The role of grassland in ecological environment

Experts have always attached importance to the ecological functions and benefits of grassland on land, but in the process of developing and utilizing grassland resources, they often only pay attention to the immediate economic benefits and ignore the ecological benefits of grassland, resulting in grassland degradation, desertification and deterioration of ecological environment. In recent years, there have been many black storms (sandstorms) in some parts of northwest China in spring, which are closely related to the destruction of grassland ecological environment. Therefore, it is of great significance to fully understand and understand the important role and position of grassland resources in terrestrial ecosystem for maintaining the good ecological environment of human beings, effectively exerting the economic benefits of grassland resources, protecting the ecological environment in the source area of the Yellow River and maintaining the sustainable economic development of the whole Yellow River basin.

1. Regulate climate and save water

Natural grassland can not only intercept considerable precipitation, but also has higher permeability than open land, which has a positive effect on soil water conservation. For example, the interception of grassland nettle in 30 minutes is 72% when the precipitation is 5 mm and 55% when the precipitation is 33 mm.

Grassland also has the ability to adjust air temperature and humidity. Compared with bare land, the humidity of large area grassland is generally about 20% higher than that of bare land, and the humidity of small area grassland is also 4% ~ 12% higher than that of bare land. The surface temperature of grassland is 3 ~ 5℃ lower than that of bare land in summer, but it is 6 ~ 6.5℃ higher than that of bare land in winter.

2. Wind and sand fixation, soil and water conservation

Herbaceous plants are pioneers in increasing and developing terrestrial green vegetation, and also "guardians" of soil and water conservation, wind prevention and sand fixation. Many research results show that grassland plays an important role in preventing soil erosion and reducing surface runoff. In addition, the ability of grassland to prevent and control soil erosion is obviously higher than that of shrub and woodland. According to the measured data of soil erosion in the Loess Plateau, the soil erosion of farmland is 40 ~ 100 times higher than that of grassland. Compared with the slope without grass, the slope with grass can reduce surface runoff by 47% and erosion by 77%.

3. Improve soil and improve soil fertility.

Natural grassland can produce a lot of organic matter. These organic residues, after decomposition, form a large number of organic particles and debris, providing nutrients for the grassland itself. Grassland vegetation has dense roots and a large amount of organic matter remains in the soil layer. The research results of Gansu Agricultural University (1982) on Tianzhu alpine meadow grassland showed that the root system in 0 ~ 50 cm soil layer was 52,200 kg/hm2 and 47,400 kg/hm2, respectively, and the nitrogen content was 657.72kg/hm2 and 8 15.28kg/hm2, respectively. Under the action of soil microorganisms, these substances can improve the physical and chemical properties of soil, promote the formation of soil aggregate structure, loosen soil, facilitate the infiltration of atmospheric precipitation and strengthen water retention capacity.

A large number of rhizobia grow in the roots of leguminous forage grass in grassland, which has the ability to fix free nitrogen in the air and provide a large amount of nitrogen fertilizer for grassland ecosystem. For example, alfalfa grassland growing for 3 years can form nitrogen 150kg/hm2 and phosphorus 45kg/hm2. The content of nutrient elements in alfalfa root system is: nitrogen 2%, phosphorus 7%, potassium 0.9%, calcium 1.3%, which is 3 ~ 7 times higher than that of cereal crops. Therefore, planting grass and fertilizing fields is one of the most economical and effective measures to improve soil.

4. Purify the air and beautify the environment

Grassland also plays an important role in purifying the air and beautifying the environment. Grassland plants can absorb carbon dioxide in the air through photosynthesis and release oxygen in the process of material circulation. Generally, grassland can absorb carbon dioxide 1.5g/m2 per hour. Some grasses can purify the dust in the air. They can absorb dust and some toxic gases in the air and convert them into protein or nontoxic salts. Grassland can also reduce noise and release negative oxygen ions (Liu Chengwu et al., 1999).

5. Foundation of grassland ecosystem

In the grassland ecosystem, grass is the only primary producer (Figure 4-5), which plays a key role in the material cycle and energy transformation of the whole ecosystem and is the foundation of the grassland ecosystem. Once the grassland is destroyed, the energy transmission of the ecosystem will be blocked and the whole ecosystem will be destroyed.

Therefore, grassland is one of the natural barriers to maintain the land environment, and it plays a very important role in the sustainable development of human society, and it is of great significance to protect the grassland ecosystem.

Figure 4-5 Food chain and food web of alpine meadow ecosystem in Qinghai-Tibet Plateau

(According to grassland science 200 1)

Figure 4-5 Food chain and network of alpine meadow ecosystem in Qinghai-Tibet Plateau