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Southeastern Asia: Vietnam into Laos and Cambodia

The Southern Annamites Montane Rain Forests [IM0152] ecoregion in the remote montane forests of Kontuey Neak, or "the dragon's tail"-in the extreme northwest of Cambodia, where the boundaries of Cambodia, Laos, and Vietnam meet-is globally outstanding for its biodiversity. The intact forests of the ecoregion are little explored; it takes two weeks of intense walking and braving hazards such as mines and bombs that lie scattered throughout the landscape to get to some of the remote areas of the ecoregion.

But the known flora and fauna attest to the region's biological diversity, which includes some of Asia's charismatic fauna. Among the larger vertebrates, the tiger (Panthera tigris), Asian elephant (Elephas maximus), douc langur (Pygathrix nemaeus), gibbon (Hylobates gabriellae), wild dog (Cuon alpinus), sun bear (Ursus malayanus), clouded leopard (Pardofelis nebulosa), gaur (Bos gaurus), banteng (Bos javanicus), and Eld's deer (Cervus eldii) are better known.

  • Scientific Code
    (IM0152)
  • Ecoregion Category
    Indo-Malayan
  • Size
    18,000 square miles
  • Status
    Vulnerable
  • Habitats

Description
Location and General Description
The Southern Annamites Montane Rain Forests [IM0152] ecoregion extends along the greater Annamite Range from central Vietnam south to the Bolovans Plateau of Laos and the Central Highlands of Vietnam. It includes a broad topographic range from lowlands with wet evergreen forests to montane habitats with evergreen hardwood and conifer forests.

The geology of this ecoregion is also extremely diverse. The Kontum Massif of exposed granitic basement rock extends over an area extending 250 km from north to south and inland for 200 km. Ngoc Linh (Ngoc Pan), at the northwestern margin of the Kontum Massif, is the highest point of the Annamite Range in central Vietnam at 2,598 m. To the south the Annamite Range includes a complex mosaic of volcanic basalts, granites, and sedimentary substrates. Chu Yang Sinh, located 80 km inland from Nha Trang, forms the highest peak in the southern Annamite Range at 2,410 m. The Dac Lac (Darlac), Pleiku, Haute Cochinchine, Djirling, and Bolovans plateaus of southern Vietnam and Laos are volcanic remnants that reach maximum elevations as high as 2,200 m. Weathered basalts in these areas produce highly fertile soils with good agricultural potential. The heavily eroded Dalat Plateau of southern Vietnam, including the peak of Lang Bian, which reaches an elevation of 2,163 m, has soils formed from schists and quartzites and extensive areas of granites and volcanic rhyolites, andesites, and dactites.

Strong climatic gradients of rainfall and temperature are present within the ecoregion. The higher Kontum Massif and Dalat plateaus of central and southern Vietnam, and to a lesser degree the plateaus of Pleiku, Haut Chhlong, Djiring, and Haut Cochinchine, all rise to elevations or have exposures sufficient to give them more humid climatic zones. The semi-humid submontane zone at elevations of about 800-1,000 m has moderate levels of rainfall, with 1,500-2,200 mm annually. The peak of this rainfall occurs in September or October under the influence of the southward return of the monsoon with northeastern winds. Mean annual temperatures are about 20-21(C. The humid submontane climate zone comprises upland areas at middle elevations below about 1,100 m that are exposed to humid winds. Mean annual rainfall generally is above 2,500 mm and quite regular, with brief dry seasons lasting three months or less. Peak months for rainfall are typically August through October. Dew is abundant in the brief dry season, and foggy mists are common. The climatic zone covers much of the Kontum Massif, Haut Chhlong, and Haut Cochinchine and small areas east of the Dac Lac (Darlac) Plateau. The final climatic zone is the lower montane climate of southern Vietnam. This zone is present in the Kontum Massif and around the Dalat Plateau, where rainfall is about 1,800-2,000 mm, and there are 3-4 dry months of less than 50 mm rainfall. Very heavy rains of more than 3,850 mm annually occur on the eastern margin of the Dalat Plateau, with no dry month. These rains peak very late in November under the influence of the northeastern monsoon winds. Morning dew and foggy mists are common throughout this zone.

