Citation Detail: WANG Xianpu. 1996. On the Restoration and Rehabilitation of Degraded Ecosystems inTropical and Subtropical China. in: Conserving China's Biodiversity (John MacKinnon, WANG Sung and etc.eds.). China Environmental Science Press. Beijing. 96-112p.

On the Restoration and Rehabilitation of
Degraded Ecosystems inTropical
and Subtropical China　

WANG Xianpu
(Institute of Botany,Chinese Academy of Sciences)

★The formation and general utilization of degraded habitats in tropical China

★Formation of degraded habitats in subtropical China and their utilization

★Establishing biodiversity conservation regions, promoting and fixing restoration, and rehabilitation of degraded ecosystems in different regions
★References

　ABSTRACT　

The restoration and rehabilitation of degraded ecosystems is an important component of nature conservation throughout the world in 1990's. The long-term goal (in about 40 years) is to restore over 30% of degraded lands in each biogeographical region by means of modern science and technology. The short-term goal (in about 10 years) is to create appropriate planning, in order to restore sustainable utilization of representative degraded habitats of main ecosystem types, particularly those which have been seriously affected by aridity, desertfication, deforestation and soil erosion (IUCN, et al., 1989). This paper mainly reviews the present situation and developmental tendency of land use after deforestation in tropical and subtropical China with a view to providing some reference for reasonable planning of land use in the future.

1. The formation and general utilization of degraded habitats in tropical China.

1.1 Geographical scope and natural features.　

The tropics of China are located at the northern margin of the Asian tropics. They include a vast extent from the southern Wanshan islands in Guangdong at 114oE in the east, to the Yadong, Nielamu of southeast Xizang at 85oE in the west. The northern boundary of the tropics in China is rather low because of the influence of the cold wave that occurs in winter. Their northern boundary is situated at 22o-25oN in central Guangdong. In southwestern Guangxi the tropics are found as far north as 24oN, owing to the following three reasons: 1) the southeast monsoon proceeds up along the Youjiang river; 2) the northern mountains hinder the cold wave from proceeding farther south; and 3) influence by the limestone stratum. The tropics in southwest Yunnan go as far as 25oN due to the effect of the Bengalese warm air mass. In southern Xizang the tropical zone even goes as far as 28o-29oN; this is the most northern tropical region in China (Comprehensive Survey Team of Qingzang Plateau of Chinese Academy of Science, 1982).

The geology and geomorphology throughout China’s tropics change in a complicated pattern. There are alluvial plains, coral islands, valleys, hills, mountains, plateaus, limestone peak forests and shrublands, etc. The topography ascends gradually from east to west. The eastern part is characterized by hills and mountains along the coast. Here, the relief gently slopes, most of the area is under the elevation of 150m, and in general the hills and mountain rise 500-1000m in elevation. The highest point is Wuzhishan mountain in Hainan with an elevation of 1879m. Throughout southwestern Guangxi are limestone mountains, mixed with granite, sandstone and shale mountains, with elevations spanning 200-700m. Some of these mountains reach elevations of over 1000m. There are also coral islands, called the South Sea Islands, distributed widely in the South China Sea. The western part of the tropics incorporates the southern margin of Yunnan plateau and the southeastern slope of the Himalayas. In general, the elevation of river valleys and basins in southern Yunnan are between 300-600m, while the mountains rise to between 1000-1500m in elevation. Southeastern Xizang is composed of high mountains and deep valleys with great relief and steep topography. Here, river valleys are generally under the elevation of 200m, while nearby summits may reach over 5000-6000m in elevation.　

The climate belongs to the tropical monsoon climate with high temperatures, and average temperature is 20o-28oC. The annual average temperature of the coldest month (January) ranges from 12o to 15oC. The absolute lowest temperature is above 5oC -- as averaged over many years, but low temperatures under 0oC may occur in some years. Annual precipitation throughout most of the area is between 1000 to 1500 mm.

The flora belongs to a part of the India-Malaysia florist region and contains many ancient plants, some of which represent an important part of the composition of the modern vegetation. The eastern tropics are mainly composed of components of the eastern flora of Malaysia mixed with some Sino-Japanese and Chinese tropical endemic plant species. The western tropics are mainly composed of India-Himalayan and Chinese tropical endemic plant species (Wang Hesheng, 1992; Wu Zhengyi, 1993). The zonal vegetation type is seasonal rain forest, which is replaced by monsoon forest after it is damaged or in dry regions. There are apparent vertical vegetational distributions in mountain areas, and this zonation is also affected by latitude. Vegetation types are rich and colourful, varying dramatically in high mountain and deep valley regions throughout the western tropics (China Vegetation Editorial Commission, 1980; Wang Xianpu, 1989, 1990).

1.2 The present situation and problems of land use.　

There has been a long history of shifting agriculture with slash and burn cultivation in this area, like that of other tropical regions in the world. In the past, the population was smaller and techniques of cultivation were primative. Within a large area of forest, such slash and burn cultivation was sustainable -- after trees in a small area were cleared and the area then deserted within 2-3 years, the forest could easily have time to regenerate. Thus, the forests were not seriously threatened, and the biodiversity was rich and varied owing to the occurrence of serial vegetation which also provided abundant food sources for herbivores, the reproduction of which attracted many predators. Actually, there were a lot of south China tigers in Guoxhou and on the Leizhou peninsula of Guangdong in the 1950's. They were so harmful for people and livestock that the villagers were scared to stop in the mountains and fields in the morning and evening. But, at present, it is difficult to find their trace, because their numbers declined dramatically when a large area of natural forests were burnt for the cultivation of Brazil rubber trees.　

Large mammals also depend on shifting cultivation to a great extent. Because most edible foods in mature tropical forests are found high in the canopy, these resources are out of the reach of terrestrial herbivores. Only cleared areas can provide food for cattle and sheep. Thus, shifting cultivation was suited to and played a significant role in the micro-agricultural economy at that time.　

