Scientific Merits and Analytical Challenges of Tree‐Ring Densitometry

X-ray microdensitometry on annually resolved tree-ring samples has gained an exceptional position in last-millennium paleoclimatology through the maximum latewood density (MXD) parameter, but also increasingly through other density parameters. For 50 years, X-ray based measurement techniques have been the de facto standard. However, studies report offsets in the mean levels for MXD measurements derived from different laboratories, indicating challenges of accuracy and precision. Moreover, reflected visible light-based techniques are becoming increasingly popular, and wood anatomical techniques are emerging as a potentially powerful pathway to extract density information at the highest resolution. Here we review the current understanding and merits of wood density for tree-ring research, associated microdensitometric techniques, and analytical measurement challenges. The review is further complemented with a careful comparison of new measurements derived at 17 laboratories, using several different techniques. The new experiment allowed us to corroborate and refresh "long-standing wisdom" but also provide new insights. Key outcomes include (i) a demonstration of the need for mass/volume-based recalibration to accurately estimate average ring density; (ii) a substantiation of systematic differences in MXD measurements that cautions for great care when combining density data sets for climate reconstructions; and (iii) insights into the relevance of analytical measurement resolution in signals derived from tree-ring density data. Finally, we provide recommendations expected to facilitate futureinter-comparability and interpretations for global change research.

[1]  D. Frank,et al.  Synoptic drivers of 400 years of summer temperature and precipitation variability on Mt. Olympus, Greece , 2015, Climate Dynamics.

[2]  M. Hughes,et al.  Separating the climatic signal from tree-ring width and maximum latewood density records , 2006, Trees.

[3]  R. Funada,et al.  The effects of tracheid dimensions on variations in maximum density of Picea glehnii and relationships to climatic factors , 2000, Trees.

[4]  David Frank,et al.  Long-term summer temperature variations in the Pyrenees , 2008 .

[5]  E. Cook,et al.  Last millennium Northern Hemisphere summer temperatures from tree rings: Part II, spatially resolved reconstructions , 2017 .

[6]  Philippe Ciais,et al.  A tree-ring perspective on the terrestrial carbon cycle , 2014, Oecologia.

[7]  B. Luckman,et al.  Summer temperatures in the Canadian Rockies during the last millennium: a revised record , 2005 .

[8]  H. Linderholm,et al.  Fennoscandia revisited: a spatially improved tree-ring reconstruction of summer temperatures for the last 900 years , 2015, Climate Dynamics.

[9]  M. Carrer,et al.  Tree-ring anatomy and carbon isotope ratio show both direct and legacy effects of climate on bimodal xylem formation in Pinus pinea , 2018, Tree physiology.

[10]  E. Nikinmaa,et al.  Above-ground woody carbon sequestration measured from tree rings is coherent with net ecosystem productivity at five eddy-covariance sites. , 2014, The New phytologist.

[11]  F. Telewski,et al.  Measuring Maximum Latewood Density By Image Analysis At The Cellular Level , 2007 .

[12]  H. Polge.  Une nouvelle méthode de détermination de la texture du bois - L'analyse densitométrique de clichés radiographiques , 1963 .

[13]  Valerie Trouet,et al.  The value of crossdating to retain high‐frequency variability, climate signals, and extreme events in environmental proxies , 2016, Global change biology.

[14]  V. V. Stasova,et al.  Effects of environmental factors on wood formation in larch (Larix sibirica Ldb.) stems , 1997, Trees.

[15]  E. Cook,et al.  Methods of Dendrochronology - Applications in the Environmental Sciences , 1991 .

[16]  E. Cook,et al.  Spatial reconstruction of Scottish summer temperatures from tree rings , 2017 .

[17]  E. Cook,et al.  Preliminary December–January inflow and streamflow reconstructions from tree rings for western Tasmania, southeastern Australia , 2015 .

[18]  Dan Smith,et al.  Multi‐century reconstructions of Pacific salmon abundance from climate‐sensitive tree rings in west central British Columbia, Canada , 2013 .

[19]  Hanna M. Mäkelä,et al.  A palaeotemperature record for the Finnish Lakeland based on microdensitometric variations in tree rings , 2014 .

[20]  J. Wilson,et al.  Comparison of video and X-ray for scanning wood density , 1991 .

[21]  H. Polge.  Fifteen years of wood radiation densitometry , 1978, Wood Science and Technology.

[22]  F. Babst,et al.  Effect of sample preparation and scanning resolution on the Blue Reflectance of Picea abies , 2009 .

[23]  Adrian Luckman,et al.  Blue Reflectance Provides a Surrogate for Latewood Density of High-latitude Pine Tree Rings , 2002 .

