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This large ecoregion extends from northern Vietnam into southeastern China, including Hainan Island. Only the Vietnamese portion of this ecoregion is considered here. Vietnam northeast of the Red River forms a part of the South China Platform and is geologically separate from the remainder of southeast Asia. The sediments here consist of a combination of exposed ancient metamorphic basement rock and marine sediments deposited in the late Paleozoic and early Triassic. Many of these sediments are limestones that have been uplifted and weathered to form an extensive karst landscape with steep topography. The highest peak in this region of Vietnam is Tsi Con Ling at 2,531 m, but most of the area is of only moderate relief. Annual rainfall in this ecoregion varies from a low of about 1,800 mm in the Red River Basin to a high of about 2,850 mm near the Chinese border, where there are only two months with less than 50 mm rainfall and no totally dry months. Temperature regimes in the north have a strong seasonality, with cool winter conditions and hot and humid summers. Very little pristine forest remains within this ecoregion. Lowland forests growing on limestone substrates commonly reach only 15-20 m in height but grow to 30-35 m on favorable sites. Few emergent trees in most stands suggest past cutting of larger trees. Dominance is mixed among a variety of tree species, with the Lauraceae, Fagaceae, and Meliaceae particularly important. This region shows strong floristic relationships with areas to the north in China, and regional endemism is high.
A complete biodiversity database is being compiled for this ecoregion as part of a large analysis that includes China. However, the area of the ecoregion that extends into northern Vietnam, and thus into this region of analysis, contains four near-endemic mammals (table 1), an indicator of the biodiversity and endemism levels that can be expected from this ecoregion. Table 1. Endemic and Near-Endemic Mammal Species.
 Current Status
Almost all of the lowland forests of the northern part of this ecoregion, which falls within a heavily populated section of Vietnam, have been cleared (MacKinnon 1997). In Myanmar, in eastern Shan State along the border with Laos and China, very large areas of forest have been cleared (IUCN 1991), but a few large blocks of habitat remain. There are sixteen protected areas (in Vietnam only) that cover 1,450 km2 of this ecoregion (table 2). Most of these protected areas are smaller than 100 km2, and the largest is only 260 km2. Table 2. WCMC (1997) Protected Areas That Overlap with the Ecoregion.
Much of the natural habitat has been altered by shifting cultivation and logging. Hunting for the wildlife trade is also a significant threat to conservation of biological diversity.
We included MacKinnon's Tropical Southern China subunit (06a), with biogeographic affinities with southern China, as part of the larger South China-Vietnam Subtropical Evergreen Forests [IM0149], which extends from southern China. However, instead of following the main tributary of the Red River, as MacKinnon does, we used the upper Red River (Yuan Jiang) as the boundary to be consistent with the boundary between two zoogeographic divisions in China: the Fujian Guangdong coast and South Yunnan Mountains (Yongzu et al. 1997). These two zoogeographic divisions largely coincide with the South China-Vietnam Subtropical Evergreen Forests [IM0149] and the Northern Triangle Subtropical Forests [IM0140] and intersect the Vietnamese border at the upper Red River tributary.
Campbell, D.G., and H.D. Hammond, editors. 1989. Floristic inventory of tropical countries. The New York Botanical Garden, New York. Chinese Vegetation Map Compilation Committee. 1979. Vegetation map of China. Map (1:10,000,000). Science Press, Beijing, China. Davis, S.D., V.H. Heywood and A.C. Hamilton. 1995. Centres of Plant Diversity: a guide and strategy for their conservation, Volume 2: Asia, Australasia and the Pacific. Worldwide Fund for Nature and IUCN – The World Conservation Union. Mackinnon, J., M. Sha, C. Cheung, G. Carey, Z. Xiang, and D. Melville. 1996. A biodiversity review of China. World Wide Fund for Nature, Hong Kong. Nowak, R. M. 1991. Walker’s Mammals of the World, Volume II, 5th Edition. Johns Hopkins University Press. Baltimore and London. Reviewed by: In process This text was originally published in the book Terrestrial ecoregions of the Indo-Pacific: a conservation assessment from Island Press. This assessment offers an in-depth analysis of the biodiversity and conservation status of the Indo-Pacific's ecoregions. For more general information on this ecoregion, go to the WildWorld version of this description. All text by World Wildlife Fund © 2001 | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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