Zhang Jianping's book Eco-tourism puts forward the type of "landscape ecological restoration eco-tourism resources" among the artificial natural eco-tourism resources. According to this view, we put forward the concept of "ecological park with natural or artificial ecological restoration and improvement". As far as the earth itself is concerned, there is no difference between good and bad. Deserts, wetlands, forests and fertile agricultural areas are all surface landscapes, which have no influence on their existence and development. But for human beings, the support of these ecosystems for human survival is very different. Humans must rely on agricultural areas, grasslands, wetlands and so on. In order to survive, there are deserts, Gobi, rocky deserts, saline-alkali land and so on. Can't be a space for human survival. Therefore, from the perspective of human needs, various ecosystems have their own advantages and disadvantages, which leads to the concept of ecosystem deterioration, recovery or improvement. The so-called ecosystem restoration refers to the excellent ecosystem that was originally very beneficial to human survival, and for some reason it degenerated into an ecosystem that is not conducive to human survival. For example, grassland or cultivated land has become a desert, fertile cultivated land has become a salt shell of barren land, and good cultivated land has become a rocky desert due to erosion, which is the deterioration of the ecosystem. But these bad ecosystems can be transformed into ecosystems that are conducive to human survival, which is the restoration area of ecosystems. Dujiangyan was built in the plain of western Sichuan, threatened by Minjiang River, and often suffered from floods. After Dujiangyan was completed, it became a land of abundance.
The deterioration, restoration and improvement of ecosystem are caused by both natural and human factors. The Taihu Lake basin, the western Sichuan plain, the desert reconstruction in Yulin area and the greening of the loess plateau in northern Shaanxi are all human reasons. Natural causes have a wide impact on ecological deterioration, restoration and improvement, such as drought and humidity of climate, ice age and interglacial period, and fluctuations of ground and sea surface. However, the change caused by natural causes takes a long time, which is difficult to observe with the short life span of human beings. Therefore, the change of ecosystem will mainly rely on human efforts and the prevention and construction of ecological environment deterioration. Therefore, it is necessary to further explore the factors that lead to the advantages and disadvantages of the ecological environment.
The quality of ecological environment is determined by three factors:
1) Water is the foundation, and its richness directly determines the type of ecological environment. The change series of water resources such as wetlands, rainforests, forests, sparse grasslands, grasslands, desert grasslands and desert Gobi are caused by the change of water resources and are flood-prone areas.
2) Land is also the foundation, and there are two directions of change from high-quality land to land extinction: ① the change from plain to mountainous area caused by soil erosion and erosion, that is, vast, thick and fertile plain land-large sloping land-barren and sporadic sloping land-rocky desert area with bare rocks; ② Divisions caused by changeable water resources, that is, flood-prone areas-wetlands-salinized land-fertile land-arid desertification land-wasteland-desert Gobi and other deserts.
3) Temperature (energy) (when rainfall is abundant) causes vegetation zoning: tropical rain forest-broad-leaved forest-coniferous forest-shrub-grassland-ice and snow plain.
It is difficult and unclear to express the function of water, soil and temperature with three-dimensional space diagram. Therefore, taking the temperature and altitude as the abscissa and the richness of water resources as the ordinate, the existence, scale and ability of supporting vegetation of land are divided into different types in this coordinate system to express ecological relations, which are divided into 16 categories (Figure 7- 1): ① Plain land area with abundant water resources; (2) Land areas prone to salinization and alkalization; ③ Wetland and rice planting area; ④ Flood-prone areas; ⑤ Large slope area; ⑥ serious soil erosion area; ⑦ barren and sporadic land areas; (8) Stone desert areas where land disappears; Pet-name ruby land or areas with or without ice and snow; Arid and water-deficient areas; Grassland; Land desertification areas; Desert grassland; Soilless deserts such as deserts and Gobi; Coastal land; Ocean. Among them, the land desertification area is superimposed on several types of land and is not divided into independent areas. Its range is marked with dotted lines in Figure 7- 1.
Figure 7- 1 Schematic diagram of ecological type relationship
See the text for the ecological area represented by numbers.
Among the nine types of nature reserves in China, the first five types can represent ecosystem areas, and their relationship with the ecological areas represented by land in this book is shown in Figure 7-2. According to their ability to support human survival, these five types of ecological zones are divided into the following order: wetland > forest > grassland > marine coast > desert. The remaining animal and plant reserves can appear in any of the five categories shown in Figure 7-2, while geological relics and paleontological relics do not belong to ecological categories, so Figure 7-2 only lists five categories. According to the above order, forest is actually a suitable area for forest growth, and it is mainly cultivated land in China, so it is better than grassland.
