Paper by Zheng Du
(Institute of Geography,
Chines Academy of Sciences, Beijing 100101, P.R. CHINA)
FRA2000 Global Ecological Zoning Workshop,
Cambridge
UK, July 28~30, 1999
The eco-geographical regions of hierarchic system is demarcated or combined with different units based on regional differentiation of the earth surface nature. It provides a regional framework for studying on regional impact and response to global change. The principle, approach of demarcation, hierarchical units, criteria and boundaries, as well as a proposed scheme of the eco-geographic regional system of China, is dealt with in the present paper.
Based on temperature conditions, moisture regimes and differences in landforms, the terrestrial surface of China are successively demarcated in a proposed framework of the eco-geographic regional system. Owing to a tremendous area with an average elevation of more than 3000 m asl and a low temperature in growing season, the Tibetan Plateau is quite different to the rest parts of China.
According to temperature conditions, relevant physical and ecological phenomenon as well as agriculture production, eleven temperature belts may be recognized in China, among them nine belts exist in the lowland area, while the other two appear on the Tibetan Plateau. On the basis of moisture regimes four regional patterns may be identified, i.e., humid, sub-humid, semiarid and arid, respectively, corresponding to the following types of natural vegetation: forest, forest-steppe (and meadow), steppe and desert. The final step in eco-geographic regional system is the demarcation of natural regions within a thermal-moisture region (or natural zone) based on variations in landforms or location regards to atmospheric processes.
A new tentative scheme of eco-geographical regions of China, including 11 temperate belts, 21 thermal-moisture regions and 48 natural districts, is proposed and several boundaries of the regional system are discussed in the present paper.
Keywords: China, eco-geographic regional system, global change
The eco-geographic regions of hierarchic system is demarcated or combined with different units based on regional differentiation of the earth surface nature. The study on the eco-regional system is an important foundation for developing physical geography. Scientifically, it provides a regional framework for studying regional response to global change, establishing monitor system of environments, applying remote sensing and geographical information system (GIS), planning network of ecological stations, analyzing experimental data and information of observation, etc. Practically, it has extensive prospects of application, providing necessary scientific basis for rational utilization of natural resources, enhancement of land productivity potential, assessment of land management policies, introduction and extension of advanced agricultural technologies, management of degraded environments, rational distribution of nature reserves, conservation of bio-diversity, as well as regional sustainable development, etc. The study on the eco-geographic regional system is of significance for inventorying national and regional background of resources and environments, planning and directing agricultural production in line with local conditions, speeding up sustainable agricultural development.
The division of eco-geographic-regional system of China applies the principle and approach suitable for the rule of physico-regional differentiation. The eco-physical regions of China should be demarcated based on real differences of the surface nature (geomorphologic structure and topographic configuration), various combinations of temperature-moisture condition and zonal vegetation and soil types (Zheng, 1989).
In fact, the regional differentiation results from the interaction between zonal and azonal factors. The zonal principle is to observe horizontal zonality of natural phenomena and to search the corresponding approach of division according to the reflection of climate on soils and vegetation. In a broad sense, zonality includes horizontal and altitudinal ones. The horizontal zonality affected mainly by planet-universe factors, is higher-level rule; while the altitudinal one controlled chiefly by topography, is lower level rule. Correspondingly the division of higher-level units is based on bio-climatic relationship, namely zonal principle, firstly reflecting the horizontal zonality then the altitudinal one. Different horizontal zones are characterized by spectrum-type of the altitudinal belts. Therefore, understanding the rule of altitudinal zonality should be based on the recognition of horizontal one. Otherwise, the spectrum type of altitudinal belts becomes the mark for identifying the horizontal zones. The higher-level division should be mainly based on the existing and advanced characteristics in the nature, highlighting the natural factors stable or hard to change; the lower-level division is mainly based on the remaining characteristics, laying stress on the natural factors sensible to change (Huang,1990).
The eco-geographic regional system of China, using deduced "top down" way from high to low levels, can be divided into both type and regional demarcation. The former is carried out in higher-level units, while the latter in lower-level units. The temperature belt and zonal moisture regime have the characteristics of type demarcation. The formed thermal-moisture regions are transitional regional units from type to regional demarcation. In demarcation of temperature belt and regional type of moisture regime, relevant temperature and aridity criteria have been worked out by considering the relationship among climate, soils and vegetation, instead of climatic isopleth as the criteria, or criteria complex proposed for demarcating boundaries. The eco-geographic regional system of China is worked out by geographical correlative approach, which lay stress on comparison of distribution
characteristics among various eco-geographical elements, with emphasis on the relationship among climate, biome, soils and their significance to agricultural production (Huang, 1990).
