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Li F, Hao D, Zhu Q, Yuan K, Braghiere RK, He L, Luo X, Wei S, Riley WJ, Zeng Y, Chen M. Vegetation clumping modulates global photosynthesis through adjusting canopy light environment. GLOBAL CHANGE BIOLOGY 2023; 29:731-746. [PMID: 36281563 PMCID: PMC10100496 DOI: 10.1111/gcb.16503] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 06/11/2022] [Accepted: 10/10/2022] [Indexed: 06/16/2023]
Abstract
The spatial dispersion of photoelements within a vegetation canopy, quantified by the clumping index (CI), directly regulates the within-canopy light environment and photosynthesis rate, but is not commonly implemented in terrestrial biosphere models to estimate the ecosystem carbon cycle. A few global CI products have been developed recently with remote sensing measurements, making it possible to examine the global impacts of CI. This study deployed CI in the radiative transfer scheme of the Community Land Model version 5 (CLM5) and used the revised CLM5 to quantitatively evaluate the extent to which CI can affect canopy absorbed radiation and gross primary production (GPP), and for the first time, considering the uncertainty and seasonal variation of CI with multiple remote sensing products. Compared to the results without considering the CI impact, the revised CLM5 estimated that sunlit canopy absorbed up to 9%-15% and 23%-34% less direct and diffuse radiation, respectively, while shaded canopy absorbed 3%-18% more diffuse radiation across different biome types. The CI impacts on canopy light conditions included changes in canopy light absorption, and sunlit-shaded leaf area fraction related to nitrogen distribution and thus the maximum rate of Rubisco carboxylase activity (Vcmax ), which together decreased photosynthesis in sunlit canopy by 5.9-7.2 PgC year-1 while enhanced photosynthesis by 6.9-8.2 PgC year-1 in shaded canopy. With higher light use efficiency of shaded leaves, shaded canopy increased photosynthesis compensated and exceeded the lost photosynthesis in sunlit canopy, resulting in 1.0 ± 0.12 PgC year-1 net increase in GPP. The uncertainty of GPP due to the different input CI datasets was much larger than that caused by CI seasonal variations, and was up to 50% of the magnitude of GPP interannual variations in the tropical regions. This study highlights the necessity of considering the impacts of CI and its uncertainty in terrestrial biosphere models.
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Affiliation(s)
- Fa Li
- Department of Forest and Wildlife EcologyUniversity of Wisconsin‐MadisonMadisonWisconsinUSA
| | - Dalei Hao
- Atmospheric Sciences and Global Change DivisionPacific Northwest National LaboratoryRichlandWashingtonUSA
| | - Qing Zhu
- Climate and Ecosystem Sciences Division, Climate Sciences DepartmentLawrence Berkeley National LaboratoryBerkeleyCaliforniaUSA
| | - Kunxiaojia Yuan
- Climate and Ecosystem Sciences Division, Climate Sciences DepartmentLawrence Berkeley National LaboratoryBerkeleyCaliforniaUSA
| | - Renato K. Braghiere
- Division of Geological and Planetary SciencesCalifornia Institute of TechnologyPasadenaCaliforniaUSA
- Jet Propulsion LaboratoryCalifornia Institute of TechnologyPasadenaCaliforniaUSA
| | - Liming He
- Canada Centre for Mapping and Earth ObservationNatural Resources CanadaOttawaOntarioCanada
| | - Xiangzhong Luo
- Department of GeographyNational University of SingaporeSingaporeSingapore
| | - Shanshan Wei
- Centre for Remote Imaging, Sensing and ProcessingNational University of SingaporeSingaporeSingapore
| | - William J. Riley
- Climate and Ecosystem Sciences Division, Climate Sciences DepartmentLawrence Berkeley National LaboratoryBerkeleyCaliforniaUSA
| | - Yelu Zeng
- Department of Forest and Wildlife EcologyUniversity of Wisconsin‐MadisonMadisonWisconsinUSA
| | - Min Chen
- Department of Forest and Wildlife EcologyUniversity of Wisconsin‐MadisonMadisonWisconsinUSA
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Effects of Aerosols on Gross Primary Production from Ecosystems to the Globe. REMOTE SENSING 2022. [DOI: 10.3390/rs14122759] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/10/2022]
Abstract
