The Experts below are selected from a list of 27144 Experts worldwide ranked by ideXlab platform
R. J. Allen - One of the best experts on this subject based on the ideXlab platform.
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Redox regime shifts in microbially mediated Biogeochemical Cycles
Biogeosciences, 2015Co-Authors: T. Bush, I. B. Butler, A. Free, R. J. AllenAbstract:Abstract. Understanding how the Earth's Biogeochemical Cycles respond to environmental change is a prerequisite for the prediction and mitigation of the effects of anthropogenic perturbations. Microbial populations mediate key steps in these Cycles, yet they are often crudely represented in Biogeochemical models. Here, we show that microbial population dynamics can qualitatively affect the response of Biogeochemical Cycles to environmental change. Using simple and generic mathematical models, we find that nutrient limitations on microbial population growth can lead to regime shifts, in which the redox state of a Biogeochemical cycle changes dramatically as the availability of a redox-controlling species, such as oxygen or acetate, crosses a threshold (a "tipping point"). These redox regime shifts occur in parameter ranges that are relevant to the present-day sulfur cycle in the natural environment and the present-day nitrogen cycle in eutrophic terrestrial environments. These shifts may also have relevance to iron cycling in the iron-containing Proterozoic and Archean oceans. We show that redox regime shifts also occur in models with physically realistic modifications, such as additional terms, chemical states, or microbial populations. Our work reveals a possible new mechanism by which regime shifts can occur in nutrient-cycling ecosystems and Biogeochemical Cycles, and highlights the importance of considering microbial population dynamics in models of Biogeochemical Cycles.
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Redox regime shifts in microbially-mediated Biogeochemical Cycles
Biogeosciences Discussions, 2015Co-Authors: T. Bush, I. B. Butler, A. Free, R. J. AllenAbstract:Abstract. Understanding how the Earth's Biogeochemical Cycles respond to environmental change is a prerequisite for the prediction and mitigation of the effects of anthropogenic perturbations. Microbial populations mediate key steps in these Cycles, yet are often crudely represented in Biogeochemical models. Here, we show that microbial population dynamics can qualitatively affect the response of Biogeochemical Cycles to environmental change. Using simple and generic mathematical models, we find that nutrient limitations on microbial population growth can lead to regime shifts, in which the redox state of a Biogeochemical cycle changes dramatically as the availability of a redox-controlling species, such as oxygen or acetate, crosses a threshold (a "tipping point"). These redox regime shifts occur in parameter ranges that are relevant to the sulfur and nitrogen Cycles in the present-day natural environment, and may also have relevance to iron cycling in the iron-containing Proterozoic and Archean oceans. We show that redox regime shifts also occur in models with physically realistic modifications, such as additional terms, chemical states, or microbial populations. Our work reveals a possible new mechanism by which regime shifts can occur in nutrient-cycling ecosystems and Biogeochemical Cycles, and highlights the importance of considering microbial population dynamics in models of Biogeochemical Cycles.
Jianqing Tian - One of the best experts on this subject based on the ideXlab platform.
