Earth and Planetary Sciences › Atmospheric Science

Tree-ring climate responses

Works Count: 28367

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Description

This cluster of papers explores the causes and impacts of climate change over the past millennia, focusing on temperature variability, tree ring analysis, historical climate reconstructions, extreme events, and precipitation variability. It encompasses studies on dendrochronology, global warming, and the shifting of tree lines in response to environmental changes.

Keywords

Climate Change; Tree Rings; Temperature Variability; Dendrochronology; Global Warming; Historical Climate; Extreme Events; Paleoclimatology; Precipitation Variability; Tree Line Shifts

Global-scale temperature patterns and climate forcing over the past six centuries

1998-04-01

Michael Mann , Raymond S. Bradley , Malcolm K. Hughes

Reduced growth of Alaskan white spruce in the twentieth century from temperature-induced drought stress

2000-06-01

Valerie Barber , Glenn P. Juday , Bruce P. Finney

Timing and climate forcing of volcanic eruptions for the past 2,500 years

2015-07-01

Michael Sigl , Mai Winstrup , Joseph R. McConnell +7 more

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Influence of volcanic eruptions on Northern Hemisphere summer temperature over the past 600 years

1998-06-01

Keith R. Briffa , P. D. Jones , Fritz Hans Schweingruber +1 more

Stable isotopes in tree rings

2004-03-05

Danny McCarroll , Neil J. Loader

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Robust estimation of background noise and signal detection in climatic time series

1996-07-01

Michael Mann , Jonathan M. Lees

Climate, History and the Modern World

2002-09-26

H. H. Lamb

We live in a world that is increasingly vulnerable to climatic shocks - affecting agriculture and industry, government and international trade, not to mention human health and happiness. Serious anxieties … We live in a world that is increasingly vulnerable to climatic shocks - affecting agriculture and industry, government and international trade, not to mention human health and happiness. Serious anxieties have been aroused by respected scientists warning of dire perils that could result from upsets of the climatic regime. In this internationally acclaimed book, Emeritus Professor Hubert Lamb examines what we know about climate, how the past record of climate can be reconstructed, the causes of climatic variation, and its impact on human affairs now and in the historical and prehistoric past. This 2nd Edition includes a new preface and postscript reviewing the wealth of literature to emerge in recent years, and discusses implications for a deeper understanding of the problems of future climatic fluctuations and forecasting.

Drought Reconstructions for the Continental United States*

1999-04-01

Edward R. Cook , David M. Meko , David W. Stahle +1 more

The development of a 2° lat × 3° long grid of summer drought reconstructions for the continental United States estimated from a dense network of annual tree-ring chronologies is described. … The development of a 2° lat × 3° long grid of summer drought reconstructions for the continental United States estimated from a dense network of annual tree-ring chronologies is described. The drought metric used is the Palmer Drought Severity Index (PDSI). The number of grid points is 154 and the reconstructions cover the common period 1700–1978. In producing this grid, an automated gridpoint regression method called “point-by-point regression” was developed and tested. In so doing, a near-optimal global solution was found for its implementation. The reconstructions have been thoroughly tested for validity using PDSI data not used in regression modeling. In general, most of the gridpoint estimates of drought pass the verification tests used. In addition, the spatial features of drought in the United States have been faithfully recorded in the reconstructions even though the method of reconstruction is not explicitly spatial in its design. The drought reconstructions show that the 1930s “Dust Bowl” drought was the most severe such event to strike the United States since 1700. Other more local droughts are also revealed in the regional patterns of drought obtained by rotated principal component analysis. These reconstructions are located on a NOAA Web site at the World Data Center-A in Boulder, Colorado, and can be freely downloaded from there.

