内蒙古地带性针茅植物对CO2和气候变化的适应性研究进展

收集了1992—2013年关于模拟CO2浓度升高及气候变化(温度升高、降水变化)对内蒙古地带性草原群落的5个建群种针茅植物(贝加尔针茅、本氏针茅、大针茅、克氏针茅、短花针茅)影响的实验研究结果表明,模拟CO2浓度升高、增温和增雨将提高针茅植物的光合作用和株高生长,但CO2处理时间延长会导致光合适应;温度和降雨变化将改变针茅植物的物候进程,但物种之间反应有差异;CO2浓度升高有助于针茅植物生物量增加,增温和干旱则相反,CO2浓度升高对干旱的影响具有补偿作用;干旱和涝渍胁迫将提高针茅植物植株C/N,CO2浓度升高将加剧水分胁迫下针茅植物植株C/N的增加效应,导致牧草品质下降。由于当前在适应性指标、针茅植物对气候变化协同作用的适应机理及其敏感性研究等方面存在的不足,导致目前无法全面比较各针茅植物对CO2和温度、降水变化的响应差异及其敏感性,因而无法预测未来在全球变化背景下,这几种针茅植物的动态变化及其在地理分布上的迁移替代规律。为科学应对气候变化,未来应加强内蒙古地带性针茅植物的适应性指标、针茅植物对多因子协同作用的适应机理及敏感性研究。

Advances in the adaptability of zonal Stipa plants to CO2 and climate change in Inner Mongolia

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.