[24]  S. Gómez,et al.  Applying methods of hard tissues preparation for wood anatomy: Imaging polished samples embedded in polymethylmethacrylate , 2018, Dendrochronologia.

[25]  L. Poorter.  The relationships of wood-, gas- and water fractions of tree stems to performance and life history variation in tropical trees. , 2008, Annals of botany.

[26]  M. Dannenberg,et al.  Seasonal climate signals from multiple tree ring metrics: A case study of Pinus ponderosa in the upper Columbia River Basin , 2016 .

[27]  H. Gärtner,et al.  The core-microtome: A new tool for surface preparation on cores and time series analysis of varying cell parameters , 2010 .

[28]  G. K. Elliott.  Wood density in conifers. , 1970 .

[29]  H. Linderholm,et al.  Using adjusted Blue Intensity data to attain high-quality summer temperature information: A case study from Central Scandinavia , 2015 .

[30]  Campbell O. Webb,et al.  Relationships among ecologically important dimensions of plant trait variation in seven neotropical forests. , 2007, Annals of botany.

[31]  Robert Evans,et al.  Rapid Measurement of the Transverse Dimensions of Tracheids in Radial Wood Sections from Pinus radiata , 1994 .

[32]  R. Wimmer,et al.  Understanding wood formation: gains to commercial forestry through tree-ring research , 2002 .

[33]  Marco Carrer,et al.  Quantitative Wood Anatomy—Practical Guidelines , 2016, Front. Plant Sci..

[34]  Annette M. Harte,et al.  Qualification of Wood Adhesives for Structural Softwood Glulam with Large Juvenile Wood Content , 2008 .

[35]  D. Frank,et al.  Growth responses to climate in a multi-species tree-ring network in the Western Carpathian Tatra Mountains, Poland and Slovakia. , 2007, Tree physiology.

[36]  D. Yamaguchi.  A simple method for cross-dating increment cores from living trees , 1991 .

[37]  K. Anchukaitis,et al.  Volcanic cooling signal in tree ring temperature records for the past millennium , 2013 .

[38]  Barbara L. Gartner,et al.  Patterns of xylem variation within a tree and their hydraulic and mechanical consequences , 1995 .

[39]  E. Mosley‐Thompson,et al.  High-resolution palaeoclimatology of the last millennium: a review of current status and future prospects , 2009 .

[40]  K. Griffin,et al.  Blue intensity from a tropical conifer’s annual rings for climate reconstruction: An ecophysiological perspective , 2018, Dendrochronologia.

[41]  E. Cook,et al.  Lack of cool, not warm, extremes distinguishes late 20th Century climate in 979-year Tasmanian summer temperature reconstruction , 2018 .

[42]  S. Los,et al.  A 1200-year multiproxy record of tree growth and summer temperature at the northern pine forest limit of Europe , 2013 .

[43]  D. Bonte,et al.  Competition, tree age and size drive the productivity of mixed forests of pedunculate oak, beech and red oak , 2018, Forest Ecology and Management.

[44]  B. Gardiner,et al.  Effect of early release from intense competition within high density natural regeneration on the properties of juvenile and mature wood of 40-year-old Sitka spruce (Picea sitchensis (Bong.) Carr.) , 2014, Annals of Forest Science.

[45]  Peter Groenendijk,et al.  Detecting long‐term growth trends using tree rings: a critical evaluation of methods , 2015, Global change biology.

[46]  B. Luckman,et al.  Blue Intensity for dendroclimatology: The BC blues: A case study from British Columbia, Canada , 2014 .

[47]  H. Gärtner,et al.  The advantage of using a starch based non-Newtonian fluid to prepare micro sections , 2013 .

[48]  E. Lehmann,et al.  Neutron imaging versus standard X-ray densitometry as method to measure tree-ring wood density , 2009, Trees.

[49]  S. Mayr,et al.  The Hydraulic Architecture of Conifers , 2015 .

[50]  I. C. Prentice,et al.  Evaluation of the terrestrial carbon cycle, future plant geography and climate‐carbon cycle feedbacks using five Dynamic Global Vegetation Models (DGVMs) , 2008 .

[51]  M Dierick,et al.  A LabVIEW® based generic CT scanner control software platform. , 2010, Journal of X-ray science and technology.

[52]  David Frank,et al.  Warmer early instrumental measurements versus colder reconstructed temperatures: shooting at a moving target , 2007 .

[53]  A. Stokes,et al.  Wood formation in trees. , 2001, Plant physiology.

[54]  Heinrich Spiecker,et al.  HIGH-FREQUENCY DENSITOMETRY - A NEW METHOD FOR THE RAPID EVALUATION OF WOOD DENSITY VARIATIONS , 2003 .