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the impacts of climate change and human activities on Biogeochemical Cycles on the qinghai tibetan plateau
Global Change Biology, 2013Co-Authors: Huai Chen, Qiuan Zhu, Changhui Peng, Yanfen Wang, Xiuqing Fang, Yongheng Gao, Dan Zhu, Gang Yang, Jianqing Tian, Xiaoming KangAbstract:With a pace of about twice the observed rate of global warming, the temperature on the Qinghai-Tibetan Plateau (Earth's third pole') has increased by 0.2 degrees C per decade over the past 50years, which results in significant permafrost thawing and glacier retreat. Our review suggested that warming enhanced net primary production and soil respiration, decreased methane (CH4) emissions from wetlands and increased CH4 consumption of meadows, but might increase CH4 emissions from lakes. Warming-induced permafrost thawing and glaciers melting would also result in substantial emission of old carbon dioxide (CO2) and CH4. Nitrous oxide (N2O) emission was not stimulated by warming itself, but might be slightly enhanced by wetting. However, there are many uncertainties in such Biogeochemical Cycles under climate change. Human activities (e.g. grazing, land cover changes) further modified the Biogeochemical Cycles and amplified such uncertainties on the plateau. If the projected warming and wetting continues, the future Biogeochemical Cycles will be more complicated. So facing research in this field is an ongoing challenge of integrating field observations with process-based ecosystem models to predict the impacts of future climate change and human activities at various temporal and spatial scales. To reduce the uncertainties and to improve the precision of the predictions of the impacts of climate change and human activities on Biogeochemical Cycles, efforts should focus on conducting more field observation studies, integrating data within improved models, and developing new knowledge about coupling among carbon, nitrogen, and phosphorus Biogeochemical Cycles as well as about the role of microbes in these Cycles.
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The impacts of climate change and human activities on Biogeochemical Cycles on the Qinghai-Tibetan Plateau
Global change biology, 2013Co-Authors: Huai Chen, Qiuan Zhu, Changhui Peng, Yanfen Wang, Xiuqing Fang, Yongheng Gao, Dan Zhu, Gang Yang, Jianqing TianAbstract:With a pace of about twice the observed rate of global warming, the temperature on the Qinghai-Tibetan Plateau (Earth's 'third pole') has increased by 0.2 °C per decade over the past 50 years, which results in significant permafrost thawing and glacier retreat. Our review suggested that warming enhanced net primary production and soil respiration, decreased methane (CH(4)) emissions from wetlands and increased CH(4) consumption of meadows, but might increase CH(4) emissions from lakes. Warming-induced permafrost thawing and glaciers melting would also result in substantial emission of old carbon dioxide (CO(2)) and CH(4). Nitrous oxide (N(2)O) emission was not stimulated by warming itself, but might be slightly enhanced by wetting. However, there are many uncertainties in such Biogeochemical Cycles under climate change. Human activities (e.g. grazing, land cover changes) further modified the Biogeochemical Cycles and amplified such uncertainties on the plateau. If the projected warming and wetting continues, the future Biogeochemical Cycles will be more complicated. So facing research in this field is an ongoing challenge of integrating field observations with process-based ecosystem models to predict the impacts of future climate change and human activities at various temporal and spatial scales. To reduce the uncertainties and to improve the precision of the predictions of the impacts of climate change and human activities on Biogeochemical Cycles, efforts should focus on conducting more field observation studies, integrating data within improved models, and developing new knowledge about coupling among carbon, nitrogen, and phosphorus Biogeochemical Cycles as well as about the role of microbes in these Cycles.
Huai Chen - One of the best experts on this subject based on the ideXlab platform.
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the impacts of climate change and human activities on Biogeochemical Cycles on the qinghai tibetan plateau
Global Change Biology, 2013Co-Authors: Huai Chen, Qiuan Zhu, Changhui Peng, Yanfen Wang, Xiuqing Fang, Yongheng Gao, Dan Zhu, Gang Yang, Jianqing Tian, Xiaoming KangAbstract:With a pace of about twice the observed rate of global warming, the temperature on the Qinghai-Tibetan Plateau (Earth's third pole') has increased by 0.2 degrees C per decade over the past 50years, which results in significant permafrost thawing and glacier retreat. Our review suggested that warming enhanced net primary production and soil respiration, decreased methane (CH4) emissions from wetlands and increased CH4 consumption of meadows, but might increase CH4 emissions from lakes. Warming-induced permafrost thawing and glaciers melting would also result in substantial emission of old carbon dioxide (CO2) and CH4. Nitrous oxide (N2O) emission was not stimulated by warming itself, but might be slightly enhanced by wetting. However, there are many uncertainties in such Biogeochemical Cycles under climate change. Human activities (e.g. grazing, land cover changes) further modified the Biogeochemical Cycles and amplified such uncertainties on the plateau. If the projected warming and wetting continues, the future Biogeochemical Cycles will be more complicated. So facing research in this field is an ongoing challenge of integrating field observations with process-based ecosystem models to predict the impacts of future climate change and human activities at various temporal and spatial scales. To reduce the uncertainties and to improve the precision of the predictions of the impacts of climate change and human activities on Biogeochemical Cycles, efforts should focus on conducting more field observation studies, integrating data within improved models, and developing new knowledge about coupling among carbon, nitrogen, and phosphorus Biogeochemical Cycles as well as about the role of microbes in these Cycles.
