Location and General Description
The Daba Shan includes several smaller ranges that define the northeastern rim of the Sichuan Basin and extend eastward toward the Changjiang (Yangtze) River Plain. The mountains have a significant effect on the regional climate by moderating winter cold in the Sichuan Basin and the plains of the Yellow River. Because the Daba Shan face plains to the south, they are relatively warm and moist and support plants and animals that have a subtropical affinity.
Low mountains in the foothills of the Daba Shan support a mixed evergreen and deciduous association of oak species (Quercus acutissima, Q. variabilis) and an arboreal member of the mint family (Labiaceae spp.). Higher elevations support warm-temperate conifer forests of Chinese red pine (Pinus massoniana) and the higher elevation pine (P. armandii).
Much of the remaining intact habitat occurs in the eastern part of this ecoregion on the slopes of 3,100 m Shennongjia Mountain Nature Reserve (704 km2), a place renowned for its medicinal plants and dense forest cover. This region conserves a large amount of primary old-growth forest, some of the last in this part of China. Shennongjia Reserve is rich in vascular plants; there are more than 2,600 species of which 32 are under national protection. Some of the more significant species include dove tree (Davidia involucrata), the vesselless relict (Tetracentron sinense), Cercidiphyllum japonicum, Emmenopterys henryi and Eucommia ulmoides.
Within the ecoregion, Shennongjia Mountain supports several threatened mammal species including the golden snub-nosed monkey (Rhinopithecus roxellana), leopard (Panther pardus), and forest musk deer (Moschus berezovskii). Reeve’s pheasant (Syrmaticus reevessi) also occurs here. Some wild mammals often come into conflict with local residents who live within the reserve. Wild pig (Sus scrofa), Himalayan black bear (Selenarctos thibetanus), and Macaca mulatta are among the more troublesome.
Three first-class protected plants occur in this ecoregion. Dawn Redwood (Metasequoia glyptostroboides) is the descendent of a genus of conifers that arose 100 million years ago and had a broad distribution across the Northern Hemisphere until the Tertiary, about 20 million years ago. Once thought long extinct, relict stands of this deciduous conifer were discovered in the 1940’s in the Daba Shan. It is now thought that a much more extensive population of this species was decimated during the Pleistocene ice ages, as were the Sequoia redwoods of California, another member of the Taxodiaceae. Those dawn redwoods that survived were sheltered during the Pleistocene on the warm south slopes of the Daba Shan.
Dove tree (Davidiana involucrata) and the conifer (Taiwania flousiana) also occur here. All three of these species are recognized because they are primitive and were greatly reduced during Pleistocene glaciations. All three survived on the southern slopes of the Qinling-Daba Mountain complex, most likely because the southern slopes are sheltered from cold winter temperatures.
Conversion of forest to agriculture, and hunting and collecting of wild plants and animals have contributed to loss of biodiversity in the mountains throughout southwest China. Situated adjacent to the Sichuan Basin, a region of thriving commerce and more than 100 million inhabitants, these mountains are likely subject to large and increasing levels of exploitation.
Types and Severity of Threats
Improved enforcement of existing conservation regulations is needed. The Shennongjia Mountain Nature Reserve conserves intact forests at the higher elevations, but the biologically diverse lower regions are degraded and subject to encroachment. Education of local people about the value of protecting wildlife would also be a positive step toward conservation of this area.
Justification of Ecoregion Delineation
The high mountains and foothills in the Daba mountain range serve as a climatic and biological barrier between temperate and subtropical zones marked by a transitional climate with high humidity and an indistinct dry season. The Han Shui river valley serves as the northern boundary and Chang Jian river the southern. The CVMCC (1979) Vegetation Map of China class classes included are: warm-temperate mixed shrub (32a), warm-temperate conifer (8a,b, 11), and evergreen, deciduous mixed forest (17). This is comparable to the Daba-Micang Mountains biogeographic subunit in Oriental Deciduous Forests according to Mackinnon et al. (1996).
Chinese Vegetation Map Compilation Committee. 1979. Vegetation map of China. Map (1:10,000,000). Science Press, Beijing, China.
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Prepared by: Chris Carpenter
Reviewed by: In process