As expected from the complex geological, topographic, and climatic gradients present in the Southern Annamites Montane Rain Forests [IM0152] ecoregion, forest structure and composition are highly variable. Reconstruction of pristine forest structure and composition has been made very difficult by the high degree of landscape degradation that has taken place, much of it as the result of swidden agricultural practices. Wet evergreen forests at 600-900 m elevation are dominated by species of Fagaceae, Myrtaceae, and Lauraceae, with high overall species richness. For the Fagaceae, as many as twenty species of Lithocarpus, five species of Castanopsis, and three species of Quercus may be present in this formation. Very large emergent trees are also present among the Anacardiaceae, Burseraceae, Dipterocarpaceae, and Schima crenata. Hopea pierrei may be the most abundant of the large trees, forming up to 90 percent of all trunks reaching more than 1 m in diameter. Lianas form an important component of this forest community. Lower-elevation areas are dominated by wet evergreen forest in mesic sites and semi-evergreen forest in drier sites.

Montane hardwood forests above 900 m elevation in this ecoregion vary in structure and composition depending on geological substrate and moisture availability. Evergreen hardwood forests generally have an upper canopy reaching to about 30 m in height. Canopy heights decline with increasing elevation and decreasing soil depth.

The family best represented in the upper canopy of these habitats is the Fagaceae, with important contributions from the Magnoliaceae, Aceraceae, Podocarpaceae, Lauraceae, and Theaceae. The diversity of conifers is high in montane forests, with five genera present (Podocarpus sensu latu., Calocedrus, Fokienia, Cephalotaxus, and Taxus). A number of significant endemic species are present, including Pinus dalatensis and P. krempfii. Epiphytes form a notable part of the biodiversity of these montane forests. Particularly diverse are the orchids in the upper canopy and ferns in the middle and lower canopy.

Pinus kesiya extends over a fairly broad range of montane areas of the Dalat Plateau and other uplands in southern Vietnam at elevations up to 1,800 m. These are less mesic habitats than those of the high-elevation humid montane forests, where more diverse conifer forests are present. Human impacts on montane landscapes have almost certainly promoted the expansion of the range of P. kesiya at the expense of what were once montane evergreen forests. Keteleeria evelyniana may be present in denser gallery forests along the margins of the pine stands but seldom as an associate of the pure pine formations. Fire is a common factor in these forests.

The highest elevations and the slopes most exposed to humid winds in the montane zone often are bathed in moist clouds. The abundant dew and fog in these areas compensate for the lack of rainfall in the short dry season, producing lush conditions of mossy forest. Conifers (Fokienia hodginsii, Podocarpus spp.), Fagaceae (Quercus spp., Lithocarpus spp.), Theaceae (Gordonia, Pyrenaria, Ternstroemia), and Ericaceae form the dominant elements of these forests.

Biodiversity Features
Of the 122 mammal species known from the ecoregion, three are near-endemic species, and two are endemic (table 1). Some of the threatened species in this assemblage include the tiger, Asian elephant, douc langur, gaur, banteng, Eld's deer, serow, clouded leopard, pygmy loris (Nycticebus pymaeus), pig-tailed macaque (Macaca nemestrina), wild dog, Malayan sun bear, and smooth-coated otter (Lutrogale perspicillata).

Table 1. Endemic and Near-Endemic Mammal Species.

  Family Species
Hylobatidae Hylobates gabriellae
Muridae* Rattus hoxaensis*
Cercopithecidae Pygathrix nemaeus
Muridae* Rattus osgoodi*
Muridae Maxomys moi

An asterisk signifies that the species' range is limited to this ecoregion.

The large habitat blocks that remain have been included within a high-priority (Level I) TCU (Dinerstein et al. 1997). But because of rampant hunting to supply the wildlife trade (WWF-Indochina 1998), tiger and prey populations have been depleted.