The selected hierarchic units are temperature belt, thermal-moisture region and physical district.
Temperature belt
Temperature, being an important factor influencing growth and distribution of plants, is hard to change on large scale or for a long time. The demarcation of terrestrial surface based on temperature conditions is necessary for understanding physical, chemical and biological processes and phenomena as well as agricultural production. In addition to temperature, landforms, vegetation, soils and other physical elements, as well as crops and cultural system are referenced for demarcating temperate belts. The temperate belt has common characteristics in temperature condition, and strongly affects land utilization. The division of temperature belt, formed during the physico-historical process, is type demarcation with common characteristics. Based on the classification criteria the belts are strictly divided and suitable for comparison.
Thermal-moisture region
Generally speaking, the combination of temperature condition and moisture regimes is the main factor to determine regional differentiation of nature on the terrestrial earth surface in a large scale. Processes of temperature varies usually according as moisture regimes, the variation brought by temperature reflects mainly differences at the same moisture regime. In a broad sense of zonality, the moisture regime is determined by precipitation and potential evaporation. Climatic factors of precipitation and potential evaporation are hard to change on a large scale or for a long period also.
From point of view of the globe, the regional moisture regime may demarcate into 4 patterns, i.e., humid, sub-humid, semiarid and arid regions, representing four types of natural vegetation and landscapes, such as forest, forest steppe (including meadow), steppe and desert. The thermal-moisture region has common characteristics of combination of temperature and moisture conditions. With large area of zonal vegetation and soils, similar altitudinal belt and combination of structure types, a thermal-moisture region has almost the same features of land use and agricultural, forest and pasture development.
Physical district
It has almost the same combination of vegetation and soil types due to differentiation of landforms or geographical locations. The structures of altitudinal belt are similar within a physical district. It usually corresponds with certain regional topographical unit, having related combination of landforms.
Main factors for demarcating boundaries of the eco-geographic regional system of China, and their criteria are described as follows.
2.1 Temperature Condition
The number of days with mean daily temperature above 10° and accumulated temperature of =10° are usually regarded as the principal criteria, because days of mean daily temperature above 10° is related to duration of the fast growing season. By comparison, the same duration with mean daily temperature =10° may have various accumulated temperature, while the same accumulated temperature may last different days of the duration with daily temperature =10° in different areas. Because duration of mean daily temperature above 5° has certain relations with growth of alpine pasture on the Tibetan Plateau and duration of mean daily temperature above 10° , two criteria can be compared with each other and with that in low altitude region.
In an area with less days of mean daily temperature above 10° and lower accumulated temperature =10°, temperature of the warmest month is proposed as subsidiary criterion. Mean temperature of the warmest month can stand for the temperature strength during the growing season. They are highly correlated with the growth and distribution of certain zonal vegetation, as well as related to crop cultivation. By contrast, mean temperature of the coldest month and average minimum temperature are taken as subsidiary criterion in a warm region.
According to temperature and its role in natural process and agricultural production, therefore, nine temperate belts may recognized in the lowland of China, they are: the cold temperate, middle temperate, warm temperate belts; northern subtropical, middle subtropical and southern subtropical belts; peripheral tropical, middle tropical and the equatorial tropical belts. On the Tibetan Plateau with lower temperature in growing season two temperate belts are identified, i.e. the plateau subpolar and the plateau temperate belts.
Table 1. Criteria for Demarcating Temperature Belt of China*
2.2 Moisture Regimes
Under certain temperature condition, moisture regime becomes limited factor affecting plant growth and distribution. By taking annual aridity (ratio of annual evapo-transpiration potential to annual precipitation) as the principal criteria, subordinated by annual precipitation, four moisture regional types are identified: humid, sub-humid, semiarid and arid (Table 2).
Table 2. Criteria for Demarcating Regional Moisture Regimes of China
Thermal-moisture region, demarcated based on moisture regimes, should reflect the variation of the ratio of evapo-transpiration potential to precipitation or the difference between them. The annual mean ratio is not enough; the picture would not be complete, unless the seasonal and long range changes have been considered.
2.3 Landforms
Within any natural zone, the landforms give rise to changes of natural conditions such as climate, moisture regime, soils and vegetation, etc. And variation of processes such as weathering, erosion, and accumulation etc., and reflects the difference of factors such as rock composition and internal force. Landforms is also one of the factors hard to change. The same landforms are characterized by different functions in various thermal-moisture regions. Therefore, physical districts should be subdivided based on landforms differentiation after the demarcation of temperature belts and thermal-moisture regions (Huang, 1989).
