Included here is a region known as Annam covering central Vietnam and the adjacent parts of Laos.

Central Annamese Mixed Submontane Forest

Forest comprising both broad-leaved and coniferous species are widespread in Central Annam at elevation ranging from 700-1500 m. Pinus kesiya is often dominant in the upper zones and can form pure stands. It commonly reaches heights of up to 35 m and can have a trunk diameter up to 1 m. Other conifers include Keteleeria evelyniana and Podocarpus neriifolius. Generally at lower altitude ranges Pinus merkusii can also become important and on well drained soils Dacrycarpus imbricatus and Dacrydium elatum may dominate. Most of the broad-leaved species tend to be confined to sub-canopy levels and include representatives of Ericaceae, Euphorbiaceae, Fagaceae, Lauraceae, Moraceae and Saurauiaceae. These trees commonly support numerous epiphytic ferns and orchids together with various parasitic shrubs like Dendrophoë varians, Korthalsella opuntia, Macrosolen chinense and Viscum articulatum. Ranging in height from 3-4 m the shrub layer typically includes species of Melastoma, Phyllanthus, the cycad Cycas pectinata and a number of dwarf palms such as Phoenix siamensis. At ground level, particularly in the lighter conifer dominated areas, there are numerous dry-tolerant ferns, grasses and forbs. Common amongst these are Elephantopus scaber, Lagenophora gracilis and species of Carex, Curcuma, Elaphoglossum, Fimbristylis, Kaempferia, Pyrrosia, Scleria, Smilax and Zingiber.

Central Annamese Broad-Leaf Evergreen Montane Forest

These forests represent the most widespread vegetation type in Central Annam mostly developing at altitudes ranging from 1400-2200 m. As night temperature often fall to 0 degrees centigrade many typical tropical species are absent such as tall woody ferns, large palms and mega herbs. The main canopy trees include Acer flabellatum, Betula alnoides, Cinnamomum cassia, Engelhardtia spicata, Itea chinensis, Lithocarpus vildaliana, Neolitsea cambodiana, Phoebe lanceolata, P. paniculata, Quercus langbianensis, Q. macrocalyx, Rhodoleia championii, Sorbus corymbifera, S. wattii, Symingtonia populnea, S. tonkinensis, Ternstroemia kwangtungensis, the Vietnam endemic Michelia foveolata (Magnoliaceae) and many more. Most canopy trees range in height from 20-30 m, but at elevations above 1500 m the giant pine Pinus dalatensis can reach 40 m or so and have a lower trunk diameter of 2 m. Other giant gymnosperms include Fokienia hodginsii. Some of these giant emergent trees can be over 1000 years old. This high level canopy provides habitat for a number of rare epiphytic orchids including Bulbophyllum hymenantum, Dendrobium christyanum, D. wattii and the endemic Bulbophyllum ngoclinhensis (Orchidaceae). Second and third tree strata can often be distinguished. Common in the second stratum are species of the families Annonaceae, Araliaceae, Lauraceae and Theaceae and these range in height from 5-10 m. In the third level, ranging from 3-4 m, there are many small trees and shrubs. Common ones include Brassaiopsis glomerulata, Enicosanthellum plagioneurum, Euonymus javanicus, Glyptopetalum gracilipes, Ilex macrococca, Lansium domesticum, Pittosporum balansae, Polygala saxicola, Schefflera metcalfiana, Strobilanthes echinata and the near endemic Glyptopetalum annamense (Celastraceae). In some of the wetter areas, particularly along streamside cliffs, climbing shrubs such as Rubus alpestris and the endemic Rubus annamense (Rosaceae) form dense thickets with Dichroa febrifuga and Strobilanthes echinata. Also in wet places large pandanas and giant tufted grasses can found, such as Thysanolaeno maxima and Sorghum species, which can reach heights of up to 5 m. At ground level there are numerous ferns and a rich herbaceous flora. Among the many genera are Anoectochilus, Arisaema, Begonia, Blastus, Carex, Chirita, Dichroa, Elatostema and Geophila. Also present are various specialized parasitic plants of the family Balanophoraceae including Balanophora fungosa and Rhopalocnemis phalloides, and saprophytic taxa such as Petrosavia (Melanthiaceae) and the orchids Didimoplexiopsis and Lecanorchis.