[55]  Dan Smith,et al.  Extending the Place Glacier mass-balance record to AD 1585, using tree rings and wood density , 2011, Quaternary Research.

[56]  George Jeronimidis,et al.  Wood Quality and its Biological Basis , 2003 .

[57]  S. Payette,et al.  Relationships between anatomical and densitometric characteristics of black spruce and summer temperature at tree line in northern Quebec , 2002 .

[58]  Paul M. Winistorfer,et al.  Direct scanning densitometry: an effect of sample heterogeneity and aperture area. , 1990 .

[59]  K. Niklas.  PLANT HEIGHT AND THE PROPERTIES OF SOME HERBACEOUS STEMS , 1995 .

[60]  M. Carrer,et al.  New research perspectives from a novel approach to quantify tracheid wall thickness , 2017, Tree physiology.

[61]  Marc Stevens,et al.  X-ray tomography as a tool for detailed anatomical analysis , 2009, Annals of Forest Science.

[62]  M. Grosjean,et al.  Multi-archive summer temperature reconstruction for the European Alps, AD 1053–1996 , 2012 .

[63]  Veerle Cnudde,et al.  Recent Micro-CT Scanner Developments at UGCT , 2014 .

[64]  Tom Levanic,et al.  Atrics – A New System for Image Acquisition in Dendrochronology , 2007 .

[65]  Gordon C. Jacoby,et al.  An image analysis system for determining densitometric and ring-width time series , 1991 .

[66]  Holger Gärtner,et al.  Microscopic preparation techniques for plant stem analysis , 2014 .

[67]  R. Wimmer,et al.  EFFECTS OF HEARTWOOD EXTRACTIVES ON MECHANICAL PROPERTIES OF LARCH , 2005 .

[68]  Alexander Katsevich,et al.  Theoretically Exact Filtered Backprojection-Type Inversion Algorithm for Spiral CT , 2002, SIAM J. Appl. Math..

[69]  V. Masson‐Delmotte,et al.  Estimates of volcanic-induced cooling in the Northern Hemisphere over the past 1,500 years , 2015 .

[70]  A 449 year warm season temperature reconstruction in the southeastern Tibetan Plateau and its relation to solar activity , 2014 .

[71]  E. Schulze,et al.  Atlas of Stem Anatomy in Herbs, Shrubs and Trees: Volume 1 , 2011 .

[72]  B. Gartner,et al.  Wood density of young-growth western hemlock: relation to ring age, radial growth, stand density, and site quality , 2004 .

[73]  Hans Beeckman,et al.  A field-to-desktop toolchain for X-ray CT densitometry enables tree ring analysis. , 2016, Annals of botany.

[74]  Rupert Wimmer.  Intra-Annual Cellular Characteristics and their Implications for Modeling Softwood Density , 1995 .

[75]  Malcolm K. Hughes,et al.  Growth Dynamics of Conifer Tree Rings: Images of Past and Future Environments , 2006 .

[76]  D. Woodcock,et al.  Wood specific gravity and its radial variations: the many ways to make a tree , 2002, Trees.

[77]  G. Decocq,et al.  Evaluating the robustness of three ring-width measurement methods for growth release reconstruction , 2017 .

[78]  Olivier Bouriaud,et al.  Influence of wood density in tree-ring based annual productivity assessments and its errors in Norway spruce , 2015 .

[79]  Saudi Arabia,et al.  The CRUTEM4 land-surface air temperature data set: construction, previous versions and dissemination via , 2013 .

[80]  N. Stenseth,et al.  Causes and Consequences of Past and Projected Scandinavian Summer Temperatures, 500–2100 AD , 2011, PloS one.

[81]  M. Bridge.  Tree-Ring Dating , 2021, Encyclopedic Dictionary of Archaeology.

[82]  D. Frank,et al.  Five centuries of Central European temperature extremes reconstructed from tree-ring density and documentary evidence , 2009 .

[83]  T. Wodzicki.  Mechanism of Xylem Differentiation in Pinus silvestrisL. , 1971 .

[84]  A. Rindby,et al.  Batch measurements of wood density on intact or prepared drill cores using x-ray microdensitometry , 2001, Wood Science and Technology.

[85]  Fritz H. Schweingruber,et al.  Tree-ring width and density data around the Northern Hemisphere: Part 1, local and regional climate signals , 2002 .

[86]  Michael N. Evans,et al.  How Well Understood Are the Processes that Create Dendroclimatic Records? A Mechanistic Model of the Climatic Control on Conifer Tree-Ring Growth Dynamics , 2011 .

[87]  H. Polge.  Établissement des courbes de variation de la densité du bois par exploration densitométrique de radiographies d'échantillons prélevés à la tarière sur des arbres vivants : applications dans les domaines Technologique et Physiologique , 1966 .

