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  • 1
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    Seasonality of temperate forest photosynthesis and daytime respiration (2016)
    Springer Nature
    In: Nature
    Details
    Publication Date: 2016-06-30
    Description: Seasonality of temperate forest photosynthesis and daytime respiration Nature 534, 7609 (2016). doi:10.1038/nature17966 Authors: R. Wehr, J. W. Munger, J. B. McManus, D. D. Nelson, M. S. Zahniser, E. A. Davidson, S. C. Wofsy & S. R. Saleska Terrestrial ecosystems currently offset one-quarter of anthropogenic carbon dioxide (CO2) emissions because of a slight imbalance between global terrestrial photosynthesis and respiration. Understanding what controls these two biological fluxes is therefore crucial to predicting climate change. Yet there is no way of directly measuring the photosynthesis or daytime respiration of a whole ecosystem of interacting organisms; instead, these fluxes are generally inferred from measurements of net ecosystem–atmosphere CO2 exchange (NEE), in a way that is based on assumed ecosystem-scale responses to the environment. The consequent view of temperate deciduous forests (an important CO2 sink) is that, first, ecosystem respiration is greater during the day than at night; and second, ecosystem photosynthetic light-use efficiency peaks after leaf expansion in spring and then declines, presumably because of leaf ageing or water stress. This view has underlain the development of terrestrial biosphere models used in climate prediction and of remote sensing indices of global biosphere productivity. Here, we use new isotopic instrumentation to determine ecosystem photosynthesis and daytime respiration in a temperate deciduous forest over a three-year period. We find that ecosystem respiration is lower during the day than at night—the first robust evidence of the inhibition of leaf respiration by light at the ecosystem scale. Because they do not capture this effect, standard approaches overestimate ecosystem photosynthesis and daytime respiration in the first half of the growing season at our site, and inaccurately portray ecosystem photosynthetic light-use efficiency. These findings revise our understanding of forest–atmosphere carbon exchange, and provide a basis for investigating how leaf-level physiological dynamics manifest at the canopy scale in other ecosystems.
    Print ISSN: 0028-0836
    Electronic ISSN: 1476-4687
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Published by Springer Nature
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  • 2
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    The potential of carbonyl sulfide as a proxy for gross primary production at flux tower sites (2011)
    Wiley
    Details
    Publication Date: 2011-11-16
    Description: Seasonal dynamics of atmospheric carbonyl sulfide (OCS) at regional and continental scales and plant OCS exchange at the leaf level have shown a close relationship with those for CO2. CO2 has both sinks and sources within terrestrial ecosystems, but the primary terrestrial exchange for OCS is thought to be leaf uptake, suggesting potential for OCS uptake as a proxy for gross primary production (GPP). We explored the utility of OCS uptake as a GPP proxy in micrometeorological studies of biosphere-atmosphere CO2 exchange by applying theoretical concepts from earlier OCS studies to estimate GPP. We partitioned measured net ecosystem exchange (NEE) using the ratio of measured vertical mole fraction gradients of OCS and CO2. At the Harvard Forest AmeriFlux site, measured CO2 and OCS vertical gradients were correlated and were related to NEE and GPP, respectively. Estimates of GPP from OCS-based NEE partitioning were similar to those from established environmental regression techniques, providing evidence that OCS uptake can potentially serve as a GPP proxy. Measured vertical CO2 mole fraction gradients at five other AmeriFlux sites were used to project anticipated vertical OCS mole fraction gradients to provide indication of potential OCS signal magnitudes at sites where no OCS measurements were made. Projected OCS gradients at sites with short canopies were greater than those in forests, including measured OCS gradients at Harvard Forest, indicating greater potential for OCS uptake as a GPP proxy at these sites. This exploratory study suggests that continued investigation of linkages between OCS and GPP is warranted.
    Print ISSN: 0148-0227
    Topics: Biology , Geosciences
    Published by Wiley on behalf of American Geophysical Union (AGU).