Figure 7-2 Location Diagram of Five Nature Reserves
The five types of ecological zones divided by nature reserves are not all ecological zones, because they only represent five ecological types that need to be protected. The 16 ecological type shown in Figure 7- 1 can basically represent the ecological situation in China, but there is no forest ecological type, because the forest can appear in the 1 1 type other than the five ecological types such as ice and snow area, grassland, desert grassland and ocean, and good cultivated land is more suitable for forest growth. It is only because of the shortage of cultivated land in China that all cultivated land should not be planted, so the forest ecosystem in China is mainly located in areas with serious soil erosion, barren scattered land areas, rocky desertification and other types, which is also the reality in China. Therefore, after joining the forest system, there are 17 ecological types.
Grain is extremely important to human society, so it is ranked according to this 17 ecological type: wetland and rice planting area > rich original cultivated land > coastal land > large slope land > flood-prone area > saline land > serious soil erosion area > drought and water shortage area > grassland > land desertification area > forest > scattered land > ocean > desert grassland > rocky desertification area >. In the above ranking, the ecological restoration or improvement area can enter the top from the bottom; Those who retreat from the front positions are all ecological deterioration areas. For example, rice can be replanted in saline-alkali areas and areas with serious soil erosion, such as Yuanyang in Henan and Ailao Mountain in Yunnan; Rocky desert areas can be transformed into forests, such as Qianling Mountain in Guiyang, Jiyuan in Henan and Yulin in Shaanxi, which greatly improve the ecosystem. The lower reaches of Tarim River in Tarim Basin were cut off, Lop Nur dried up and Populus euphratica forest died, which was the deterioration of ecological environment.
In the above ranking, grassland ranks ahead of forest and ocean because the food provided by the latter per unit area is not as good as grassland, but if edible fruit trees such as chestnut and walnut are planted, the forest can be transformed into a perennial agricultural area. A large number of edible plants and animals are planted in the ocean, so that it can develop into a marine farm and pasture, and its ecological status will be promoted to the front of the grassland.
From the relationship shown in Figure 7- 1, it can also be seen that any one of the three factors that determine the type of ecosystem can worsen the ecosystem to a certain extent, or the deterioration of one factor will lead to the deterioration of other factors and jointly cause the deterioration of the ecological environment; Sometimes, multiple factors can deteriorate at the same time, resulting in the deterioration of the ecological environment. On the contrary, when restoring or improving the ecosystem, we can also improve the ecological environment by improving one factor, such as the drought of cultivated land or grassland, which can be solved by water diversion irrigation. When the temperature in North China Plain is low, greenhouses can be built to grow vegetables. Sometimes two factors must be solved at the same time, such as covering the soil layer to solve the fluidity of the desert and diverting water for irrigation to solve the drought of the desert. Hani terrace in Ailao Mountain, Yunnan Province not only transforms the hillside into stepped flat land, but also transforms the whole hillside into artificial wetland by combining water diversion. There are many terraces in Sichuan, and there are also terraces in dry fields in the north, but the effect is far less than the former, because it is not combined with water conservancy construction. Some ecological problems can't be solved directly, such as rocky desertification in mountainous areas. Local small areas can be filled with soil to restore their original appearance, but it is impossible to restore them in large areas. But strengthening water resources can make up for the shortage of land by planting trees in rocky mountainous areas, and then build desert perennial agriculture; Another example is planting rice on saline-alkali land, which can be discharged into the sea with water. Some factors of ecological environment can also influence each other, forming a vicious circle or a virtuous circle. For example, the drought in the Tarim basin and the northern margin of the Qinghai-Tibet Plateau, the general view is that the Himalayas have blocked the northward movement of water vapor in the Indian Ocean. This is of course one of the reasons, but the current extreme drought is the result of the interaction and vicious circle between the plateau and the basin. Because there was a lot of water in the Tarim River during the Qin and Han Dynasties, it was the desertification in the Tarim Basin that reduced the precipitation in the northern margin of the plateau, which led to the decrease of river flow into the basin and accelerated the process of desertification in the basin. The interaction between the