The Experts below are selected from a list of 288 Experts worldwide ranked by ideXlab platform
Lucy Rowland - One of the best experts on this subject based on the ideXlab platform.
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linking hydraulic traits to tropical forest function in a size structured and trait driven Model tfs v 1 hydro
Geoscientific Model Development, 2016Co-Authors: Bradley O Christoffersen, Manuel Gloor, Sophie Fauset, Nikolaos M Fyllas, David Galbraith, Timothy R Baker, B Kruijt, Lucy RowlandAbstract:Abstract. Forest ecosystem Models based on heuristic water stress functions poorly predict tropical forest response to drought partly because they do not capture the diversity of hydraulic traits (including variation in tree size) observed in tropical forests. We developed a continuous porous media approach to Modeling plant Hydraulics in which all parameters of the constitutive equations are biologically interpretable and measurable plant hydraulic traits (e.g., turgor loss point πtlp, bulk elastic modulus e, hydraulic capacitance Cft, xylem hydraulic conductivity ks,max, water potential at 50 % loss of conductivity for both xylem (P50,x) and stomata (P50,gs), and the leaf : sapwood area ratio Al : As). We embedded this plant Hydraulics Model within a trait forest simulator (TFS) that Models light environments of individual trees and their upper boundary conditions (transpiration), as well as providing a means for parameterizing variation in hydraulic traits among individuals. We synthesized literature and existing databases to parameterize all hydraulic traits as a function of stem and leaf traits, including wood density (WD), leaf mass per area (LMA), and photosynthetic capacity (A max ), and evaluated the coupled Model (called TFS v.1-Hydro) predictions, against observed diurnal and seasonal variability in stem and leaf water potential as well as stand-scaled sap flux. Our hydraulic trait synthesis revealed coordination among leaf and xylem hydraulic traits and statistically significant relationships of most hydraulic traits with more easily measured plant traits. Using the most informative empirical trait–trait relationships derived from this synthesis, TFS v.1-Hydro successfully captured individual variation in leaf and stem water potential due to increasing tree size and light environment, with Model representation of hydraulic architecture and plant traits exerting primary and secondary controls, respectively, on the fidelity of Model predictions. The plant Hydraulics Model made substantial improvements to simulations of total ecosystem transpiration. Remaining uncertainties and limitations of the trait paradigm for plant Hydraulics Modeling are highlighted.
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Linking hydraulic traits to tropical forest function in a size-structured and trait-driven Model (TFS v.1-Hydro)
2016Co-Authors: Bradley O Christoffersen, Manuel Gloor, Sophie Fauset, Nikolaos M Fyllas, Timothy R Baker, Lucy Rowland, David R. Galbraith, Rosie A. Fisher, Oliver J. Binks, Sanna A. SevantoAbstract:Abstract. Forest ecosystem Models based on heuristic water stress functions poorly predict tropical forest response to drought because they do not capture the diversity of hydraulic traits (including variation in tree size) observed in tropical forests. We developed a Richards’ equation-based Model of plant Hydraulics in which all parameters of its constitutive equations are biologically-interpretable and measureable plant hydraulic traits (e.g., turgor loss point πtlp, bulk elastic modulus ε, hydraulic capacitance Cft, xylem hydraulic conductivity ks,max, water potential at 50 % loss of conductivity for both xylem (P50,x) and stomata (P50,gs), and the leaf:sapwood area ratio Al:As). We embedded this plant Hydraulics Model within a forest simulator (TFS) that Modeled individual tree light environments and their upper boundary condition (transpiration) as well as provided a means for parameterizing individual variation in hydraulic traits. We synthesized literature and existing databases to parameterize all hydraulic traits as a function of stem and leaf traits wood density (WD), leaf mass per area (LMA) and photosynthetic capacity (Amax) and evaluated the coupled Model’s (TFS-Hydro) predictions against diurnal and seasonal variability in stem and leaf water potential as well as stand-scaled sap flux. Our hydraulic trait synthesis revealed coordination among leaf and xylem hydraulic traits and statistically significant relationships of most hydraulic traits with more easily measured plant traits. Using the most informative empirical trait-trait relationships derived from this synthesis, the TFS-Hydro Model parameterization is capable of representing patterns of coordination and trade-offs in hydraulic traits. TFS-Hydro successfully captured individual variation in leaf and stem water potential due to increasing tree size and light environment, with Model representation of hydraulic architecture and plant traits exerting primary and secondary controls, respectively, on the fidelity of Model predictions. The plant Hydraulics Model made substantial improvements to simulations of total ecosystem transpiration under control conditions, but the absence of a vertically stratified soil hydrology Model precluded improvements to the simulation of drought response. Remaining uncertainties and limitations of the trait paradigm for plant Hydraulics Modeling are highlighted.
