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Gymnosperms of Sichuan
This page is based on the Plant Resources of Sichuan, published by the Department of Biology, Sichuan United University, September 1994. I have merely minimized discussion of non-gymnosperm taxa. Most of the language is quoted directly.
1. Some General Characteristics of the Sichuanese Flora
1.1. Tropic-subtropic and temperate species dominate
Sichuan has 88 species and 27 genera of gymnosperms in 9 families. The province lies on the border of the subtropics and tropics and its landscape is notably diverse, which has proved beneficial for a rich evolution. Nonetheless, the high mountain areas in Sichuan's west and southwest also provide important centers of diversity for temperate genera.
1.2. Endemic genera are numerous
Sichuan's area is large and its ecological conditions vary from alpine-arctic to subtropical. The recent rising of the Himalayas and the relatively mild glacial periods also were auspicious for the formation of an abundant biodiversity. [...] [A]t low altitude forests or cultivated near temples Gingko biloba can often be found. Single-species genera [...] endemic to south-west China: [...] Cathaya Chun et Kuang, Metasequoia Hu et Cheng, [...] These great numbers of indigenous plants indicate Sichuan's flora is both ancient and special. [...]
1.3. Many relict species prove antiquity
Sichuan's vegetational history is quite long, its western part has been above sea level since paleozoic times [Guan 1990]. As elsewhere, during mesozoic times it bore are cycadophyte-pteridophyte covering. The climate became dryer during the Cretaceous (most forests disappeared), but in the Tertiary became warmer again. Most crucial, East Asia was lucky to pass a milder Quarternary glacial period than comparable areas in Europe or North America, thus many species could survive here. Although during the quartery glacial periods in the west Sichuan high mountain ridges glaciers formed, this has not affected the survival of many ancient species, many of them moving south via the Hengduan Mountains (p.e. fir forests moved down to 1500m in Xichang, or even 1100m in Panzhihua [Liu 1977]), and then radiating again in the Quaternary. [...] Sichuan harbors three very famous"living fossils": Gingko, Cathaya and Metasequoia, other ancient gymnosperms are the pre-Jurassic Cycas, the Cretaceous Pinus, Picea, Torreya, Cephalotaxus, as well as Keteleeria, Abies, Tsuga, Cryptomeria, Cunninghamia, Podocarpus and Ephedra for the Tertiary. [...]
1.4. Gymnosperm diversity
With 88 species in 27 genera and 9 families Sichuan is China's richest province in gymnosperms (nationwide we count 232 species, 34 genera, 10 families), so 79.4% of the Chinese genera or 37.9% of China's species are represented. Most abundant are the Pinaceae (43 spp.), followed by the Cupressaceae (17 spp.), Cephalotaxaceae (6 spp.), Taxodiaceae, Podocarpaceae, Ephedraceae (5 spp. each), Gingkoaceae and Cycadaceae (1 sp. each). 14 species (15.9%) are endemic. The other Sichuanese gymnosperms are occuring in neighboring provinces, too, as in Yunnan (46 spp.), Hubei (31 spp.), Gansu and Guizhou (each 30 spp.), Tibet and Shaanxi (each 23 spp.) and Qinghai (only 9 common spp.).
The plant community of Sichuan developed from a paleomediterranean-cretaceous plant community and can now be considered as subtropical. For its rich evolution the rising of the western part of the province was very auspicious: many habitats become disconnected during glacial periods providing many oppurtinities for further diversification. The differences the alpine and subtropic areas can be summarized as follows: In the western mountains, albeit the number of genera being low (mainly Abies, Picea, Pinus, Tsuga, Larix and Sabina), their distribution is wide, but according to geomorphology, mosaic and gradient distributions do often form. Here Picea and Abies are particular dominant, with the exception of Abies fargesii West Sichuan contains all provincial representatives of these two genera, and is being a major center of diversity nationwide. Here you'll find extremely cold-resistant species like Picea likiangensis var. balfouriana and Abies squamata which survive up to 4500m and 4600m respectively. On the other hand Abies ernestii and Picea wilsonii are more adapted to warmer environments at 2200-2800m with a maximum of 3200m. The former although belonging to the genus Abies grows well on dry slopes, whereas Picea wilsonii will grow in damp ravines! Many examples like this demonstrate a high degree of diversification.
On the other hand, in the eastern part of the province, gymnosperms do not coin the whole vegetation, but many tertiary relict plants survived. Interesting examples are Metasequoia glyptostroboides, Glyptostrobus pensilis, Cathaya argyrophylla, Fokienia hodginsii, Amentotaxus argentotaenia, Thuja sutchuenensis, Gingko biloba, Pseudotsuga sinensis, Keteleeria davidiana, Cunninghamia lanceolata, Torreya fargesii, Taxus sinensis, Cephalotaxus fortunei etc.