Central Annamese Mixed Cloud Forest & Summit Thicket

At elevations mainly above 2000 m near the summits of central Annam montane forest gives way to wet cloud forest, which in turn gives way to thicket on the summits. At these altitudes temperatures can fall to below zero and the forests have a simple vertical structure basically consisting of canopy, shrub and herbaceous layers. The canopy ranges from 8-12 m in height and is largely composed of gnarled specimens of Diplopanax vietnamensis, Symingtonia populnea together with species of Rhododendron and Sorbus. Most are festooned with mosses and ferns such as Hymenophyllum exsertum, Macroglena gemmatum, Mecodium badium and Vandenboschia auriculata, but presumably because of the low temperatures epiphytic orchids are uncommon. The poorly developed shrub layer is typically represented by species of Acanthaceae. On the summits the thicket consists of stunted, often very densely intertwined, gnarled trees and shrubs. These range in height from 2-4 m and typical include members of the Ericaceae such as Gaultheria leucocarpa, Lyonia ovalifolia, Rhododendron lyi, R. irroratum, R. viali, Vaccinium chuni, V. dunalianum and V. sprengelii. Species of the bamboo genus Arundinaria may also be present. Representatives of other plant families are likely to include Elaeocarpus darlacensis (Elaeocarpaceae), Ilex crenata (Aquifoliaceae), Stranvaesia davidiana (Rosaceae) and Skimmia arborescens (Rutaceae). Epiphytic mosses and lichens are common. The undergrowth also largely consists of mosses particularly Sphagnum species. The only common terrestrial herbs are the orchids Goodyera foliosa and G. schlechtendaliana.

Southern Annamese Closed Evergreen Montane Forest

These forests represent the most typical vegetation in Southern Annam. They occur at altitudes ranging from 700-1200 m on slopes composed of silicate rock. Canopy trees range in height from 25-30 m and in some cases up to 35 m. Typical species include Acer labellatum, Actinodaphne cochinchinensis, Calophyllum thorelii, Camellia tsaii, Castanopsis echinocarpa, Cinnamomum burmanii, Dipterocarpus hasseltii, Lepisanthes langbianensis, Lindera cubeba, Lithocarpus agaregalum, Machilus odoratissimus, Manglietia duclouxii, Michelia constricta, Neolitsea zeylanica, Pyrenaria poilanei, Quercus angustinii, Rhodoleia championii, Schima crenata, Talauma hodgsonii, Xerospermum donnaiensis and the endemic or near endemic Castanopsis chevalieri and C. ferox (Fagaceae), Actinodaphne pilosa, Lindera chenii and Machilus chinensis (Lauraceae). Gymnoperm canopy trees include Dacrycarpus imbricatus, Dacrydium elatum, Elaeocarpus kontumensis, Nageia wallichiana and Podocarpus neriifolius. The sub-canopy ranges from 15-25 m and common here are Acer heptaphlebium, Archidendron clypearia, Carpinus viminea, Choerospondias axillaris, Dendropanax chevalieri, Eurya trichocarpa, Heteropanax fragans, Illicium cambodianum, Litsea lancifolia, Macropanax concinnum, Meliosma lepidota, Michelia subulifera, Photinia prunifolia, Prunus javanica, Sorbus corymbifera, Sterculia nobilis, Symplocos adenophyllum, Vaccinium iteophyllum and the endemic or near endemic Styrax annamensis (Styracaceae). In the undergrowth the vegetation is particularly rich with numerous species of shrubs and treelets. Some of the most common include Acer oblongum, Allomorpha inaequata, Euodia callophylla, Euonymus laxiflorus, Illicium tenuifolium, Litsea lancifolia, Meliosma lepidata, Pittosporum merrillianum, Pseudodissochaeta septentrionalis, Psychotria rubra, Vaccinium viscifolium and the endemic Polyosma annamensis, P. nhatrangensis (Saxifragaceae), Gordonia bidoupensis (Theaceae) and the near endemic Eriobotrya poilanei (Rosaceae). The undergrowth of these forests is also important for a number of small palms like Licuala bracteata and Pinanga duperreana and tree ferns such as Cibotium barometz, Cyathea contaminans, C. gigantea and Ctenitopsis austro-sinensis although some of the Cyathea species can exceed 10 m in height. Another important feature are various mega herbs such as Musa bakeri and species of Alpinia, Amomum and Hedychium. At ground level, the terrestrial herb layer is not particularly well developed usually covering less than 10% of the forest floor. Common species include Acanthephippium striatum, Chloranthus erectus, Huperzia serrata, Phyllagathis megalocentra, Polygala karensium, Staurogyne major and the endemic Calanthe velutina (Orchidaceae), Pentaphragma gamopetalum and P. honbaense (Pentaphragmataceae). Finally these forests support a rich assemblage of woody lianas and epiphytes. Among the common lianas are Actinidia latifolia, Alyxia pseudochina, Ancistrocladus cochinchinensis, Gnetum montanum, Kadsura coccinea and Stauntonia cavaleriana, while the multitude of epiphytes includes the endemic orchids Coelogyne sanderae and Sunipia annamensis (Orchidaceae). These are accompanied by various epiphytic shrubs like the endemic Schefflera tribracteata (Araliaceae) and the parasitic Macrosolen annamicus (Loranthaceae).