However, with the increase in population and concomitant development of science, a large area of slash and burn cultivation will cause a decline in the productive capability of the land, will damage the normal successional course of vegetation, and will eliminate the capacity of the forest to naturally restore itself. A large area of grassland may replace the forest. In particular, the increased distribution of grassland dominated by Imperata cylindrica not only prevents progressive succession of vegetation, but also hinders the growing of cultivated plants. Although the formation of large areas of rice fields may establish a steady agricultural base, the original forest landscape will be thoroughly transformed and natural biodiversity will decline to a montonous condition.　

In order to maintain regional ecological balance, it is necessary to keep a basic ratio and rational spatial pattern between primary forests, productive development of agroforestry, and construction of cities, towns, villages and roads. Because of a the lack of research on this issue, the ecological environment of many places may be seriously harmed and unable to carry on ecological process normally. The results may be serious, such as soil erosion, water source shortage, decline of cycle capacity of nitrogen and nutrition, dramatic change of regional climate, and acceleration of the extinction rate of species. In turn, these results may negatively affect the productive development of industry and agriculture, and diminish the living level of inhabitants. Obviously, it is extremely urgent to develop regional or watershed planning by the principle of resources conservation combined with sustainable use. Such a program will enable the construction of a sustainable society (Wang Xianpu, 1994).　

In the tropics of China, particularly in the Tai villages of Xishuangbanna, courtyard economy is well managed. Here, timber and fuel trees, woody oil and food trees, fruit trees, medicinal plants and vegetables -- in short, everything that one expects to find in a dense natural forest -- occur in the hills and mountains around the villages. However, artificial timber aforestration is rarely practiced after cutting of natural forests; most of the timber trees come from wild ones of natural forests. Owing to the rapid development of tropical economic crops and transformation of the micro-agricultural economy, the natural and court managed model mentioned above has been replaced by a large scale of reclamation. We have now had several decades to reflect on the advantages and disadvantages of these changes. It seems essential to conduct further research on a model of coexistance between natural resources and modernization, and a sustainable developmental strategy.

1.2.1 The afforestation of large areaa of the Brazilian rubber tree

In the early 1950's, due to urgent needs dictated by political and economic aspects in the world, a large risk was taken: the Brazilian rubber tree (Hevea brasiliensis) was introduced and widely cultivated in Hainan and Xishuangbanna, Yunnan. There was no hesitation to sacriface a large area of natural forest in order to get necessary rubber to meet economic and military demands. From the view point of ecology this introduction produced a series of problems: the plant was at risk because the absolute lowest temperature in winter may go beyond its endurance, and the frequent typhoon, rare and irregular annual precipitation, lower fertility and strong evaporating intensity of soil, etc. were not favorable for its growth. In a word: cold, wind, and drought calamities were key factors preventing its development over large areas. Hope for success depended on choosing approproate micro-habitats and the practise of intensive cultivation. This predication has been provided by more 40 years of experience (Wang Xianpu, 1984). Traditionally, cultivation of the Brazil rubber tree cannot go beyond 17oN. Nevertheless this barrier has been broken down recently through multiple efforts. Now it is possible to grow the species as far north as 22o30' N, through breeding many new varieties of high quality and with resistance to wind, drought and cold. The species may now be cultivated and managed with techniques suited to terrace, hill and mountain. The result has been establishment of a new ecosystem of Brazil rubber forest with a shelter forest network and green cover adapted to northern tropical environments. The largest cultivated area is over 300,000 ha, and China now occupies the fourth position of 28 countries of cultivating Brazil rubber trees in the world. Its yield of dry rubber has reached 100,000 tons, occupying the sixth position in the world. Although serious calamities occur in some places every year, the total yield increases continuously. Annual mean production per ha and individual tree also has been relatively steady or increasing. There is significant argument about whether it is worthwhile to develop Brazil rubber forests in the economy. Some analyses show that certain areas of natural forest have been damaged to some extent, but that the occurrence of large areaa of artificial forest also have played a great role in safeguarding regional ecological balance and in promoting local economic development and people's living level. It should be indicated that many Brazil rubber tree plantations were established after deforestation, with many new towns created and new social structures formed. Most of the inhabitants moved to new towns from other places, and their income and living level are higher than that of native people. As a result, a series of ecological, social and economic contradictions have occurred concerning proposals to restrain the development of rubber property (Wang Xianpu, 1986, 1987). From the view point of biodiversity conservation and sustainable use, there are many species in the tropics, and many local species are worthy of being developed economically. That is to say, we should not merely pay attention to the Brazil rubber tree in these areas. In order to break away from monotonous landscape composed of a single species or variety, we need to maintain the original primary forests, to concentrate on those resources within tropical regions that may have economic value, and to initiate a diversified economy in line with local conditions. At present, the development of a market economy has great influences on the development of rubber property in China. In addition, it is difficult to compare products from the distribution center of the Brazilian rubber tree with those from China, both in price and in quality. Since domestic products cannot compete with foreign ones, economic comparisons are difficult, yet these comparisons unavoidably affect the extent and development of rubber plantations in China. If government can not effectively regulate this economic endeavor, all that has been achieved will certainly be spoiled. One hundred million individual Brazilian rubber trees, which have been cultivated over many years, will be damaged. It seems that relevant governmental departments should weigh up the gains and losses to all aspects concerning this introduced tree and make necessary scientific policy.

1.2.2 The afforestation of large areas of Eucalyptus

In the process of developing Brazil rubber trees throughout the tropics of China, some locations, such as terraces and hills of north Hainan, south Guangxi and Leizhou peninsula of Guangdong, proved difficult to plant successfully due to damage caused by windstorms, cold and low levels of soil nutrients. After planting the sugarcane for several years, which resulted in a severe loss of soil fertility, local farmers finally made the decision to cultivate Eucalyptus, which now has engulfed the tropics and subtropics throughout the world. Eucalyptus comes from Australia, it grows rapidly, sprouts intensely and adapts easily to poor soil. Several Eucalyptus species such as E. exerta, E. rudis, E. citriodora and some new varieties, are widely planted. It is true that the timber quality and value of individuals over 20 years old can be high, if they are cultivated with appropriate management measures. Since most people are anxious to get benefits and to use the wood for paper-industry, continuous cultivation on the same land made soil fertility to become lower and lower. This reduction in soil fertility causes entire forest plantations to become jeopardized. It seems indispensable to carry out sustainable development in this area according to the requirement of biodiversity use and agroforestry.