China is a mountainous country, with mountains, plateaus and hills occupying 2/3 of the total land area. The topographical configuration, altitude and the landforms type-combination of mountainous and plateau regions bring about several complicated issues to the physico-geographical regionalization. They are the zonality and azonality, relationship between horizontal zones and altitudinal belts, comparison of spectra of the altitudinal belt and the determination of representative basements, as well as demarcation lines of the physico-geographical regionalization, etc.
Influenced by the regional differentiation of the Tibetan plateau, the criteria for landforms classification are different. For example, the lower limit of extreme alpine is at elevation of 5000~5500 m asl, approaching the lower limit of subnival belt located between the end of continental existing glaciers and the snowline within the plateau. The lower limit of the plateau and the boundary between alpine and middle mountains are about 3500 (4000) m, near the upper limit of montane forest. Generally speaking, above the boundary in the alpine, frozen mechanical weathering is strong, with developed solifluction, coarse accumulated materials, and slow process of soil-formation. Under the boundary in humid conditions, fluvial process is getting strong. Middle and lower mountains have boundaries at elevation of 1000 m asl, and the part below the boundary belongs to periphery out of the plateau (Zhang, et al., 1982).
In mountainous and plateau regions the altitudinal belt is often conspicuous, sometimes overshadowing the horizontal zonation. From the point of view of “three dimensional zonality” the mountainous and plateau regions are subdivided according to their objective reality such as the topographical features, combination of the temperature-moisture regimes as well as the zonal type of vegetation and soils, etc. The spectrum of the altitudinal belt, including the spectrum-structure, base belt, prevailing belt and the type-combination of respective belts, should be comparatively studied in order to demarcate the physico-geographical division in mountainous and plateau regions.
The mountainous and plateau region is remarkable in its absolute and relative elevation, river valleys sandwiched with mountain ridges, the horizontal zonation is closely correlated with the altitudinal belt. It is necessary for reflecting regional differentiation of physico-geographical characteristics to determine the proper basement as the representative.
The plateau not only has plateau's montane area with altitudinal-horizontal zonality type, but also has plateau's proper with plateau's zonality, and montane areas with obvious altitudinal zonality existing in the rim and inner part of the plateau. Therefore, the comparative study on the spectrum type of altitudinal belts in various mountains of the plateau, including analysis of its structure type, determination of basic and dominant belts and suitable classification, is needed not only for systematically recognizing the characteristics of altitudinal belts, but also the important basis for studying physico-regional system on the plateau.
Based on simplified and important differences of plain land and hilly / mountainous land, some 48 natural regions are recognized.
Table 3. Eco-Geographical Regional System of China
As regards the system of eco-geographical regions of China, several key boundaries, such as the northern limit of the tropical belt, the northern limit of subtropical belt, boundaries between plateau subpolar and plateau temperate are discussed as follows
3.1 Northern Limit of the Tropical Belt
Based on Koeppen’s classification, the most popular scheme of climatic classification, the polar limit of tropical climate is defined by the isotherm of 18° for the coldest month, another thoughtful criterion ever used in defining tropical climate is “absolutely frostless”, the minimum temperature is not a stress factor for plants growth.
The tropical belt in China is situated in northern periphery of the tropical realm on the earth. The thermal criteria include mean temperature of the coldest month and the absolutely minimum temperature. Owing to strong cold waves in winter the minimum temperature might bring about serious damage to rubber and some tropical crops, which are sensitive to low temperature. Therefore, a three fold division of the tropical realm may be considered on the basis of thermal regimes. The northern limit of the peripheral tropical is the northern limit of frostless the year round, corresponding with the isotherm of 15° for the coldest month. While the northern limit of the middle tropical is the limit of the isotherm of 18° for the coldest month, tropical crops do not subjected to cold damages in winter (Huang, 1990).
3.2 Northern Limit of the Subtropical Belt
In connection with the nomenclature of the subdivision of the thermal belts for their designation, a peculiarity is the highly developed subtropicality in China. An acceptable characterization of subtropical climate is: tropical heat in summer with low temperature in winter. As to the northern boundary of the realm, there is a choice between the polar limit of the distribution of winter wheat to
the north of Beijing and the Qinling-Huaihe line on the southern boundary of the North China Plain. In the Area in between, the summer temperature is comparable to that in the tropics, and the winter coldness is not so severe as to exclude winter wheat. These together with the cultivation of cotton, rice, grapes and a number of other warm season copes are features usual to, but not criteria for, subtropical regions. The total absence of citrus fruits and the failure of vegetable cultivation in winter deny the designation subtropical.