[88]  O. Lenz,et al.  Methodische Probleme bei der radiographisch-densitometrischen Bestimmung der Dichte und der Jahrringbreiten von Holz , 1976 .

[89]  Cyrille B K Rathgeber,et al.  Woody biomass production lags stem-girth increase by over one month in coniferous forests , 2015, Nature Plants.

[90]  Bert Masschaele,et al.  3D tree-ring analysis using helical X-ray tomography , 2014 .

[91]  R. Sánchez‐Salguero,et al.  Towards a better understanding of long-term wood-chemistry variations in old-growth forests: A case study on ancient Pinus uncinata trees from the Pyrenees. , 2018, The Science of the total environment.

[92]  Marco Carrer,et al.  ROXAS – A new tool to build centuries-long tracheid-lumen chronologies in conifers , 2014 .

[93]  RosnerS.,et al.  Wood density as a screening trait for drought sensitivity in Norway spruce1 , 2014 .

[94]  D. J. Cown,et al.  A wood densitometer using direct scanning with X-rays , 1983, Wood Science and Technology.

[95]  David Frank,et al.  The influence of sampling design on tree‐ring‐based quantification of forest growth , 2014, Global change biology.

[96]  K. Briffa,et al.  A 1,400-year tree-ring record of summer temperatures in Fennoscandia , 1990, Nature.

[97]  Edward R. Cook,et al.  The 'segment length curse' in long tree-ring chronology development for palaeoclimatic studies , 1995 .

[98]  Paolo Cherubini,et al.  On the 'Divergence Problem' in Northern Forests: A review of the tree-ring evidence and possible causes , 2008 .

[99]  Scott St. George,et al.  Large-scale, millennial-length temperature reconstructions from tree-rings , 2018, Dendrochronologia.

[100]  J. Leban,et al.  Relationships between the intra-ring wood density assessed by X-ray densitometry and optical anatomical measurements in conifers. Consequences for the cell wall apparent density determination , 2004 .

[101]  H. Linderholm,et al.  A 970-year-long summer temperature reconstruction from Rogen, west-central Sweden, based on blue intensity from tree rings , 2018 .

[102]  E. Cook,et al.  THE SMOOTHING SPLINE: A NEW APPROACH TO STANDARDIZING FOREST INTERIOR TREE -RING WIDTH SERIES FOR DENDROCLIMATIC STUDIES , 1981 .

[103]  Q. Hua,et al.  A new method for dating tree-rings in trees with faint, indeterminate ring boundaries using the Itrax core scanner , 2018 .

[104]  D. Ray,et al.  Assessment of tree response to drought: validation of a methodology to identify and test proxies for monitoring past environmental changes in trees. , 2011, Tree physiology.

[105]  M. Carrer,et al.  Disentangling the climate-driven bimodal growth pattern in coastal and continental Mediterranean pine stands. , 2017, The Science of the total environment.

[106]  David Frank,et al.  Orbital forcing of tree-ring data , 2012 .

[107]  J. Lloyd.  DISTRIBUTION OF EXTRACTIVES IN PINUS RADIATA EARLYWOOD AND LATEWOOD , 1978 .

[108]  Martin A. R. Munro,et al.  Summer temperature in northeastern Siberia since 1642 reconstructed from tracheid dimensions and cell numbers of Larix cajanderi , 2003 .

[109]  B. Muys,et al.  Climate driven trends in tree biomass increment show asynchronous dependence on tree-ring width and wood density variation , 2018 .

[110]  M. Wahab,et al.  A 382-year reconstruction of August mean minimum temperature from tree-ring maximum latewood density on the southeastern Tibetan Plateau, China , 2016 .

[111]  The use of X-ray densitometric methods in dendrochronology. , 1970 .

[112]  Miroslav Svoboda,et al.  Forest disturbances under climate change. , 2017, Nature climate change.

[113]  M. Wilmking,et al.  Different maximum latewood density and blue intensity measurements techniques reveal similar results , 2018, Dendrochronologia.

[114]  K. Briffa,et al.  Large-scale temperature inferences from tree rings: a review , 2004 .

[115]  Gerard Mourou,et al.  Terahertz pulse imaging for tree-ring analysis: a preliminary study for dendrochronology applications , 2009 .

[116]  P. Huybers,et al.  Implications of Liebig’s law of the minimum for tree-ring reconstructions of climate , 2017 .

[117]  Yu-jiang Yuan,et al.  Temperature reconstruction from tree-ring maximum latewood density of Qinghai spruce in middle Hexi Corridor, China , 2012, Theoretical and Applied Climatology.

[118]  L. Graumlich,et al.  Reflected-light image analysis of conifer tree rings for reconstructing climate , 1996 .