two accelerated the process of drought. If this vicious circle is cut off, the whole ecosystem will be completely improved. For example, on the basis of the South-to-North Water Diversion Project and the East-to-West Water Diversion Project, building a forest belt (desert-type perennial agricultural area) with a length of about 2500km from the Tengger Desert through the Gobi in the middle and the Gobi in front of the Kunlun Mountains can improve the drought situation in the whole northwest region, including the northern edge of the Qinghai-Tibet Plateau, and at least restore the state in the Qin and Han Dynasties, and even the precipitation reaches North China. The factors that determine the ecological advantages and disadvantages are as polarized as those in the United States. If the temperature is too low, it will become a snowfield, and if the temperature is too high, it will not be suitable for human habitation, and it will also bring a series of problems such as sea level rise. The ground rises rapidly, the land becomes less, and there is a stone desert. Land subsidence can expand the plain area, but it will be threatened by seawater intrusion, such as land subsidence in North China Plain. Too much water will cause floods, and too little water will make the land lose its productivity and die out through desertification. It is precisely because of this polarization that the water that caused the disaster should be transferred to the water-deficient areas, which plays a dual role in killing pests and promoting benefits. Ecology is a big system, and there must be a unified scheme to solve all kinds of problems at the same time. In this way, the ecological outlook of our country can be completely improved. The land area is 960× 104km2, and the sea area is 473× 104km2, which can provide living materials and form a unified large land resource. If this can be done, the contribution of ecotourism will be enormous.
There are two types of ecological zones that need to be restored and improved, namely, compound with scenic spots and pure ecology. For example, Dujiangyan is a famous scenic tourist area and an area where human factors improve the ecology; The forest in the rocky desert of Wuwang, Henan Province and the forest in the karst landform of Maolan, Guizhou Province are not only famous scenic spots, but also areas where natural factors improve the ecology. However, the improvement of ecological restoration in most areas is not of great tourism value, such as the transformation of desert in Yulin area, the greening of Dagouhe forest farm and rocky mountain in the west of Jiyuan City, Henan Province, and the greening of dry-hot valley of Jinsha River, etc., all of which are artificial ecological upgrading, but only have the scientific value of scientific research, scientific investigation and exchange of production experience, and have no tourism value, so they belong to pure ecological parks, not ecological parks compounded with scenic spots.
Second, the ecosystem deterioration area.
The sharp decline of forests, land desertification and soil erosion are the most prominent problems of ecosystem deterioration in China. Since the devastating flood in the Yangtze River, the state has attached great importance to forest protection, and given subsidies and rewards to returning farmland to forests and artificial afforestation. The sharp decline of forests is no longer a serious problem. On the contrary, ecosystems in some areas have been restored and improved.
1. Desertification
(1) Drought in Lop Nur
There are taitema lake, Kala Heshun Lake and Lop Nur in the east of Tarim Basin, and there are rivers between the three lakes, which are collectively called Lop Nur Depression. Lop Nur once had an area of 5,350 square kilometers and was the terminal lake of Tarim River and Peacock River. Due to the intensification of drought in Tarim Basin, the water consumption in the upper reaches and coastal areas of Tarim River has increased, and the area has gradually decreased to 3006km2, which is 65,438+0,942. At 1952, only Peacock River flows into Lop Nur alone due to the dam at the mouth of Laiyi River. The area of 1962 is only 660km2, and the water surface of 1975 disappears. 1952 After the dam is built, Tarim River and Dongershen Lake flow into taitema lake, with an area of150km2; . The area of 1962 is only 88km2；; The main body dried up in 198 1 year; During the period of 1987, Lop Nur was completely dried up and completely desertified.
(2) The disappearance of Juyanze and Juyan Oasis
Heihe River is the largest river in the middle of Hexi Corridor, with Juyanze at its tail, covering an area of 726km2, and Juyan Oasis along the coast, which was called Juyanzai in Han Dynasty. Tang, Xixia and Yuan set up Kenai City here. Wang Wei's famous phrase "The desert is lonely and the smoke is straight, and the long river sets the yen" shows that Heihe was still a big river at that time. In the fifth year of Hongwu in the Ming Dynasty, Zhu Yuanzhang ordered the Western Expedition, Ji was guarding the city, and Feng cut off the water. Since then, the river has flowed northward, Juyanze has dried up, and the oasis has become a part of the Badain Jaran Desert.