In the version of Koeppen’s classification modified by Trewartha, 0° for the coldest month has been suggested for the Boundary between C and D climate. This isotherm in East China fits nicely the Qingling-Huaihe line, the best known geographical divide in China. It is considered as the northern boundary of the realm (Huang,1990).
3.3 Boundary between Plateau Subpolar and Plateau Temperate
In discussions on thermal conditions, one problem arose. The existence of the huge Tibetan Plateau, with an area of about 2.5 million square kilometers and an average elevation exceeding 4000m, upsets totally the pattern of temperature at the earth surface. Concerning with this unique feature, the plateau was considered a separate realm in distinction to the rest of China not only in temperature but also in numerous other aspects.
The plateau may be divided into plateau subpolar, plateau temperate and montane subtropical zones on the basis of temperature conditions. The number of days with mean daily temperature above 10° is regarded as the principal criterion, mean temperature of the warmest month as the subsidiary criterion. Days of mean daily temperature above 10° are related to the duration of fast growing season, while mean temperature of the warmest month can stand for the thermal strength during the plant growing season. They are highly correlated with the growth and distribution of certain plants of the zonal vegetation, as well as related to agricultural plants. Because duration of mean daily temperature above 5° has certain relations with growth of alpine pasture, as well as with duration of mean daily temperature above 10°, two criteria can be compare with each other, also can have comparison with that in lowland region.
The demarcation line in mountainous and plateau regions is characterized by transitional and gradual feature, Several major demarcation lines run along main ridges or transit across flanks of the mountains, others may be drawn at piedmonts of the mountains. It depends mainly on the regional differentiation of spectra of the altitudinal belt.
Bailey,R.G. Explanatory supplement to ecoregions map of the continents, Environmental Conservation, 1989, 16(4): 307~309.
Bailey,R.G. Design of ecological networks for monitoring global change, Environmental Conservation, 1991, 18(2): 173~175.
Bailey, R.G., Description of the Ecoregions of the United States, U. S. Department of Agriculture, Miscellaneous Publication, No. 1391, 2nd. Edition, Revised and Enlarged, 1995, 1~108.
Bailey, R.G. Ecosystem Geography, Springer-Verlag, New York, Berlin, Heidelberg, 1996, 1~204.
Hou Xueyu, 1988. Natural Ecological Regionalization of China and the Strategy of Agricultural Development. Science Press, Beijing (In Chinese).
Huang Bingwei, 1989. An Outline of the physico-geographical regionalization of China. In: Geographical Symposium, 21., Science Press, Beijing, 10~20 (In Chinese).
Huang Bingwei, 1990. Some themes of integrated physical geography. In:“Progress in Geographical Research - The 50th Anniversary of the Establishment of the Institute of Geography, Chinese Academy of Sciences, Science Press, Beijing, China.
Huang Bingwei, 1991. Climatic division and physico-geographical division of China: Retrospects and Prospects. Climatological Notes, Vol. 41. University of Tsukuba.
Zhang Rongzu, Zheng Du, Yang Qinye, 1982. The Physical Geography of Xizang (Tibet).
Science Press, Beijing, 1~178. (In Chinese)
Zheng Du, 1989. A study on problems of the physico-geographical regionalization in mountainous and plateaus regions. In: Geographical Symposium, 21., Science Press, Beijing, 21~28 (In Chinese).
Zheng Du, 1996. The system of physico-geographical regions of the Qinghai-Xizang (Tibet)
Plateau. Science in China (Series D), 39(4): 410~417.
Zheng Du, Yang Qinye, etc.,1997. A Study on the Physico-Geographical Regional System. China Environmental Science Press, Beijing, 1~167 (In Chinese).