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The role of increasing temperature variability in European summer heatwaves

2004-01-01

Christoph Schär , Pier Luigi Vidale , Daniel Lüthi +4 more

Long-Term Aridity Changes in the Western United States

2004-10-08

Edward R. Cook , Connie A. Woodhouse , C. Mark Eakin +2 more

The western United States is experiencing a severe multiyear drought that is unprecedented in some hydroclimatic records. Using gridded drought reconstructions that cover most of the western United States over … The western United States is experiencing a severe multiyear drought that is unprecedented in some hydroclimatic records. Using gridded drought reconstructions that cover most of the western United States over the past 1200 years, we show that this drought pales in comparison to an earlier period of elevated aridity and epic drought in AD 900 to 1300, an interval broadly consistent with the Medieval Warm Period. If elevated aridity in the western United States is a natural response to climate warming, then any trend toward warmer temperatures in the future could lead to a serious long-term increase in aridity over western North America.

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Central England temperatures: Monthly means 1659 to 1973

1974-07-01

Gordon Manley

Abstract An up‐to‐date Table is provided of the monthly and seasonal means representative of the air over central England from 1659 onward, incorporating some minor revisions and extensions of the … Abstract An up‐to‐date Table is provided of the monthly and seasonal means representative of the air over central England from 1659 onward, incorporating some minor revisions and extensions of the earlier Table (Manley 1953 and 1959). Comments on its construction, and on the prospect of further extension backward in time, are added.

A re-assessment of high elevation treeline positions and their explanation

1998-07-16

Christian Körner

Low-Frequency Signals in Long Tree-Ring Chronologies for Reconstructing Past Temperature Variability

2002-03-22

Jan Esper , Edward R. Cook , Fritz Hans Schweingruber

Preserving multicentennial climate variability in long tree-ring records is critically important for reconstructing the full range of temperature variability over the past 1000 years. This allows the putative “Medieval Warm … Preserving multicentennial climate variability in long tree-ring records is critically important for reconstructing the full range of temperature variability over the past 1000 years. This allows the putative “Medieval Warm Period” (MWP) to be described and to be compared with 20th-century warming in modeling and attribution studies. We demonstrate that carefully selected tree-ring chronologies from 14 sites in the Northern Hemisphere (NH) extratropics can preserve such coherent large-scale, multicentennial temperature trends if proper methods of analysis are used. In addition, we show that the average of these chronologies supports the large-scale occurrence of the MWP over the NH extratropics.

Persistent Positive North Atlantic Oscillation Mode Dominated the Medieval Climate Anomaly

2009-04-02

Valérie Trouet , Jan Esper , Nicholas E. Graham +3 more

The Medieval Climate Anomaly (MCA) was the most recent pre-industrial era warm interval of European climate, yet its driving mechanisms remain uncertain. We present here a 947-year-long multidecadal North Atlantic … The Medieval Climate Anomaly (MCA) was the most recent pre-industrial era warm interval of European climate, yet its driving mechanisms remain uncertain. We present here a 947-year-long multidecadal North Atlantic Oscillation (NAO) reconstruction and find a persistent positive NAO during the MCA. Supplementary reconstructions based on climate model results and proxy data indicate a clear shift to weaker NAO conditions into the Little Ice Age (LIA). Globally distributed proxy data suggest that this NAO shift is one aspect of a global MCA-LIA climate transition that probably was coupled to prevailing La Niña-like conditions amplified by an intensified Atlantic meridional overturning circulation during the MCA.

Highly variable Northern Hemisphere temperatures reconstructed from low- and high-resolution proxy data

2005-02-10

Anders Moberg , D. M. Sonechkin , Karin Holmgren +2 more

European Seasonal and Annual Temperature Variability, Trends, and Extremes Since 1500

2004-03-04

Jürg Luterbacher , Daniel Dietrich , Elena Xoplaki +2 more

Multiproxy reconstructions of monthly and seasonal surface temperature fields for Europe back to 1500 show that the late 20th- and early 21st-century European climate is very likely (>95% confidence level) … Multiproxy reconstructions of monthly and seasonal surface temperature fields for Europe back to 1500 show that the late 20th- and early 21st-century European climate is very likely (>95% confidence level) warmer than that of any time during the past 500 years. This agrees with findings for the entire Northern Hemisphere. European winter average temperatures during the period 1500 to 1900 were reduced by approximately 0.5 degrees C (0.25 degrees C for annual mean temperatures) compared to the 20th century. Summer temperatures did not experience systematic century-scale cooling relative to present conditions. The coldest European winter was 1708/1709; 2003 was by far the hottest summer.