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The impacts of climate change and human activities on Biogeochemical Cycles on the Qinghai-Tibetan Plateau
Global change biology, 2013Co-Authors: Huai Chen, Qiuan Zhu, Changhui Peng, Yanfen Wang, Xiuqing Fang, Yongheng Gao, Dan Zhu, Gang Yang, Jianqing TianAbstract:With a pace of about twice the observed rate of global warming, the temperature on the Qinghai-Tibetan Plateau (Earth's 'third pole') has increased by 0.2 °C per decade over the past 50 years, which results in significant permafrost thawing and glacier retreat. Our review suggested that warming enhanced net primary production and soil respiration, decreased methane (CH(4)) emissions from wetlands and increased CH(4) consumption of meadows, but might increase CH(4) emissions from lakes. Warming-induced permafrost thawing and glaciers melting would also result in substantial emission of old carbon dioxide (CO(2)) and CH(4). Nitrous oxide (N(2)O) emission was not stimulated by warming itself, but might be slightly enhanced by wetting. However, there are many uncertainties in such Biogeochemical Cycles under climate change. Human activities (e.g. grazing, land cover changes) further modified the Biogeochemical Cycles and amplified such uncertainties on the plateau. If the projected warming and wetting continues, the future Biogeochemical Cycles will be more complicated. So facing research in this field is an ongoing challenge of integrating field observations with process-based ecosystem models to predict the impacts of future climate change and human activities at various temporal and spatial scales. To reduce the uncertainties and to improve the precision of the predictions of the impacts of climate change and human activities on Biogeochemical Cycles, efforts should focus on conducting more field observation studies, integrating data within improved models, and developing new knowledge about coupling among carbon, nitrogen, and phosphorus Biogeochemical Cycles as well as about the role of microbes in these Cycles.
T. Bush - One of the best experts on this subject based on the ideXlab platform.
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Redox regime shifts in microbially mediated Biogeochemical Cycles
Biogeosciences, 2015Co-Authors: T. Bush, I. B. Butler, A. Free, R. J. AllenAbstract:Abstract. Understanding how the Earth's Biogeochemical Cycles respond to environmental change is a prerequisite for the prediction and mitigation of the effects of anthropogenic perturbations. Microbial populations mediate key steps in these Cycles, yet they are often crudely represented in Biogeochemical models. Here, we show that microbial population dynamics can qualitatively affect the response of Biogeochemical Cycles to environmental change. Using simple and generic mathematical models, we find that nutrient limitations on microbial population growth can lead to regime shifts, in which the redox state of a Biogeochemical cycle changes dramatically as the availability of a redox-controlling species, such as oxygen or acetate, crosses a threshold (a "tipping point"). These redox regime shifts occur in parameter ranges that are relevant to the present-day sulfur cycle in the natural environment and the present-day nitrogen cycle in eutrophic terrestrial environments. These shifts may also have relevance to iron cycling in the iron-containing Proterozoic and Archean oceans. We show that redox regime shifts also occur in models with physically realistic modifications, such as additional terms, chemical states, or microbial populations. Our work reveals a possible new mechanism by which regime shifts can occur in nutrient-cycling ecosystems and Biogeochemical Cycles, and highlights the importance of considering microbial population dynamics in models of Biogeochemical Cycles.