1.2.3. The introduction of foreign pine trees　

There are only few native species of pines that occur in tropical China. Pinus latteri and Pinus fenzeliana are mainly distributed in the mountainous environment there, although they are very few in number. Pinus massoniana has been cultivated in the area, but it grows poorly due to its succeptibility to insect pests and diseases. Several years ago, Pinus elliotii, introduced from Gallebi, was introduced. It grows well in dry and poor terraces and hills along the coast. Its strong wind-resistance attracts people to widely cultivate the species. Some people even intend to replace local Pinus massoniana populations with Pinus elliotti. Because large areas of pure stands have been planted, serious diseases and problems due to insect pests occurred 10 years after the species was introduced. The leaves of trees became yellow, and many trees gradually died. In the meantime, the diseases spread very fast. Farmers have had to adapt segregated measures and to control potential outbreaks on their lands. In short, foreign species of pine should not be introduced over large areas without prior long-term observation and experiment.

1.3. Rational distribution of land use　

The above examples make clear that it is unwise to concentrate on the development of so-called fast growing and high economic trees over wide areas without paying attention to conservation and management of natural forests. It is absolutely necessary to take advantage of local resources and to choose development of native growing fast, precious and high economic species. As the IUCN-WWF Plant Conservation Plan indicates, it is unwise to concentrate research and development only on a small number of crops and trees such as rice, wheat, Eucalyptus and poplar. We should pay attention to conservation, research and utilization of wild species and their germplasm resources. We should also stress the rational distribution of primary forests, as well as artificial ecosystems, with the aim to form a mosaic, in order to ensure the possibility of sustainable development of China's natural resources (Wang Xianpu, 1988; IUCN Conservation Monitoring Centre et al., 1984).

1.3.1. Coastal terraces and hills region in Hainan, Guangdong and Guangxi　

The sandy coastal land of this region has formed a shelter forest belt extending several hundred km through the successful introduction of Casurina equisetifolia, which in turn has played a great role both in improvement of the regional ecological environment and in the local economy. It seems beneficial to establish more and better-adapted native trees following the formation of this shelter belt. Such an activity, taking advantage of the pioneer tree and its role in improving the micro-environment, would lead to the construction of a higher quality of shelter belt. (like the forest belt composed of Vatica hainnanensis along the coastline of Wanning county in Hainan; Hu, 1992) . Unfortunately, the litter produced by Casurina equisetifolia preclude introductions of native trees. It is not only unable to promote cycling of soil nutrients, but also causes land productivity to degenerate. It is even difficult to grow more Casurina equisetifolia. The shelter belt in many locations has been destroyed. Given this present situation, we ought to increase silvicultural species in line with local conditions, such as with introductions of Cocos nucifera, Pandanus tectorius, Hibiscus tiliaceus, Acacia confusa, Vatica hainanensis, Micrcos paniculata, Litsea glutinosa, Vitex quinata, Barringtonia asiatica, Hermandia origera, Calophyllum inophyllum and Ficus spp., etc.

The terrace and hill environments under the elevation of 500m are mostly occupied by Brazilian rubber forest and Eucalyptus forest, in additon to the rice fields. Pinus elliotii forest occurs in some locations. Within the Brazilian rubber forest are found very few species in silviculture, such as Casurina equisetifolia, Eucalyptus spp., and Acacia confusa. In a word, this region features only a dull landscape and few species. At present, an important task of biodiversity conservation and sustainable use is to enrich cultivated areas, to increase the number of species there (and the number of ecosystems composed of them), and especially to enhance the introduction and breeding of native growing species (especially those that occurred there originally and those that grow quickly; Wang Xianpu, 1994) . According to long-term observation and experience, the following species are worthy of development in line with local conditions: Anthocephalus chinensis, Chukrasia tabularis, Melia toosendan, Toona cillata, Toona microcarpa, Choerospondias axillaris, Gmelina hainanensis, Terminalia hainanensis, Vatica hainanensis, Hopea hainanensis, Hopea exalata, etc. Varied tropical fruit trees should also be encouraged, such as: Litchi chinensis, Euphoria longan, Mangifera indica, Artocarpus heterophyllus, Clausena lansium, Psidium guajava, Averrhoa carambola, Syzygium jambos, Canarium album, Canarium pimela, Dracontomelon duperreanum, Annas comosus and Tamarindus indica, etc. We should choose some fast-growing species of Leguminosae, such as: Albizzia spp., Acacia spp. and Leucaena spp. in dry and poor locations. Dwarf wood management should be included in these efforts, especially after the soil has been improved. Research and development projects on fuel wood in southeast Asia are a valuable reference and benchmark for us (Salleh, 1994) . The following species are also merit cultivation: Castanopsis hystrix, Dalbergia odorifera, Homalium hainanense, Madhuca hainanenensis, Michelia mediocris, Alseodaphne hainanensis, Sindora glabra, Manglietia hainanensis and Calamus spp,. ect. in mountains above 500m elevation. (Zhu Yue, 1988).

1.3.2. The limestone mountain region in southwest Guangxi　

This region mainly includes the extensive range of the Zuojiang and Youjiang river basins and southeast Yunnan. The strata of this region are composed primarily of limestone mixed with granite, sandstone and shale. The region is higher in the northwest, with elevations between 1000-1300m, and inclines to the southeast where elevations of 100-500m occur. The Daqingshan mountain location in the southern part has some peaks with elevations of 1000m. This region has high annual accumulated temperatures, although the absolute lowest temerature there may be quite low (due to obstruction and concomitant stagnation of cold air in the southern mountains). The Brazilian rubber tree was planted in this region for nearly 20 years, but the species was difficult to adapt to the local conditions. When advective radiation frost occurred, individuals growing in the lowlands were seriously damaged and those growing on slopes were dramatically exterminated. As a result, all forests were destroyed completely. Residents in the area now are obliged to plant sisal hemp (Agave sisalana) (Li et al., 1965). On the contrary, the Brazilian rubber forest can still exist in southeastern Guangxi and western Guangdong. Here, although at a more northern latitude, the cold wave is only weakly affected due to local conditions.