An Overview of the Global Historical Climatology Network Temperature Database

1997-12-01

Thomas C. Peterson , Russell S. Vose

The Global Historical Climatology Network version 2 temperature database was released in May 1997. This century-scale dataset consists of monthly surface observations from ~7000 stations from around the world. This … The Global Historical Climatology Network version 2 temperature database was released in May 1997. This century-scale dataset consists of monthly surface observations from ~7000 stations from around the world. This archive breaks considerable new ground in the field of global climate databases. The enhancements include 1) data for additional stations to improve regional-scale analyses, particularly in previously data-sparse areas; 2) the addition of maximum–minimum temperature data to provide climate information not available in mean temperature data alone; 3) detailed assessments of data quality to increase the confidence in research results; 4) rigorous and objective homogeneity adjustments to decrease the effect of nonclimatic factors on the time series; 5) detailed metadata (e.g., population, vegetation, topography) that allow more detailed analyses to be conducted; and 6) an infrastructure for updating the archive at regular intervals so that current climatic conditions can constantly be put into historical perspective. This paper describes these enhancements in detail.

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DENDROCLIM2002: A C++ program for statistical calibration of climate signals in tree-ring chronologies

2004-03-09

Franco Biondi , Kishor Waikul

Surface air temperature and its changes over the past 150 years

1999-05-01

P. D. Jones , Mark New , D. E. Parker +2 more

We review the surface air temperature record of the past 150 years, considering the homogeneity of the basic data and the standard errors of estimation of the average hemispheric and … We review the surface air temperature record of the past 150 years, considering the homogeneity of the basic data and the standard errors of estimation of the average hemispheric and global estimates. We present global fields of surface temperature change over the two 20‐year periods of greatest warming this century, 1925–1944 and 1978–1997. Over these periods, global temperatures rose by 0.37° and 0.32°C, respectively. The twentieth‐century warming has been accompanied by a decrease in those areas of the world affected by exceptionally cool temperatures and to a lesser extent by increases in areas affected by exceptionally warm temperatures. In recent decades there have been much greater increases in night minimum temperatures than in day maximum temperatures, so that over 1950–1993 the diurnal temperature range has decreased by 0.08°C per decade. We discuss the recent divergence of surface and satellite temperature measurements of the lower troposphere and consider the last 150 years in the context of the last millennium. We then provide a globally complete absolute surface air temperature climatology on a 1° × 1° grid. This is primarily based on data for 1961–1990. Extensive interpolation had to be undertaken over both polar regions and in a few other regions where basic data are scarce, but we believe the climatology is the most consistent and reliable of absolute surface air temperature conditions over the world. The climatology indicates that the annual average surface temperature of the world is 14.0°C (14.6°C in the Northern Hemisphere (NH) and 13.4°C for the Southern Hemisphere). The annual cycle of global mean temperatures follows that of the land‐dominated NH, with a maximum in July of 15.9°C and a minimum in January of 12.2°C.

