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Michaletz S.T.,University of Arizona | Michaletz S.T.,Los Alamos National Laboratory | Weiser M.D.,University of Oklahoma | Zhou J.,University of Oklahoma | And 9 more authors.
Trends in Ecology and Evolution | Year: 2015

Building a more predictive trait-based ecology requires mechanistic theory based on first principles. We present a general theoretical approach to link traits and climate. We use plant leaves to show how energy budgets (i) provide a foundation for understanding thermoregulation, (ii) explain mechanisms driving trait variation across environmental gradients, and (iii) guide selection on functional traits via carbon economics. Although plants are often considered to be poikilotherms, the data suggest that they are instead limited homeotherms. Leaf functional traits that promote limited homeothermy are adaptive because homeothermy maximizes instantaneous and lifetime carbon gain. This theory provides a process-based foundation for trait-climate analyses and shows that future studies should consider plant (not only air) temperatures. Plants are generally considered to be poikilotherms that do not thermoregulate. However, empirical data show that plants are actually limited homeotherms that do thermoregulate.Plant thermoregulation and limited homeothermy decouples physiological functioning from climatic variation to promote metabolic homeostasis and maximize carbon assimilation and fitness.Energy budgets and carbon economics provide a mechanistic theory for understanding and predicting these relationships. Specifically, theory suggests that thermoregulation evolved via natural selection on traits to maximize lifetime carbon gain, growth, production, and fitness across climate gradients.Future studies need to consider plant tissue (and not only air) temperatures. © 2015. Source


Arnott J.C.,University of Michigan | Osenga E.C.,Aspen Global Change Institute | Cundiff J.L.,Aspen Center for Environmental Studies | Katzenberger J.W.,Aspen Global Change Institute
Journal of Forestry | Year: 2015

Climate change and a growing wildland-urban interface create new challenges for forest managers and restoration practitioners. In this shifting environment, effective public communication of scientific understanding of forest ecosystems and their changing state can be crucial. As a potential tool to help meet this communication need, we present a model for an index of forest health piloted in the Rocky Mountains of Colorado. The index presents ratings of forest health through the lens of public goals, using selected climatic, ecological, and socioeconomic data. A set of indicators combined with judgment about the metrics of health and how to weight them yields a quantitative rating system with a score for each indicator. Coproduced via a partnership between nongovernmental organizations, managers, and researchers, the result is a still evolving prototype of an educational resource with potential to also act as a decision support tool for tracking forest health and gauging management strategies. © 2015 Society of American Foresters. Source


Blonder B.,Copenhagen University | Blonder B.,University of Arizona | Nogues-Bravo D.,Copenhagen University | Borregaard M.K.,University of Oxford | And 15 more authors.
Ecology | Year: 2015

We present a framework to measure the strength of environmental filtering and disequilibrium of the species composition of a local community across time, relative to past, current, and future climates. We demonstrate the framework by measuring the impact of climate change on New World forests, integrating data for climate niches of more than 14 000 species, community composition of 471 New World forest plots, and observed climate across the most recent glacial-interglacial interval. We show that a majority of communities have species compositions that are strongly filtered and are more in equilibrium with current climate than random samples from the regional pool. Variation in the level of current community disequilibrium can be predicted from Last Glacial Maximum climate and will increase with near-future climate change. © 2015 by the Ecological Society of America. Source


News Article | August 30, 2016
Site: http://www.chromatographytechniques.com/rss-feeds/all/rss.xml/all