In the limestone region, which is mostly bare mountain with sparse vegetative cover, excellent timber trees such as Burretiodendron hsienmu and Garcinia paucinervis are cut, and other tree speecies are used as fire wood. The natural forests can be rapidly restored if the hillsides are closed (protected) to facilitate afforestation (Su, 1990). In the area, it is a taboo to burn the grass or cultivate waste land, thus after two years soils are washed away and large areas of bare mountain are formed. Limestone mountains are then not considered as land suitable for silviculture for a long time. In fact, they are abandoned. Practice, however, proves that limestone mountains are suitable for the development of forestry. In general, the following species can be chosen to plant on limestone mountains under the elevation of 700m: Toona sinensis, Radermachera sinica, Zenia insignis, Deutizanthus tonkinensis, Ailanthus guangxiensis, Alphonsea mollis, Saraca chinensis, Horsfieldia hainanensis, Bischofia javanica, Parashorea chinensis, Burretiodendron hsienmu and Garcinia paucinervis, etc. The following species can be planted on sites above 700m elevation: Adina racemosa, Wrightia pubescens, Pterospermum truncatolobatum, Cinnamomum saxatile, Lysidice rhodostegia, Toona sinensis and Radermachera sinica, etc. We can cultivate Cephalomappa siensis by use of a dwarf model, and Pennisetum purpureum may be planted in many round depressions, in order to scientifically organize and develop food sources for native cattle and goats. The following species can be chosen and used on mountains with acid soils under 700m elevation: Anthocephalus chinensis, Melia toosendan, Chukrasis tabularis, Toona ciliata, Hopea chinensis, Vatica guangxiensis, Madhuca subquincuncialis, Eberhardtia aurata and Acrocarpus fraxinifolius, etc. The following species can also be considered on sites above 700m elevation: Castanopsis hystrix, Erythrophloeum fordii, Mytilaria laosensis, Tsoongiodendron odorum, Michelia macclurei var. sublanea, Michelia hedysosperma, Toona microcarpa, Symingtonia populnea, etc. (Guangxi Institute of Botany, 1965; Guangxi Forestry Department et al., 1980). The above mentioned tropical fruits in the region are also suited to be developed here. IIIicium verum, Cinnamomum cassia are specific species of this region and also worthy to be considered.

1.3.3. The hill and mountain region in southern Yunnan　

This region mainly includes Xishuangbanna, and southern parts of Honghe and Dehong Autonomous prefectures. The relief within the region rises and falls. The geomorphic structure is mainly composed of plateau mountains with many broad valleys and basins. These are surrounded by circular hills and mountains with elevations from 500-1000m. Some peaks reach elevations of 1300-1500m; the highest peak is above 2000m. The hills and mountains mainly consist of granite, sandstone and shale. Because there are many breaches in southern part, the southwest monsoon can flow into the interior. When the monsoon meets the towering mountains and the gradually increasing relief, the humid air goes upward and forms abundant rainfall and high temperatures. This effect, in turn, causes the formation at 21oN of a tropical climate. There is a large area of tropical forest, however it was largely destroyed during the development of the Brazilian rubber forest. Shifting cultivation prevails continuously in degraded habitats, and it causes many sites to be very difficult to restore. There are only a few artificial timber forests, economic forests and fruit plantations. Brazilian rubber forest can be seen everywhere, and its area is rather smaller than Hainan island, occuping the second position in China. At present, its situation is the same as on Hainan: awaiting a new decision on how to proceed. The cultural landscape is also excessively monotomous for a tropical area. It is an important way to better conserve existing primary tropical forest, to fully utilize the perspective of wildlife resources and to improve the features of degraded habitats. Therefore, we should develop tropical fruit trees in a big way, establish artificial timber forests, fuel forests and economic forests by use of native fast-growing and precious species, abiding by the principle of ecological agriculture, except setting up agricultural bases of having high and stable production. In the meantime, we should promote the restoration of secondary ecosystems (Wang Xianpu, 1987). Generally speaking, the following species are worthy to be developed at locations under the elevation of 800m: Anthocephalus chinensis, Duabanga grandiflora, Melia toosendan, Gmelina arborea, Chukrassia tabularis var. velutina, Cassia siamea, Dracontomelon macrocarpum, Meusa magassarium, Acrocarpus fraxinifolius, Ailanthus fordii, Pterospermum lanceaefolium, Parashorea chinensis, Vatica fleuryana, Homalium laoticum, Horsfieldia tetratapala, etc. The following species can be considered on mountains above 800m elevation: Castanopsis hystrix, Schima wallichii, Cinnamomum porrectum, Toona ciliata, Toona microcarpa, Choerospondias axillaris, Michelia hedysosperma, Manglietia microgyne, Manglietia wangii, Camptotheca acuminata, Phoebe macrocarpa and Phoebe puwenensis, etc. (Xu et al, 1982; Yu et al., 1982; Pei, 1982). The tropical fruit trees mentioned above should be more widely developed.

2. Formation of degraded habitats in subtropical China and their utilization

2.1. Geographical extent and physical features　

Owing to the effect of the monsoon from the Pacific and Indian Oceans, the subtropics of China are called humid subtropics of monsoon type, and these are endemic to the region of east Asia. This subtropical region is different from the subtropics with winter rainfall as found in the Mediterranean region. The humid subtropics of monsoon type in China occupy an area covering about one-forth of the country. Its northern boundary lies from Qinling mountain to the Huaiyhe river at 32o- 34oN. The southern border is near the Tropic of cancer. The eastern boundary is located at Taiwan and the southeast seashore of the continent and islands around it. The western border includes the east slope of the Xizang plateau down to south of the western edge of Yunnan. The range of latitude from north to south is 11o-12o. It may be divided into three subzones: the north, the central and the south, because of temperature differences. The extent of longitude strides across 28o from east to west and may be divided into two parts: the east and the west, owing to the difference of rainfall distribution pattern and species composition. The zoned vegetation is evergreen broadleaf forest in acid soil mountains, and mixed evergreen and deciduous broadleaf forest in limestone mountains. The vertical distribution of vegetation in mountain areas is very apparent, particularly in the area of high mountains and deep valleys in the western part. A series of similar vegetation types appear to the south and north and from low to high elevations (China Vegetation Editorial Commission, 1980; Wang Xianpu, 1990; Zhu, 1958).

