Hunan

Relief

More than one-fourth of Hunan’s terrain lies at an elevation above 1,640 feet (500 metres), and much of it is well over 3,000 feet (900 metres) above sea level. The highlands in the west run from northeast to southwest, forming the eastward edge of the Guizhou Plateau, whose extension, the Xuefeng Mountains, lies in the heart of the province. These mountains are composed mainly of slate, quartzite, and sandstone, deeply incised by river valleys. The Nan Mountains in the south run from east to west at elevations of between 500 and 3,300 feet (150 and 1,000 metres), forming a broad mountain border between Hunan, Guangdong, and Guangxi. They are largely dome-shaped and granitic, although limestone and red clay are found in lower-lying areas. In the east the mountain ranges of Zhuguang and Wugong form the border with Jiangxi. The Zhuguang Mountains, in the extreme southeast of the province, rise to a height of 6,600 feet (2,000 metres).

The uplands of the west, south, and east fall steadily in elevation toward the plain of Dongting Lake in the north, which is contiguous with the Hubei Plain and forms part of the floodplain of the Yangtze River. The part of the plain within the borders of Hunan has an area of some 3,800 square miles (9,800 square km); it has been formed by silt carried down from the mountains by the Yangtze and its right-bank tributaries. Dongting Lake is a broad and shallow seasonal lake, consisting of the remnants of a former inland sea that once filled the Yangtze basin. Its area varies considerably between summer and winter, and the lake has dried up significantly since the 1950s. Nonetheless, it is still the second largest freshwater lake in China, surpassed only by Lake Poyang in Jiangxi.

Drainage

Hunan’s entire river system drains into Dongting Lake, with the exception of the Lin Stream, which divides into two parts, with one distributary draining directly into the Yangtze River and the other into Dongting Lake. The western highlands are drained by the Yuan River and by the Zi and Li streams. The Yuan and Zi are torrents in their upper courses; fast-flowing in summer, they run through deep gorges, broadening out to wider valleys in their lower courses. Hunan’s largest river, the Xiang, rises in the heart of the Nan Mountains, as do its tributaries. Many smaller rivers that rise in the mountains along the eastern border flow westward to join the Xiang in its northward course.

Much of the low-lying land around Dongting Lake is subject to flooding when the rivers come down in spate during the summer months. The system of dikes built to contain the floodwaters is supplemented by a vast network of electric pumping stations. These pumps drain the fields when waterlogged and irrigate them in times of drought. In the dry hill lands, numerous large and medium-sized water-control projects have been built. In these projects, valleys are dammed and “mountain pools” are formed, from which channels are led to the arid land. One of these schemes—the Shaoshan Irrigation System—diverts some of the upper waters of the Lian Stream, thus irrigating the dry hill land, and also controls flooding in the river’s lower reaches; the irrigated area has been converted from single-crop to double-crop rice land.

Soils

The soils of the province are largely pedalferic (rich in alumina and iron) and are mainly lateritic (leached, iron-bearing) yellow earths or red clays. In the hilly regions of central and southern Hunan, the soils are for the most part lateritic clays that are strongly acidic and poor in organic material. The alluvial soils of the northern plains are less acidic and are used for growing rice.

Climate

The north generally experiences more extreme weather conditions than does the south. In winter, occasional waves of cold air from Mongolia sweep southward, injuring tea bushes and fruit trees in northern Hunan. The average minimum winter temperature is 43 °F (6 °C). Summers are long and humid, the average maximum summer temperature being 86 °F (30 °C). The north has an average of 260 frost-free days per year, while in the south the average is 300 days. Precipitation (almost entirely as rain) is ample, with the maximum precipitation occurring between spring and summer. The total annual rainfall of 56 inches (1,420 mm) decreases from south to north. Hunan lies in the path of the wet monsoons, which pass from west to east along the Yangtze basin in summer, bringing with them at times long periods of heavy rain, resulting in extensive flooding of low-lying lands.

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Plant and animal life

The natural vegetation of Hunan was originally dense deciduous and coniferous forest. Over the centuries, as the population has increased, all the lowlands and much of the highlands have been cleared to make way for cultivation. Despite this vast deforestation, however, large stands of pine, cedar, bamboo, and camphor are found in the western highlands. Other important trees and shrubs include tung (from which tung oil is obtained), tea (from which tea seed oil is obtained), and liquidambar. Bamboo groves planted along the roadsides are characteristic of Hunan and supply the province’s handicraft industries. As elsewhere in central and southern China, groves of bamboo, camphor, and cedar are usually found around villages, contributing greatly to the charm of the countryside.

Hunan traditionally has had a wide range of fauna, including such large mammals as tigers, leopards, wolves, and deer. However, human encroachment has led to the decline and near-disappearance of many species. Birdlife is abundant, and Dongting Lake is a major habitat for aquatic birds in East Asia; notable species include the lesser white-fronted goose (Anser erythropus), hooded crane (Grus monacha), and the Chinese sparrowhawk (Accipiter soloensis). The lake also abounds in fish, including many species of carp, and it is home to the endangered finless porpoise (Neophocaena phocaenoides).