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  • 3
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    Imaging Spectroscopy- and Lidar- derived Estimates of Canopy Composition and Structure to Improve Predictions of Forest Carbon Fluxes and Ecosystem Dynamics (2014)
    Wiley
    Details
    Publication Date: 2014-02-20
    Description: [1]  The composition and structure of vegetation are key attributes of ecosystems, affecting their current and future carbon, water, and energy fluxes. Information on these attributes has traditionally come from ground-based inventories of the plant canopy within small sample plots. Here we show how imaging spectrometry and waveform lidar can be used to provide spatially-comprehensive estimates of forest canopy composition and structure that can improve the accuracy of the carbon flux predictions of a size-structured terrestrial biosphere model, reducing its RMSEs from 85%-104% to 37%-57%. The improvements are qualitatively and quantitatively similar to those obtained from simulations initialized with ground measurements, and approximately doubles the estimated rate of ecosystem carbon uptake as compared to a potential vegetation simulation. These results suggest that terrestrial biosphere model simulations can utilize modern-remote sensing data on vegetation composition and structure to improve their predictions of the current and near-term future functioning of the terrestrial biosphere.
    Print ISSN: 0094-8276
    Electronic ISSN: 1944-8007
    Topics: Geosciences , Physics
    Published by Wiley on behalf of American Geophysical Union (AGU).
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  • 4
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    A Deep Learning Parameterization for Ozone Dry Deposition Velocities (2019)
    Wiley
    Details
    Publication Date: 2019
    Description: Abstract The loss of ozone to terrestrial and aquatic systems, known as dry deposition, is a highly uncertain process governed by turbulent transport, interfacial chemistry, and plant physiology. We demonstrate the value of using Deep Neural Networks (DNN) in predicting ozone dry deposition velocities. We find that a feedforward DNN trained on observations from a coniferous forest site (Hyytiälä, Finland) can predict hourly ozone dry deposition velocities at a mixed forest site (Harvard Forest, Massachusetts) more accurately than modern theoretical models, with a reduction in the normalized mean bias (0.05 versus ~0.1). The same DNN model, when driven by assimilated meteorology at 2° × 2.5° spatial resolution, outperforms the Wesely scheme as implemented in the GEOS‐Chem model. With more available training data from other climate and ecological zones, this methodology could yield a generalizable DNN suitable for global models.
    Print ISSN: 0094-8276
    Electronic ISSN: 1944-8007
    Topics: Geosciences , Physics
    Published by Wiley on behalf of American Geophysical Union (AGU).
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  • 5
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    Response of a deciduous forest to the Mount Pinatubo eruption: enhanced photosynthesis (2003)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 2003-03-29
    Description: Volcanic aerosols from the 1991 Mount Pinatubo eruption greatly increased diffuse radiation worldwide for the following 2 years. We estimated that this increase in diffuse radiation alone enhanced noontime photosynthesis of a deciduous forest by 23% in 1992 and 8% in 1993 under cloudless conditions. This finding indicates that the aerosol-induced increase in diffuse radiation by the volcano enhanced the terrestrial carbon sink and contributed to the temporary decline in the growth rate of atmospheric carbon dioxide after the eruption.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Gu, Lianhong -- Baldocchi, Dennis D -- Wofsy, Steve C -- Munger, J William -- Michalsky, Joseph J -- Urbanski, Shawn P -- Boden, Thomas A -- New York, N.Y. -- Science. 2003 Mar 28;299(5615):2035-8.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Environmental Sciences Division, Building 1509, Oak Ridge National Laboratory, Oak Ridge, TN 37831-6335, USA. lianhong-gu@ornl.gov〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/12663919" target="_blank"〉PubMed〈/a〉
    Keywords: Aerosols ; *Atmosphere ; *Carbon Dioxide/metabolism ; Climate ; *Ecosystem ; Mathematics ; Models, Statistical ; Nonlinear Dynamics ; Philippines ; *Photosynthesis ; Regression Analysis ; Scattering, Radiation ; Seasons ; Sunlight ; Temperature ; Trees/*metabolism ; *Volcanic Eruptions
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
    Published by American Association for the Advancement of Science (AAAS)
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  • 6
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    Carbon in Amazon forests: unexpected seasonal fluxes and disturbance-induced losses (2003)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 2003-12-04