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Drought-induced shift of a forest–woodland ecotone: Rapid landscape response to climate variation

1998-12-08

Craig D. Allen , David D. Breshears

In coming decades, global climate changes are expected to produce large shifts in vegetation distributions at unprecedented rates. These shifts are expected to be most rapid and extreme at ecotones, … In coming decades, global climate changes are expected to produce large shifts in vegetation distributions at unprecedented rates. These shifts are expected to be most rapid and extreme at ecotones, the boundaries between ecosystems, particularly those in semiarid landscapes. However, current models do not adequately provide for such rapid effects—particularly those caused by mortality—largely because of the lack of data from field studies. Here we report the most rapid landscape-scale shift of a woody ecotone ever documented: in northern New Mexico in the 1950s, the ecotone between semiarid ponderosa pine forest and piñon–juniper woodland shifted extensively (2 km or more) and rapidly (<5 years) through mortality of ponderosa pines in response to a severe drought. This shift has persisted for 40 years. Forest patches within the shift zone became much more fragmented, and soil erosion greatly accelerated. The rapidity and the complex dynamics of the persistent shift point to the need to represent more accurately these dynamics, especially the mortality factor, in assessments of the effects of climate change.

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HISTALP—historical instrumental climatological surface time series of the Greater Alpine Region

2006-07-06

Ingeborg Auer , Reinhard Böhm , Anita Jurković +7 more

Abstract This paper describes the HISTALP database, consisting of monthly homogenised records of temperature, pressure, precipitation, sunshine and cloudiness for the ‘Greater Alpine Region’ (GAR, 4–19°E, 43–49°N, 0–3500m asl). The … Abstract This paper describes the HISTALP database, consisting of monthly homogenised records of temperature, pressure, precipitation, sunshine and cloudiness for the ‘Greater Alpine Region’ (GAR, 4–19°E, 43–49°N, 0–3500m asl). The longest temperature and air pressure series extend back to 1760, precipitation to 1800, cloudiness to the 1840s and sunshine to the 1880s. A systematic QC procedure has been applied to the series and a high number of inhomogeneities (more than 2500) and outliers (more than 5000) have been detected and removed. The 557 HISTALP series are kept in different data modes: original and homogenised, gap‐filled and outlier corrected station mode series, grid‐1 series (anomaly fields at 1° × 1°, lat × long) and Coarse Resolution Subregional (CRS) mean series according to an EOF‐based regionalisation. The leading climate variability features within the GAR are discussed through selected examples and a concluding linear trend analysis for 100, 50 and 25‐year subperiods for the four horizontal and two altitudinal CRSs. Among the key findings of the trend analysis is the parallel centennial decrease/increase of both temperature and air pressure in the 19th/20th century. The 20th century increase (+1.2 °C/+ 1.1 hPa for annual GAR‐means) evolved stepwise with a first peak near 1950 and the second increase (1.3 °C/0.6hPa per 25 years) starting in the 1970s. Centennial and decadal scale temperature trends were identical for all subregions. Air pressure, sunshine and cloudiness show significant differences between low versus high elevations. A long‐term increase of the high‐elevation series relative to the low‐elevation series is given for sunshine and air pressure. Of special interest is the exceptional high correlation near 0.9 between the series on mean temperature and air pressure difference (high‐minus low‐elevation). This, further developed via some atmospheric statics and thermodynamics, allows the creation of ‘barometric temperature series’ without use of the measures of temperature. They support the measured temperature trends in the region. Precipitation shows the most significant regional and seasonal differences with, e.g., remarkable opposite 20th century evolution for NW (9% increase) versus SE (9% decrease). Other long‐ and short‐term features are discussed and indicate the promising potential of the new database for further analyses and applications. Copyright © 2006 Royal Meteorological Society.