2.2. The present situation and problems of land use　

Although the number of species in the humid subtropics in China is less than that found in the tropics, it is superior than that found in the temperate region. There are many endemic species. For a long time, local people have exploited many economic plant species, which have been widely cultivated, forming an important economic mainstay in the region.

2.2.1. The establishment of artificial timber forests　

Managed models of shifting cultivation also exist in the humid subtropics of China. Slash-and-burn cultivation has been commonly used, but people often planted some economic trees when reclaiming and cultivating wasteland (such as Cunninghamia lanceolata and Aleurites fordii). When soil fertility declined making it impossible to plant crops, trees were grown which have come to form a woodland. In the meantime, people are also accustomed to afforesting some degraded sites. Pinus massoniana, Pinus yunnanenssi, Cupressus funebris, Cupressus duclouxii are in common use. Recently airplanes have been used to spread the seed of pines, and this method has apparently been successful. It may be said that with the exception of slash-and-burn cultivation in only a few areas, most of this region is increasing in areas of green cover. However, silvicultural quality is not yet high enough. For a period, people were called to establish large areas (over 70 ha) of coniferous forests. The main species were Pinus massonian, Pinus yunnanensis and Cunninghamia lanceolata. Opinions have even been expressed that natural forests should be cut to make room for the planting of China fir (Cunninghamia lanceolata). In the meantime, when China fir was subject to afforestation, emphasis was often given to reclaimation and cultivation of wasteland, cherishing illusions of becoming useful timber within several years. This species was cultivated from the foot of mountain to the top. Any shrubs and herbs were cleared from the land surface. It seems that efforts were made to eliminate all competitors of the pine. In fact, many invisible insects and little animals had to switch to catch food from cultivated trees, due to lack of food sources from native plants. As a result, serious diseases and insect pests appeared in China fir forests. So people should be warned to pay attention to this lesson. They should exploit native fast growing broadleaf species and use them instead of the China fir. Large areas of coniferous forests should not be encouraged. It should be considered as a great achievement that the relic endangered species -- Metasequoia glyptostroboides has been used as a silvicultural tree species, and it is widely cultivated in moist habitats on plains and banks.

This region also contains the bamboo, Phyllastachys pubescen. Large areas of bamboo forest can be found in many places. It is closely related to people's living. It may be said that it is a plant for making money by local people. Unfortunately, recent extensive cutting has caused a tendency for these forests to decline. It is urgently needed to strengthen the tending of woods -- to replant, to enlarge cultivation, and to enable forests to obtain rapid restoration and development.

2.2.2. The development of economic trees.　

This region is used to develop diverse economic trees, which mostly are endemic species of China, such as Camellia oleosa, Camellia sinensis, Aleurites fordii, Sapium sebiferum, Rhus verniciflua, Eucommia ulmoides, Cinnamomum camphora, Castanea mollissma, Juglands regia, Magnolia officinalis, Morus alba, Ginkgo biloba, Traachycarpus excelsa, etc. Their cultivation plays a large role in the sustainable use of degraded habitats, and becomes an important part of the development of local economies and enhancement of people's living level. But, these species are roughly managed because people are more busy with crop cultivation. The decline of Camellia oleosa forests is mainly because its cover layer is often uprooted to make compost for crop demand and its cycle of nutrients is destroyed. The problem exists, however, that such development suffers from bad quality, difficulty of transportation, bad sale and low prices, etc. Therefore, there are ups and downs in the economic uses of such resources, and these change periodically with strong or weak management of the people. In order to solve this problem, at first we need to establish the idea of regional comprehensive agricultural systems and equally to think of developing crop production, forestry, animal husbandry, fisheries, handicrafts, etc., so that we are able to promote vigorous economic development.

2.2.3. Management of secondary deciduous broadleaf forests　

After zonal vegetation of this region is damaged, a deciduous broadleaf forest stage always appears among the successional stages in the natural restoration process (Wang Xianpu, 1990). This successional stage may include Alniphyllum fortunei forest, Styrax japonica forest, Liquidambar formosana forest, Populus adenopoda forest, Betula luminifera forests, Carpinus fargesii forest, Quercus variabilis forest, Quercus fabri forest, Quercus acutissima forest and Alnus nepalensis forest, etc. All these trees have certain economic values. The stability of these forests can be maintained through active forest management if it is determined that there are demonstrable needs from the sustainable use of their products. If it is determined that there is the need to restore these forests to evergreen broadleaf forests, appropriate measures may also be taken. The deciduous broad leaf forests should not be cut to make room for cultivated crops or planting of China fir. Such replacement can be viewed as stupid, because losses outweigh the potential gains.

2.3. Enriching biodiversity in cultivated areas　

This region has rich economic plant species, and it is essential that we develop a proper perspective on their use. More species should be chosen for cultivation through experimental study. And a rational arrangement and distribution scheme for the incorporation of many economical plants in cultivated areas should be put into force to avoid the pattern of dull landscapes promulgated by the cultivation of a single species or variety.

2.3.1. Southern subtropics　

This region belongs to a transitional area between the subtropics and tropics. It includes an extensive range of hills and mountains in central and southern Taiwan, coastal hills in Fujian and Guangdong, the Zhujiang river delta, hills and mountains in Guangdong and Guangxi, limestone mountains in Yunnan, Guizhou, and Guangxi, middle-elevation mountains and narrow valleys in central and southern Yunnan. There is a large environmental difference from the east to west, but there are also many common species, which can provide increased development in degraded habitats. In general, the following species are worthy to be considered in hills and mountains composed of acid red and yellow soil: Toona ciliata, Toona microcarpa, Choerospondias axillaris, Schima wallichii, Michelia macelurea var. sublanea, Tsoongiodendron odorum, Symingtonia populnea, Castanopsis hystrix, Erythrophloeum fordii, Mytilaria laosensis, IIIicium verum and Cinnamomum cassia, etc. The following species are suited to be developed in limestone mountain habitats: Lysidice rhodostegia, Acrocarpus fraxinifolius, Toona sinensis, Zenia insignis, Kalopanax pictus, and Pterospermum heterophyllum, etc.