    Description: The net ecosystem exchange of carbon dioxide was measured by eddy covariance methods for 3 years in two old-growth forest sites near Santarem, Brazil. Carbon was lost in the wet season and gained in the dry season, which was opposite to the seasonal cycles of both tree growth and model predictions. The 3-year average carbon loss was 1.3 (confidence interval: 0.0 to 2.0) megagrams of carbon per hectare per year. Biometric observations confirmed the net loss but imply that it is a transient effect of recent disturbance superimposed on long-term balance. Given that episodic disturbances are characteristic of old-growth forests, it is likely that carbon sequestration is lower than has been inferred from recent eddy covariance studies at undisturbed sites.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Saleska, Scott R -- Miller, Scott D -- Matross, Daniel M -- Goulden, Michael L -- Wofsy, Steven C -- da Rocha, Humberto R -- de Camargo, Plinio B -- Crill, Patrick -- Daube, Bruce C -- de Freitas, Helber C -- Hutyra, Lucy -- Keller, Michael -- Kirchhoff, Volker -- Menton, Mary -- Munger, J William -- Pyle, Elizabeth Hammond -- Rice, Amy H -- Silva, Hudson -- New York, N.Y. -- Science. 2003 Nov 28;302(5650):1554-7.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Earth and Planetary Sciences, Harvard University, Cambridge, MA 02138, USA. saleska@fas.harvard.edu〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/14645845" target="_blank"〉PubMed〈/a〉
    Keywords: Brazil ; Carbon/*analysis/metabolism ; Carbon Dioxide/*analysis/metabolism ; Confidence Intervals ; *Ecosystem ; Oxygen Consumption ; Photosynthesis ; Rain ; *Seasons ; *Trees/growth & development/metabolism ; Wood
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
    Published by American Association for the Advancement of Science (AAAS)
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  • 7
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    Sensitivity of boreal forest carbon balance to soil thaw (1998)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 1998-01-16
    Description: We used eddy covariance; gas-exchange chambers; radiocarbon analysis; wood, moss, and soil inventories; and laboratory incubations to measure the carbon balance of a 120-year-old black spruce forest in Manitoba, Canada. The site lost 0.3 +/- 0.5 metric ton of carbon per hectare per year (ton C ha-1 year-1) from 1994 to 1997, with a gain of 0.6 +/- 0.2 ton C ha-1 year-1 in moss and wood offset by a loss of 0.8 +/- 0.5 ton C ha-1 year-1 from the soil. The soil remained frozen most of the year, and the decomposition of organic matter in the soil increased 10-fold upon thawing. The stability of the soil carbon pool ( approximately 150 tons C ha-1) appears sensitive to the depth and duration of thaw, and climatic changes that promote thaw are likely to cause a net efflux of carbon dioxide from the site.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Goulden -- Wofsy -- Harden -- Trumbore -- Crill -- Gower -- Fries -- Daube -- Fan -- Sutton -- Bazzaz -- Munger -- New York, N.Y. -- Science. 1998 Jan 9;279(5348):214-7.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉M. L. Goulden, S. C. Wofsy, B. C. Daube, S.-M. Fan, D. J. Sutton, A. Bazzaz, J. W. Munger, Department of Earth and Planetary Sciences, Harvard University, Cambridge, MA 02138, USA. J. W. Harden and T. Fries, U.S. Geological Survey, Menlo Park, CA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/9422691" target="_blank"〉PubMed〈/a〉
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
    Published by American Association for the Advancement of Science (AAAS)
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  • 8
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    Factors controlling long- and short-term sequestration of atmospheric CO2 in a mid-latitude forest (2001)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 2001-11-27
    Description: Net uptake of carbon dioxide (CO2) measured by eddy covariance in a 60- to 80-year-old forest averaged 2.0 +/- 0.4 megagrams of carbon per hectare per year during 1993 to 2000, with interannual variations exceeding 50%. Biometry indicated storage of 1.6 +/- 0.4 megagrams of carbon per hectare per year over 8 years, 60% in live biomass and the balance in coarse woody debris and soils, confirming eddy-covariance results. Weather and seasonal climate (e.g., variations in growing-season length or cloudiness) regulated seasonal and interannual fluctuations of carbon uptake. Legacies of prior disturbance and management, especially stand age and composition, controlled carbon uptake on the decadal time scale, implying that eastern forests could be managed for sequestration of carbon.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Barford, C C -- Wofsy, S C -- Goulden, M L -- Munger, J W -- Pyle, E H -- Urbanski, S P -- Hutyra, L -- Saleska, S R -- Fitzjarrald, D -- Moore, K -- New York, N.Y. -- Science. 2001 Nov 23;294(5547):1688-91.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Division of Engineering and Applied Science and Department of Earth and Planetary Science, Harvard University, Cambridge, MA 02138, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/11721047" target="_blank"〉PubMed〈/a〉