Aerosols affect the gross primary productivity (GPP) of plants by absorbing and scattering solar radiation. However, it is still an open question whether and to what extent the effects of aerosol on the diffuse fraction (Df) can enhance GPP globally. We quantified the aerosol diffuse fertilization effect (DFE) and incorporated it into a light use efficiency (LUE) model, EC-LUE. The new model is driven by aerosol optical depth (AOD) data and is referred to as AOD-LUE. The eddy correlation variance (EC) of the FLUXNET2015 dataset was used to calibrate and validate the model. The results showed that the newly developed AOD-LUE model improved the performance in simulating GPP across all ecosystem types (R2 from 0.6 to 0.68), with the highest performance for mixed forest (average R2 from 0.71 to 0.77) and evergreen broadleaf forest (average R2 from 0.34 to 0.45). The maximum LUE of diffuse photosynthetic active radiation (PAR) (3.61 g C m−2 MJ−1) was larger than that of direct PAR (1.68 g C m−2 MJ−1) through parameter optimization, indicating that the aerosol DFE seriously affects the estimation of GPP, and the separation of diffuse PAR and direct PAR in the GPP model is necessary. In addition, we used AOD-LUE to quantify the impact of aerosol on GPP. Specifically, aerosols impaired GPP in closed shrub (CSH) by 6.45% but enhanced the GPP of grassland (GRA) and deciduous broadleaf forest (DBF) by 3.19% and 2.63%, respectively. Our study stresses the importance of understanding aerosol-radiation interactions and incorporating aerosol effects into regional and global GPP models.
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The Impact of the Spectral Radiation Environment on the Maximum Absorption Wavelengths of Human Vision and Other Species. Life (Basel) 2021; 11:life11121337. [PMID: 34947867 PMCID: PMC8707699 DOI: 10.3390/life11121337] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2021] [Revised: 11/29/2021] [Accepted: 11/30/2021] [Indexed: 12/04/2022] Open
Abstract
Since the earliest development of the eye (and vision) around 530 million years ago (Mya), it has evolved, adapting to different habitats, species, and changing environmental conditions on Earth. We argue that a radiation environment determined by the atmosphere played a determining role in the evolution of vision, specifically on the human eye, which has three vision regimes (photopic-, scotopic-, and mesopic vision) for different illumination conditions. An analysis of the irradiance spectra, reaching the shallow ocean depths, revealed that the available radiation could have determined the bandwidth of the precursor to vision systems, including human vision. We used the radiative transfer model to test the existing hypotheses on human vision. We argue that, once on the surface, the human photopic (daytime) and scotopic (night-time) vision followed different evolutionary directions, maximum total energy, and optimum information, respectively. Our analysis also suggests that solar radiation reflected from the moon had little or no influence on the evolution of scotopic vision. Our results indicate that, apart from human vision, the vision of only a few birds, rodents, and deep-sea fish are strongly correlated to the available radiation within their respective habitats.
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Dye AW, Rastogi B, Clemesha RES, Kim JB, Samelson RM, Still CJ, Williams AP. Spatial Patterns and Trends of Summertime Low Cloudiness for the Pacific Northwest, 1996-2017. GEOPHYSICAL RESEARCH LETTERS 2020; 47:e2020GL088121. [PMID: 33041386 PMCID: PMC7540517 DOI: 10.1029/2020gl088121] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/26/2020] [Revised: 06/16/2020] [Accepted: 07/24/2020] [Indexed: 05/13/2023]
Abstract
Summertime low clouds are common in the Pacific Northwest (PNW), but spatiotemporal patterns have not been characterized. We show the first maps of low cloudiness for the western PNW and North Pacific Ocean using a 22-year satellite-derived record of monthly mean low cloudiness frequency for May through September and supplemented by airport cloud base height observations. Domain-wide cloudiness peaks in midsummer and is strongest over the Pacific. Empirical orthogonal function (EOF) analysis identified four distinct PNW spatiotemporal modes: oceanic, terrestrial highlands, coastal, and northern coastal. There is a statistically significant trend over the 22-year record toward reduced low cloudiness in the terrestrial highlands mode, with strongest declines in May and June; however, this decline is not matched in the corresponding airport records. The coastal mode is partly constrained from moving inland by topographic relief and migrates southward in late summer, retaining higher late-season low cloud frequency than the other areas.
