The environment of the Qin Mountains is a
deciduous forest ecoregion. The Qin Mountains form the
watershed of the
Yellow River and
Yangtze River basins; historically, the former was home to deciduous
broadleaf forests, while the latter has milder winters with more rainfall, and was generally covered in warmer, temperate, evergreen broadleaf forests. Thus, the Qin Mountains are commonly used as the demarcation line between
northern and southern China. The low-elevation forests of the Qin foothills are dominated by temperate deciduous trees, like
oaks (
Quercus acutissima,
Q. variabilis),
elm (
Ulmus spp.),
common walnut (
Juglans regia),
maple (
Acer spp.),
ash (
Fraxinus spp.) and
Celtis spp. Evergreen species of these low-elevation forests include broadleaf
chinquapins (
Castanopsis sclerophylla), ring-cupped oaks (
Quercus glauca), and
conifers, like
Pinus massoniana. At the middle elevations, conifers, like
Pinus armandii, are mixed with broadleaf
birch (
Betula spp.), oaks (
Quercus spp.), and
hornbeams (
Carpinus spp.); from about , these mid-elevation forests give way to a
subalpine forest of
firs (
Abies fargesii, A. chensiensis),
Cunninghamia, and
birch (
Betula spp.), with
rhododendrons (
Rhododendron fastigiatum) abundant in the
understory. Timber harvesting reached a peak in the 18th century in the Qinling Mountains. The region is home to the endemic
Qinling panda (
Ailuropoda melanoleuca qinlingensis), a brown-and-white
subspecies of the
giant panda (
A. melanoleuca), which is protected with the help of the
Changqing and
Foping nature reserves. The
Chinese giant salamander (
Andrias davidianus), at , is one of the largest
amphibians in the world, and is
critically endangered; it is locally pursued for food, and for use of its body parts in
traditional Chinese medicine. An environmental education program is being undertaken to encourage sustainable management of wild populations in the Qin Mountains, and
captive-breeding programs have also been set up. == Weapons of mass destruction ==