Chinese name: grassland ecosystem mbth: grassland ecosystem main body: plants, animals, microorganisms and environmental types: meadow grassland, typical grassland and desert grassland status quo: basic unit of material circulation and energy exchange ecological status quo: introduction of ecological barrier, characteristics and status quo, causes of destruction, overload and overgrazing, unsuitable farming, restoration countermeasures, scientific management, artificial grassland, upgrading system, brief introduction Grassland ecosystem is a biological community with various herbs as the main body. The main research object of grassland ecology is the grassland ecosystem whose purpose is to manage the production of herbivores and obtain animal products. It came into being with the development of modern animal husbandry, and its core is to study and clarify the structure and function of grassland ecosystem, the ecological relationship between subsystems and the regulation methods, so as to provide a basis for giving full play to the production potential of grassland resources and establishing an optimized production system. Grassland Ecosystem The grassland ecosystem in China is an important part of temperate grassland ecosystem in Eurasia. Its main body is the temperate grassland in Northeast-Inner Mongolia. According to the different natural conditions and ecological school districts, grassland ecosystem in China can be roughly divided into three types: meadow grassland, typical grassland and desert grassland. Key points: Grassland ecosystem is distributed in arid areas with little annual rainfall. Compared with forest ecosystem, the species of animals and plants in grassland ecosystem are much less, and the community structure is not as complicated as the former. In different seasons or years, the rainfall is very uneven, so the structure of population and community often changes greatly. Tropical Grassland Ecosystem Due to overgrazing, rodents and insect pests, the grassland area in China is decreasing, and some pastures are facing the threat of desertification. Therefore, it is necessary to strengthen the rational utilization and protection of grasslands. The plants on the grassland are mainly herbs, and some grasslands have a small amount of shrubs. Due to the scarcity of rainfall, trees are very scarce. Animals there have adapted to life on the grassland, and most of them have the behavior characteristics of digging holes or running fast. There are many rodents on the grassland, almost all of which live underground. Gazelle, antelope, rhinoceros, jerboa, fox and other animals that are good at running all live on the grassland. Amphibians and aquatic animals are very scarce in grassland ecosystem due to water shortage. Grassland is an important production base of animal husbandry. In China's vast grassland, a large number of domestic animals are raised, such as Xinjiang fine-wool sheep, Ilima, Sanhema, Tan sheep and Kuqa high-skinned sheep. These livestock can provide people with a lot of meat, milk and fur. In addition, the grassland can also adjust the climate and prevent the land from being eroded by wind and sand. The total grassland area in the world is 4.5 billion hectares, accounting for 24% of the land area, second only to forest ecosystems. In the proportion of fixed energy in biosphere, grassland ecosystem is about 1 1.6%, and it also ranks second in terrestrial ecosystem. Grassland ecosystem is located in an area with strong continental climate and little precipitation, and the annual precipitation is generally 250-450 mm, which varies greatly. Evaporation often exceeds precipitation. In addition, there are many sunny days and a large amount of solar radiation in these areas. This climatic condition makes the components of grassland ecosystem present some adaptive characteristics. Primary producers are mainly composed of herbaceous plants, most of which have structures adapted to arid climate, such as shrinking leaves, wax layer and hair layer, to reduce transpiration and prevent excessive water loss. The spatial vertical structure of grassland ecosystem is usually divided into three layers: herb layer, ground layer and root layer. The structure of each layer is relatively simple, and there are no complex and diverse niches in the forest ecosystem. The consumers of grassland ecosystem are mainly large herbivores suitable for running, such as wild donkeys and antelopes. There are also many races such as grass rabbits and locusts. There are also many rodents living in caves, such as voles, weasels, marmots, pikas and zokor. Carnivores include sand foxes, ferrets and wolves. Carnivorous birds include eagles, falcons and harriers, while other birds are mainly larks, larks, grouse and ground birds. Some of them live in caves. Grassland is also one of the main natural ecosystem types in China. According to the Statistical Yearbook of China (1988), the available grassland area in China is 336.5 million hectares, accounting for about 7. 1% of the total grassland area in the world. There are many types of grasslands in China. On the whole, the grassland in Inner Mongolia is dominated by perennial and xerophytic low-temperature herbs, and the grass species are mainly Gramineae, among which Stipa and Leymus chinensis are the most representative. The former is tufted grass, and the latter is rhizomatous grass. The rhizomatous grass has been developed, which plays an important role in preventing wind and fixing sand. Central China is a sparse grassland, dominated by Stipa grandis; The west is a desert grassland, dominated by Stipa Gobi. Grassland plays an important role in nature protection. It is not only an important geographical barrier, but also a natural defense line to stop the spread of desert, which plays the role of ecological barrier. In addition, it is a natural base for human beings to develop animal husbandry. Generally speaking, the species diversity of grassland ecosystem is far less than that of forest ecosystem, but the structure of food web is also very complicated (Figure 6- 1 1). The utilization rate of light energy is not as high as that of forest ecosystem, which is usually about 0. 