2. Phytogeography of Sichuan
A glance on the map of present distribution of tree societies shows that Sichuan can be divided into three major landforms. In the eastern part lies the subtropic Sichuan basin (including the major cities as Chengdu, Chongqing etc.) surrounded by mostly lower mountains (1500-2000m), such as the Micang and Daba Mountains in the north, the Wu and Qiyao Mountains in the east, the Dalou Mountains in the south, Longmen, Emei, Lower and Upper Liang Mountains in the west. The north-western part of the province, however, is characterized by the adjacent Qinghai-Tibet plateau grasslands (3500-4500m). Between the basin and the grassland a zone of high mountain coniferous forests can be found (3000-4000m).
2.1. The basin (east & central Sichuan) and evergreen broad-leaved woodlands (south-west Sichuan)
This region is situated south-east of the counties Pingwu, Maowen, Baoxing, Kangding, Luding, Jiulong and Muli, it thus comprises nearly the whole province with the only exception of the Gansun and Aba Tibetan autonomous regions. In the Sichuan basin and its surrounding lower mountains the climate is hot in summer, mild in winter, frosts are seldom, rain is plenty (1000-1200mm p.a.) all over the year, it's moist and misty. Average annual temperatures mainly range between 16-19 C. In the Hengduan mountains regions in south-west Sichuan, monsoon periods gradually become more distinct: winters are quite dry, whereas summers are very damp. The typical vegetation comprises subtropical evergreen broad-leaved forests [...], subtropical coniferous woods (Pinaceae, Taxodiaceae, Cupressaceae) and bamboo stands. The natural conditions are very good in this area, but as the densely populated basin is mainly used for agriculture, wild plants are confined to wastelands, riversides or village woods. The east is characterized by south-eastern monsoons, the climate is very humid, frosts are seldom, there is no distinguished arid period, which supports humid evergreen broad-leaved forests [...] and subtropical coniferous forest (mainly composed of Pinus massoniana, Cunninghamia lanceolata and Cupressus funebris). The fertile center of the basin is dominanted by a long agricultural history, so dominant trees are Pinus, Abies, Cupressus, many Bambusoidae, Lauraceae, Alnus, Eucalyptus etc. [...] [P]lants found in the mountains around the basin are: [...] Pinus, Taxus, Cupressus, Ephedra as representative gymnosperm genera [...]
Of the western Sichuan highlands, the southern part is also influenced by the monsoon climate in the procumbent lower mountains surrounding the basin, drought and rain period are clearly distinguishable. This area is characterized by broad-leaved woods [...] or subtropical conferous forests (Pinus yunnanensis, Keteleeria evelyniana, Cupressus duclouxiana). [...]
2.2. Alpine coniferous forests (western Sichuan)
This region is located west of the counties Pingwu, Maowen, Baoxing, Kangding, Jiulong and Muli and southeast of Dengke, Zhuqing (Dege county), Hexi (Seda county), Nanmuda and Chazhenliangzi (Rangtang county), Huangshengguan (Songpan county) and Ruoergai. It comprises the whole counties of Nanping, Songpan, Heishui, Lixian, Maerkang, Jinchuan, Xiaojin, Danba, Kangding, Daofu, Qianning, Xinlong, Dege, Baiyu, Yajiang, Yilun, Batang, Xiangcheng, Daocheng, Derong, Litang and parts of the counties Ruoergai, Hongyuan, Rangtang, Wenchuan, Maowen, Gansun, Luhuo, Dengke and Muli. This zone borders to the Qinghai-Tibet high plateau, its moutains are steep and, while being rich in geothermic energy, its geomorphology is complex. Its eastern mountain valleys abundant in spruces, firs and pines, form the (somewhat overlogged) major wood resource for Sichuan. In its west, subalpine shrublands and meadows begin to dominate. For some river valleys, an average annual precipitation of ca. 600mm and an annual medium temperature of 12°C might be given, but local climatic conditions are varying very much according to altitude.
[...]
2.3. High plateau grass- and shrublands (north-western Sichuan)
This region is situated north-west of the line Dengke, Zhuqing (Dege county), Hexi (Seda county), Nanmuda (Rangtang county), Aba, Chazhenliangzi, Huangshengguan (Songpan county) to Ruoergai. It wholly or partially contains the counties Shiju, Aba, Dengke, Dege, Seda, Gansun, Luhuo, Tangrang, Hongyuan, Ruoergai and Songpan and belongs to the Qinghai-Tibet high plateau. From 3,300-4,000m in the east it gradually rises to 3,900-4,500m in the west. The river valleys are broad and not deeply incised and hills are quite flat, so mostly the height difference between river bed and surrounding hilltops does not exceed 400m. This climate is cold (medium temperature ca. -1 C) and dry (precipitation about 650mm), irradiation is intensive. Grasslands (Roegneria nutans, Poa pratensis, Agrostis schneideri, used for grazing yaks and sheep) dominate, intertwined with shrublands and marshlands. At some places, fragmented subalpine coniferous woods occur.