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Affiliation(s)
- Alex W. Dye
- Department of Forest Ecosystems and SocietyOregon State UniversityCorvallisORUSA
- USDA Forest Service Corvallis Forestry Sciences LaboratoryPacific Northwest Research StationCorvallisORUSA
| | - Bharat Rastogi
- Cooperative Institute for Research in Environmental SciencesUniversity of Colorado BoulderBoulderCOUSA
- Global Monitoring LaboratoryNational Oceanic and Atmospheric AdministrationBoulderCOUSA
| | | | - John B. Kim
- USDA Forest Service Corvallis Forestry Sciences LaboratoryPacific Northwest Research StationCorvallisORUSA
| | - Roger M. Samelson
- College of Earth, Ocean, and Atmospheric SciencesOregon State UniversityCorvallisORUSA
| | - Christopher J. Still
- Department of Forest Ecosystems and SocietyOregon State UniversityCorvallisORUSA
| | - A. Park Williams
- Lamont‐Doherty Earth ObservatoryColumbia UniversityPalisadesNYUSA
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Li C, Jia X, Ma J, Liu P, Yang R, Bai Y, Hayat M, Liu J, Zha T. Linking diffuse radiation and ecosystem productivity of a desert steppe ecosystem. PeerJ 2020; 8:e9043. [PMID: 32411524 PMCID: PMC7207212 DOI: 10.7717/peerj.9043] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2019] [Accepted: 04/02/2020] [Indexed: 11/20/2022] Open
Abstract
Radiation components have distinct effects on photosynthesis. In the desert steppe ecosystem, the influence of diffuse radiation on carbon fixation has not been thoroughly explored. We examined this diffusion and its effect on ecosystem productivity was examined during the growing season from 2014 to 2015 on the basis of eddy covariance measurements of CO2 exchange in a desert steppe ecosystem in northwest China. Our results indicated that the gross ecosystem production (GEP) and diffuse photosynthetically active radiation (PARdif) peaked when the clearness index (CI) was around 0.5. The maximum canopy photosynthesis (Pmax) under cloudy skies (CI < 0.7) was 23.7% greater than under clear skies (CI ≥ 0.7). When the skies became cloudy in the desert steppe ecosystem, PARdif had a greater effect on GEP. Additionally, lower vapor pressure deficits (VPD ≤ 1 kPa), lower air temperatures (Ta ≤ 20 °C), and non-stressed water conditions (REW ≥ 0.4) were more conducive for enhanced ecosystem photosynthesis under cloudy skies than under clear skies. This may be due to the comprehensive effects of VPD and Ta on stomatal conductance. We concluded that cloudiness can influence diffuse radiation components and that diffuse radiation can increase the ecosystem production of desert steppe ecosystems in northwest China.
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Affiliation(s)
- Cheng Li
- Yanchi Research Station, School of Soil and Water Conservation, Beijing Forestry University, Beijing, China.,Key Laboratory of State Forestry Administration on Soil and Water Conservation, Beijing Forestry University, Beijing, China
| | - Xin Jia
- Yanchi Research Station, School of Soil and Water Conservation, Beijing Forestry University, Beijing, China.,Key Laboratory of State Forestry Administration on Soil and Water Conservation, Beijing Forestry University, Beijing, China
| | - Jingyong Ma
- Yanchi Research Station, School of Soil and Water Conservation, Beijing Forestry University, Beijing, China.,Key Laboratory of State Forestry Administration on Soil and Water Conservation, Beijing Forestry University, Beijing, China
| | - Peng Liu
- Yanchi Research Station, School of Soil and Water Conservation, Beijing Forestry University, Beijing, China.,Key Laboratory of State Forestry Administration on Soil and Water Conservation, Beijing Forestry University, Beijing, China
| | - Ruizhi Yang
- Yanchi Research Station, School of Soil and Water Conservation, Beijing Forestry University, Beijing, China.,Key Laboratory of State Forestry Administration on Soil and Water Conservation, Beijing Forestry University, Beijing, China
| | - Yujie Bai
- Yanchi Research Station, School of Soil and Water Conservation, Beijing Forestry University, Beijing, China.,Key Laboratory of State Forestry Administration on Soil and Water Conservation, Beijing Forestry University, Beijing, China
| | - Muhammad Hayat
