Included here are the forests of New Guinea, the Aru Islands, Misool Island, Salawati, Weigeo, the Schouten Islands, the Trobriand Isands, Murua Island, the D’Entrecasteaux Islands and the Louisaide Archipeligo.

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 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.

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. Here 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. 

References

Chapman, V. J. 1977. Wet coastal formations of Indio-Malesia and Papua New Guinea. In: Ecosystems of the World 1 - Wet Coastal Ecosystems. Ed. V. J. Chapman. Elsevier Scientific Publishing Company.

Conn, B. J. 1995. Handbook of the Flora of Papua New Guinea. Vol. III. Melbourne University Press.

Henty, E.E. (ed). 1981. Handbook of the flora of Papua New Guinea. Vol. II. Melbourne University Press.

Leith, H. & Werger, M. J. A. 1989. Ecosystems of the World 14B - Tropical Rain Forests. Elsevier Scientific Publishing Company.

Oatham, M. & Beehler, B. M. 1998. Richness, taxonomic composition, and species patchiness in three lowland forest plots in Papua New Guinea. In: Forest Biodiversity Research, Monitoring and Modeling. Eds. F. Dallmeier and J. A. Comiskey. Man and the Biosphere Series, Volume 40. The Parthenon Publishing Group.

Paijmans, K. (ed). 1976. New Guinea Vegetation. Commonwealth Scientific and Industrial Research Organisation in association with the Australian National University Press, Canberra.

Polak, M. 2000. The botanical diversity in the Ayawasi area, Iran Jaya, Indonesia. Biodiversity and Conservation, 9: 1345-1375.

Steenis, C. G. G. J. van. 1957. Outline of the vegetation types in Indonesia and some adjacent regions. Proceedings of the Pacific Scientific Congress, 8: 61-97.

Womersley. J. S. (ed). 1978. Handbook of the flora of Papua New Guinea. Vol. I. Melbourne University Press.