@article{worm_saffer_takeuchi_walden-schreiner_jones_meentemeyer_2024, title={Border Interceptions Reveal Variable Bridgehead Use in the Global Dispersal of Insects}, volume={10}, ISSN={["1466-8238"]}, DOI={10.1111/geb.13924}, abstractNote={ABSTRACT Aim The global, human‐mediated dispersal of invasive insects is a major driver of ecosystem change, biodiversity loss, crop damage and other effects. Trade flows and invasive species propagule pressure are correlated, and their relationship is essential for predicting and managing future invasions. Invaders do not disperse exclusively from the species' native range. Instead, the bridgehead effect, where established, non‐native populations act as secondary sources of propagule, is recognised as a major driver of global invasion. The resulting pattern of global spread arises from a mixture of global interactions between invasive species, their vectors and, their invaded ranges, which has yet to be fully characterised. Location Global. Time Period 1997–2020. Major Taxa Studied Insects. Methods We analysed 319,283 border interception records of 514 insect species from a broad range of taxa from four national‐level phytosanitary organisations. We classified interceptions as coming from species native range or from bridgehead countries and examined taxonomic autocorrelation of global movement patterns between species. Results While 65% of interceptions originated from bridgehead countries, highlighting the importance of the bridgehead effect across taxa, patterns among individual species were highly variable and taxonomically correlated. Forty per cent of species originated almost exclusively from their native range, 28% almost exclusively from their non‐native range and 32% from a mix of source locations. These patterns of global dispersal were geographically widespread, temporally consistent, and taxonomically correlated. Conclusions Dispersal exclusively from bridgeheads represents an unrecognised pattern of global insect movement; these patterns emphasise the importance of the bridgehead effect and suggest that bridgeheads provide unique local conditions that allow invaders to proliferate differently than in their native range. We connect these patterns of global dispersal to the conditions during the human driven global dispersal of insects and provide recommendations for modellers and policymakers wishing to control the spread of future invasions.}, journal={GLOBAL ECOLOGY AND BIOGEOGRAPHY}, author={Worm, Thom and Saffer, Ariel and Takeuchi, Yu and Walden-Schreiner, Chelsey and Jones, Chris and Meentemeyer, Ross}, year={2024}, month={Oct} }
 @article{saffer_worm_takeuchi_meentemeyer_2024, title={GIATAR: a Spatio-temporal Dataset of Global Invasive and Alien Species and their Traits}, volume={11}, ISSN={["2052-4463"]}, DOI={10.1038/s41597-024-03824-w}, abstractNote={Monitoring and managing the global spread of invasive and alien species requires accurate spatiotemporal records of species presence and information about the biological characteristics of species of interest including life cycle information, biotic and abiotic constraints and pathways of spread. The Global Invasive and Alien Traits And Records (GIATAR) dataset provides consolidated dated records of invasive and alien presence at the country-scale combined with a suite of biological information about pests of interest in a standardized, machine-readable format. We provide dated presence records for 46,666 alien taxa in 249 countries constituting 827,300 country-taxon pairs in locations where the taxon's invasive status is either alien, invasive, or unknown, joined with additional biological information for thousands of taxa. GIATAR is designed to be quickly updateable with future data and easy to integrate into ongoing research on global patterns of alien species movement using scripts provided to query and analyze data. GIATAR provides crucial data needed for researchers and policymakers to compare global invasion trends across a wide range of taxa.}, number={1}, journal={SCIENTIFIC DATA}, author={Saffer, Ariel and Worm, Thom and Takeuchi, Yu and Meentemeyer, Ross}, year={2024}, month={Sep} }
