Sustainable Agriculture and Food: Four volume set (Earthscan Reference Collections)

Integrated Farming Systems at Different Scales 461

are distinct, though most areas have suffered human disturbances. On the humid
slopes, less than 2500masl, the original forest vegetation features subtropical mixed
evergreen–deciduous broadleaf forests. The dominant species are in the genera
Quercus, Alnus, Lithocarpus, Liquidambar, Populus, Castanopsis and Cyclobalanop-
sis. Most of these trees are somewhat cold-resistant evergreens, mixed with some
temperate deciduous broadleaf trees. The forests have a complex form with a three-
layer structure. The first layer consists of deciduous broadleaf trees, while in the
second and third layers are evergreen broadleaf trees. On the forest floor the bam-
boo, Sinarundinaria chungii, grows. The deciduous broadleaf trees are mainly of
the beech family, which reflects the extreme humidity of the local environment.
The representative species of evergreen broadleaf trees are Cyclobalanopsis glauca of
the beech family, Phoebe bourpei of the laurel family, and Schima superba of the tea
family. Between 2500m to 3000m there are mixed coniferous broad-leaved forests.
From 3000m to 4000m and even higher is the sub-alpine forest belt, dominated
by species of spruce and fir. Alpine scrub, meadows and nival vegetation can be
found in areas higher than 4000m. In the Hengduan Mountains are valleys with
less precipitation, where the so-called dry and hot valley vegetation occurs.
In the middle reaches of the Yangtze River the zonal vegetation is mixed ever-
green and deciduous broad-leaved forests, growing on yellowish-brown soil. The
natural forests are mainly distributed on mountains and hills. The forests are green
all year round and contain an arbour layer, a shrub layer and a herbaceous layer. The
trees are mainly in the genera Cyclobalanopsis and Castanopsis of the beech family
and associated deciduous trees of beech, walnut and maple. Among the coniferous
trees, masson pine (Pinus massoniana) and Chinese fir (Cunninghamia lanceolata) are
dominant below 600–800m. Above this, Huangshan pine (Pinus hwangshanensis)

Table 18.17 Climatic conditions of the major cities along the Yangtze River

City Mean annual temperature (°C) Annual precipitation (mm)

Yushu 2.9 480.5

Changdu 7.5 477.7

Huili 15.1 1130.9

Yibin 18.0 1177.3

Chongqing 18.3 1079.4

Yueyang 17.0 1302.4

Yichang 16.8 1164.1

Wuhan 16.3 1204.5

Jiujiang 17.0 1412.3

Anqing 16.5 1389.2

Wuhu 16.0 1169.8

Nanjing 15.3 1031.3

Shanghai 15.7 1123.7