- Yanchi Research Station, School of Soil and Water Conservation, Beijing Forestry University, Beijing, China.,Key Laboratory of State Forestry Administration on Soil and Water Conservation, Beijing Forestry University, Beijing, China
| | - Jinglan Liu
- School of Ecology and Nature Conservation, Beijing Forestry University, Beijing, China
| | - Tianshan Zha
- Yanchi Research Station, School of Soil and Water Conservation, Beijing Forestry University, Beijing, China.,Key Laboratory of State Forestry Administration on Soil and Water Conservation, Beijing Forestry University, Beijing, China
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Abstract
Abstract:Tropical montane cloud forests (TMCFs) are dynamic ecosystems defined by frequent, but intermittent, contact with fog. The resultant microclimate can vary considerably over short spatial and temporal scales, affecting the ecophysiology of TMCF plants. We synthesized research to date on TMCF carbon and water fluxes at the scale of the leaf, plant and ecosystem and then contextualized this synthesis with tropical lowland forest ecosystems. Mean light-saturated photosynthesis was lower than that of lowland forests, probably due to the effects of persistent reduced radiation leading to shade acclimation. Scaled to the ecosystem, measures of annual net primary productivity were also lower. Mean rates of transpiration, from the scale of the leaf to the ecosystem, were also lower than in lowland sites, likely due to lower atmospheric water demand, although there was considerable overlap in range. Lastly, although carbon use efficiency appears relatively invariant, limited evidence indicates that water use efficiency generally increases with altitude, perhaps due to increased cloudiness exerting a stronger effect on vapour pressure deficit than photosynthesis. The results reveal clear differences in carbon and water balance between TMCFs and their lowland counterparts and suggest many outstanding questions for understanding TMCF ecophysiology now and in the future.
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Wang S, Huang K, Yan H, Yan H, Zhou L, Wang H, Zhang J, Yan J, Zhao L, Wang Y, Shi P, Zhao F, Sun L. Improving the light use efficiency model for simulating terrestrial vegetation gross primary production by the inclusion of diffuse radiation across ecosystems in China. ECOLOGICAL COMPLEXITY 2015. [DOI: 10.1016/j.ecocom.2015.04.004] [Citation(s) in RCA: 39] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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Voelker SL, Meinzer FC, Lachenbruch B, Brooks JR, Guyette RP. Drivers of radial growth and carbon isotope discrimination of bur oak (Quercus macrocarpa Michx.) across continental gradients in precipitation, vapour pressure deficit and irradiance. PLANT, CELL & ENVIRONMENT 2014; 37:766-79. [PMID: 24004466 DOI: 10.1111/pce.12196] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/02/2012] [Revised: 08/12/2013] [Accepted: 08/15/2013] [Indexed: 05/08/2023]
Abstract
Tree-ring characteristics are commonly used to reconstruct climate variables, but divergence from the assumption of a single biophysical control may reduce the accuracy of these reconstructions. Here, we present data from bur oaks (Quercus macrocarpa Michx.) sampled within and beyond the current species bioclimatic envelope to identify the primary environmental controls on ring-width indices (RWIs) and carbon stable isotope discrimination (Δ(13) C) in tree-ring cellulose. Variation in Δ(13) C and RWI was more strongly related to leaf-to-air vapour pressure deficit (VPD) at the centre and western edge of the range compared with the northern and wettest regions. Among regions, Δ(13) C of tree-ring cellulose was closely predicted by VPD and light responses of canopy-level Δ(13) C estimated using a model driven by eddy flux and meteorological measurements (R(2) = 0.96, P = 0.003). RWI and Δ(13) C were positively correlated in the drier regions, while they were negatively correlated in the wettest region. The strength and direction of the correlations scaled with regional VPD or the ratio of precipitation to evapotranspiration. Therefore, the correlation strength between RWI and Δ(13) C may be used to infer past wetness or aridity from paleo wood by determining the degree to which carbon gain and growth have been more limited by moisture or light.