 @article{kim_koop_fowler_israel_takeuchi_lieurance_2023, title={Addition of finer scale data and uncertainty analysis increases precision of geospatial suitability model for non-native plants in the US}, volume={484}, ISSN={["1872-7026"]}, url={http://dx.doi.org/10.1016/j.ecolmodel.2023.110458}, DOI={10.1016/j.ecolmodel.2023.110458}, abstractNote={“Proto3” is a geospatial model used by the United States Department of Agriculture (USDA) Plant Protection and Quarantine to predict the potential distribution of non-native weed species in the continental U.S. as part of routine weed risk assessments (WRA). While performing as well as other methods, this tool has the benefit of being simple to produce, expanding accessibility and reproducibility. However, it has the tendency to overestimate potential distributions. To address this shortcoming, this paper introduces the “Proto4” model and compares it with the established and mechanistically similar “Proto3” model currently used. Both models overlay Plant Hardiness Zones, precipitation, and Köppen-Geiger climate classes with global distribution of a plant species and rely on semi-qualitative assessments of a plant's affinity for each of the climate categories. However, Proto4 uses more detailed layers of the Plant Hardiness Zones and Köppen-Geiger climate classes, adds elevation as a fourth predictive variable to increase the precision of predictive maps. Additionally, we incorporate uncertainty to spatially distinguish regions of different potential suitability. We compared the performance of both models by estimating the predicted distributions of 30 broadly distributed, invasive plants in the U.S. with Proto3 and Proto4. We found that on average, the Proto4 model produces predicted distributions that are nearly 780,000 square kilometers (an area larger than the state of Texas) smaller than the Proto3, while only failing to capture a median of fewer than 0.5% more georeferenced points. Furthermore, the inclusion of uncertainty classes adds to the utility of Proto4 by distinguishing areas with greater and lesser degrees of evidence that a particular area is suitable for an invasive species, providing more information to help select invasive species prevention and management prioritization strategies.}, journal={ECOLOGICAL MODELLING}, publisher={Elsevier BV}, author={Kim, Seokmin and Koop, Anthony and Fowler, Glenn and Israel, Kimberly and Takeuchi, Yu and Lieurance, Deah}, year={2023}, month={Oct} }
 @article{takeuchi_tripodi_montgomery_2023, title={SAFARIS: a spatial analytic framework for pest forecast systems}, volume={3}, ISSN={["2673-8600"]}, url={http://dx.doi.org/10.3389/finsc.2023.1198355}, DOI={10.3389/finsc.2023.1198355}, abstractNote={Non-native pests and diseases pose a risk of economic and environmental damage to managed and natural U.S. forests and agriculture. The U.S. Department of Agriculture (USDA) Animal and Plant Health Inspection Service (APHIS) Plant Protection and Quarantine (PPQ) protects the health of U.S. agriculture and natural resources against invasive pests and diseases through efforts to prevent the entry, establishment, and spread of non-native pests and diseases. Because each pest or disease has its own idiosyncratic characteristics, analyzing risk is highly complex. To help PPQ better respond to pest and disease threats, we developed the Spatial Analytic Framework for Advanced Risk Information Systems (SAFARIS), an integrated system designed to provide a seamless environment for producing predictive models. SAFARIS integrates pest biology information, climate and non-climate data drivers, and predictive models to provide users with readily accessible and easily customizable tools to analyze pest and disease risks. The phenology prediction models, spread forecasting models, and other climate-based analytical tools in SAFARIS help users understand which areas are suitable for establishment, when surveys would be most fruitful, and aid in other analyses that inform decision-making, operational efforts, and rapid response. Here we introduce the components of SAFARIS and provide two use cases demonstrating how pest-specific models developed with SAFARIS tools support PPQ in its mission. Although SAFARIS is designed to address the needs of PPQ, the flexible, web-based framework is publicly available, allowing any user to leverage the available data and tools to model pest and disease risks.}, journal={FRONTIERS IN INSECT SCIENCE}, publisher={Frontiers Media SA}, author={Takeuchi, Yu and Tripodi, Amber and Montgomery, Kellyn}, year={2023}, month={Jul} }