[119]  Peng Zhang,et al.  Last millennium Northern Hemisphere summer temperatures from tree rings: Part I: the long term context , 2016 .

[120]  Ö. Danell,et al.  RELATIONSHIPS BETWEEN WOOD DENSITY AND TRACHEID DIMENSIONS IN PINUS SYLVESTRIS L. , 2007 .

[121]  R. Wimmer,et al.  The influence of temperature on latewood lignin content in treeline Norway spruce compared with maximum density and ring width , 2000, Trees.

[122]  P. Jones,et al.  Tree-ring evidence of the widespread effects of explosive volcanic eruptions , 1995 .

[123]  T. Wigley,et al.  On the Average Value of Correlated Time Series, with Applications in Dendroclimatology and Hydrometeorology , 1984 .

[124]  Henri E Cuny,et al.  Cell size and wall dimensions drive distinct variability of earlywood and latewood density in Northern Hemisphere conifers. , 2017, The New phytologist.

[125]  V. Masson‐Delmotte,et al.  Climate response to the Samalas volcanic eruption in 1257 revealed by proxy records , 2017 .

[126]  G. Lesnino.  The laser-sandblasting method: A new method for the qualitative annual ring analysis of conifers , 2004, Wood Science and Technology.

[127]  K. Miller.  High resolution palaeoclimatology of the Holocene Sub Polar North Atlantic , 2009 .

[128]  M. Zawadzka,et al.  Zastosowanie intensywności odbicia światła niebieskiego w datowaniu drewna historycznego , 2016 .

[129]  F. Ewers,et al.  Relationships among xylem transport, biomechanics and storage in stems and roots of nine Rhamnaceae species of the California chaparral. , 2007, The New phytologist.

[130]  Jesper Björklund,et al.  RAPTOR: row and position tracheid organizer in R , 2018 .

[131]  H. Linderholm,et al.  Legacies of pre-industrial land use can bias modern tree-ring climate calibrations , 2012 .

[132]  J. Chave,et al.  Towards a Worldwide Wood Economics Spectrum 2 . L E a D I N G D I M E N S I O N S I N W O O D F U N C T I O N , 2022 .

[133]  D. Frank,et al.  Intra-annual dynamics of non-structural carbohydrates in the cambium of mature conifer trees reflects radial growth demands. , 2013, Tree physiology.

[134]  M. Mikoláš,et al.  Influence of sampling and disturbance history on climatic sensitivity of temperature-limited conifers , 2018, The Holocene.

[135]  M. Carrer,et al.  How does climate influence xylem morphogenesis over the growing season? Insights from long-term intra-ring anatomy in Picea abies , 2017, Annals of botany.

[136]  J. Sperry,et al.  Size and function in conifer tracheids and angiosperm vessels. , 2006, American journal of botany.

[137]  G. Helle,et al.  Climate signals derived from cell anatomy of Scots pine in NE Germany. , 2013, Tree physiology.

[138]  H. Linderholm,et al.  Improving a tree-ring reconstruction from west-central Scandinavia: 900 years of warm-season temperatures , 2011 .

[139]  A. Wiedenhoeft,et al.  An Advancement in Removing Extraneous Color From Wood for Low-Magnification Reflected-Light Image Analysis of Conifer Tree Rings , 2007 .

[140]  R. Wilson,et al.  Dendrochronologically Dated Pine Buildings from Scotland: The SCOT2K Native Pine Dendrochronology Project , 2017 .

[141]  M. Vartiainen,et al.  Dendrochronological investigation of wood extractives , 2010, Wood Science and Technology.

[142]  S. Jansen,et al.  Xylem plasticity in response to climate. , 2012, The New phytologist.

[143]  A. V. Daryin,et al.  A multi-proxy approach for revealing recent climatic changes in the Russian Altai , 2011, Climate Dynamics.

[144]  David C. Wilson,et al.  Facilitating tree-ring dating of historic conifer timbers using Blue Intensity , 2017 .

[145]  K. Briffa,et al.  Radiodensitometric-dendroclimatological conifer chronologies from Lapland (Scandinavia) and the Alps (Switzerland) , 2008 .

[146]  E. Zorita,et al.  New Tree-Ring Evidence from the Pyrenees Reveals Western Mediterranean Climate Variability since Medieval Times , 2017 .

[147]  D. Frank,et al.  Divergence pitfalls in tree-ring research , 2009 .

[148]  Cyrille B K Rathgeber,et al.  Kinetics of tracheid development explain conifer tree-ring structure. , 2014, The New phytologist.

[149]  F. Ewers,et al.  CAVITATION RESISTANCE AMONG 26 CHAPARRAL SPECIES OF SOUTHERN CALIFORNIA , 2007 .