2.3.2. Central subtropics　

This region is typical of the subtropical region, including hills and mountains to the south of Changjiang river, the Sichuan basin, mountains in Guizhou, Hubei and Hunan, Nanling mountains, Miaoling mountains, basins and valleys in the plateau of central Yunnan, high mountains and deep valleys in western Sichuan, and northern and western Yunnan. This region has complicated environmental conditions. It is one of the mega-biodiversity areas in China and contains many endemic and relic species. Different places have their own representative species. The following species, which have wide adaptability, may be provided to be chosen and developed: Liriodendron chinese, Manglietia fordiana, Michelia maudiae, Idesia polycarpa, Bretschneidera sinensis, Pseueosassafras tzumu, Phoebe bournei, Tapiscia sinensis, Camptotheca acuminata, Fagus longipetiolata, Fagus lucida, Castanopsis carlesii, Castanopsis fargesii, Schima argentea, Taiwania cryptomerioides, etc. The following species are suited to be cultivated in limestone mountain habitats: Keteleeria calcarea, Kalopanax pictus, Broussonetia papyrifera, Cyclobalanopsis glauca, Gleditsia sinensis, Cladrastis platycarpa, Pteroceltis tatarinowii, etc.

2.3.3. Northern subtropics　

This region is a transitional area between the subtropics and warm temperate zone. It includes plains in the lower reaches of the Changjiang river, hills to the north of the Changjiang river, Tongbaishan mountains, Dabeishan mountains, Qinling and Dabashan mountains, etc. Different places have large environmental differences. Acid yellow brown soil is characteristic of some habitats, and here species such as Kalopanax pictus, Liriodendron chinese, Tapiscia sinensis, Idesia polycarpa, Corylus chinensis, Fagus bashanica, Cercidiphyllum japonicum and Eucommia ulmioides, etc., occur (Chen, 1990).

3. Establishing biodiversity conservation regions, promoting and fixing restoration, and rehabilitation of degraded ecosystems in different regions

When foreign species are introduced to the tropics of China, the result is often a dull landscape, poor species and degraded environment. Although some attention has been given to the development of some native species in subtropical China, there still exists the need to avoid the domination of single species of introduced flora. Such monocultures cause outbreaks of disease and insect pests, bring about serious water and soil erosion, and lead to a decline of land fertility and loss of natural biodiversity. It is necessary to give attention to the development of native fast growing broad-leaved trees, to advocate establishment of block or belt mixed coniferous and deciduous forests, to enhance capacity for improvement of soils, to heighten regional environmental quality, to prevent and kill off vectors responsible for diseases and insect pests, and to adopt a requirement of regional economic development (Jiang, 1994).

3.1. The basic implication of biodiversity conservation regions　

Biodiversity conservation regions have been advanced in the process of drawing up the Convention on Biological Diversity. The aim is to carry out the principle to closely combine resource conservation with sustainable use, to realize synchronization of biodiversity conservation and economic construction, to exploit gradually biological resources having economic value and developmental perspective, and to promote economic development (Wang, 1992, 1994). Biosphere reserves and the potential to cluster such reserves put emphasis on the multifunctional roles that may be played by reserves. These roles include close integration of objectives with those of local people, thus helping them to carry on land planning with rational utilization (Wang Xianpu, 1985, 1986). Agenda 21 of China points out that 20 biodiversity conservation regions based on representative reserves should be established by the year 2000,. All national protected areas and important biogeographical provinces should also choose appropriate sites to set up biodiversity conservation regions (National Plan Commission, 1994).

3.2. Criteria for choosing locations of biodiversity conservation regions

A biodiversity conservation region is an examplary site, not all locations are suited for this designation. Such sites need to be chosen appropriately, and the selection should serve as an example for the selection of future sites. Other regions may then absorb experiences and carry on popularization of this initiative in line with local conditions. The main criteria for choosing such a site should be as follows:

3.2.1. The habitat conditions are more complicated and the biodiversity is more varied (including different blocks composed of primary, secondary and artificial ecosystems) than comparative areas. The area should not be smaller than 100,000 ha, and it should be representative of a particular environment. The main requirement should be for the area to contain key species and indicator species. The area should enable natural ecological process and species evolution to occur, thus ensuring that biodiversity conservation and sustainable use can take place in close combination and at the same time.

3.2.2. The local government must include the formation of the biodiversity conservation region in their projections of economic construction or social developmental planning, and must appropriate this activity with a certain budget.

3.2.3. We should establish a specifically managed institution to plan out rational use of such lands and to define the appropriate scale of investment and other practical details.

3.2.4. Local people must support the comprehensive developmental principle of combining biodiversity conservation with sustainable use and be willing to put their own production into the overall planning of this region. In a word, the success and failure of a biodiversity conservation region will depend on the common recognition and coordination of local governments, people, and responsible departments of resource management. Relevant manpower and material resources must be organized to sum up experiments in practical processes and to make strenuous efforts for realizing predetermined goals. These objectives must be made continuously, and with constant feedback between all parties.

3.3. The establishment of a network of biodiversity conservation regions tropical and subtropical China.

According to the above mentioned criteria, and based on urgent demand, the probable sites of establishment may be chosen as follows.

3.3.1. The mountains of central and southern Hainan.

The tropical forests of this region in Hainan are well preserved and contain rich biodiversity. There is a large area of mountains, which can supply development. Some reserves have been established, but only very small parts are actually conserved. The biodiversity conservation region may be set up based on the Bawangling reserve in Changjiang county, Jianfengling reserve in Yuedong county, Diaoluoshan reserve in Lingshui county, or Wuzhishan reserve in Qiongzhong county (Wang Xianpu, 1988; Jiang, 1991).

3.3.2. The limestone mountains in southwestern Guangxi　

Large areas of limestone mountain are seldom seen in tropical areas. The nature of flora in this area of limestone mountain belongs to a special part of the India-Malaysia floristic region -- called the florist county of borderlands in China and Vietnam. Here, certain areas of limestone seasonal rain forest are better preserved and with a richer biodiversity than found elsewhere. Many species have a special nature and certain developmental potential. The biodiversity conservation region may be defined based on Longgang reserve in Longzhou county and Longrui reserve in Ningming county.