 @article{montgomery_petras_takeuchi_katsar_2022, title={Contaminated consignment simulation to support risk-based inspection design}, volume={5}, ISSN={["1539-6924"]}, url={https://doi.org/10.1111/risa.13943}, DOI={10.1111/risa.13943}, abstractNote={AbstractInvasive nonnative plant pests can cause extensive environmental and economic damage and are very difficult to eradicate once established. Phytosanitary inspections that aim to prevent biological invasions by limiting movement of nonnative plant pests across borders are a critical component of the biosecurity continuum. Inspections can also provide valuable information about when and where plant pests are crossing national boundaries. However, only a limited portion of the massive volume of goods imported daily can be inspected, necessitating a highly targeted, risk‐based strategy. Furthermore, since inspections must prioritize detection and efficiency, their outcomes generally cannot be used to make inferences about risk for cargo pathways as a whole. Phytosanitary agencies need better tools for quantifying pests going undetected and designing risk‐based inspection strategies appropriate for changing operational conditions. In this research, we present PoPS (Pest or Pathogen Spread) Border, an open‐source consignment inspection simulator for measuring inspection outcomes under various cargo contamination scenarios to support recommendations for inspection protocols and estimate pest slippage rates. We used the tool to estimate contamination rates of historical interception data, quantify tradeoffs in effectiveness and workload for inspection strategies, and identify vulnerabilities in sampling protocols as changes in cargo configurations and contamination occur. These use cases demonstrate how this simulation approach permits testing inspection strategies and measuring quantities that would otherwise be impossible in a field‐based setting. This work represents the first steps toward a decision support tool for creating dynamic inspection protocols that respond to changes in available resources, workload, and commerce trends.}, journal={RISK ANALYSIS}, author={Montgomery, Kellyn and Petras, Vaclav and Takeuchi, Yu and Katsar, Catherine S.}, year={2022}, month={May} }
 @article{takeuchi_benavides_johnson_follett_hossain_navarro_giraldo_2022, title={Pathway analysis: Likelihood of coffee berry borer (Hypothenemus hampei Ferrari) introduction into the Hawaiian Islands by air passenger travel}, publisher={Hawaiian Entomological Society}, author={Takeuchi, Yu and Benavides, Pablo and Johnson, Melissa A and Follett, Peter A and Hossain, Mohammad Khalid and Navarro, Lucio and Giraldo, Marisol}, year={2022} }
 @article{jones_skrip_seliger_jones_wakie_takeuchi_petras_petrasova_meentemeyer_2022, title={Spotted lanternfly predicted to establish in California by 2033 without preventative management}, volume={5}, ISSN={["2399-3642"]}, url={https://doi.org/10.1038/s42003-022-03447-0}, DOI={10.1038/s42003-022-03447-0}, abstractNote={AbstractModels that are both spatially and temporally dynamic are needed to forecast where and when non-native pests and pathogens are likely to spread, to provide advance information for natural resource managers. The potential US range of the invasive spotted lanternfly (SLF, Lycorma delicatula) has been modeled, but until now, when it could reach the West Coast’s multi-billion-dollar fruit industry has been unknown. We used process-based modeling to forecast the spread of SLF assuming no treatments to control populations occur. We found that SLF has a low probability of first reaching the grape-producing counties of California by 2027 and a high probability by 2033. Our study demonstrates the importance of spatio-temporal modeling for predicting the spread of invasive species to serve as an early alert for growers and other decision makers to prepare for impending risks of SLF invasion. It also provides a baseline for comparing future control options.}, number={1}, journal={COMMUNICATIONS BIOLOGY}, author={Jones, Chris and Skrip, Megan M. and Seliger, Benjamin J. and Jones, Shannon and Wakie, Tewodros and Takeuchi, Yu and Petras, Vaclav and Petrasova, Anna and Meentemeyer, Ross K.}, year={2022}, month={Jun} }