    Keywords: Algorithms ; *Atmosphere/analysis ; Biomass ; Biometry ; Carbon/metabolism ; Carbon Dioxide/*metabolism ; Climate ; *Ecosystem ; New England ; Nitrogen/analysis ; Probability ; Seasons ; Soil/analysis ; Time Factors ; Trees/growth & development/*metabolism
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
    Published by American Association for the Advancement of Science (AAAS)
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  • 9
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    The Amazon basin in transition (2012)
    Nature Publishing Group (NPG)
    Details
    Publication Date: 2012-01-20
    Description: Agricultural expansion and climate variability have become important agents of disturbance in the Amazon basin. Recent studies have demonstrated considerable resilience of Amazonian forests to moderate annual drought, but they also show that interactions between deforestation, fire and drought potentially lead to losses of carbon storage and changes in regional precipitation patterns and river discharge. Although the basin-wide impacts of land use and drought may not yet surpass the magnitude of natural variability of hydrologic and biogeochemical cycles, there are some signs of a transition to a disturbance-dominated regime. These signs include changing energy and water cycles in the southern and eastern portions of the Amazon basin.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Davidson, Eric A -- de Araujo, Alessandro C -- Artaxo, Paulo -- Balch, Jennifer K -- Brown, I Foster -- C Bustamante, Mercedes M -- Coe, Michael T -- DeFries, Ruth S -- Keller, Michael -- Longo, Marcos -- Munger, J William -- Schroeder, Wilfrid -- Soares-Filho, Britaldo S -- Souza, Carlos M Jr -- Wofsy, Steven C -- England -- Nature. 2012 Jan 18;481(7381):321-8. doi: 10.1038/nature10717.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉The Woods Hole Research Center, 149 Woods Hole Road, Falmouth, Massachusetts 02540-1644, USA. edavidson@whrc.org〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/22258611" target="_blank"〉PubMed〈/a〉
    Keywords: Brazil ; *Carbon Cycle ; *Climate Change ; Droughts ; *Ecosystem ; Fires ; Forestry ; Rain ; Rivers ; Seasons ; Trees/*metabolism
    Print ISSN: 0028-0836
    Electronic ISSN: 1476-4687
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Published by Nature Publishing Group (NPG)
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  • 10
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    Increase in forest water-use efficiency as atmospheric carbon dioxide concentrations rise (2013)
    Nature Publishing Group (NPG)
    Details
    Publication Date: 2013-07-12
    Description: Terrestrial plants remove CO2 from the atmosphere through photosynthesis, a process that is accompanied by the loss of water vapour from leaves. The ratio of water loss to carbon gain, or water-use efficiency, is a key characteristic of ecosystem function that is central to the global cycles of water, energy and carbon. Here we analyse direct, long-term measurements of whole-ecosystem carbon and water exchange. We find a substantial increase in water-use efficiency in temperate and boreal forests of the Northern Hemisphere over the past two decades. We systematically assess various competing hypotheses to explain this trend, and find that the observed increase is most consistent with a strong CO2 fertilization effect. The results suggest a partial closure of stomata-small pores on the leaf surface that regulate gas exchange-to maintain a near-constant concentration of CO2 inside the leaf even under continually increasing atmospheric CO2 levels. The observed increase in forest water-use efficiency is larger than that predicted by existing theory and 13 terrestrial biosphere models. The increase is associated with trends of increasing ecosystem-level photosynthesis and net carbon uptake, and decreasing evapotranspiration. Our findings suggest a shift in the carbon- and water-based economics of terrestrial vegetation, which may require a reassessment of the role of stomatal control in regulating interactions between forests and climate change, and a re-evaluation of coupled vegetation-climate models.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Keenan, Trevor F -- Hollinger, David Y -- Bohrer, Gil -- Dragoni, Danilo -- Munger, J William -- Schmid, Hans Peter -- Richardson, Andrew D -- England -- Nature. 2013 Jul 18;499(7458):324-7. doi: 10.1038/nature12291. Epub 2013 Jul 10.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Organismic and Evolutionary Biology, Harvard University, Cambridge, Massachusetts 02138, USA. tkeenan@oeb.harvard.edu〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/23842499" target="_blank"〉PubMed〈/a〉
    Keywords: Atmosphere/chemistry ; Carbon Dioxide/*analysis ; *Ecosystem ; Plant Leaves/chemistry ; Trees/*chemistry ; Water/*analysis
    Print ISSN: 0028-0836
    Electronic ISSN: 1476-4687
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Published by Nature Publishing Group (NPG)
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