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Affiliation(s)
- Steven L Voelker
- Biology Department, Southern Oregon University, 1250 Siskiyou Blvd., Ashland, OR, 97520, USA
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Carbone MS, Park Williams A, Ambrose AR, Boot CM, Bradley ES, Dawson TE, Schaeffer SM, Schimel JP, Still CJ. Cloud shading and fog drip influence the metabolism of a coastal pine ecosystem. GLOBAL CHANGE BIOLOGY 2013; 19:484-97. [PMID: 23504786 DOI: 10.1111/gcb.12054] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/15/2012] [Revised: 09/18/2012] [Accepted: 10/01/2012] [Indexed: 05/10/2023]
Abstract
Assessing the ecological importance of clouds has substantial implications for our basic understanding of ecosystems and for predicting how they will respond to a changing climate. This study was conducted in a coastal Bishop pine forest ecosystem that experiences regular cycles of stratus cloud cover and inundation in summer. Our objective was to understand how these clouds impact ecosystem metabolism by contrasting two sites along a gradient of summer stratus cover. The site that was under cloud cover ~15% more of the summer daytime hours had lower air temperatures and evaporation rates, higher soil moisture content, and received more frequent fog drip inputs than the site with less cloud cover. These cloud-driven differences in environmental conditions translated into large differences in plant and microbial activity. Pine trees at the site with greater cloud cover exhibited less water stress in summer, larger basal area growth, and greater rates of sap velocity. The difference in basal area growth between the two sites was largely due to summer growth. Microbial metabolism was highly responsive to fog drip, illustrated by an observed ~3-fold increase in microbial biomass C with increasing summer fog drip. In addition, the site with more cloud cover had greater total soil respiration and a larger fractional contribution from heterotrophic sources. We conclude that clouds are important to the ecological functioning of these coastal forests, providing summer shading and cooling that relieve pine and microbial drought stress as well as regular moisture inputs that elevate plant and microbial metabolism. These findings are important for understanding how these and other seasonally dry coastal ecosystems will respond to predicted changes in stratus cover, rainfall, and temperature.
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Affiliation(s)
- Mariah S Carbone
- National Center for Ecological Analysis and Synthesis, Santa Barbara, CA 93101, USA.
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Niinemets Ü, Keenan TF. Measures of light in studies on light-driven plant plasticity in artificial environments. FRONTIERS IN PLANT SCIENCE 2012; 3:156. [PMID: 22822407 PMCID: PMC3398413 DOI: 10.3389/fpls.2012.00156] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/28/2012] [Accepted: 06/25/2012] [Indexed: 05/06/2023]
Abstract
Within-canopy variation in light results in profound canopy profiles in foliage structural, chemical, and physiological traits. Studies on within-canopy variations in key foliage traits are often conducted in artificial environments, including growth chambers with only artificial light, and greenhouses with and without supplemental light. Canopy patterns in these systems are considered to be representative to outdoor conditions, but in experiments with artificial and supplemental lighting, the intensity of artificial light strongly deceases with the distance from the light source, and natural light intensity in greenhouses is less than outdoors due to limited transmittance of enclosure walls. The implications of such changes in radiation conditions on canopy patterns of foliage traits have not yet been analyzed. We developed model-based methods for retrospective estimation of distance vs. light intensity relationships, for separation of the share of artificial and natural light in experiments with combined light and for estimation of average enclosure transmittance, and estimated daily integrated light at the time of sampling (Q(int,C)), at foliage formation (Q(int,G)), and during foliage lifetime (Q(int,av)). The implications of artificial light environments were analyzed for altogether 25 studies providing information on within-canopy gradients of key foliage traits for 70 species × treatment combinations. Across the studies with artificial light, Q(int,G) for leaves formed at different heights in the canopy varied from 1.8- to 6.4-fold due to changing the distance between light source and growing plants. In experiments with combined lighting, the share of natural light at the top of the plants varied threefold, and the share of natural light strongly increased with increasing depth in the canopy. Foliage nitrogen content was most strongly associated with Q(int,G), but photosynthetic capacity with Q(int,C), emphasizing the importance of explicit description of light environment during foliage lifetime. The reported and estimated transmittances of enclosures varied between 0.27 and 0.85, and lack of consideration of the reduction of light compared with outdoor conditions resulted in major underestimation of foliage plasticity to light. The study emphasizes that plant trait vs. light relationships in artificial systems are not directly comparable to natural environments unless modifications in lighting conditions in artificial environments are taken into account.