 @misc{xia_ouyang_takeuchi_2021, title={A Brief Review of Resseliella citrifrugis (Diptera: Cecidomyiidae), a Lesser-Known Destructive Citrus Fruit Pest}, volume={12}, ISSN={["2155-7470"]}, url={https://doi.org/10.1093/jipm/pmab033}, DOI={10.1093/jipm/pmab033}, abstractNote={AbstractThe gall midge, Resselielia citrifrugis Jiang (Diptera: Cecidomyiidae), is a major citrus pest in China. The pest occurs widely in regions with tropical, subtropical, and temperate climates. Larvae feed inside the fruit, leading to premature fruit drop or damaged fruits. An infested fruit can have hundreds of larvae in it. The extent of losses varies, usually between 10 and 100%, depending on the grove management level. Resselielia citrifrugis hosts include common citrus varieties. China has no area-wide management program against the pest. Field pest management measures include grove sanitation, fruit bagging, and pesticide applications. This review identifies three scientific and technological gaps that need to be filled to protect the U.S. citrus industry from this pest. First, the taxonomical and systematic status of R. citrifrugis needs to be clarified and validated before the pest can be effectively regulated. Second, traps and/or lures for early detection of the pest need to be developed before the pest arrival. Third, pest risk mitigation measures against the pest need to be evaluated and strengthened.}, number={1}, journal={JOURNAL OF INTEGRATED PEST MANAGEMENT}, publisher={Oxford University Press (OUP)}, author={Xia, Yulu and Ouyang, Ge-Cheng and Takeuchi, Yu}, editor={Tindall, KellyEditor}, year={2021}, month={Jan} }
 @article{jones_jones_petrasova_petras_gaydos_skrip_takeuchi_bigsby_meentemeyer_2021, title={Iteratively forecasting biological invasions with PoPS and a little help from our friends}, volume={6}, ISSN={["1540-9309"]}, url={http://dx.doi.org/10.1002/fee.2357}, DOI={10.1002/fee.2357}, abstractNote={Ecological forecasting has vast potential to support environmental decision making with repeated, testable predictions across management‐relevant timescales and locations. Yet resource managers rarely use co‐designed forecasting systems or embed them in decision making. Although prediction of planned management outcomes is particularly important for biological invasions to optimize when and where resources should be allocated, spatial–temporal models of spread typically have not been openly shared, iteratively updated, or interactive to facilitate exploration of management actions. We describe a species‐agnostic, open‐source framework – called the Pest or Pathogen Spread (PoPS) Forecasting Platform – for co‐designing near‐term iterative forecasts of biological invasions. Two case studies are presented to demonstrate that iterative calibration yields higher forecast skill than using only the earliest‐available data to predict future spread. The PoPS framework is a primary example of an ecological forecasting system that has been both scientifically improved and optimized for real‐world decision making through sustained participation and use by management stakeholders.}, number={7}, journal={FRONTIERS IN ECOLOGY AND THE ENVIRONMENT}, publisher={Wiley}, author={Jones, Chris M. and Jones, Shannon and Petrasova, Anna and Petras, Vaclav and Gaydos, Devon and Skrip, Megan M. and Takeuchi, Yu and Bigsby, Kevin and Meentemeyer, Ross K.}, year={2021}, month={Jun} }
 @article{takeuchi_koch_nelson_2021, title={Recent Immigrant Insect Fauna—Another Look at a Classic Analysis}, volume={12}, ISSN={2155-7470}, url={http://dx.doi.org/10.1093/jipm/pmab034}, DOI={10.1093/jipm/pmab034}, abstractNote={Abstract