Mesoscale Disturbance and Ecological Response to Decadal Climatic Variability in the American Southwest

1998-12-01

Thomas W. Swetnam , Julio L. Betancourt

Ecological responses to climatic variability in the Southwest include regionally synchronized fires, insect outbreaks, and pulses in tree demography (births and deaths). Multicentury, tree-ring reconstructions of drought, disturbance history, and … Ecological responses to climatic variability in the Southwest include regionally synchronized fires, insect outbreaks, and pulses in tree demography (births and deaths). Multicentury, tree-ring reconstructions of drought, disturbance history, and tree demography reveal climatic effects across scales, from annual to decadal, and from local (<102 km2) to mesoscale (104–106 km2). Climate–disturbance relations are more variable and complex than previously assumed. During the past three centuries, mesoscale outbreaks of the western spruce budworm (Choristoneura occidentalis) were associated with wet, not dry episodes, contrary to conventional wisdom. Regional fires occur during extreme droughts but, in some ecosystems, antecedent wet conditions play a secondary role by regulating accumulation of fuels. Interdecadal changes in fire–climate associations parallel other evidence for shifts in the frequency or amplitude of the Southern Oscillation (SO) during the past three centuries. High interannual, fire–climate correlations (r = 0.7 to 0.9) during specific decades (i.e., circa 1740–80 and 1830–60) reflect periods of high amplitude in the SO and rapid switching from extreme wet to dry years in the Southwest, thereby entraining fire occurrence across the region. Weak correlations from 1780 to 1830 correspond with a decrease in SO frequency or amplitude inferred from independent tree-ring width, ice core, and coral isotope reconstructions. Episodic dry and wet episodes have altered age structures and species composition of woodland and conifer forests. The scarcity of old, living conifers established before circa 1600 suggests that the extreme drought of 1575–95 had pervasive effects on tree populations. The most extreme drought of the past 400 years occurred in the mid–twentieth century (1942–57). This drought resulted in broadscale plant dieoffs in shrublands, woodlands, and forests and accelerated shrub invasion of grasslands. Drought conditions were broken by the post-1976 shift to the negative SO phase and wetter cool seasons in the Southwest. The post-1976 period shows up as an unprecedented surge in tree-ring growth within millennia-length chronologies. This unusual episode may have produced a pulse in tree recruitment and improved rangeland conditions (e.g., higher grass production), though additional study is needed to disentangle the interacting roles of land use and climate. The 1950s drought and the post-1976 wet period and their aftermaths offer natural experiments to study long-term ecosystem response to interdecadal climate variability.

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Are treelines advancing? A global meta‐analysis of treeline response to climate warming

2009-08-13

Melanie A. Harsch , Philip E. Hulme , Matt S. McGlone +1 more

Treelines are temperature sensitive transition zones that are expected to respond to climate warming by advancing beyond their current position. Response to climate warming over the last century, however, has … Treelines are temperature sensitive transition zones that are expected to respond to climate warming by advancing beyond their current position. Response to climate warming over the last century, however, has been mixed, with some treelines showing evidence of recruitment at higher altitudes and/or latitudes (advance) whereas others reveal no marked change in the upper limit of tree establishment. To explore this variation, we analysed a global dataset of 166 sites for which treeline dynamics had been recorded since 1900 AD. Advance was recorded at 52% of sites with only 1% reporting treeline recession. Treelines that experienced strong winter warming were more likely to have advanced, and treelines with a diffuse form were more likely to have advanced than those with an abrupt or krummholz form. Diffuse treelines may be more responsive to warming because they are more strongly growth limited, whereas other treeline forms may be subject to additional constraints.

Temperature as a potent driver of regional forest drought stress and tree mortality

2012-09-28

Park Williams , Craig D. Allen , Alison K. Macalady +7 more

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Global Signatures and Dynamical Origins of the Little Ice Age and Medieval Climate Anomaly

2009-11-27

Michael Mann , Zhihua Zhang , Scott Rutherford +6 more

Patterns of Change The global climate record of the past 1500 years shows two long intervals of anomalous temperatures before the obvious anthropogenic warming of the 20th century: the warm … Patterns of Change The global climate record of the past 1500 years shows two long intervals of anomalous temperatures before the obvious anthropogenic warming of the 20th century: the warm Medieval Climate Anomaly between roughly 950 and 1250 A.D. and the Little Ice Age between around 1400 and 1700 A.D. It has become increasingly clear in recent years, however, that climate changes inevitably involve a complex pattern of regional changes, whose inhomogeneities contain valuable insights into the mechanisms that cause them. Mann et al. (p. 1256 ) analyzed proxy records of climate since 500 A.D. and compared their global patterns with model reconstructions. The results identify the large-scale processes—like El Niño and the North Atlantic Oscillation—that can account for the observations and suggest that dynamic responses to variable radiative forcing were their primary causes.