2. Rocky desertification
In mountainous areas and hilly areas where the ground rises or the altitude is slightly higher, running water will cause soil erosion, and further erosion will take away all the soil layers, leaving bare rocks and deserts. China is a mountainous country, so rocky desertification is one of the serious ecological problems in China, especially in the southwest. The rocky desertification area in Sichuan, Chongqing, Yunnan, Guizhou, Guangxi and other provinces (autonomous regions and municipalities) is above 1 100 million mu, and the rocky desertification area in Guizhou accounts for one third of the whole province.
Third, the area of ecosystem restoration and improvement.
1. Constructed wetland
Wetland is an important ecosystem, known as kidney of the earth, and its protection has become a hot issue of global concern. In fact, paddy fields (including terraces) are typical constructed wetlands. Building terraces means building artificial wetlands. In addition to all the functions of wetlands, rice fields have many other ecological values, the most important of which are the following four aspects:
1) Resist erosion of land by flowing water and reduce river siltation. The ability of running water to erode land depends on the runoff and velocity formed during rainfall. Runoff formed by precipitation on sloping land will carry sediment, causing soil erosion and land erosion. However, after the runoff enters the paddy field, it will become still water, and the velocity is close to zero, and the sediment it carries will be deposited in the paddy field, reducing the amount of sediment entering the river. The annual sediment discharge of the Yellow River is about three times that of the Yangtze River, and the annual runoff of the Yangtze River is about 12.5 times that of the Yellow River, so the sediment discharge per cubic meter of the Yellow River is about 37.5 times that of the Yangtze River. In addition to the weak anti-erosion ability of loess in the Loess Plateau, paddy fields widely distributed in the source area of the Yangtze River system should be a more important reason. Therefore, it is possible to reduce the sediment concentration of the Yellow River to the level of the Yangtze River by building rice terraces around the Loess Plateau in combination with water conservancy construction.
2) Retain floods, stagger flood peaks, adjust river flow and reduce floods. When it rains, rainwater accumulates in paddy fields and then gradually enters the river, which can stagger the flood peaks and stabilize the river flow. In the past, people only paid attention to the water storage capacity of lakes. In fact, paddy fields also have this function. The existing paddy fields in China are about 38× 104km2. If the water storage depth is 0.5m, its water storage capacity will exceed the total water storage capacity of lakes in southeast China and Yunnan-Guizhou Plateau, and its regulation function will surpass that of lakes, which can solve or alleviate the flood disasters in many areas.
3) Paddy field has dual functions of water storage and agricultural production, which can solve the contradiction between water storage and farming.
4) Developing terraced fields upstream of the reservoir can not only slow down siltation, but also expand the storage capacity.
Take Yuanyang terraced fields as an example. There is no plain in Yuanyang county, and terraces are embedded in ravines and mountains of 400~2000m m, where mountains and rivers are connected and ravines are criss-crossing. So there are Hani people living here, and terraces are also called Hani terraces.
The unified construction of water conservancy and terraced fields is the essence of Yuanyang terraced fields technology. Many terraced fields in Yuanyang have dangerous terrain. The roadside is a cliff, and under the cliff is a terrace. In Bada, the Hani people cut out 5000 terraces, which are as beautiful as ladders hanging from heaven. In the busy farming season, in order to save time on the way, local people live in sheds, which float on the vast sea like boats.
2. Dujiangyan project with disaster reduction and irrigation efficiency.
Water transfer can eliminate the flood disaster in the transfer-out area and increase the water resources in the transfer-in area, which has the effect of double ecological improvement and is a measure to simultaneously reduce disasters and promote benefits. Dujiangyan is not only a world-famous water conservancy project, but also a popular tourist attraction. Dujiangyan was originally built to alleviate the flood in Chengdu Plain. Because of the large flow of Minjiang River, the rising water in Chengdu Plain will be flooded. The prime minister of Shu enlightened him to open the bottle mouth and build a canal to introduce part of the river water into Tuojiang River, thus eliminating the flood in Chengdu Plain. Later, after Qin destroyed Shu, Li Bing, the county magistrate, developed irrigation on the original basis of Dujiangyan, which achieved high economic benefits and made Sichuan a land of abundance. It can be seen that the construction of Dujiangyan has also improved the ecological grade of the water resources transfer-out area and the transfer-in area.
Because the time of floods in different river basins in China is different, we can use this time difference to spread the experience of Dujiangyan water diversion to the whole country, connect the river basins, help each other and benefit each other, and lead the floods that caused floods to other river basins and turn them into water resources in the introduced areas. For example, it is easy to communicate between the Yangtze River and Huanghuai, and between Songhua River and Liaohe River.