               In 1978, Reece Sailer published a seminal retrospective entitled ‘Our Immigrant Insect Fauna.’ His goals were to better understand the origins and historical patterns of alien insect species introductions into the United States and establish a baseline for future work to improve our ability to respond to environmental and agricultural well-being threats. We updated Sailer’s study to include information on species introduced recently into the United States and that are now targeted by regulatory agencies. The recent trends (recorded through 2016) are different from those reported by Sailer. Asian-origin species are much more important than in 1978 and predominate today. Nevertheless, introductions from all parts of the world have continued. Although the diversity of alien species’ origins has increased through time, there has not been a corresponding change in the rate of introductions of species of phytosanitary importance. This finding is inconsistent with our original assumption of a positive nonlinear relationship with international trade imports. Our findings will assist in identifying and prioritizing potential high-risk plant pests as well as enhancing biosecurity capacities.}, number={1}, journal={Journal of Integrated Pest Management}, publisher={Oxford University Press (OUP)}, author={Takeuchi, Yu and Koch, Frank H and Nelson, Stacy A C}, editor={Green, JodyEditor}, year={2021}, month={Jan} }
 @article{kim_hantula_kaitera_zambino_woodward_richardson_stewart_spaine_shaw_takeuchi_et al._2022, title={Recovery Plan for Scots Pine Blister Rust Caused by Cronartium pini}, volume={23}, ISSN={["1535-1025"]}, url={https://doi.org/10.1094/PHP-06-21-0099-RP}, DOI={10.1094/PHP-06-21-0099-RP}, abstractNote={ Scots pine blister rust caused by Cronartium pini, which includes the fungal rust pathogen with either a heteroecious life cycle (previously known as Cronartium flaccidum) or an autoecious life cycle (formerly known as Peridermium pini or Endocronartium pini), is capable of infecting many Eurasian pines including Pinus sylvestris (Scots pine). The heteroecious form of C. pini completes its life cycle alternating between pines and various species of flowering plants (Angiospermae); the related autoecious form spreads directly from pine to pine. If the Scots pine blister rust pathogen possesses or gains the capacity to infect North American pines, the economic and ecological impacts could be significant. Scots pine is one of the most widely distributed conifers in the world, and it has become naturalized in the northeastern and midwestern United States. Scots pine blister rust is also called resin-top disease and top-dieback of pine. Symptoms in pine include stem swelling, branch flagging, excessive pitch flow, and top-kill, and, in the alternate hosts, leaf spotting. The rust pathogen is spread in nature by wind-borne spores, which require live hosts for infection. However, the rust pathogen can also be transported on infected plant materials that can be nonsymptomatic. Early infections of host plant infections by C. pini are difficult to detect and diagnose, but molecular techniques offer a potential approach for early detection and diagnosis. This recovery plan is intended to provide a brief summary of the disease, assess the status of critical recovery components, and identify disease management research, extension, and education needs. }, number={1}, journal={PLANT HEALTH PROGRESS}, publisher={Scientific Societies}, author={Kim, Mee-Sook and Hantula, Jarkko and Kaitera, Juha and Zambino, Paul J. and Woodward, Stephen and Richardson, Bryce A. and Stewart, Jane E. and Spaine, Pauline and Shaw, David C. and Takeuchi, Yu and et al.}, year={2022}, pages={105–130} }
 @article{krishnankutty_bigsby_hastings_takeuchi_wu_lingafelter_nadel_myers_ray_jeffrey_2020, title={Predicting Establishment Potential of an Invasive Wood-Boring Beetle, Trichoferus campestris (Coleoptera: Cerambycidae) in the United States}, volume={113}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-85084134943&partnerID=MN8TOARS}, DOI={10.1093/aesa/saz051}, abstractNote={AbstractSolid wood packaging material (WPM) is widely recognized as a high-risk pathway for transport and potential introduction of wood-boring insects, including longhorned beetles in the family Cerambycidae. These beetles also are occasionally imported in finished wood products, such as