Abstract:Stipa plants, distributed in arid and semi-arid regions, are sensitive to drought caused by the decrease of precipitation and changes of other climatic factors. What the effects of global change on Stipa plants were studied would help to understand the response and adaptability of zonal steppe plants to global change in Inner Mongolia. The impacts of elevated CO2, warming and precipitation change on five zonal and constructive Stipa species (S. Baicalensis, S. bungeana, S. grandis, S. krylovii and S. breviflora) in Inner Mongolia were reviewed based on simulating experimental results from 1992 to 2013. The main objective is to reveal the response and adaptation mechanism of the zonal Stipa plants to CO2 and climate change in Inner Mongolia, and we hope to provide sound knowledge for further studying the effects of global change on the zonal Stipa plants. Increasing CO2 concentration, temperature and precipitation all enhanced the photosynthesis and height of Stipa plants, while the plant photosynthetic acclimation would appear with the processing time longer of CO2 treatment. Temperature and precipitation changes would affect the phenological process of Stipa plants, but the responses to temperature and precipitation change were different among different species. Elevated CO2 increased and warming and drought decreased the biomass of Stipa plants. Elevated CO2 could alleviate the effect of drought on plant photosynthesis and growth. Drought and water logging stress increased C/N of Stipa plants, and elevated CO2 would aggravate the C/N of Stipa plants under drought. Therefore, the forage quality would decrease. Although many simulations of the adaptability of zonal Stipa plants to CO2 and climate change in Inner Mongolia had been done, there were still a lot of insufficiencies as follows: (1) Lack of study on the adaptability indexes: Many researches focus on the responses of the physiological ecology, structural and functional characteristics of Stipa plants to CO2 and climate change. But the relationships among the same and different indexes of all the five Stipa species were not studied and too many indexes were used to studying the adaptability to global change, and it is very difficult to find the representative and indicative adaptability indexes in the responses of Stipa plants to global change. So it is impossible for comprehensively evaluating and comparing the adaptabilities of Stipa plants to CO2 and climate change now. (2) Lack of study on the adaptation mechanism of Stipa plants to the synergistic effects of climatic factors: Current studies mostly concerned the impacts of single factor such as elevation of CO2 concentration, warming and water stress on Stipa plants, but rarely concerned the synergistic effects of the environmental factors. The research of the synergistic effects of all the three environmental factors had not been reported so far. In fact, the three environmental factors simultaneously change and work on Stipa plants under global change, and there would be interactions among the factors on Stipa plants (enhancing or alleviating effects). Therefore, the adaptability of Stipa plants under global change could not be well understood if the effects of only one environmental factor on Stipa plants were concerned and studied. (3) Lack of study on the sensitivity of Stipa plants to CO2 and climate change: many experiments did not have enough treatmental gradients in present researches. For instance, only one or two drought stress levels for precipitation change and only elevation of temperature or CO2 concentration were usually designed in the simulative experiments. Many studies have shown that the effects of the environmental factors on Stipa plants presented the parabolic relationships but not linear relationships. Therefore, the adaptation mechanisms and sensitivity threshold of Stipa plants to CO2 and climate change could not be exactly revealed if there are not enough treatmental factor gradients designed in the simulative experiments. Because of the insufficiencies above, we can't compare the differences in responses and sensitivities of the five kinds of Stipa plants to the change of CO2, temperature and precipitation. Therefore, we can't predict the dynamic changes of the Stipa plants and their geographical migration and substitution laws under future global change. Future studies should add enough environmental factor gradients, take into account the synergistic effects among the factors, and select sensitive indexes to comprehensively analyze the response of Stipa plants to CO2 and climate change in different intensity, time and duration. It would help us to fully reveal the impacts of CO2 and climate change on the structure and function processes of Stipa plants and their control mechanisms, and then explore the adaption degree, threshold and vulnerability of Stipa plants to CO2 and climate change under global change.