A new study has found that plants regulate their leaf temperature with some independence from the surrounding air temperature, a trait that increases carbon uptake through photosynthesis. The research offers promise for refining Earth system models that help predict climate change impacts and feedbacks. "This research combines theory for leaf energy flows with globally distributed temperature data for diverse plant taxa to show that leaves generally do not match air temperature, but instead thermoregulate," said Sean Michaletz, a plant ecologist at Los Alamos National Laboratory, which led the study. Los Alamos studies and models climate change and related impacts as part of its mission to maintain the nation's energy security. "The end result is that leaves are generally warmer than air in cold temperatures, and cooler than air in warm temperatures." In the paper recently published in Nature Plants, Michaletz and the team developed a novel theory that combined energy budgets, which account for incoming and outgoing thermal energy fluxes in a leaf, with the carbon economics theory, which posits that leaf form and function are ultimately constrained by the efficiency of the leaf's structure in processing carbon. By synthesizing these theories, the team showed how leaf thermoregulation helps to maximize leaf photosynthesis and, therefore, the total lifetime carbon gain of a leaf. The team's theory is key to developing a more quantitative plant ecology that examines the origins of leaf thermoregulation, or the process whereby leaf temperature varies from ambient air temperature. Their research shows that plant functions are decoupled from ambient temperatures, a finding that will support improved climate models. Most plants photosynthesize, converting light energy and carbon dioxide from the atmosphere into sugars that become leaves, stems and roots. Leaf thermoregulation is critical for plant carbon economics because leaf temperatures determine the speed of photosynthesis and respiration. Because it is generally assumed that plants take on the temperature of the environment, many current Earth system models for predicting plant-atmosphere feedbacks assume that plant physiology operates at the ambient air temperature. However, data from the team's study show that leaf temperature can differ dramatically from air temperatures. This decoupling weakens the link between the climate and plant functions, limiting climactic impacts on plant growth and the carbon budgets of an ecosystem. Michaletz, McDowell and their colleagues at the Laboratory conduct this research to help identify linkages among climate, plant traits and plant physiology rates. These recent research results may help to improve Earth system models and predict climate change impacts and feedbacks. Michaletz, a Los Alamos Director's Postdoctoral Fellow, and his mentor Nate McDowell published their Nature Plants paper in collaboration with authors from the University of Arizona, University of Oklahoma, Tsinghua University, Lawrence Berkeley Laboratory, Smithsonian Tropical Research Institute, University of Pennsylvania, The Santa Fe Institute, The iPlant Collaborative, Aspen Center for Environmental Studies.


News Article
Site: http://phys.org/biology-news/

"This research combines theory for leaf energy flows with globally distributed temperature data for diverse plant taxa to show that leaves generally do not match air temperature, but instead thermoregulate," said Sean Michaletz, a plant ecologist at Los Alamos National Laboratory, which led the study. Los Alamos studies and models climate change and related impacts as part of its mission to maintain the nation's energy security. "The end result is that leaves are generally warmer than air in cold temperatures, and cooler than air in warm temperatures." In the paper recently published in Nature Plants, Michaletz and the team developed a novel theory that combined energy budgets, which account for incoming and outgoing thermal energy fluxes in a leaf, with the carbon economics theory, which posits that leaf form and function are ultimately constrained by the efficiency of the leaf's structure in processing carbon. By synthesizing these theories, the team showed how leaf thermoregulation helps to maximize leaf photosynthesis and, therefore, the total lifetime carbon gain of a leaf. The team's theory is key to developing a more quantitative plant ecology that examines the origins of leaf thermoregulation, or the process whereby leaf temperature varies from ambient air temperature. Their research shows that plant functions are decoupled from ambient temperatures, a finding that will support improved climate models. Most plants photosynthesize, converting light energy and carbon dioxide from the atmosphere into sugars that become leaves, stems and roots. Leaf thermoregulation is critical for plant carbon economics because leaf temperatures determine the speed of photosynthesis and respiration. Because it is generally assumed that plants take on the temperature of the environment, many current Earth system models for predicting plant-atmosphere feedbacks assume that plant physiology operates at the ambient air temperature. However, data from the team's study show that leaf temperature can differ dramatically from air temperatures. This decoupling weakens the link between the climate and plant functions, limiting climactic impacts on plant growth and the carbon budgets of an ecosystem. Michaletz, McDowell and their colleagues at the Laboratory conduct this research to help identify linkages among climate, plant traits and plant physiology rates. These recent research results may help to improve Earth system models and predict climate change impacts and feedbacks. Michaletz, a Los Alamos Director's Postdoctoral Fellow, and his mentor Nate McDowell published their Nature Plants paper in collaboration with authors from the University of Arizona, University of Oklahoma, Tsinghua University, Lawrence Berkeley Laboratory, Smithsonian Tropical Research Institute, University of Pennsylvania, The Santa Fe Institute, The iPlant Collaborative, Aspen Center for Environmental Studies. More information: Sean T. Michaletz et al, The energetic and carbon economic origins of leaf thermoregulation, Nature Plants (2016). DOI: 10.1038/nplants.2016.129

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