The fundamental factor that determines the ecological quality is water, and the fundamental direction to solve the water problem is to guide the excess water that caused the flood to the needed place. So as long as there is enough water in other places in the desert, the ecological level can be improved and it will become an oasis.
3. Rice planting can improve saline-alkali land into artificial wetland.
Many technologies of Dujiangyan project are beyond the reach of modern water conservancy projects. However, it is the essence of Dujiangyan water conservancy project that irrigation makes the land salinized.
6000 ~ 7000 years ago, people in the plains of Tigris River and Euphrates River knew how to lead the river water to farmland, so Mesopotamia in the plains of the two rivers became the oldest irrigation area in the world. However, irrigation did not turn this place into fertile land, but formed a thick white salt shell. On the surface, Dujiangyan irrigation system has not taken any measures to solve the problem of salinization, but there is no sign of salinization for more than two thousand years, because it sends soluble elements (saline-alkali components) separated from rock weathering into the ocean. When rice is planted in Dujiangyan irrigation area, saline-alkali land enters the sea with water, and many places in China use this method to transform saline-alkali land. For example, in the 1970s, rice/kloc-0.5 million mu was planted in saline-alkali land in Panjin and Yingkou, Liaoning Province, with a yield of 400 kg per unit area, which can be desalinated in 3-5 years, thus improving the local ecosystem level. Yuanyang was once the hardest hit area of salinization in Henan Province, and the saline-alkali land occupied 80% of the cultivated land area, but rice planting was a great success. This irrigation method should be used in all places where a large amount of water can be diverted.
4. Storing water underground can improve the level of ecosystem.
In landscape classification, we regard spring scenery as the source of rivers, because there must be a corresponding stream or small ditch every spring, even if it cannot be the main source of a river because of its unfavorable location, it must be the source of supply for the river. Surface precipitation time is short, but rivers flow all the year round. The reason is that precipitation seeps into the ground, forming a huge reservoir, which is supplied to the river in time and evenly. The fact that precipitation accumulates underground can be directly seen in many scenic spots, such as Longgong Scenic Area in Guizhou, where surface water enters the spiral pond in the upper reaches of Longgong; In karst scenic spots, precipitation can be seen everywhere entering underground sinkholes; In the countryside of Sanmenxia City, Henan Province, there are still many patio kilns. The patio kiln is a 6 ~ 7m deep pit dug on the flat ground, and the pit wall is open. Rainwater and daily water all enter the ground through the seepage well in the hospital. The patio kiln can dig wells to get water, which shows that it is a small underground reservoir. When it rains, rainwater seeps into the ground and is stored underground, and water is pumped from the well at ordinary times. Therefore, the problem of water shortage can be solved by building rainwater harvesting projects on the loess plateau and other water-deficient land, extensively building seepage wells, storing most of the precipitation underground, and then drilling wells to take water for irrigation and life. Precipitation mainly supplies the Yellow River in the form of spring water (clear water), which can also solve the sediment problem of the Yellow River.
The allowable annual water production of Dawu Water Source in Zibo is 1.42 × 108 m3, and the actual average water production for many years is 1.9 × 108 m3. In the dry season, the groundwater level drops to-10m, and in the wet season, Taihe Reservoir releases water to He Zi Beach, with an annual recharge of nearly 65,438.
Storing water underground is a world trend. For example, in Berlin, Germany, groundwater is used as drinking water, and the groundwater replenished by river bank filtration accounts for 40 ~ 70% of the total water. The Ganges valley in India is flooded in rainy season, but the flood in dry season can't meet the demand. Scholars of Harvard University in the United States suggest that a large amount of groundwater should be extracted and utilized during the dry season to make room for groundwater storage, and the excess river water should be stored in the groundwater aquifer to realize the recycling of groundwater and surface water.
As mentioned above, groundwater storage can raise the ecological grade of arid and water-deficient land to the grade of water-rich land.
5. Stone desert can be turned into forest.
Maolan Nature Reserve, located in Libo County, southern Guizhou Province, is a typical karst landform. In all karst areas in the world, including most karst areas in China, forests have long since disappeared, leaving only bare limestone and dolomite barren hills. However, within 2× 104 hm2 of Maolan Nature Reserve, there are dense forests of 1.937× 104 hm2, accounting for 92% of the total land area. Compared with the desolate scene of karst areas in the world, this relatively stable forest ecosystem can not but become a rare treasure, which points out the direction for mankind to conquer barren hills by using "stone desert".
