Background,aim,and scope The tectonic uplift of the Cenozoic Tibetan Plateau has produced a chain effect,which is an excellent location for Earth system science research,and its uplift process,mechanism and environmen...Background,aim,and scope The tectonic uplift of the Cenozoic Tibetan Plateau has produced a chain effect,which is an excellent location for Earth system science research,and its uplift process,mechanism and environmental effects are the hot spot and frontier of the current research.The“Tibetan Plateau uplift-weathering-CO_(2) concentration-global climate change”model was put forward by Raymo and Ruddiman to interpret the Late Cenozoic climate change.However,there are still some questions suspended,such as does the weathering of the Tibetan Plateau have the ability to control the global climate?How to explain the modern-like global CO_(2) concentration starting at about 24 Ma?Here,a short space was taken to present a brainstorm about the above questions on account of existing geological pieces of evidence.Materials and methods In this paper,we integrate the formation and evolution of the Yangtze River and Pearl River,the origin and development of the Asian inland aridification-monsoon system,the Cenozoic tectonic uplift process of the Tibetan Plateau,and the westerly winds to discuss and analyze the relationship between the Cenozoic CO_(2) concentration changes and the uplift of the Tibetan Plateau and why the CO_(2) concentration similar to the present was formed at about 24 Ma.Results Similar correspondence of the surface uplift history of Xizang,other global mountains,and the declining CO_(2) concentration could support the theory Tibetan Plateau weathering inf luences CO_(2) concentration.Starting from 24 Ma,the most important character was the uplift and erosion of Xizang and Himalaya,collaborating with Ocean Iron Fertilization(OIF)together as an entity to control the atmospheric CO_(2) concentration because the great Asian rivers,Asian monsoons,and westerlies connected Xizang and surrounded seas together through materials transportation.Discussion Paleogeographic reconstructions from 40 Ma to 20 Ma illustrate that the main topographic change occurred in the Andes,Cordillera orogenic belt,and Xizang.We comprise a comprehensive set of evidence from independent data,which correspond temporally with the tipping point(about 24 Ma)of the atmospheric CO_(2) and we noticed that modern-like Asia monsoon,inland aridity,Asian great rivers,and climate zone formed at about 24 Ma and also there are tectonic activities for the Andes and Rockies.We raised the possibility that the modern-like atmospheric CO_(2) concentration at about 24 Ma was caused by the above geological factors.Here the rivers,monsoon,and westerlies are termed as“connectors”.In addition,these Asian rivers originated from Xizang,the monsoon,and inner Asian aridification are strongly a function of the uplift and growth of Xizang,thus,Xizang here is named as“trigger”.The distinct character of“trigger-connectors”model is that this not only takes the monsoon,westerlies,and the global great rivers into consideration but also expands the range which inf luences atmospheric CO_(2) concentration,from local points to a vast area since about 24 Ma,such as from Tibetan Plateau to Asia,including surrounded seas,after about 24 Ma.However,because the opening of the Late Oligocene-Early Miocene Antarctic periphery straits is highly coincident with the onset of modern-like global atmospheric CO_(2) concentration,we are forced to consider that they also had a significant impact on the reduction of atmospheric CO_(2) concentrations at this time.Conclusions“Trigger-connectors”was put forward to explain the Cenozoic CO_(2) variation,especially modern-like global CO_(2) concentration since about 24 Ma.Recommendations and perspectives Here we use the“trigger-connectors”model to explain the formation of modern-like CO_(2) concentrations starting at about 24 Ma,but there are still some problems.The most important premise for the“trigger-connectors”model is the constructed Cenozoic CO_(2) concentration record is reliable,which is the foundation of our hypothesis.In the future,potential improvements should focus on topographic reconstructions of Xizang and the global mountains.Here we have concentrated on Xizang in the considered timeslices but still,pay less attention to other global orogenic belts.Collaborations with geologist experts in those regions could provide valuable feedback to evaluate their potential role of them in CO_(2) evolution.What is more,considerable progress may be achieved with the addition and consideration of more and new geological data.展开更多
Aims Given the key functional role of understorey plant communities and the substantial extent of forest cover at the global scale,investigating understorey community responses to elevated CO_(2)(eCO_(2))concentration...Aims Given the key functional role of understorey plant communities and the substantial extent of forest cover at the global scale,investigating understorey community responses to elevated CO_(2)(eCO_(2))concentrations,and the role of soil resources in these responses,is important for understanding the ecosystem-level consequences of rising CO_(2)concentrations for forest ecosystems.Here,we evaluated how experimentally manipulating the availabilities of the two most limiting resources in an extremely phosphorus-limited eucalypt woodland in eastern Australia(i.e.water and phosphorus)can modulate the response of the understorey community to eCO_(2)in terms of germination,phenology,cover,community composition and leaf traits.Methods We collected soil containing native soil seed bank to grow experimental understorey plant communities under glasshouse conditions.Important Findings Phosphorus addition increased total plant cover,particularly during the first 4 weeks of growth and under high water conditions,a response driven by the graminoid component of the plant community.However,the treatment differences diminished as the experiment progressed,with all treatments converging at〜80%lant cover after〜11 weeks.In contrast,plant cover was not affected by eCO_(2).Multivariate analyses reflected temporal changes in the composition of plant communities,from pots where bare soil was dominant to high-cover pots dominated by a diverse community.However,both phosphorus addition and the interaction between water availability and CO_(2)affected the temporal trajectory of the plant community during the experiment.eCO_(2)also increased community-level specific leaf area,suggesting that functional adaptation of plant communities to CO_(2)may precede the onset of compositional responses.Given that the response of our seed bank-derived understorey community to CO_(2)developed over time and was mediated by interactions with phosphorus and water availability,our results suggest a limited role of eCO_(2)in shaping plant communities in water-limited systems,particularly where low soil nutrient availability constrains productivity responses.展开更多