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Fundamentals of tree-ring research

2010-11-01

James H. Speer‬

Although there are other scientific means of dating climatic and environmental events, dendrochronology provides the most reliable of all palaeorecords. This comprehensive text addresses all of the subjects that a … Although there are other scientific means of dating climatic and environmental events, dendrochronology provides the most reliable of all palaeorecords. This comprehensive text addresses all of the subjects that a reader who is new to the field will need to know and will be a welcome reference for practitioners at all levels. It includes a history of the discipline, biological and ecological background, principles of the field, basic scientific information on the structure and growth of trees, the complete range of dendrochronology methods, and a full description of each of the relevant subdisciplines.

Asian Monsoon Failure and Megadrought During the Last Millennium

2010-04-22

Edward R. Cook , Kevin J. Anchukaitis , Brendan M. Buckley +3 more

Of Monsoons and Megadroughts The Asian monsoon is the weather system that has the greatest effect on the greatest number of people in the world. Naturally then, knowing better how … Of Monsoons and Megadroughts The Asian monsoon is the weather system that has the greatest effect on the greatest number of people in the world. Naturally then, knowing better how climate change might affect the monsoon is tremendously important. One obstacle that prevents a better understanding of future behavior is a poor knowledge of its past. Cook et al. (p. 486 ; see the Perspective by Wahl and Morrill ) help to fill this gap with a 700-year reconstruction of the monsoon from tree-ring data obtained throughout Asia. The reconstruction chronicles monsoon failures and megadroughts, as well as patterns of precipitation, and can thus be compared with other relevant climate records to allow links with sea-surface temperatures to be better understood.

Extracting a Climate Signal from 169 Glacier Records

2005-03-04

J.J. Oerlemans

I constructed a temperature history for different parts of the world from 169 glacier length records. Using a first-order theory of glacier dynamics, I related changes in glacier length to … I constructed a temperature history for different parts of the world from 169 glacier length records. Using a first-order theory of glacier dynamics, I related changes in glacier length to changes in temperature. The derived temperature histories are fully independent of proxy and instrumental data used in earlier reconstructions. Moderate global warming started in the middle of the 19th century. The reconstructed warming in the first half of the 20th century is 0.5 kelvin. This warming was notably coherent over the globe. The warming signals from glaciers at low and high elevations appear to be very similar.

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A world‐wide study of high altitude treeline temperatures

2004-04-14

Christian Körner , Jens Paulsen

Abstract Aim At a coarse scale, the treelines of the world's mountains seem to follow a common isotherm, but the evidence for this has been indirect so far. Here we … Abstract Aim At a coarse scale, the treelines of the world's mountains seem to follow a common isotherm, but the evidence for this has been indirect so far. Here we aim at underpinning this with facts. Location We present the results of a data‐logging campaign at 46 treeline sites between 68° N and 42° S. Methods We measured root‐zone temperatures with an hourly resolution over 1–3 years per site between 1996 and 2003. Results Disregarding taxon‐, landuse‐ or fire‐driven tree limits, high altitude climatic treelines are associated with a seasonal mean ground temperature of 6.7 °C (±0.8 SD; 2.2 K amplitude of means for different climatic zones), a surprisingly narrow range. Temperatures are higher (7–8 °C) in the temperate and Mediterranean zone treelines, and are lower in equatorial treelines (5–6 °C) and in the subarctic and boreal zone (6–7 °C). While air temperatures are higher than soil temperatures in warm periods, and are lower than soil temperatures in cold periods, daily means of air and soil temperature are almost the same at 6–7 °C, a physics driven coincidence with the global mean temperature at treeline. The length of the growing season, thermal extremes or thermal sums have no predictive value for treeline altitude on a global scale. Some Mediterranean ( Fagus spp.) and temperate South Hemisphere treelines ( Nothofagus spp.) and the native treeline in Hawaii ( Metrosideros ) are located at substantially higher isotherms and represent genus‐specific boundaries rather than boundaries of the life‐form tree. In seasonal climates, ground temperatures in winter (absolute minima) reflect local snow pack and seem uncritical. Main conclusions The data support the hypothesis of a common thermal threshold for forest growth at high elevation, but also reflect a moderate region and substantial taxonomic influence.