3.3.3. The Xishuangbanna region in Yunnan　

A large area of primary seasonal rain forest which well preserved and contains rich biodiversity occurs in the Xishuangbanna region. Many wildlife species here have a developmental perspective. Ideally, the biodiversity conservation region should be established around the Mengla reserve, Menglun reserve in Mengla county or Mengyang reserve in Jinghong county.

3.3.4. The high mountain and deep valley region in western Sichuan　

This region belongs to the mountainous northern end of the Hengduan mountain range. Primary humid subtropical forests are well preserved and of a large area with apparent vegetational vertical distribution here. This is an important region in which biodiversity is concentrated in eastern subtropical China. In the meantime, it is also a famous site for abundant endemic species of China. Giant pandas are common here. The biodiversity conservation region may be established based on Wolong reserve, in which a special region with governmental functions has been established. Actually, the reserve is also a leading organization for biodiversity conservation regions. It is easy to establish protocols for relevant work if guiding policy is well-defined (Wolong Reserve Management Department et al., 1992).

3.3.5. The high mountain and deep valley region in western Yunnan.　

This region belongs to the mountains along the southern margin of the Hengduan mountain range. Primary humid subtropical forests are well preserved in large areas and with apparent representative vertical distribution of vegetation. This is also an important region, in which biodiversity is concentrated in the western subtropics of China with large amounts of Chinese endemic species. The biodiversity conservation region may be defined on the basis of Gaoligongshan or Nujiang reserves. The region will enable close promotion of economic development of different countries along the Mekong river (Yunnan Forestry Research and Planning College, 1989; Yunnan Science and Technology Commission et al., 1990).

3.3.6. Limestone mountains in southern Guizhou　

A large area of limestone forest characteristic of the humid subtropics is well preserved in Maolan, Libo county, according to existing information. Here, rich and special elements of plant biodiversity exist, as well as available diverse wildlife resources. Visitors from domestic and foreign countries are attracted to this area by its beautiful Karst scenery. The biodiversity conservation region may be defined by the Maolan reserve. It will potentially play a great role in the restoration of secondary ecosystems in extensive limestone mountain habitats and in the improvement of local people's living level (Guizhou Forestry Department, 1990).

3.3.7. The Shennongjia region in Hubei　

Shennongjia mountain maintains a certain area of primary subtropical forests in central China with apparent vegetational vertical distribution and rich biodiversity. The biodiversity conservation region here may be established based on the Shennongjia reserve. Like in the case of the Wolong reserve, it has also set up a government special area and is a leading institution with a definite policy toward establishment and management of biodiversity conservation regions. Its policies carry forward those expressed in the Convention on Biological Diversity (Wang Xianpu, 1995).

3.3.8. Nanling mountain　

The Nanling mountain watershed of Changjiang and Zhujiang rivers extends across the contiguous areas of Guangdong, Guangxi, Hunan and Jiangxi. Its flora blends together elements of central, eastern and southern China and contains a rich biodiversity. There are many species that serve as substitutes to those in west Yunnan, located in the western subtropics. The area is rich in endemic and relic species of wildlife resources. The biodiversity conservation region may be established based on the Huaping reserve in Longsheng county, Miaoershan reserve in Xinan county, Guangxi or two Mangshan reserves by the border of Hunan and Guangdong. It will promote the development of the local economy and enhance the living level of local people (Comprehensive Survey Team of Huaping Reserve, in Guangxi, 1986; Comprehensive Survey Team of Southern Mountain of Chinese Academy of Sciences, 1990).

3.3.9. Mountains in Zhejiang and Fujian　

The subtropical forests of this region are better preserved than any in eastern China, and they contain many endemic species and rich biological resources. The Wuyishan reserve in Fujian has carried on management for several years according to requirements for biosphere reserves, accumulating abundant experience. This experience can be utilized by other reserves, making it a model for the establishment of biodiversity conservation regions (Wang Xianpu 1989, 1994). Baishanzu-Fengyang reserve in Zhejiang has also similar conditions.

3.3.10. Dabeishan mountain in western Anhui　

The forests of this region are the best preserved of those anywhere in the northern subtropics. They contain elements of rich biodiversity. Many endemic species exist in this area, which acts as a zone of convergence between the flora of southern and northern of China. Here the biodiversity conservation region can be established based on the Yaoluoping or Jinzhai reserves in Anhui. It may be important to promote the development of comprehensive agriculture around the reserves (Wang Xianpu 1989, 1994). It may be predetermined that the establishment and gradual improvement of a network of biodiversity conservation regions can lead to exploitation of biological resources having developmental perspective. It will play great role for the promotion of regional development of industry and agriculture, and march on toward a fine future for the coexistence of nature and modernization in the 21st century.

Acknowledgements

I thank Professor Andrew Smith, international member of the Biodiversity Working Group, for editing the translated text of this manuscript. 　　

References

Chen Junyi (ed.). 1990. China Flora Encyclopaedia, Shanghai Culture Press (in Chinese).

China Vegetation Editorial Committee. 1980. The Vegetation of China, Science Press (in Chinese).

Comprehensive Survey Team of Qingzang Plateau of Chinese Academy of Sciences. 1982. The Vegetation of Xizang, Science Press (in Chinese).

Comprehensive Survey Team of Southern Mountain of Chinese Academy of Sciences. 1990. The Comprehensive Study of Natural Resources Exploitation and Land Renovation of Nanling Mountain in Hunan, Academic Books and Periodicals Press (in Chinese).

Comprehensive Survey Team of Xishuangbanna Nature Reserve. 1987. The Comprehensive Survey Report of Xishuangbanna Nature Reserve, Yunnan Science and Technology Press (in Chinese).

Guangxi Institute of Botany. 1965. The Plants of Making Green, Guilin, Guangxi Institute of Botany (in Chinese).

Guangxi Forestry Department, et al. 1980. The Silvicultural Techniques of broadleaf Trees, Guangxi People Press (in Chinese).