Southern Annamese Humid Montane and Cloud Forest

At elevations exceeding 1500 m humid conditions prevail allowing the development of mixed, humid forests dominated by species of Fagaceae, Lauraceae, Magnoliaceae and Theaceae mixed with huge emergent conifers. The main conifers are Fokienia hodginsii, Pinus dalatensis, P. wangii and the endemic Pinus krempfii (Pinaceae). All of these species can reach heights of 45 m or so and have lower trunk diameters of up to 2 m. They can live for considerable periods and some have ages exceeding 1000 years. Other gymnosperms include Dacrycarpus imbricatus, Dacrydium elatum, Keteleeria evelyniana, Nageia fleuryi, Podocarpus nerifolius and the near endemic Cephalotaxus mannii (Cephalotaxaceae). At high altitudes the slopes are often shrouded in moist clouds and this compensates for the lack of rainfall during the short dry season. All of the above mentioned gymnosperms can found here but the angiosperm composition changes somewhat with species such as Elaeocarpus darlacensis, Illicium tenuifolium, Quercus poillanei, Sorbus corymbifera and Symingtonia populnea becoming conspicuous. However, at slightly higher altitudes these give way the ericaceous woodlands in which Lyonia ovalifolia, Rhododendron langbianense, Vaccinium greenwayae, V. harmandianum and the endemic or near endemic Lyonia annamense, L. chapaensis and Rhododendron fleuryi (Ericaceae) become dominant. The ground layer includes various terrestrial herbs many of which can be described as lithophytes. These include Anemone poilanei, Arisaema balansae, Calanthe clavata, Carex baccans, Goodyera schlechtendaliana, Hydrocotyle chinense, Nephelaphyllum tenuifolium, Viola tonkinensis and the endemic or near endemic Sonerila annamitica (Melastomataceae). Lithophytes found on mossy cliffs include the orchids Bulbophyllum tixierii and the endemic Amitostigma bidupense (Orchidaceae). Mosses dominate the epiphytic flora but also present are various ferns and orchids such as Bulbophyllum reptans, Ceratostylis radiata, Coelogyne mooreana, Epigeneium amplum, Eria siamensis, Monomeria dichroma, Otochilus fuscus and the endemic Cleisocentron klossii and Panisea albiflora (Orchidaceae).

References

Averyanov, L. V., Phan Ke Loc, Nguyen Tien Hiep & Harder, D. K. 2003. Phytogeographic review of Vietnam and adjacent areas of Eastern Indochina. Komarovia, 3: 1-83.

Baltzer, M. C., Nguyen, Thi Dao & Shore, R G. (eds.). 2001. Towards a vision for Biodoversity Conservation in the Forests of the Lower Mekong Ecoregion Complex. WWF. Indochina Programme, Hanoi, Vietnam.

Campbell, D. G. & Hammond, H. D. 1989. Floristic Inventory of Tropical Countries. The New York Botanical Garden.

Hill, M., Chan, L. M. & Harrison, E. 1996. Ba Na Nature Reserve – site description and conservation evaluation. The Society for Environmental Exploration, Londan and the Xuan Mai Forestry College, Hanoi.

Vidal, J. E. 1979. Outlines of the ecology and vegetation of the Indochinese Peninsula. In: Tropical Botany. Eds. K. Larsen and L. B. Holm-Nielsen. Academic Press.

Vidal, J. E. 1997. Paysages vegetaux et Plantes de la Peninsule indochinoise. Karthala and Agency of Francophony, Paris.

Walker, E. H. & Pendleton, R. L. 1953. A survey of the vegetation of southeastern Asia. The Indo-Chinese Province of the Pacific Basin. Proceedings of the 8th Pacific Science Congress, 4: 99-144.

Werger, M. J. A., Nghia, N. H. & Zuidema, P. A. 1967. Demography of threatened tree species in Vietnam. Plant Ecology and Plant Science Group, Utrecht University, Tropenbos International and the Forest Science institute of Vietnam.

Williams, L. 1965. Vegetation of Southeast Asia. Studies of Forest Types. 1963-1965. Agricultural Research Services. U.S. Department of Agriculture.