Grassland occupies a certain area on the earth. In Eurasia, the grassland extends in a continuous belt from the lower reaches of the Danube River in Europe to the east, passes through Romania, the former Soviet Union and Mongolia, and enters China and Inner Mongolia Autonomous Region, forming the widest grassland belt in the world. In North America, the grassland starts from South saskatchewan river in the north and reaches Texas in the latitude direction, forming a north-south grassland belt. In addition, there are small areas of grasslands in South America, Oceania and Africa.
There are both panicum miliaceum and perennial herbs on the grassland. Among perennial herbs, Gramineae is especially dominant. The species and quantity of grass can account for 20% ~ 50% of the grassland area, and it can account for more than 60% ~ 90% in the particularly lush grassland. There are mainly Stipa, Festuca, Cryptomeria, Illicium, Agropyron and Poa. These plants are the owners of the grassland, they construct the environment of the grassland community and are the constructive species of the community. In addition, there are many dicotyledonous plants and other weeds on the grassland, such as wild peas, Sanguisorba officinalis, day lilies, wormwood leaves and so on. Sometimes they grow in pieces, and sometimes they are scattered all over the grassland, making the green grassland colorful. In addition to herbs, there are many shrubs growing on the grassland, such as Kochia scoparia, Thyme, Caragana, Artemisia frigida, Artemisia ordosica, Artemisia donkeys and so on. Some of them are clustered, some are connected together, and many of them are favorite foods for cattle, horses and sheep. For example, wood skin is called "pilaf" of sheep by ethnic herders. It can be seen how high its nutritional value is.
Because grassland plants grow in semi-arid and semi-humid areas, and the ecological environment is harsh, a life form dominated by ground bud plants has been formed. Under this climatic condition, the xerophytic structure of grassland plants is obvious, the leaf area is reduced and the leaves are rolled in. Stomatal subsidence, developed mechanical and protective tissues, developed underground parts of plants, and the closure degree of underground roots far exceeds that of aboveground parts. This is a method to adapt to the arid environment. The root system of most grassland plants is shallow, and the root layer is concentrated in the soil layer of 0~30 cm, and the main part of fine roots is located in the underground range of 5~ 10 cm, which can quickly absorb water after rain.
The seasonal change of grassland community is very obvious, and its growth and development are greatly affected by rain. The main constructive plants on the grassland all reach the peak in growth and development at the beginning of the rainy season from June to July. There are also some plants whose growth and development change greatly with the change of precipitation. In dry years, until June, because there was no rain, the grassland was still yellow, and only after the first rain did the green leaves grow rapidly. In the years with more spring rains, the grassland presents green landscape earlier. Some plant species only grow weakly vegetative seedlings in dry years and have no sexual reproduction, but in rainy years, their leaves grow very high and produce a lot of fruits to reproduce.
The grassland in China is a part of the Eurasian grassland area. From the Songliao Plain in the northeast, through the Inner Mongolia Plateau and directly to the Loess Plateau, it has formed a continuous strip distribution from northeast to northwest. In addition, grasslands are also distributed in the foothills of the Qinghai-Tibet Plateau and Altai Mountain in Xinjiang, as well as mountainous areas in desert areas. The grassland in China is similar to the grassland in Eurasia, and the composition of plant species in different regions is very different. But Stipa is more common, so Stipa is of great significance to grassland vegetation. To some extent, it can be used as an indicator species of grassland, especially Eurasian grassland.
Grassland in China can be divided into four types: meadow grassland, typical grassland, desert grassland and alpine grassland. Meadow grassland is mainly distributed in the eastern edge of Songliao Plain and Inner Mongolia Plateau. Stipa Baikal, Leymus chinensis and Chrysanthemum are the constructive species, and there are a large number of mesophytes. The species composition is very rich and the coverage is also very large; Typical grasslands are distributed in Inner Mongolia, the southwest of Northeast China, the central and western parts of the Loess Plateau and within a certain altitude range of Altai Mountain, Tianshan Mountain and Qilian Mountain. Stipa grandis, Stipa krylovii, Stipa Benjamin, Stipa grandis, Artemisia frigida, Thyme and other plants are used as constructive species. Compared with meadow grassland, the species composition is poor and the coverage is small. However, xerophytic tufted grasses are absolutely dominant in the grass group; Desert grasslands are mainly distributed in central Inner Mongolia, northern Loess Plateau and the low mountains of Qilian Mountain and Tianshan Mountain. Stipa arenaria, Stipa Gobi, Stipa orientalis, Allium fistulosum, Artemisia argyrophyllum, etc. are constructive species, but there are a large number of early shrubs in the community. The species composition is poor, and the height of grass layer, community coverage and productivity are obviously lower than those of typical grassland. Alpine grassland is a kind of grassland with high altitude and dry and cold climate. It is mainly distributed in the towering Qinghai-Tibet Plateau, Pamirs Plateau and high-altitude areas of Qilian Mountain and Tianshan Mountain. It is composed of perennial herbs, rhizomatous Carex and small subshrubs, and cushion plants appear. The main constructive species are Stipa purpurea, Stipa sessilifolia, Stipa pinnata, Stipa Yin Hui, Stipa Robinia, Carex tibetica and Artemisia argyi. Species composition is not only scarce, but also sparse grass group, simple structure, low grass layer and low productivity.