furniture and decorative items. A targeted effort to identify wood borers intercepted as larvae in WPM at U.S. ports between 2012 and 2018 revealed that one of the most frequently intercepted species was Trichoferus campestris (Faldermann), a cerambycid native to Asia. Trichoferus campestris is a pest of quarantine concern in the United States, Canada, and Europe. The establishment risk of this beetle in the United States is high because of its frequent introduction through multiple pathways and its potential to inhabit natural and urban forests as well as agricultural systems. In this study, we compiled port interception and detection data to examine risk based on historical introductions and pathways. We tested whether the intended destination of cargo intercepted with T. campestris-infested WPM can be used as a predictor of inland introductions, assuming that individuals of T. campestris are likely to be moved through established trade routes between export–import partners. We also developed maps to predict likely areas of introduction and establishment in the United States based on pathway analysis and climate suitability data. The maps will enable informed prioritization of resources in pest surveillance, and may serve as models for other wood borers identified in the WPM and wood products pathway.}, number={2}, journal={Annals of the Entomological Society of America}, author={Krishnankutty, S.M. and Bigsby, K. and Hastings, J. and Takeuchi, Y. and Wu, Y. and Lingafelter, S.W. and Nadel, H. and Myers, S.W. and Ray, A.M. and Jeffrey, M.}, year={2020}, pages={88–99} }
 @article{magarey_newton_hong_takeuchi_christie_jarnevich_kohl_damus_higgins_millar_et al._2018, title={Comparison of four modeling tools for the prediction of potential distribution for non-indigenous weeds in the United States}, volume={20}, ISSN={["1573-1464"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-85029595135&partnerID=MN8TOARS}, DOI={10.1007/s10530-017-1567-1}, number={3}, journal={BIOLOGICAL INVASIONS}, publisher={Springer Science and Business Media LLC}, author={Magarey, Roger and Newton, Leslie and Hong, Seung Cheon and Takeuchi, Yu and Christie, David and Jarnevich, Catherine S. and Kohl, Lisa and Damus, Martin and Higgins, Steven I. and Millar, Leah and et al.}, year={2018}, month={Mar}, pages={679–694} }
 @article{graham_gottwald_timmer_filho_van den bosch_irey_taylor_magarey_takeuchi_2014, title={Response to "Potential distribution of citrus black spot in the United States based on climatic conditions", Er et al. 2013}, volume={139}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84899736286&partnerID=MN8TOARS}, DOI={10.1007/s10658-014-0426-5}, number={2}, journal={European Journal of Plant Pathology}, author={Graham, J.H. and Gottwald, T.R. and Timmer, L.W. and Filho, A.B. and Van Den Bosch, F. and Irey, M.S. and Taylor, E. and Magarey, R.D. and Takeuchi, Y.}, year={2014}, pages={231–234} }
 @article{graham_gottwald_timmer_bergamin_bosch_irey_taylor_magarey_takeuchi_2014, title={Response to "Potential distribution of citrus black spot in the United States based on climatic conditions", Er et al. 2013}, volume={139}, number={2}, journal={European Journal of Plant Pathology}, author={Graham, J. H. and Gottwald, T. R. and Timmer, L. W. and Bergamin, A. and Bosch, F. and Irey, M. S. and Taylor, E. and Magarey, R. D. and Takeuchi, Y.}, year={2014}, pages={231–234} }
 @inbook{fowler_takeuchi_2012, title={Mapping, climate and geographic information for risk analysis}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84890230584&partnerID=MN8TOARS}, booktitle={Plant Pest Risk Analysis: Concepts and Application}, author={Fowler, G. and Takeuchi, T.}, year={2012}, pages={151–163} }