More than 410 bird species are known from this ecoregion. Five of these species are near endemic, and five are endemic (table 2). Among the other bird species that need conservation attention are the globally threatened white-winged duck (Cairina scutulata), the critically endangered Edwards's pheasant (Lophura edwardsi), and the threatened Siamese fireback (Lophura diardi), green peafowl (Pavo muticus), and Germain's peacock-pheasant (Polyplectron germaini). Several other species such as the great hornbill (Buceros bicornis), Austen's brown hornbill (Anorrhinus austeni), wreathed hornbill (Aceros undulatus), and crested argus (Rheinardia ocellata) are indicators of low disturbance levels and relatively intact forests. The ecoregion also overlaps with two EBAs identified by BirdLife International, the Da Lat Plateau (145) and South Vietnamese Lowlands (144), which have eight and three restricted-range bird species, respectively (Stattersfield et al. 1998).

Table 2. Endemic and Near-Endemic Bird Species.

  Family Common Name Species
Phasianidae Edwards's pheasant Lophura edwardsi
Phasianidae Germain's peacock-pheasant Polyplectron germaini
Phasianidae Crested argus Rheinardia ocellata
Timaliidae Collared laughingthrush* Garrulax yersini*
Timaliidae Golden-winged laughingthrush* Garrulax ngoclinhensis*
Timaliidae Short-tailed scimitar-babbler Jabouilleia danjoui
Timaliidae Grey-faced tit-babbler Macronous kelleyi
Timaliidae Black-crowned barwing* Actinodura sodangorum*
Timaliidae Grey-crowned crocias* Crocias langbianis*
Fringillidae Vietnamese greenfinch* Carduelis monguilloti*

An asterisk signifies that the species' range is limited to this ecoregion.

Current Status
More than 75 percent of this ecoregion's natural habitat has been converted or degraded. The remaining forest is distributed in small, isolated fragments. There are sixteen protected areas that average 150 km2 and cover almost 2,500 km2, or 5 percent of the ecoregion area (table 3). Many of these protected areas are paper parks that lack good management and effective protection.

Table 3. WCMC (1997) Protected Areas That Overlap with the Ecoregion.

  Protected Area Area (km2) IUCN Category
Bach Ma [IM0141] 160 II
Dong Hua Sao [IM0202] 400 VIII
Ngoc Linh 200 IV
Kong Cha Rang 210 IV
Kon Kai Kinh 200 IV
Bana-Nui Chua 60 IV
Nui Thanh [IM0211] 20 UA
Rung Kho Phan Rang [IM0211] 30 IV
Deo Ngoau Muc [IM0211] 30 ?
Kalon Song Mao [IM0211] 30 IV
Chu Yang Sinh 190 IV
Thuong Da Nhim 390 IV
Mt. Lang Bian 110 IV
Nam Lung 120 IV
Nui Dai Binh 100 IV
Phnom Nam Lyr [IM0210] 160 IV
Total 2,410  

Ecoregion numbers of protected areas that overlap with additional ecoregions are listed in brackets.

Types and Severity of Threats
Because of the high elevations and steep slopes of this ecoregion, the human population density here is moderate (MacKinnon 1997). However, anthropogenic influences are pervasive throughout the ecoregion in the form of regular burning to create open woodlands and shifting cultivation. Large areas in the Da Lat Plateau in Vietnam have been cleared for settlements, plantations, and agriculture. Shifting cultivation is prevalent in the upper slopes. Bolovans Plateau is severely threatened by clearing of the forested area for coffee plantations. Wildlife poaching and excessive harvesting of NTFPs are severely threatening the integrity of Dong Hua Sao.

Justification of Ecoregion Delineation
In a previous analysis of conservation units across the Indo-Malayan realm, MacKinnon (1997) included the coastal habitats of Vietnam, Cambodia, and Thailand in the Coastal Indochina biounit (05). This biounit consisted of four subunits, and each includes large areas of different vegetation types. In keeping with our rules for delineating ecoregions, we extracted the wet evergreen forests that cover the mountain range and plateaus (to the south of the Hai Van Pass) from the adjacent dry forests and placed them in the Southern Annamites Montane Rain Forests [IM0152].

References
References for this ecoregion are currently consolidated in one document for the entire Indo-Pacific realm.
Indo-Pacific Reference List

Prepared by: Eric Wikramanayake, Philip Rundel, and Ramesh Boonratana
Reviewed by:

 

The Global 200

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