文摘Background,aim,and scope The tectonic uplift of the Cenozoic Tibetan Plateau has produced a chain effect,which is an excellent location for Earth system science research,and its uplift process,mechanism and environmental effects are the hot spot and frontier of the current research.The“Tibetan Plateau uplift-weathering-CO_(2) concentration-global climate change”model was put forward by Raymo and Ruddiman to interpret the Late Cenozoic climate change.However,there are still some questions suspended,such as does the weathering of the Tibetan Plateau have the ability to control the global climate?How to explain the modern-like global CO_(2) concentration starting at about 24 Ma?Here,a short space was taken to present a brainstorm about the above questions on account of existing geological pieces of evidence.Materials and methods In this paper,we integrate the formation and evolution of the Yangtze River and Pearl River,the origin and development of the Asian inland aridification-monsoon system,the Cenozoic tectonic uplift process of the Tibetan Plateau,and the westerly winds to discuss and analyze the relationship between the Cenozoic CO_(2) concentration changes and the uplift of the Tibetan Plateau and why the CO_(2) concentration similar to the present was formed at about 24 Ma.Results Similar correspondence of the surface uplift history of Xizang,other global mountains,and the declining CO_(2) concentration could support the theory Tibetan Plateau weathering inf luences CO_(2) concentration.Starting from 24 Ma,the most important character was the uplift and erosion of Xizang and Himalaya,collaborating with Ocean Iron Fertilization(OIF)together as an entity to control the atmospheric CO_(2) concentration because the great Asian rivers,Asian monsoons,and westerlies connected Xizang and surrounded seas together through materials transportation.Discussion Paleogeographic reconstructions from 40 Ma to 20 Ma illustrate that the main topographic change occurred in the Andes,Cordillera orogenic belt,and Xizang.We comprise a comprehensive set of evidence from independent data,which correspond temporally with the tipping point(about 24 Ma)of the atmospheric CO_(2) and we noticed that modern-like Asia monsoon,inland aridity,Asian great rivers,and climate zone formed at about 24 Ma and also there are tectonic activities for the Andes and Rockies.We raised the possibility that the modern-like atmospheric CO_(2) concentration at about 24 Ma was caused by the above geological factors.Here the rivers,monsoon,and westerlies are termed as“connectors”.In addition,these Asian rivers originated from Xizang,the monsoon,and inner Asian aridification are strongly a function of the uplift and growth of Xizang,thus,Xizang here is named as“trigger”.The distinct character of“trigger-connectors”model is that this not only takes the monsoon,westerlies,and the global great rivers into consideration but also expands the range which inf luences atmospheric CO_(2) concentration,from local points to a vast area since about 24 Ma,such as from Tibetan Plateau to Asia,including surrounded seas,after about 24 Ma.However,because the opening of the Late Oligocene-Early Miocene Antarctic periphery straits is highly coincident with the onset of modern-like global atmospheric CO_(2) concentration,we are forced to consider that they also had a significant impact on the reduction of atmospheric CO_(2) concentrations at this time.Conclusions“Trigger-connectors”was put forward to explain the Cenozoic CO_(2) variation,especially modern-like global CO_(2) concentration since about 24 Ma.Recommendations and perspectives Here we use the“trigger-connectors”model to explain the formation of modern-like CO_(2) concentrations starting at about 24 Ma,but there are still some problems.The most important premise for the“trigger-connectors”model is the constructed Cenozoic CO_(2) concentration record is reliable,which is the foundation of our hypothesis.In the future,potential improvements should focus on topographic reconstructions of Xizang and the global mountains.Here we have concentrated on Xizang in the considered timeslices but still,pay less attention to other global orogenic belts.Collaborations with geologist experts in those regions could provide valuable feedback to evaluate their potential role of them in CO_(2) evolution.What is more,considerable progress may be achieved with the addition and consideration of more and new geological data.
基金R.O.-H.is supported by a Ramon y Cajal Fellowship from MICIU(RYC-2017-22032)projects(PID2019-106004RA-I00).
文摘Aims Given the key functional role of understorey plant communities and the substantial extent of forest cover at the global scale,investigating understorey community responses to elevated CO_(2)(eCO_(2))concentrations,and the role of soil resources in these responses,is important for understanding the ecosystem-level consequences of rising CO_(2)concentrations for forest ecosystems.Here,we evaluated how experimentally manipulating the availabilities of the two most limiting resources in an extremely phosphorus-limited eucalypt woodland in eastern Australia(i.e.water and phosphorus)can modulate the response of the understorey community to eCO_(2)in terms of germination,phenology,cover,community composition and leaf traits.Methods We collected soil containing native soil seed bank to grow experimental understorey plant communities under glasshouse conditions.Important Findings Phosphorus addition increased total plant cover,particularly during the first 4 weeks of growth and under high water conditions,a response driven by the graminoid component of the plant community.However,the treatment differences diminished as the experiment progressed,with all treatments converging at〜80%lant cover after〜11 weeks.In contrast,plant cover was not affected by eCO_(2).Multivariate analyses reflected temporal changes in the composition of plant communities,from pots where bare soil was dominant to high-cover pots dominated by a diverse community.However,both phosphorus addition and the interaction between water availability and CO_(2)affected the temporal trajectory of the plant community during the experiment.eCO_(2)also increased community-level specific leaf area,suggesting that functional adaptation of plant communities to CO_(2)may precede the onset of compositional responses.Given that the response of our seed bank-derived understorey community to CO_(2)developed over time and was mediated by interactions with phosphorus and water availability,our results suggest a limited role of eCO_(2)in shaping plant communities in water-limited systems,particularly where low soil nutrient availability constrains productivity responses.