There are various types of karst forests in nature reserves, including funnel forests, depression forests, basin forests and canyon forests. The dense subtropical virgin forest is lush, completely wild virgin forest, stretching 80 kilometers and 20 kilometers wide, and it is the only karst forest area on the earth. Whether it is steep conical peaks, peak clusters and peak forests, or swamp wetlands, they are covered with lush evergreen forests. Seen from the air, it looks like a huge green ocean with rough waves. The forest blocks the sunlight, and almost no sunlight can reach the ground through the thick canopy.
The funnel forest consists of trees with a height of 30-40m, which are distributed at the bottom of the funnel pit with a depth of100-200m and a diameter of100-200m, and grow from the steep cliff to the top of the cliff. The karst depression is huge and flat, which can be used as farmland, while the forest grows on the karst cone-shaped peaks around the depression. The forest in the basin grows in the open and flat basin, and the lush forest grows in the valley, making it a green corridor.
The rocks here are rugged and varied in shape, but all the rocks are covered with green plants. Trees grow along the cracks in rocks, and developed roots can go deep into the cracks. The roots of some trees develop into a dense root network around rocks, while others plunge into caves. Ferns and mosses cover the wet ground and are green. The reason why Maolan karst area can cover forests is that there are abundant water sources, which are divided into high and low levels, and water is everywhere on the ground and underground. Rivers, springs, ponds ... provide water for nourishing forests and ensure that plants can grow on rocks.
Maolan Nature Reserve and Guiyang Qianling Mountain Park are limestone rocky desertification, Henan Wuwang World Geopark is granite quartzite rocky desertification, Henan Madaoyan Forest Park is granite rocky desertification, Henan Jiyuan Dagouhe Forest Farm and Hunan Zhuzhou suburban hills are sandy shale rocky desertification, all of which are densely forested, which proves that all kinds of rocky rocky rocky rocky desertification can be turned into forests under moderate moisture conditions, that is to say, they can be developed into desert-type perennial agricultural areas, that is, chestnuts can be planted.
Different types of rocks in rocky desert have different solutions to water sources. The karst underground reservoir in Longshan County, Hunan Province is built at the outlet of underground river in limestone area. The karst cave space is used to store water, and the outlet of karst cave is small, with low dam construction cost, no flood and no evaporation loss. The water in the reservoir permeates around, which can raise the groundwater level to near the surface and ensure the water demand of the rocky desert forest. If this measure can be popularized in Guizhou, most rocky desertification areas can be developed into perennial agricultural areas, which will greatly improve the ecological level and economic benefits of Guizhou.
6. Human efforts can improve the level of the ecosystem.
Generally, when the ground elevation rises to a certain height, the forest belt will be replaced by the grassland belt, but the upper limit of the forest belt can be increased by artificial measures. People in Daocheng County, Ganzi Tibetan Autonomous Prefecture, Sichuan Province planted a 10,000-mu Populus cathayensis forest with an area of 32,000 mu and a stretch of more than 20 kilometers on the Qinghai-Tibet Plateau above 3,800 meters above sea level. On average, each person planted more than one acre of poplars, and all poplars were planted on pebbles in the river beach. The original gray-yellow wasteland has become a life belt in the forbidden zone of life. The international forest industry agrees that successful afforestation in high altitude areas has great scientific value. The dry and hot valley at the intersection of Heishui River and Jinshajiang River in ningnan county, Liangshan Prefecture, Sichuan Province is called Death Valley, with the highest temperature of over 42℃ and the surface temperature of 78℃, which is the biggest obstacle to the construction of ecological barrier in the upper reaches of the Yangtze River. 1964, the forestry department conducted seedling raising and afforestation experiments here. After screening and comparing dozens of tree species, Casuarina equisetifolia has the best effect, and then Leucaena leucocephala was introduced from Australia. With the joint efforts of the people in the county, the floodplain and barren hills are covered with green clothes. "This is really a miracle that human beings have overcome drought." Forest is the main body of terrestrial ecosystem, which stores about 80% of carbon in global terrestrial ecosystem. Needless to say, its importance is not high, but the forest coverage rate in China is not high. There is a shortage of land in China, and there is not enough land for afforestation. Therefore, afforestation in harsh environment has opened up a new direction for improving the level of ecosystem and forest coverage in China.