[150]  B. Gardiner,et al.  Models for predicting wood density variation in Scots pine , 2014 .

[151]  A. Di Fiore,et al.  Variation in wood density determines spatial patterns inAmazonian forest biomass , 2004 .

[152]  Harold C. Fritts,et al.  Tree Rings and Climate. , 1978 .

[153]  J. R. Bassett,et al.  Xylem Development of Loblolly Pine During Irrigation and Simulated Drought , 1975 .

[154]  K. McCulloh,et al.  Traits, properties, and performance: how woody plants combine hydraulic and mechanical functions in a cell, tissue, or whole plant. , 2014, The New phytologist.

[155]  Dan Smith,et al.  Climate and glacier mass balance trends from ad 1780 to present in the Columbia Mountains, British Columbia, Canada , 2013 .

[156]  K. Briffa,et al.  A tree-ring densitometric transect from Alaska to Labrador , 1993 .

[157]  F. Biondi,et al.  Environmental drivers of cambial phenology in Great Basin bristlecone pine. , 2016, Tree physiology.

[158]  E. Vaganov,et al.  Temperature-induced responses of xylem structure of Larix sibirica (Pinaceae) from the Russian Altay. , 2013, American journal of botany.

[159]  V. Trouet,et al.  A pan-European summer teleconnection mode recorded by a new temperature reconstruction from the northeastern Mediterranean (ad 1768–2008) , 2012 .

[160]  Bert Masschaele,et al.  High-resolution proxies for wood density variations in Terminalia superba. , 2011, Annals of botany.

[161]  Deliang L. Chen,et al.  1200 years of warm-season temperature variability in central Scandinavia inferred from tree-ring density , 2015 .

[162]  P. F. Berry,et al.  The Determination of Wood Density Using Beta Rays , 1959 .

[163]  B. Luckman,et al.  Utilising historical tree-ring data for dendroclimatology: A case study from the Bavarian Forest, Germany , 2004 .

[164]  Harold C. Fritts,et al.  The X-Ray Technique as Applied to Dendroclimatology , 1978 .

[165]  G. Jacoby,et al.  Boreal temperature variability inferred from maximum latewood density and tree-ring width data, Wrangell Mountain region, Alaska , 2003, Quaternary Research.

[166]  Yu Sun,et al.  Reconstructing mean maximum temperatures of May–August from tree-ring maximum density in North Da Hinggan Mountains, China , 2012 .

[167]  Kenji Kawamura,et al.  A global multiproxy database for temperature reconstructions of the Common Era , 2017, Scientific Data.

[168]  K. Briffa,et al.  Tree-Ring Density Networks for Climate Reconstruction , 1996 .

[169]  M. Zimmermann,et al.  Hydraulic Architecture of Whole Plants and Plant Performance , 2002 .

[170]  D. Frank,et al.  Summer temperature variations in the European Alps, A.D. 755-2004 , 2006 .

[171]  N. Loader,et al.  Blue intensity for dendroclimatology : Should we have the blues? Experiments from Scotland , 2014 .

[172]  A. Deslauriers,et al.  ASSESSMENT OF CAMBIAL ACTIVITY AND XYLOGENESIS BY MICROSAMPLING TREE SPECIES: AN EXAMPLE AT THE ALPINE TIMBERLINE , 2006 .

[173]  A. Crivellaro,et al.  Comparative axial widening of phloem and xylem conduits in small woody plants , 2014, Trees.

[174]  Risto Jalkanen,et al.  Blue intensity in Pinus sylvestris tree-rings: developing a new palaeoclimate proxy , 2007 .

[175]  H. P. Brown,et al.  Textbook of wood technology. Vol. 1. Structure, identification, defects and uses of the commercial woods of the United States. , 1949 .

[176]  B. Sundberg,et al.  Function and dynamics of auxin and carbohydrates during earlywood/latewood transition in scots pine. , 2001, Plant physiology.

[177]  Ana I. García-Cervigón,et al.  Drought-induced increase in water-use efficiency reduces secondary tree growth and tracheid wall thickness in a Mediterranean conifer , 2014, Oecologia.

[178]  D. Frank,et al.  Characterization and climate response patterns of a high-elevation, multi-species tree-ring network in the European Alps , 2005 .

[179]  F. H. Schweingruber,et al.  Influence of volcanic eruptions on Northern Hemisphere summer temperature over the past 600 years , 1998, Nature.

[180]  Fritz H. Schweingruber,et al.  Tree-ring based reconstruction of summer temperatures at the Columbia Icefield, Alberta, Canada, AD 1073-1983 , 1997 .