 @article{kubiske_zak_pregitzer_takeuchi_2002, title={Photosynthetic acclimation of overstory Populus tremuloides and understory Acer saccharum to elevated atmospheric CO<inf>2</inf> concentration: Interactions with shade and soil nitrogen}, volume={22}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-0036000103&partnerID=MN8TOARS}, DOI={10.1093/treephys/22.5.321}, abstractNote={We exposed Populus tremuloides Michx. and Acer saccharum Marsh. to a factorial combination of ambient and elevated atmospheric CO2 concentrations ([CO2]) and high-nitrogen (N) and low-N soil treatments in open-top chambers for 3 years. Our objective was to compare photosynthetic acclimation to elevated [CO2] between species of contrasting shade tolerance, and to determine if soil N or shading modify the acclimation response. Sun and shade leaf responses to elevated [CO2] and soil N were compared between upper and lower canopy leaves of P. tremuloides and between A. saccharum seedlings grown with and without shading by P. tremuloides. Both species had higher leaf N concentrations and photosynthetic rates in high-N soil than in low-N soil, and these characteristics were higher for P. tremuloides than for A. saccharum. Electron transport capacity (Jmax) and carboxylation capacity (Vcmax) generally decreased with atmospheric CO2 enrichment in all 3 years of the experiment, but there was no evidence that elevated [CO2] altered the relationship between them. On a leaf area basis, both Jmax and Vcmax acclimated to elevated [CO2] more strongly in shade leaves than in sun leaves of P. tremuloides. However, the apparent [CO2] × shade interaction was largely driven by differences in specific leaf area (m2 g−1) between sun and shade leaves. In A. saccharum, photosynthesis acclimated more strongly to elevated [CO2] in sun leaves than in shade leaves on both leaf area and mass bases. We conclude that trees rooted freely in the ground can exhibit photosynthetic acclimation to elevated [CO2], and the response may be modified by light environment. The hypothesis that photosynthesis acclimates more completely to elevated [CO2] in shade-tolerant species than in shade-intolerant species was not supported.}, number={5}, journal={Tree Physiology}, author={Kubiske, M.E. and Zak, D.R. and Pregitzer, K.S. and Takeuchi, Y.}, year={2002}, pages={321–329} }
 @article{takeuchi_kubiske_isebrands_pregtizer_hendrey_karnosky_2001, title={Photosynthesis, light and nitrogen relationships in a young deciduous forest canopy under open-air CO<inf>2</inf> enrichment}, volume={24}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-0035666015&partnerID=MN8TOARS}, DOI={10.1046/j.0016-8025.2001.00787.x}, abstractNote={AbstractLeaf photosynthesis (Ps), nitrogen (N) and light environment were measured on Populus tremuloides trees in a developing canopy under free‐air CO2 enrichment in Wisconsin, USA. After 2 years of growth, the trees averaged 1·5 and 1·6 m tall under ambient and elevated CO2, respectively, at the beginning of the study period in 1999. They grew to 2·6 and 2·9 m, respectively, by the end of the 1999 growing season. Daily integrated photon flux from cloud‐free days (PPFDday,sat) around the lowermost branches was 16·8 ± 0·8 and 8·7 ± 0·2% of values at the top for the ambient and elevated CO2 canopies, respectively. Elevated CO2 significantly decreased leaf N on a mass, but not on an area, basis. N per unit leaf area was related linearly to PPFDday,sat throughout the canopies, and elevated CO2 did not affect that relationship. Leaf Ps light‐response curves responded differently to elevated CO2, depending upon canopy position. Elevated CO2 increased Pssat only in the upper (unshaded) canopy, whereas characteristics that would favour photosynthesis in shade were unaffected by elevated CO2. Consequently, estimated daily integrated Ps on cloud‐free days (Psday,sat) was stimulated by elevated CO2 only in the upper canopy. Psday,sat of the lowermost branches was actually lower with elevated CO2 because of the darker light environment. The lack of CO2 stimulation at the mid‐ and lower canopy was probably related to significant down‐regulation of photosynthetic capacity; there was no down‐regulation of Ps in the upper canopy. The relationship between Psday,sat and leaf N indicated that N was not optimally allocated within the canopy in a manner that would maximize whole‐canopy Ps or photosynthetic N use efficiency. Elevated CO2 had no effect on the optimization of canopy N allocation.}, number={12}, journal={Plant, Cell and Environment}, author={Takeuchi, Y. and Kubiske, M.E. and Isebrands, J.G. and Pregtizer, K.S. and Hendrey, G. and Karnosky, D.F.}, year={2001}, pages={1257–1268} }