Table 1. Criteria for Demarcating Temperature Belt of China
Criterion Temperature Belt |
Principal Criteria |
Supplemental Criteria | ||
Duration with mean daily temperature =10oC (days) |
Accumulated temperature of
duration temperature |
Mean temperature of the warmest month(oC) |
Mean Temperature of the coldest month(oC) | |
Cold Temperate |
< 100 |
<1600 |
< 16 |
< -30 |
Middle Temperate |
100 ~ 170 |
1600~3200 |
16 ~ 24 |
- 30 ~ -16 |
Warm Temperate |
171 ~ 220 |
3200~4500 |
- |
> -16 ~ 0 |
Northern Subtropical |
> 220 |
>4500 |
- |
> 0 ~ 5 |
Middle Subtropical |
> 230~240 |
>5000 |
- |
5 ~ 10 |
Southern Subtropical |
> 300 |
> 6000 ~6500 |
- |
10 ~ 15 |
Peripheral Tropical |
365 |
> 8000 |
- |
15 ~ 18 |
Middle Tropical |
365 |
> 8000 |
- |
18 ~ 24 |
Equatorial Tropical |
365 |
> 8000 |
- |
> 24 |
Plateau Subpolar |
< 50 |
- |
< 10(12) |
-18 ~ -10(-12) |
Plateau Temperate |
50 ~ 180 |
- |
12 ~ 18 |
-10(-12) ~ 0 |
Table 2. Criteria for Damarcating Regional Moisture Regimes of China
Criterion |
Annual aridity (E/P) |
Natural vegetation potential |
Related land use issues |
|
(Superhumid) |
=0.49 |
Rainforest |
- |
|
Humid |
0.50~0.99 |
Forest |
- |
|
Sub-humid |
1,00~1.49 |
Forest steppe /(Meadow) |
Secondary Salinization |
|
Semiarid |
1.50~4.00 |
(Meadow-steppe) Steppe (Desert steppe) |
Rain fed Cultivation |
|
Arid |
=4.00 |
Desert |
No cultivation without irrigation |
Table 3. Eco-Geographical Regional System of China
moisture thermal |
D arid |
C semiarid |
B sub-humid |
A humid |
I Cold temperate |
IA IA1 Northern Da Hinggan Mts. | |||
II Middle temperate |
IID IID1W.Nei-Mongol High Plain & Hetao IID2 Alxa & Hexi Corridor IID3 Junggar Basin IID4 Altay Mts. & Tacheng Basin IID5 Ili Basin |
IIC IIC1 SW Song-Liao Plain IIC2 S.Da Hinggan Mts. IIC3 E.Nei-Mongol High Plain |
IIB IIB1 CentralSong-Liao Plain IIB2 Middle Da Hinggan Mts. IIB3 Piedmont Plain & Hills of Sanhe |
IIA IIA1 Sanjiang Plain IIA2 Eastern Mts of NE China IIA3 Eastern Piedmont Plain of NE China |
III Warm temperate |
IIID IIID1 Tarim and Turpan Basins |
IIIC IIIC1 Loess Highlands of Central Shanxi, N. Shaanxi & E. Gansu |
IIIB IIIB1 Hills&Mts.of Central Shandong IIIB2 North China Plain IIIB3 Mts. & Hills of North China IIIB4 Plains of S.Shanxi & Weihe Valley |
IIIA IIIA1 Hills & Mts. of Liaodong & E. Shandong |
IV Northern subtropical |
IVA IVA1 Huainan & Middle- Lower Reaches of Changjiang River IVA2 Hanzhong Basin | |||
V Middle subtropical |
VA VA1 Hills of S. Changjiang VA2 Mts. of S. Changjiang & Nanling VA3 Guizhou Plateau VA4 Sichuan Basin VA5 Yunnan Plateau VA6 Southern Slopes of E. Himalayas | |||
VI Southern subtropical |
VIA VIA1 Central and N. Taiwan VIA2 Hills & Plains of Fujian, Guangdong and Guangxi VIA3 Mts. & Hills of Central Yunnan | |||
VII Peripheral tropical |
VIIA VIIA1 Lowlands of S. Taiwan VIIA2 Central & N.Hainan Island and Leizhou Peninsular VIIA3 Hills & Valleys of S. Yunnan | |||
VIII Middle tropical |
VIIIA VIIIA1 S. Hainanand Dongsha, Xisha, Zhongsha Islands | |||
IX Equatorial tropical |
IXA IXA1 Nansha Islands | |||
HI Plateau sub-polar |
HID HID1 Kunlun Mts. & Plateau |
H I C HIC1Plateau with Broad Valley of S.Qinghai HIC2 Plateau with Lake Basin of Qiangtang |
HIB HIB1 Hilly Plateau of Golog-Nagqu |
|
HII Plateau temperate |
HIID HIID1 Qaidam Basin HIID2 N. Slopes of the Kunlun Mts. HIID3 Ngari Mountains |
HIIC HIIC1 Plateau & Mts. of E. Qinghai and Qilian HIIC2 Mts. of S. Xizang |
HIIA/B HIIA/B1 High Mountains and Gorges of |
1 Under auspices of the National Science Foundation of China (No. 49731020)
* For all tables see end of document