[181]  H. Peltola,et al.  Quantifications of dendrochronological information from contrasting microdensitometric measuring circumstances of experimental wood samples. , 2012, Applied radiation and isotopes : including data, instrumentation and methods for use in agriculture, industry and medicine.

[182]  C. Rathgeber,et al.  Linking intra-tree-ring wood density variations and tracheid anatomical characteristics in Douglas fir (Pseudotsuga menziesii (Mirb.) Franco) , 2006 .

[183]  P. Baas.  Functional and Ecological Xylem Anatomy. Uwe Hacke (ed.), xii + 281 pp., illus., 2015. Springer, ISBN 978-3-319-15782-5 (978-3-319-15783-2 e-book). Price USD 169.00 (hard cover) or USD 139.00 (e-book). , 2015 .

[184]  Andrea Hevia,et al.  Common trends in elements? Within- and between-tree variations of wood-chemistry measured by X-ray fluorescence - A dendrochemical study. , 2016, The Science of the total environment.

[185]  M. Battaglia,et al.  Wood properties in a long-lived conifer reveal strong climate signals where ring-width series do not. , 2013, Tree physiology.

[186]  J. Smerdon,et al.  Revising mid-latitude summer-temperatures back to AD 600 based on a wood 1 density network 2 , 2015 .

[187]  Helena Pereira,et al.  Wood Chemistry in Relation to Quality , 2004 .

[188]  C. Ballaré,et al.  Dual role of lignin in plant litter decomposition in terrestrial ecosystems , 2010, Proceedings of the National Academy of Sciences.

[189]  Edward R. Cook,et al.  Methods of Dendrochronology , 1990 .

[190]  Dan Smith,et al.  Intra-annual dendroclimatic reconstruction for northern British Columbia, Canada, using wood properties , 2014, Trees.

[191]  J. Esper,et al.  Development of tree-ring maximum latewood density chronologies for the western Tien Shan Mountains, China: Influence of detrending method and climate response , 2013 .

[192]  M. Parker,et al.  The Use of Engelmann Spruce Latewood Density for Dendrochronological Purposes , 1971 .

[193]  H. Linderholm,et al.  Reconstructing 800 years of summer temperatures in Scotland from tree rings , 2017, Climate Dynamics.

[194]  H. Linderholm,et al.  Advances towards improved low-frequency tree-ring reconstructions, using an updated Pinus sylvestris L. MXD network from the Scandinavian Mountains , 2013, Theoretical and Applied Climatology.

[195]  K. Briffa,et al.  A Closer Look at Regional Curve Standardization of Tree-Ring Records: Justification of the Need, a Warning of Some Pitfalls, and Suggested Improvements in Its Application , 2011 .

[196]  M. K. Cleaveland.  Climatic Response of Densitometric Properties in Semiarid Site Tree Rings , 1986 .

[197]  J. Esper,et al.  Ecological and climatological signals in tree-ring width and density chronologies along a latitudinal boreal transect , 2016 .

[198]  P. Huybers,et al.  Arctic tree rings as recorders of variations in light availability , 2014, Nature Communications.

[199]  Malcolm K. Hughes,et al.  Tree rings and volcanic cooling , 2012 .

[200]  E. Dolgova.  June-September temperature reconstruction in the Northern Caucasus based on blue intensity data. , 2016 .

[201]  G. Helle,et al.  Relationship between wood anatomy, tree-ring widths and wood density of Pinus sylvestris L. and climate at high latitudes in northern Sweden , 2014 .

[202]  Régent Guay,et al.  A new automatic and interactive tree ring measurement system based on a line scan camera , 1992 .

[203]  Jens Hansen,et al.  Conifer carbohydrate physiology : Updating classical views , 1997 .

[204]  Thomas M. Melvin,et al.  A “signal-free” approach to dendroclimatic standardisation , 2008 .

[205]  K. Briffa,et al.  Potential bias in ‘updating’ tree-ring chronologies using regional curve standardisation: Re-processing 1500 years of Torneträsk density and ring-width data , 2013 .

[206]  B. Zobel,et al.  Wood Variation and Wood Properties , 1989 .

[207]  John Finn Siau,et al.  Transport Processes in Wood , 1984, Springer Series in Wood Science.

[208]  E. Cook,et al.  Wood density provides new opportunities for reconstructing past temperature variability from southeastern Australian trees , 2016 .

[209]  M EASURING WOOD SPECIFIC GRAVITY … CORRECTLY 1 , 2010 .

[210]  F. Mothe,et al.  Analyse microdensitométrique appliquée au bois : méthode de traitement des données utilisée à l'Inra-ERQB (programme Cerd) , 1998 .

[211]  G. B. Williamson,et al.  Measuring wood specific gravity...Correctly. , 2010, American journal of botany.

