philipsonii (Araliaceae), Rhododendron culminicolum (Ericaceae), Rubus megacarpus (Rosaceae) and Sarcopteryx coriacea (Sapindaceae). There are also a number of endemic epiphytic shrubs such as Agapetes viridiflora (Ericaceae), Coryphopteris ledermannii (Thelypteridaceae), Dimorphanthera nigropunctata (Ericaceae), Diplycosia edulis (Ebenaceae), Rhododendron papuanum (Ericaceae) and Rhus caudata (Anacardiaceae), and these are joined by occasional lianas such as the endemic Palmeria clemensae (Monimiaceae). The rich endemic tree fern assemblage

Copyright © 2010 Peter Martin Rhind includes Cyathea arfakensis, C. foersteri, C. ledermannii, C. percrassa and C. rigens, with some reaching heights of up to 10 m. In addition to bryophytes, ferns such as the endemic Dicksonia hieronymi (Dicksoniaceae), Elaphoglossum idenburgensis (Elaphoglossaceae) and Gleichenia pulchra (Gleicheniaceae), and orchids make up the ground layer.

Papuan Eucalypt Savanna Savannas dominated by eucalyptus trees occur from sea level to about 1700 m, but only in areas that have a pronounced dry season. They also tend to be confined to hilly terrains like the Port Moresby region on the south coast. The main species are Eucalyptus confertifolia, E. papuana (not endemic) and E. tereticornis; the latter can reach heights of over 30 m. The general view is that most of the lowland eucalypt savannas represent disclimax communities that have developed in response to a long history of burning by humans. All of these eucalypts originated in Australia and mainly spread outwards from the central south coast. Nevertheless, pockets of natural eucalypt savanna are thought to have existed prior to human intervention in areas unsuited to forest development. Lower story trees and shrubs are usually sparsely distributed but may include Albizia procera, Antidesma ghaesembilla, Cycas media, Desmodium umbellatum, Timonius timons and several endemic species such as Albizia carrii (Fabaceae), Grevillea papuana (Proteaceae) and Horsfieldia coryandra (Myristicaceae).

Papuan Tree Fern Savanna Savanna characterized by tree ferns appears to be unique to Papua New Guinea, and yet here it cover large tracts of land between altitudes ranging from 2700 – 3300 m and can be found on many of the high mountains. The tree ferns are all atypical species of the genus Cyathea since most other members of this genus are forest dwellers characteristic of tropical mountain forests. On Papua New Guinea, however, certain endemic species, such as Cyathea dicksonioides and C. pruinosa (Cyatheaceae) have broken away from this ancestral habitat becoming adapted to open grassland where they need to be tolerant of periodic burning, occasional draughts and large diurnal temperature fluctuations. This has been partly achieved by developing a thick fibrous ‘bark’, but these species are far from stunted and certain species, such as the endemic Cyathea muelleri can reach heights of 10 m. The dominant savanna grasses at these altitudes include the endemic or near endemic species Danthonia archboldii and Deschampsia klossi and to a lesser extent Dichelachne novoguineensis (Poaceae). Other endemic species include trees such as Dacrycarpus expansus (Podocarpaceae), various epiphytic shrubs such as Agapetes costata and Rhododendron caespitosum (Ericaceae), and many herbaceous species like Cynoglossum glabellum (Boraginaceae).

Papuan Alpine Grassland Above the tree line at about 3900 m extensive grasslands occur. The species composition and structure of these grasslands can vary considerable with differences in altitude, soil depth, drainage conditions and degree of exposure, and may for example, range from stunted tussocks of Deschampsia klossii to a continous sward of Monostachya oreoboloides. Other grasses include species of Danthonia (such as D. archboldii, D. vestita, D. schneideri and D. semiannularis), Festuca (such as F. papuana) and Poa (such as P. callosa and P. crassicaulis). Sedges, including the endemic Carex bilateralis and C. sarawaketensis (Cyperaceae), may be present in some of the wetter area. Shrubs are also often present, but become scarce and mostly dwarfed to less than 20 cm above altitudes of about 4000 m. Dimorphanthera alpivaga (Ericaceae), Hypericum papuanum (Hypericaceae), Rhododendron pusillum and Vaccinium amblyandrum (Ericaceae) and Trochocarpa dekockii (Epacridaceae) are just a few of the endemic shrubs likely to be encountered. Small tree ferns, like the endemic Cyathea subtripinnata (Cyatheaceae) may

Copyright © 2010 Peter Martin Rhind also be encountered. Amongst the herbaceous elements are various endemic species of Epilobium such as E. detznerianum, E. hooglandii and E. keysseri (Onagraceae), while other endemic herbs include Geranium monticola (Geraniaceae), Potentilla irianensis (Rosaceae) and Trigonotis inoblita (Boraginaceae). Cushion herbs, like the endemic Oreomyrrhis azorellacea and O. papuana (Apiaceae), mosses, lichens and ferns abound in places sometimes having a a higher coverage than grasses. The fern Gleichenia vulcanica may in places be dominant up to about 4000 m, and the unusual endemic finger fern Papuapteris linearis (Dryopteridaceae) is often a conspicuous feature among tussock grasses on Mount Wilhelm.

References

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