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Affiliation(s)
- Ülo Niinemets
- Institute of Agricultural and Environmental Sciences, Estonian University of Life SciencesTartu, Estonia
| | - Trevor F. Keenan
- Department of Organismic and Evolutionary Biology, Harvard UniversityCambridge, MA, USA
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Urban O, Klem K, Ač A, Havránková K, Holišová P, Navrátil M, Zitová M, Kozlová K, Pokorný R, Šprtová M, Tomášková I, Špunda V, Grace J. Impact of clear and cloudy sky conditions on the vertical distribution of photosynthetic CO2uptake within a spruce canopy. Funct Ecol 2011. [DOI: 10.1111/j.1365-2435.2011.01934.x] [Citation(s) in RCA: 101] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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Buenning NH, Noone DC, Riley WJ, Still CJ, White JWC. Influences of the hydrological cycle on observed interannual variations in atmospheric CO18O. ACTA ACUST UNITED AC 2011. [DOI: 10.1029/2010jg001576] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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Interannual variability in the oxygen isotopes of atmospheric CO2 driven by El Niño. Nature 2011; 477:579-82. [PMID: 21956330 DOI: 10.1038/nature10421] [Citation(s) in RCA: 178] [Impact Index Per Article: 13.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2010] [Accepted: 08/04/2011] [Indexed: 11/08/2022]
Abstract
The stable isotope ratios of atmospheric CO(2) ((18)O/(16)O and (13)C/(12)C) have been monitored since 1977 to improve our understanding of the global carbon cycle, because biosphere-atmosphere exchange fluxes affect the different atomic masses in a measurable way. Interpreting the (18)O/(16)O variability has proved difficult, however, because oxygen isotopes in CO(2) are influenced by both the carbon cycle and the water cycle. Previous attention focused on the decreasing (18)O/(16)O ratio in the 1990s, observed by the global Cooperative Air Sampling Network of the US National Oceanic and Atmospheric Administration Earth System Research Laboratory. This decrease was attributed variously to a number of processes including an increase in Northern Hemisphere soil respiration; a global increase in C(4) crops at the expense of C(3) forests; and environmental conditions, such as atmospheric turbulence and solar radiation, that affect CO(2) exchange between leaves and the atmosphere. Here we present 30 years' worth of data on (18)O/(16)O in CO(2) from the Scripps Institution of Oceanography global flask network and show that the interannual variability is strongly related to the El Niño/Southern Oscillation. We suggest that the redistribution of moisture and rainfall in the tropics during an El Niño increases the (18)O/(16)O ratio of precipitation and plant water, and that this signal is then passed on to atmospheric CO(2) by biosphere-atmosphere gas exchange. We show how the decay time of the El Niño anomaly in this data set can be useful in constraining global gross primary production. Our analysis shows a rapid recovery from El Niño events, implying a shorter cycling time of CO(2) with respect to the terrestrial biosphere and oceans than previously estimated. Our analysis suggests that current estimates of global gross primary production, of 120 petagrams of carbon per year, may be too low, and that a best guess of 150-175 petagrams of carbon per year better reflects the observed rapid cycling of CO(2). Although still tentative, such a revision would present a new benchmark by which to evaluate global biospheric carbon cycling models.
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Griffis TJ, Lee X, Baker JM, Billmark K, Schultz N, Erickson M, Zhang X, Fassbinder J, Xiao W, Hu N. Oxygen isotope composition of evapotranspiration and its relation to C4photosynthetic discrimination. ACTA ACUST UNITED AC 2011. [DOI: 10.1029/2010jg001514] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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Zona D, Oechel WC, Richards JH, Hastings S, Kopetz I, Ikawa H, Oberbauer S. Light-stress avoidance mechanisms in aSphagnum-dominated wet coastal Arctic tundra ecosystem in Alaska. Ecology 2011; 92:633-44. [DOI: 10.1890/10-0822.1] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
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Xiao W, Lee X, Griffis TJ, Kim K, Welp LR, Yu Q. A modeling investigation of canopy-air oxygen isotopic exchange of water vapor and carbon dioxide in a soybean field. ACTA ACUST UNITED AC 2010. [DOI: 10.1029/2009jg001163] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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