Bradley O Christoffersen - One of the best experts on this subject based on the ideXlab platform.
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linking hydraulic traits to tropical forest function in a size structured and trait driven Model tfs v 1 hydro
Geoscientific Model Development, 2016Co-Authors: Bradley O Christoffersen, Manuel Gloor, Sophie Fauset, Nikolaos M Fyllas, David Galbraith, Timothy R Baker, B Kruijt, Lucy RowlandAbstract:Abstract. Forest ecosystem Models based on heuristic water stress functions poorly predict tropical forest response to drought partly because they do not capture the diversity of hydraulic traits (including variation in tree size) observed in tropical forests. We developed a continuous porous media approach to Modeling plant Hydraulics in which all parameters of the constitutive equations are biologically interpretable and measurable plant hydraulic traits (e.g., turgor loss point πtlp, bulk elastic modulus e, hydraulic capacitance Cft, xylem hydraulic conductivity ks,max, water potential at 50 % loss of conductivity for both xylem (P50,x) and stomata (P50,gs), and the leaf : sapwood area ratio Al : As). We embedded this plant Hydraulics Model within a trait forest simulator (TFS) that Models light environments of individual trees and their upper boundary conditions (transpiration), as well as providing a means for parameterizing variation in hydraulic traits among individuals. We synthesized literature and existing databases to parameterize all hydraulic traits as a function of stem and leaf traits, including wood density (WD), leaf mass per area (LMA), and photosynthetic capacity (A max ), and evaluated the coupled Model (called TFS v.1-Hydro) predictions, against observed diurnal and seasonal variability in stem and leaf water potential as well as stand-scaled sap flux. Our hydraulic trait synthesis revealed coordination among leaf and xylem hydraulic traits and statistically significant relationships of most hydraulic traits with more easily measured plant traits. Using the most informative empirical trait–trait relationships derived from this synthesis, TFS v.1-Hydro successfully captured individual variation in leaf and stem water potential due to increasing tree size and light environment, with Model representation of hydraulic architecture and plant traits exerting primary and secondary controls, respectively, on the fidelity of Model predictions. The plant Hydraulics Model made substantial improvements to simulations of total ecosystem transpiration. Remaining uncertainties and limitations of the trait paradigm for plant Hydraulics Modeling are highlighted.
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Linking hydraulic traits to tropical forest function in a size-structured and trait-driven Model (TFS v.1-Hydro)
2016Co-Authors: Bradley O Christoffersen, Manuel Gloor, Sophie Fauset, Nikolaos M Fyllas, Timothy R Baker, Lucy Rowland, David R. Galbraith, Rosie A. Fisher, Oliver J. Binks, Sanna A. SevantoAbstract:Abstract. Forest ecosystem Models based on heuristic water stress functions poorly predict tropical forest response to drought because they do not capture the diversity of hydraulic traits (including variation in tree size) observed in tropical forests. We developed a Richards’ equation-based Model of plant Hydraulics in which all parameters of its constitutive equations are biologically-interpretable and measureable plant hydraulic traits (e.g., turgor loss point πtlp, bulk elastic modulus ε, hydraulic capacitance Cft, xylem hydraulic conductivity ks,max, water potential at 50 % loss of conductivity for both xylem (P50,x) and stomata (P50,gs), and the leaf:sapwood area ratio Al:As). We embedded this plant Hydraulics Model within a forest simulator (TFS) that Modeled individual tree light environments and their upper boundary condition (transpiration) as well as provided a means for parameterizing individual variation in hydraulic traits. We synthesized literature and existing databases to parameterize all hydraulic traits as a function of stem and leaf traits wood density (WD), leaf mass per area (LMA) and photosynthetic capacity (Amax) and evaluated the coupled Model’s (TFS-Hydro) predictions against diurnal and seasonal variability in stem and leaf water potential as well as stand-scaled sap flux. Our hydraulic trait synthesis revealed coordination among leaf and xylem hydraulic traits and statistically significant relationships of most hydraulic traits with more easily measured plant traits. Using the most informative empirical trait-trait relationships derived from this synthesis, the TFS-Hydro Model parameterization is capable of representing patterns of coordination and trade-offs in hydraulic traits. TFS-Hydro successfully captured individual variation in leaf and stem water potential due to increasing tree size and light environment, with Model representation of hydraulic architecture and plant traits exerting primary and secondary controls, respectively, on the fidelity of Model predictions. The plant Hydraulics Model made substantial improvements to simulations of total ecosystem transpiration under control conditions, but the absence of a vertically stratified soil hydrology Model precluded improvements to the simulation of drought response. Remaining uncertainties and limitations of the trait paradigm for plant Hydraulics Modeling are highlighted.