1- 1.4%. Meadow grassland in the former Soviet Union can reach 65,438+0.32%, while desert grassland such as China is less than 0.65,438+0%. Water is often the decisive factor of primary productivity of grassland ecosystem. According to statistics, the average net primary productivity of grassland ecosystem in the world is 500 g/m2 a, but it is only100-400 g/m2 a in temperate arid regions with insufficient water, and it can be increased to 600-1500 g/m2 a in subtropical grasslands with sufficient water. The maximum net primary productivity of grassland ecosystem can reach 3000-4500 g/m2 a (breymeyer, 1978). In the primary productivity of grassland ecosystem, underground biomass accounts for a large proportion. The distribution of primary productivity of meadow grassland in China is underground/aboveground =2.29. Generally speaking, the primary productivity of grassland belongs to the middle or lower level in all terrestrial ecosystems. The conversion efficiency of primary production from food chain to herbivores and carnivores is about 1%-20%. Take a cow as an example. About 48% of the plant energy consumed by a cow is to maintain normal physiological activities, 43% of the energy is discharged in the form of feces, and only 9% is used for the construction of body tissues. However, the energy conversion efficiency varies greatly among different species or strains. Selecting suitable animal species, establishing a reasonable food chain and improving the transformation efficiency of primary production are one of the main topics in grassland ecology research. A series of ecological problems, such as grassland degradation, alkalization and desertification, climate deterioration and serious rodent damage, exist in most grasslands in China to varying degrees, which are the ecological consequences caused by unreasonable utilization of grasslands by human beings. One of the signs of grassland degradation is the decrease of grass yield. According to the survey, the forage yield of various grasslands in China is generally 30-50% lower than that in the 1950s and 1960s. For example, in urumqi county, Xinjiang, the average grassland yield per mu was 85 kg in 1965, and it has dropped to 53 kg in 1982, with an average annual decrease of 1.5 kg. The second sign of grassland degradation is the change of forage quality, the decrease of edible forage and the increase of poisonous weeds, which makes the utilization value of forage decline. For example, in Guoluo area of Qinghai, weeds and poisonous weeds only accounted for 65,438+09-365,438+0% of the total grass before grassland degradation, and increased to 30-50% after degradation, while high-quality grass decreased from 33-565,438+0% to 4-65,438+09%. Grassland degradation and sparse vegetation lead to climate deterioration, and the number of windy days and sandstorm days gradually increases in many places (Table 6- 1). The deterioration of climate has promoted the process of grassland degradation and desertification. China is one of the countries that suffer the most from desertification in the world. The desertification area in northern China has reached nearly 6.5438+0.8 million square kilometers. In the 20 years from the end of 1950s to the end of 1970s, 39,000 square kilometers of land resources have been lost due to desertification. The rodent problem in the grassland is getting more and more serious. According to the statistics of 1982 national grassland rodent control conference, the area of rodent infestation in grassland pastoral areas in China is 66 million hectares, and the density of rat holes in some grasslands is as high as more than 4600 per hectare. The grassland was completely destroyed and lost its use value. It is estimated that our country loses about 5 billion kilograms of pasture every year due to rodent damage, and the direct economic loss is more than one billion yuan. The occurrence of rodent damage is not only the bad result of the imbalance of grassland ecosystem, but also one of the reasons for the further deterioration of grassland ecological environment For a long time, China's animal husbandry production is not based on the quantity and quality of livestock products, but on the total growth rate of livestock or the net growth rate of livestock on hand. As a result, more and more livestock are raised, but the grassland area occupied by each livestock is less and less, the growth rate of livestock is decreasing, and the stocking time is constantly extending, which will inevitably increase the carrying capacity of livestock and break the internal balance of livestock and grass. Grassland degradation caused by overload and overgrazing is a gradual process. With the increase of livestock per unit area, the more grass is grazed, the less grass seeds are available to maintain grass regeneration, and the yield of grass will either decrease or poisonous weeds will increase. If this situation is not controlled, there will be a vicious circle: the number of edible forage grass per unit area decreases, but the number of livestock is large, so livestock have to increase the range and frequency of foraging, which intensifies the physical damage to the soil structure of grassland and further limits the growth of forage grass. This long-term vicious circle will gradually make the grassland barren, degenerate and even desertification. Among the causes of grassland desertification in northern China, overgrazing is the second most important factor (Table 6-2). According to research, in the hundreds of years after the invasion of European colonists, desertification in some American States was caused by overgrazing. Both man-made and natural factors can control the carrying capacity of grassland, but man-made control is conscious control, which can achieve the effect of developing animal husbandry and protecting the ecological balance of grassland and is beneficial. However, natural control is the response of grassland ecosystem overload and overgrazing, and it is a disastrous control, which often leads to the death of a large number of livestock and affects the development of animal husbandry. In the process of human development, reclaiming grassland has always been one of the main ways to increase cultivated land area. Moreover, in ancient and modern times, many grasslands have indeed become "big granaries". However, because grasslands are mostly located in arid and cold areas with harsh climatic conditions and fragile ecological balance, blind reclamation and improper management after reclamation often lead to the failure of grain production and the destruction of the original vegetation of grasslands. There are examples and lessons at home and abroad. For example, Qinghai Province, China, reclaimed nearly 400,000 hectares in grassland areas in 1950s, and abandoned 2 1000 hectares in 1963. Some land can not be cultivated at all after reclamation, which not only wastes a lot of manpower and material resources, but also destroys grassland vegetation. 