中国北方典型草原和北美北部混合型草原群落特征比较

The Comparison in Characteristics of Communlties Between the True Steppe of North China and the Mixed Prairie of North America.

中国北方典型草原和北美北部混合型草原均处在北半球内陆中纬度地区.由于气候条件的相似性,两地草原的群落特征表现出某些相似之处.两地草原的优势植物和某些常见种不仅有着相以或相同的生理生态特征,还有着较为密切的亲缘关系,有些种为两个大陆所共有.由于两地草原夏季的降水条件不同,植物群落的夏季季相有较大差异.

Both the true steppe of North China and the mixed prairie of North America are situated in the inland regions of mid-latitudes of the Northern Hemisphere. The plant communities are similar in structure because of the climatic similarities of the two regions. Basically the vegetation of both over most of their range are supported by the grassland types of the perennial bunch and rhizomatous grasses. The basical live forms of elements in the communities are perennial and subshrubby. Bunch grasses and rhizomatous grasses are important and form dominant synusiae. Within the dominants and common species some ones are physiogically or ecologically similar and some are, genetically related and even same ones between the two continents. There is a difference in structure of taxon, for example, the species of legume and their forages are richer in the true steppe of North China than in the mixed prairie of North America. Because the hydrothermal patterns from the climate are different, there are different proportions of photosynthetic pathway types in the grass flora of the two regions. The Ct grasses are 18%～36% in the northern mixed prairie and 7%'-'12% in the mesothermal-true steppe.