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Redox regime shifts in microbially-mediated Biogeochemical Cycles
Biogeosciences Discussions, 2015Co-Authors: T. Bush, I. B. Butler, A. Free, R. J. AllenAbstract:Abstract. Understanding how the Earth's Biogeochemical Cycles respond to environmental change is a prerequisite for the prediction and mitigation of the effects of anthropogenic perturbations. Microbial populations mediate key steps in these Cycles, yet are often crudely represented in Biogeochemical models. Here, we show that microbial population dynamics can qualitatively affect the response of Biogeochemical Cycles to environmental change. Using simple and generic mathematical models, we find that nutrient limitations on microbial population growth can lead to regime shifts, in which the redox state of a Biogeochemical cycle changes dramatically as the availability of a redox-controlling species, such as oxygen or acetate, crosses a threshold (a "tipping point"). These redox regime shifts occur in parameter ranges that are relevant to the sulfur and nitrogen Cycles in the present-day natural environment, and may also have relevance to iron cycling in the iron-containing Proterozoic and Archean oceans. We show that redox regime shifts also occur in models with physically realistic modifications, such as additional terms, chemical states, or microbial populations. Our work reveals a possible new mechanism by which regime shifts can occur in nutrient-cycling ecosystems and Biogeochemical Cycles, and highlights the importance of considering microbial population dynamics in models of Biogeochemical Cycles.
Sylvain Moreau - One of the best experts on this subject based on the ideXlab platform.
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Role of sea ice in global Biogeochemical Cycles: emerging views and challenges
Quaternary Science Reviews, 2013Co-Authors: Martin Vancoppenolle, Frédéric Brabant, Gauthier Carnat, Laurent Bopp, Delphine Lannuzel, Klaus M Meiners, Gurvan Madec, Bruno Delille, Christine Michel, Sylvain MoreauAbstract:Observations from the last decade suggest an important role of sea ice in the global Biogeochemical Cycles, promoted by (i) active biological and chemical processes within the sea ice; (ii) fluid and gas exchanges at the sea ice interface through an often permeable sea ice cover; and (iii) tight physical, biological and chemical interactions between the sea ice, the ocean and the atmosphere. Photosynthetic micro-organisms in sea ice thrive in liquid brine inclusions encased in a pure ice matrix, where they find suitable light and nutrient levels. They extend the production season, provide a winter and early spring food source, and contribute to organic carbon export to depth. Under-ice and ice edge phytoplankton blooms occur when ice retreats, favoured by increasing light, stratification, and by the release of material into the water column. In particular, the release of iron - highly concentrated in sea ice - could have large effects in the iron-limited Southern Ocean. The export of inorganic carbon transport by brine sinking below the mixed layer, calcium carbonate precipitation in sea ice, as well as active ice-atmosphere carbon dioxide (CO2) fluxes, could play a central role in the marine carbon cycle. Sea ice processes could also significantly contribute to the sulphur cycle through the large production by ice algae of dimethylsulfoniopropionate (DMSP), the precursor of sulphate aerosols, which as cloud condensation nuclei have a potential cooling effect on the planet. Finally, the sea ice zone supports significant ocean-atmosphere methane (CH4) fluxes, while saline ice surfaces activate springtime atmospheric bromine chemistry, setting ground for tropospheric ozone depletion events observed near both poles. All these mechanisms are generally known, but neither precisely understood nor quantified at large scales. As polar regions are rapidly changing, understanding the large-scale polar marine Biogeochemical processes and their future evolution is of high priority. Earth system models should in this context prove essential, but they currently represent sea ice as biologically and chemically inert. Palaeoclimatic proxies are also relevant, in particular the sea ice proxies, inferring past sea ice conditions from glacial and marine sediment core records and providing analogues for future changes. Being highly constrained by marine biogeochemistry, sea ice proxies would not only contribute to but also benefit from a better understanding of polar marine Biogeochemical Cycles.