3. Predatory exploitation of resources by human beings: As can be seen from Table 6-2, among many factors that destroy grassland ecological environment, natural factors account for less than 6%, and the increase of population and the enhancement of economic activities have caused great pressure on grassland ecosystem. Especially the predatory exploitation of grassland resources has also caused serious damage to some grasslands. For example, Nostoc flagelliforme, mushrooms and medicinal materials grow on the grassland in Sunite Right Banner, Inner Mongolia. Every harvest season, thousands of people flock to the grassland and dig up a lot of these plants, destroying 20% of the grassland of this flag. The protection of grassland ecosystem has attracted the attention of the state. China's grassland law has been officially implemented since June 1985 65438+ 10/0/day, which marks that China's understanding of grassland status and the deterioration of grassland ecological environment has reached a new level, and it is also the beginning of grassland ecosystem in China from natural utilization to scientific management. According to the specific situation of our country, the protection and restoration countermeasures of grassland ecosystem should focus on the following aspects: scientific management One of the main reasons for the destruction of grassland ecosystem in China is the long-term lack of scientific and effective management measures. Internationally, since the late 1960s, systematic analysis has been applied to the scientific management of grassland ecosystem (Eoodall, 1979). However, up to now, most grasslands in China are still in a backward state of "grazing on grass" and "relying on the sky to raise livestock". Strengthening the research on the basic theories of grassland ecology, such as livestock carrying capacity, the best mode of animal husbandry production and scientific management technology, is the first problem to be paid attention to in grassland ecosystem protection countermeasures. Including reforming some backward management policies, implementing moderate grazing, fixing livestock by grass, developing seasonal animal husbandry to reduce the pressure on grassland, providing opportunities for pasture to recuperate and develop grassland vegetation, and implementing scientific management methods. Effective measures to protect and restore the structure and function of grassland ecosystem have been proved, such as building fences in artificial grassland, implementing rotational cultivation in different regions, and rationally utilizing grassland. Otherwise, problems such as grassland degradation in China will continue to develop. According to the prediction of Grassland Research Institute of China Academy of Agricultural Sciences, if the current animal husbandry production and management policy cannot be improved as soon as possible, the annual decline rate of grassland production in Inner Mongolia will reach 2.3% in the next 15 year, and the grassland production in major animal husbandry provinces and regions in China will decrease by 15% and 30% respectively in 2000 and 19 year. In addition, in the long run, through technological transformation and appropriate increase in investment, centralized management of grass industry will have greater economic benefits. With the development of animal husbandry and the protection of grassland ecological environment, it is necessary to cultivate grassland and plant feed in order to obtain higher economic and environmental benefits. At present, the area of artificial grassland in China only accounts for 0.4% of the total grassland area, which is only 1/25 of that of the United States and the Soviet Union. According to experts' estimation, planting 0.5- 1% forage grass can increase the total production capacity by 0.5- 1.0 times. It can be seen that the development of artificial grassland industry is a measure that can obtain huge economic benefits in a short period of time and is also conducive to the restoration of grassland ecosystem. At present, the law of world agricultural development is that the proportion of animal husbandry (especially herbivores) is increasing day by day. Most developed countries have completed the transformation from agriculture to animal husbandry or both, and the output value of animal husbandry accounts for more than 50% of the total agricultural output value. Grassland in China accounts for about 40% of the total land area, which is three times that of existing farmland. Moreover, there are tens of millions of hectares of barren hills and slopes in southern China, which has great potential for developing animal husbandry. According to statistics, the area of barren hills and grass slopes in Yunnan Province is five times that of farmland, eight times that of Guizhou and 1.7-4.8 times that of Sichuan. These areas have good hydrothermal climate conditions, grass can be evergreen all the year round, grass grows fast, and the output per unit area is generally 3-4 times that of the north, so it is the main base for developing grass industry in China. Grass is the link between agriculture, forestry and animal husbandry. We should make full use of these natural and resource conditions, develop grass industry and animal husbandry and form a new agricultural production structure system. This is also an effective measure to make up for the shortage of cultivated land in these areas and reduce the pressure on cultivated land. Modern grass production in pastoral areas is a comprehensive undertaking including planting, animal husbandry and aquaculture, and it is also a knowledge-intensive industry. For example, in the process of forage production, it involves scientific research problems such as breeding, introduction and prevention of natural enemies. In animal husbandry, it involves grazing methods, fattening and feeding, and the balance between livestock and grass. The processing and utilization of livestock products should adopt modern biotechnology and comprehensive processing to obtain valuable products, such as cultivating edible fungi, feeding waste and producing biogas. Therefore, the development of modern grass industry in pastoral areas will form a new system of animal husbandry production that conforms to ecological laws and protect and promote the recovery and development of grassland ecosystem.