[...]
In short, the vertical distribution is quite distinct anywhere in Sichuan: we can distinguish the agricultural region (below 1,200m), a surrounding secondary shrubland area (900 to 1,500m), an evergreen broad-leaved forest belt (1,400 to 2,000m), a zone where evergreen broad-leaved and deciduous forests mix (1,800 to 2,500m), subalpine and alpine conifers (2,500 to 3,200m), alpine shrublands and meadows (3,200 to 4,500m) and alpine rock vegetation (above 4,500m).
3. Plant Resources in Sichuan
[...]
3.1. Pharmaceutical plants
3.1.1. Diversity
[...]
Cephalotaxus fortunei protects against cancer, the reserves are 5 tons distributed Nanping and Wenchuan county, not included minor deposits in other counties like Tianquan, Shimian and Lushan. [...]
3.1.2. Distribution of pharmaceutical plants: some examples
[...] At altitudes from 2,000 to 2,800m subalpine coniferous forests dominate (mostly Abies fargesii, other components are secondary Populus spp., Betula spp. and Pinus armandii). [...]
Located on the western edge of the Sichuan basin, the vertical plant distribution of Mt. Erlang reads like this: In the lower strata below 1,800m evergreen broad-leaved forests dominate [...] Approaching to the 1,800m line, [...] one can also find subtropical coniferous forests (Cunninghamia lanceolata, Cupressus funebris, Pinus massoniana) or interspersed Phyllostachys pubescens bamboo associations. [...] At altitudes from 1,800 to 2,000 meters, deciduous and evergreen forests confuse. [...] At altitudes from 2,200 to 3,200m alpine conifers are clearly dominant. Its upper part is almost exclusively composed of Abies faxoniana, Picea brachytyla and Tsuga chinensis. [...]
The greater Liangshan mountains in southwestern Sichuan are jointly influenced by both the south-eastern and south-western monsoons, so the composition and vertical distribution has both features of that in alpine mountains and valleys. Below 2,600m, the vegetation is dominated by broad-leaved forests [...] The subalpine forest zone ranges from 2,600 to 3,800m, its lower part is dominated by Tsuga dumosa, Ts. chinensis, Acer spp. and Betula spp. The upper coniferous woods are composed of Picea likiangensis, Abies georgei, A. forrestii and A. fabri. [...]
In the Hengduan mountain slopes belonging to south-west Sichuan, the distribution can be characterized as following: The upper and middle Minjiang River valley (below 1,000m) is filled with evergreen broad-leaved forests, subtropical coniferous forests (mostly Cunninghamia lanceolata), shrublands [...] or deciduous oak forests. [...] At altitudes of 1,600 to 2,000m evergreen and decidous broad-leaved forests mix, in dry river valleys there are shrublands [...] When advancing to heights of 2,000 to 3,800m subalpine conifers dominate (Abies ernestii, A. faxoniana, A. fabri, Picea purpurea, P. asperata, Cyclobalanopsis glauca, at protected sites Tsuga chinensis). [...]
3.2. Other plants of economic value
[...] As for tannins, there are of course huge reserves in tree-barks of west Sichuan subalpine conifers like Pinus densata, Picea asperata, P. likiangensis, P. purpurea, Abies ernestii, A. faxoniana, A. georgei, A. squamata, Larix potaninii and L. potaninii var. macrocarpa. [...]
4. Cited Literature
Guan Zhongtian (1990), The forest changes in South-west China during diverse geological periods, in: Li Chengbiao [Ed.], Ecological Study of Sichuan Forest, Sichuan Publishing House of Science & Technology, Chengdu, pp. 187-208.
Li Chengbiao (1990), General geographical divisions of Sichuan forests, in: Li Chengbiao [Ed.], Ecological Study of Sichuan Forest, op.cit., pp. 295-307.
Liu Yandong (1977), Pollen at lower Jiegeda and its meaning for the dynamics of quarternary glacial periods, J. Bot. Sin.
Wu C.Y. (1991), The areal-type of Chinese genera of seed plants, Acta Botanica Yunnanica, Suppl. IV.
Academia Sinica (1960), Pharmaceutical Flora of Sichuan, Sichuan People's Press, Chengdu.
Vegetation of Sichuan (1980), Sichuan People's Press, Chengdu.
Exploitation of Animal and Plant Resources in Sichuan (1988), Sichuan Social Sciences Press, Chengdu.
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