Guangxi Forestry Department. 1993. Guangxi Nature Reserves, China Forestry Press (in Chinese)

Guangxi Comprehensive Survey Team of Huaping Forest Area. 1986. Report on comprehensive Research of Huaping Forest Area in Guangxi, Shandong Science and Technology Press (in Chinese)

Guangxi Comprehensive Survey Team of Longgang Reserve. 1988. Report on Comprehensive Survey of Longganf Reserve in Guangxi, Guihaia, Additamentum 1 (in Chinese with English Summary).

Guizhou Forest Department. 1987. Report on Scientific Research of Forest in Limestone Mountain in Maolan, Guizhou, People’s Press (in Chinese with English Summary).

Hu Yujia et al. 1992. The tropical rain forest in Hainan Island, Guangdong High Education Press (in Chinese).

IUCN Conservation Monitoring Center et al. 1984. The IUCN/WWF Plant conservation program, 1984-1985, Gland, Switzerland.

IUCN et al. 1989. Goals and objectives for world conservation, IUCN bulletin 20 (1-3) 8.

Jiang Youxu. 1991. The tropical forest ecosystem of Jianfengling mountain in Hainan Island, China, Science Press (in Chinese).

Jiang Youxu. 1994. The environmental monitoring and assessment of environmental benefit of forestry construction engineering, Natural Resources 6:16-24 (in Chinese).

Li Zhiji et al. 1965. The ecological geographical distribution of main economic trees in Guangxi and their overall arrangement, Acta Phytoecologica et Geobotanica Sinica: 3 (1): 1-49 (in Chinese).

National plan commission et al. 1994. Agenda of 21 Century of China, China Environment sciences Press (in Chinese)

Pei Shengji. 1982. A preliminary study of enthobotany in Xishuangbanna, Report on research of tropical plants 16-23, Yunnan People Press (in Chinese)

Salleh, M. N. 1994. Multipurpose tree species of F/FRED research network, Farm Forestry News (Forestry/Fuelwood Research and DevelopmetePeoject) 6 (2): 1-4.

Su Zhongmin et al. 1990. The analysis of effectiveness closing hillsides to facilitate afforestation in limestone mountain of Guangxi, Guihaia 10 (4): 345-350 (in Chinese with English Summary).

Wang Hesheng. 1992. Florist Geography, Science Press (in Chinese).

Wang Xianpu. 1984. On the achievement and problems of cultivating brazil rubber tree in Hainan island from view point of ecology, Science and Technology of Tropical Crops 3: 6-9 (in Chinese)

Wang Xianpu. 1985. The basic concept of reserves cluster and its application, Guihaia: 5 (4): 409-412 (in Chinese).

Wang Xianpu. 1986. Environmental and Socia-Economica Aspects of Tropical Deforestation in China, Environmental and Socia-Economic Aspects of Tropical deforestation in Asia and Pacific, 65-71, United Nation, ESCAP, Bangkok.

Wang Xianpu et al. 1987. The perspective of construction of natural protected areas in Xishuangbanna, Yunnan, Guihaia 7 (3): 245-249 (in Chinese).

Wang Xianpu. 1987. The effect of tropical deforestation on environmental and socio-ecnomic aspects in tropics of China, Journal of Southwest Teacher University 3: 62-70 (in Chinese with English Summary).

Wang Xianpu. 1988. The achievement and future tasks of IUCN-WWF joint plant conservation program, Guihaia: 8 (4): 365-370 (in Chinese).

Wang Xianpu. 1988. The construction of protected areas in Hainan island in relation to economic development, Rural eco-environment 2: 31-34 (in Chinese).

Wang Xianpu et al. 1989. The theory and practice of natural protected area, China Environment Sciences Press (in Chinese).

Wang Xianpu et al. 1989. Floristic inventory of tropical China, in floristic inventory of tropical countries (ed. D. G. Campbell), New York.

Wang Xianpu. 1990. The phytocoenlogical features and rational use of subtropical deciduous broadleaf forest in Guangxi, Guihaia 10 (4): 307-319 (in Chinese with English Summary).

Wang Xianpu. 1990. Natural conservation and eco-development of tropical hills and mountains in China, Collected work of natural conservation, 320-330, China Environment Sciences Press (in Chinese)

Wang Xianpu. 1990. Natural conservation and eco-development of southeast subtropical hills and mountains in China, Collected work of natural conservation, 314-319, China Environment Sciences Press (in Chinese).

Wang Xianpu. 1992. The conservation of biodiversity in west coast and marine area of Shenzhen city, Guangdong, Journal of Plant Resources and Environment: 1 (1): 1-5 (in Chinese with English summary).

Wang Xianpu et al. 1994. The theory and practice of biodiversity, China Environment Sciences Press (in Chinese).

Wang Xianpu. 1994. On the synchronous development of environment protection and economic construction, Rural Eco-environment 10 (2)55-56 (in Chinese).

Wang Xianpu. 1995. The basic features and management of Shennongjia reserve in Hubei, China's Biosphere Reserves 1: 22-27 (in Chinese).

Wolong Reserve Service et al. 1992. The animal, plant resources and conservation in Wolong reserve, Sichuan Science and Technology Press (in Chinese).

Wu Zhenyi et al. 1983. The physical geography-plant geography (Vol. 1)Science Press (in Chinese).

Xu Zaifu et al. 1982. The conservation of tropical plant germplasm in Xishuangbanna, Report on Tropical Plant Research 7-15, Yunnan People Press (in Chinese).

Yu Pinghua et al. 1982. The study of ethnotimbers in Xishuangbanna, Report on Tropical Plant Research 108-115, Yunnan People Press (in Chinese).

Yunnan Forestry Survey and Planning Institute. 1989. Protected area of Yunnan, China Forestry Press (in Chinese)

Yunnan Science and Technology Commission et al. 1990. The study of developmental strategy of biological resources in Yunnan, Yunnan Science and Technology Press (in Chinese).

Zhu Kezhen. 1958. The subtropics of China, Science Bulletin 17: 1-6 (in Chinese).

Zhu Yue et al. 1988. The Guidelines of Hainan development, 160-167, Hunan Science and Technology Press.