[212]  B. Muys,et al.  Using X-ray CT based tree-ring width data for tree growth trend analysis , 2017 .

[213]  J. Esper,et al.  Northern European summer temperature variations over the Common Era from integrated tree‐ring density records , 2014 .

[214]  J. Camarero,et al.  Minimum wood density of Juniperus thurifera is a robust proxy of spring water availability in a continental Mediterranean climate , 2014 .

[215]  P. Hietz,et al.  Wood density and its radial variation in six canopy tree species differing in shade-tolerance in western Thailand , 2009, Annals of botany.

[216]  N. Breda,et al.  Wood density proxies of adaptive traits linked with resistance to drought in Douglas fir (Pseudotsuga menziesii (Mirb.) Franco) , 2014, Trees.

[217]  E. Cook,et al.  A strong regional temperature signal in low‐elevation Huon pine , 2013 .

[218]  P. Fonti,et al.  Xylem plasticity allows rapid hydraulic adjustment to annual climatic variability , 2013, Trees.

[219]  Ernst-Detlef Schulze,et al.  Intra-annual variability of anatomical structure and δ13C values within tree rings of spruce and pine in alpine, temperate and boreal Europe , 2009, Oecologia.

[220]  D. Bonte,et al.  Distinct growth responses to drought for oak and beech in temperate mixed forests. , 2019, The Science of the total environment.

[221]  Holger Gärtner,et al.  Studying global change through investigation of the plastic responses of xylem anatomy in tree rings. , 2010, The New phytologist.

[222]  P. Sheppard.  Overcoming Extraneous Wood Color Variation During Low-Magnification Reflected-Light Image Analysis of Conifer Tree Rings , 1999 .

[223]  F. Schweingruber.  Tree Rings: Basics and Applications of Dendrochronology , 1988 .

[224]  Pei Xing,et al.  Absence of late-summer warming trend over the past two and half centuries on the eastern Tibetan Plateau , 2014 .

[225]  J. Fletcher,et al.  Uses of X-rays for density determinations and dendrochronology. , 1970 .

[226]  M. Leuenberger,et al.  Exploring blue intensity-comparison of blue intensity and MXD data from Alpine spruce trees , 2015 .

[227]  C. Edwards,et al.  Reconstructing Holocene climate from tree rings: The potential for a long chronology from the Scottish Highlands , 2012 .

[228]  The influence of elevational differences in absolute maximum density values on regional climate reconstructions , 2015, Trees.

[229]  F. Wangaard,et al.  Variation in The Cell-Wall Density of Wood , 2007 .

[230]  Minimum wood density of conifers portrays changes in early season precipitation at dry and cold Eurasian regions , 2017, Trees.

[231]  Fleur Longuetaud,et al.  X-ray microdensitometry of wood: A review of existing principles and devices , 2017 .

[232]  Fritz H. Schweingruber,et al.  Fennoscandian summers from ad 500: temperature changes on short and long timescales , 1992 .

[233]  E. Cook,et al.  Tree-Ring-Reconstructed Summer Temperatures from Northwestern North America during the Last Nine Centuries , 2013 .

[234]  D. McCarroll,et al.  The climate sensitivity of Norway spruce [Picea abies (L.) Karst.] in the southeastern European Alps , 2008, Trees.

[235]  X. Shao,et al.  Temperature reconstruction from tree‐ring maximum density of Balfour spruce in eastern Tibet, China , 2009 .

[236]  E. Cook,et al.  Tree-ring reconstructed summer temperature anomalies for temperate East Asia since 800 C.E. , 2013, Climate Dynamics.

[237]  P. Sheppard,et al.  Solving the magnification irony in microscope-based reflected light image analysis of conifer tree rings , 2006 .

[238]  E. Cook,et al.  Tests of the RCS Method for Preserving Low-Frequency Variability in Long Tree-Ring Chronologies , 2003 .

[239]  Charles J. Robinove,et al.  Digital image measurement of the area and anatomical structure of tree rings , 1986 .

[240]  D. Frank,et al.  Diverse climate sensitivity of Mediterranean tree-ring width and density , 2010, Trees.

[241]  V. Trouet,et al.  A 1200+ year reconstruction of temperature extremes for the northeastern Mediterranean region , 2018, International Journal of Climatology.

[242]  Kristina Seftigen,et al.  Blue intensity and density from northern Fennoscandian tree rings, exploring the potential to improve summer temperature reconstructions with earlywood information , 2014 .

[243]  R. Wellwood,et al.  Relationships Between Cell-Wall Composition and Cell-Wall Density , 2007 .

[244]  Jörg Franke,et al.  Spectral biases in tree-ring climate proxies , 2013 .