Location and General Description
This ecoregion includes the extensive hill country that lies to the south of the lower Yangtze River Basin and north of the tropical coastal plains of southeastern China. It extends from China’s southeast coast westward to the Guizhou and Yunnan Plateaus. The granitic Nanling Mountain Range is a major landscape feature here, with elevations of 500 to 1,500 m. Interspersed among the granite are substantial areas of Paleozoic limestone including karst pinnacles and "sugarloaf hills" that support distinctive vegetation adapted to the seasonal drought conditions associated with this kind of subtrate. Rivers drain either northward into the Changjiang (Yangtze) River or southward into the Zhujiang (Pearl) River.
The climate here is mild. Precipitation patterns are monsoon-dominated with summer precipitation and hot weather during the spring. Climatic influences from central China bring more winter precipitation to this area than to the seasonal tropical areas that lie to the southwest. This part of China is also subject to frequent typhoons (cyclonic storms equivalent to the North American hurricanes that usually occur during the late summer and fall)
Forests of the Nanling Mountain Range are dominated by chestnut (Castanopsis spp.) and other members of the oak family (Quercus spp., Cyclobalanopsis spp.), with Schima spp., a member of the tea family (Theaceae spp.) and various laurels (Lauraceae spp.) as important associates. This combination of oak, laurel and Schima spp. identifies this forest with other regions of montane subtropical Asia that are widespread from Taiwan westward to the foothills of the Nepal Himalaya. Drier sites are dominated by the oaks, especially Quercus spp.. Limestone forests occur below 1,000 m and support semi-deciduous broadleaf forest dominated by Cyclobalanopsis glauca, Cinnamomum calcarea, Ulmus parvifolia, Bridelia fordii, and Celtis spp. in moist places and Canthium dicoccum, Cornus fordii, and Sapium rotundifolium on drier, sites with shallow soils.
The forests of southwest Guangxi Province are typical of this ecoregion. Here the composition of the forest growing on the sandstone and shale hills is quite different from the forest growing on the limestone hills, although both share the dominant tree species Eberhardtia aurata, Hopea chinensis and Saraca chinensis. Because they are poorly suited to agriculture, limestone hills support the most extensive seasonal forests, including endemic species like Parashorea chinensis and other members of the tropical family Dipterocarpaceae.
Subtropical forests of the lowlands are now nearly extirpated. Dominant trees include Fagaceae (Castanopsis spp., Cyclobalanopsis spp., Fagus spp.), the tea family, Theaceae (Shima spp., Camellia spp.) and the laurel family, Lauraceae (Phoebe spp., Persea spp., Cinnamomum spp.) and a protected laurel species, Cryptocaria chinensis, the bark of which produces a valuable aromatic oil.
Several first-class protected mammals with restricted ranges occur in Guangxi Province, much of which is included in this ecoregion. They are the white-headed leaf monkey (Presbytis leucocephalus), Francois’ leaf monkey (P. francoisi), and southern serow (Naemorhedus sumatraensis). Pangolin (Manis pentadactyla), a second-class protected mammal, also ranges widely throughout the province.
First-class protected birds include Cabot’s tragopan (Tragopan caboti) and black stork (Ciconia nigra). Several amphibians and reptiles are listed as well, including the giant salamander (Megalobatrachus davidiana) and green turtle (Chelonia mydas).
The ecoregion is rich in bird species. Particular areas within the ecoregion typically contain 400 species or more. Migratory passerine species may overwinter in the subtropical forests or pass through the area en route to wintering grounds in tropical Southeast Asia. Silver oriole (Oriolus traillii) is a restricted range species that visits forested hillsides during the summer months. Rivers and lakes (now much diminished) provide crucial winter habitat to many water birds
The Nanling Shan Mountain Area is recognized as a center of plant diversity and endemism. The less accessible karst limestone hills provide refuge for subtropical vegetation and several mammal species of conservation significance. Three first-class protected plants are Camellia chrysantha, the subtropical conifer Cathaya argyrophylla, and the tree fern Cyathea spinulosa.
Bamboo is a diverse and important component of the forest, especially in the limestone areas, and may form closed stands on disturbed sites. One ecologically significant species is spiny bamboo (Bambusa arunidinacea),
This ecoregion also provides native habitat for a number of commercially important food plants including tea, citrus, longgan and lychee, which may have first come into cultivation in this area. The laurel, Neolitsea sericea, is endemic to the islands that lie opposite the mouth of the Changjiang (Yangtze) River. Tertiary relict plant species occur in the Nanling Mountains, including threatened subtropical conifers such as Cathaya argyrophylla, Amentotaxus argotaenia, Cephalotaxus oliveri and Liriodendron chinense, a member of the magnolia family.
Most native vegetation has been extirpated throughout this ecoregion. Exceptions are those species that live on steep inaccessible hillsides, especially in the limestone areas poorly suited to agriculture. Lowlands have been converted to rice paddy agriculture for centuries. Some areas have been more recently converted to plantations of the native conifers Pinus massoniana and Cunninghamia lanceolata.
Types and Severity of Threats
Conversion of agricultural land to farming, hunting and the collection of rare species for sale, and inadequate management within existing protected areas are all the main threats to biodiversity in this region.
Justification of Ecoregion Delineation
This ecoregion includes: warm-temperate conifers (8 a,b,c, 10); evergreen broadleaf (21a,c); and warm-temperate mixed shrub (32a, 33 ) from the CVMCC (1979) Vegetation Map of China. Also included are broadleaf mixed forests (18, 19) and cultivation/plantation (73b). The area is comparable to the Southeastern Coast biogeographic subunit (01c) in the Chinese subtropical forests according to Mackinnon et al. (1996).
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Prepared by: Chris Carpenter
Reviewed by: In process