Akhilanand Pati Tiwari - One of the best experts on this subject based on the ideXlab platform.
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Design of decentralized PI and LQR controllers for level and pressure regulation of steam drum of advanced heavy water reactor
2018 Indian Control Conference (ICC), 2020Co-Authors: P. Panwar, T. U. Bhatt, S. Mukhopadhyay, Akhilanand Pati TiwariAbstract:This paper deals with the design of an effective control strategy for level and pressure control of Advanced heavy water reactor(AHWR) steam drum. Thermal Hydraulics Model is utilized for controller design, which sufficiently captures inverse phenomena taking place in steam drum. Decentralized PI, PI control with static decoupling and LQR control techniques are developed. A comparison of controllers performance is made to justify that LQR design outperforms other two controllers.
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CCA - Gain scheduled steam drum level controller for Advanced Heavy Water Reactor
2013 IEEE International Conference on Control Applications (CCA), 2013Co-Authors: K. N. V. Sairam, T. U. Bhatt, Akhilanand Pati TiwariAbstract:Gain scheduled P-I plus feed forward controller is designed for the steam drum level of Advanced Heavy Water Reactor(AHWR) by incorporating the coupling effects due to reactor power and steam pressure transients under Alternate and Normal mode of reactor operation. A simplified thermal Hydraulics Model is developed for the controller design which incorporates swell and shrink effects of steam drum level as well as varying plant dynamics.
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Gain scheduled steam drum level controller for Advanced Heavy Water Reactor
2013 IEEE International Conference on Control Applications (CCA), 2013Co-Authors: K. N. V. Sairam, T. U. Bhatt, Akhilanand Pati TiwariAbstract:Gain scheduled P-I plus feed forward controller is designed for the steam drum level of Advanced Heavy Water Reactor(AHWR) by incorporating the coupling effects due to reactor power and steam pressure transients under Alternate and Normal mode of reactor operation. A simplified thermal Hydraulics Model is developed for the controller design which incorporates swell and shrink effects of steam drum level as well as varying plant dynamics.
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Coupled neutronics-thermal Hydraulics Model of Advanced Heavy Water Reactor for control system studies
2008 Annual IEEE India Conference, 2008Co-Authors: S. R. Shimjith, Akhilanand Pati Tiwari, Bijnan BandyopadhyayAbstract:A coupled neutronics-thermal Hydraulics Model of advanced heavy water reactor (AHWR) which can be used for control system studies, simulation etc. is presented in this paper. A nodal Model is developed for core neutronics and a simple two-phase thermal Hydraulics Model is developed from first principles. Neutronics-thermal Hydraulics coupling is achieved through the void reactivity feedback Model. Selection of a suitable nodalization scheme through steady state analysis is discussed, and dynamic response of the Model is also presented.
Christopher B. Field - One of the best experts on this subject based on the ideXlab platform.
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Tree mortality predicted from drought-induced vascular damage
Nature Geoscience, 2015Co-Authors: William R. L. Anderegg, Alan Flint, Cho-ying Huang, Lorraine Flint, Joseph A. Berry, Frank w. Davis, John S. Sperry, Christopher B. FieldAbstract:The projected responses of forest ecosystems to warming and drying associated with twenty-first-century climate change vary widely from resiliency to widespread tree mortality^ 1 , 2 , 3 . Current vegetation Models lack the ability to account for mortality of overstorey trees during extreme drought owing to uncertainties in mechanisms and thresholds causing mortality^ 4 , 5 . Here we assess the causes of tree mortality, using field measurements of branch hydraulic conductivity during ongoing mortality in Populus tremuloides in the southwestern United States and a detailed plant Hydraulics Model. We identify a lethal plant water stress threshold that corresponds with a loss of vascular transport capacity from air entry into the xylem. We then use this hydraulic-based threshold to simulate forest dieback during historical drought, and compare predictions against three independent mortality data sets. The hydraulic threshold predicted with 75% accuracy regional patterns of tree mortality as found in field plots and mortality maps derived from Landsat imagery. In a high-emissions scenario, climate Models project that drought stress will exceed the observed mortality threshold in the southwestern United States by the 2050s. Our approach provides a powerful and tractable way of incorporating tree mortality into vegetation Models to resolve uncertainty over the fate of forest ecosystems in a changing climate. Forests may be vulnerable to future droughts. A tree mortality threshold based on plant Hydraulics suggests that increased drought may trigger widespread dieback in the southwestern United States by mid-century.
Timothy R Baker - One of the best experts on this subject based on the ideXlab platform.
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linking hydraulic traits to tropical forest function in a size structured and trait driven Model tfs v 1 hydro
Geoscientific Model Development, 2016Co-Authors: Bradley O Christoffersen, Manuel Gloor, Sophie Fauset, Nikolaos M Fyllas, David Galbraith, Timothy R Baker, B Kruijt, Lucy RowlandAbstract:Abstract. Forest ecosystem Models based on heuristic water stress functions poorly predict tropical forest response to drought partly because they do not capture the diversity of hydraulic traits (including variation in tree size) observed in tropical forests. We developed a continuous porous media approach to Modeling plant Hydraulics in which all parameters of the constitutive equations are biologically interpretable and measurable plant hydraulic traits (e.g., turgor loss point πtlp, bulk elastic modulus e, hydraulic capacitance Cft, xylem hydraulic conductivity ks,max, water potential at 50 % loss of conductivity for both xylem (P50,x) and stomata (P50,gs), and the leaf : sapwood area ratio Al : As). We embedded this plant Hydraulics Model within a trait forest simulator (TFS) that Models light environments of individual trees and their upper boundary conditions (transpiration), as well as providing a means for parameterizing variation in hydraulic traits among individuals. We synthesized literature and existing databases to parameterize all hydraulic traits as a function of stem and leaf traits, including wood density (WD), leaf mass per area (LMA), and photosynthetic capacity (A max ), and evaluated the coupled Model (called TFS v.1-Hydro) predictions, against observed diurnal and seasonal variability in stem and leaf water potential as well as stand-scaled sap flux. Our hydraulic trait synthesis revealed coordination among leaf and xylem hydraulic traits and statistically significant relationships of most hydraulic traits with more easily measured plant traits. Using the most informative empirical trait–trait relationships derived from this synthesis, TFS v.1-Hydro successfully captured individual variation in leaf and stem water potential due to increasing tree size and light environment, with Model representation of hydraulic architecture and plant traits exerting primary and secondary controls, respectively, on the fidelity of Model predictions. The plant Hydraulics Model made substantial improvements to simulations of total ecosystem transpiration. Remaining uncertainties and limitations of the trait paradigm for plant Hydraulics Modeling are highlighted.
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Linking hydraulic traits to tropical forest function in a size-structured and trait-driven Model (TFS v.1-Hydro)
2016Co-Authors: Bradley O Christoffersen, Manuel Gloor, Sophie Fauset, Nikolaos M Fyllas, Timothy R Baker, Lucy Rowland, David R. Galbraith, Rosie A. Fisher, Oliver J. Binks, Sanna A. SevantoAbstract:Abstract. Forest ecosystem Models based on heuristic water stress functions poorly predict tropical forest response to drought because they do not capture the diversity of hydraulic traits (including variation in tree size) observed in tropical forests. We developed a Richards’ equation-based Model of plant Hydraulics in which all parameters of its constitutive equations are biologically-interpretable and measureable plant hydraulic traits (e.g., turgor loss point πtlp, bulk elastic modulus ε, hydraulic capacitance Cft, xylem hydraulic conductivity ks,max, water potential at 50 % loss of conductivity for both xylem (P50,x) and stomata (P50,gs), and the leaf:sapwood area ratio Al:As). We embedded this plant Hydraulics Model within a forest simulator (TFS) that Modeled individual tree light environments and their upper boundary condition (transpiration) as well as provided a means for parameterizing individual variation in hydraulic traits. We synthesized literature and existing databases to parameterize all hydraulic traits as a function of stem and leaf traits wood density (WD), leaf mass per area (LMA) and photosynthetic capacity (Amax) and evaluated the coupled Model’s (TFS-Hydro) predictions against diurnal and seasonal variability in stem and leaf water potential as well as stand-scaled sap flux. Our hydraulic trait synthesis revealed coordination among leaf and xylem hydraulic traits and statistically significant relationships of most hydraulic traits with more easily measured plant traits. Using the most informative empirical trait-trait relationships derived from this synthesis, the TFS-Hydro Model parameterization is capable of representing patterns of coordination and trade-offs in hydraulic traits. TFS-Hydro successfully captured individual variation in leaf and stem water potential due to increasing tree size and light environment, with Model representation of hydraulic architecture and plant traits exerting primary and secondary controls, respectively, on the fidelity of Model predictions. The plant Hydraulics Model made substantial improvements to simulations of total ecosystem transpiration under control conditions, but the absence of a vertically stratified soil hydrology Model precluded improvements to the simulation of drought response. Remaining uncertainties and limitations of the trait paradigm for plant Hydraulics Modeling are highlighted.