Causes of Climate Change Over the Past 1000 Years

2000-07-14

Thomas J. Crowley

Recent reconstructions of Northern Hemisphere temperatures and climate forcing over the past 1000 years allow the warming of the 20th century to be placed within a historical context and various … Recent reconstructions of Northern Hemisphere temperatures and climate forcing over the past 1000 years allow the warming of the 20th century to be placed within a historical context and various mechanisms of climate change to be tested. Comparisons of observations with simulations from an energy balance climate model indicate that as much as 41 to 64% of preanthropogenic (pre-1850) decadal-scale temperature variations was due to changes in solar irradiance and volcanism. Removal of the forced response from reconstructed temperature time series yields residuals that show similar variability to those of control runs of coupled models, thereby lending support to the models' value as estimates of low-frequency variability in the climate system. Removal of all forcing except greenhouse gases from the approximately 1000-year time series results in a residual with a very large late-20th-century warming that closely agrees with the response predicted from greenhouse gas forcing. The combination of a unique level of temperature increase in the late 20th century and improved constraints on the role of natural variability provides further evidence that the greenhouse effect has already established itself above the level of natural variability in the climate system. A 21st-century global warming projection far exceeds the natural variability of the past 1000 years and is greater than the best estimate of global temperature change for the last interglacial.

Northern hemisphere temperatures during the past millennium: Inferences, uncertainties, and limitations

1999-03-15

Michael Mann , Raymond S. Bradley , Malcolm K. Hughes

Building on recent studies, we attempt hemispheric temperature reconstructions with proxy data networks for the past millennium. We focus not just on the reconstructions, but the uncertainties therein, and important … Building on recent studies, we attempt hemispheric temperature reconstructions with proxy data networks for the past millennium. We focus not just on the reconstructions, but the uncertainties therein, and important caveats. Though expanded uncertainties prevent decisive conclusions for the period prior to AD 1400, our results suggest that the latter 20th century is anomalous in the context of at least the past millennium. The 1990s was the warmest decade, and 1998 the warmest year, at moderately high levels of confidence. The 20th century warming counters a millennial‐scale cooling trend which is consistent with long‐term astronomical forcing.

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Variations in northern vegetation activity inferred from satellite data of vegetation index during 1981 to 1999

2001-09-01

Liming Zhou , C. Tucker , Robert K. Kaufmann +3 more

The northern high latitudes have warmed by about 0.8°C since the early 1970s, but not all areas have warmed uniformly [ Hansen et al ., 1999]. There is warming in … The northern high latitudes have warmed by about 0.8°C since the early 1970s, but not all areas have warmed uniformly [ Hansen et al ., 1999]. There is warming in most of Eurasia, but the warming rate in the United States is smaller than in most of the world, and a slight cooling is observed in the eastern United States over the past 50 years. These changes beg the question, can we detect the biotic response to temperature changes? Here we present results from analyses of a recently developed satellite‐sensed normalized difference vegetation index (NDVI) data set for the period July 1981 to December 1999: (1) About 61% of the total vegetated area between 40°N and 70°N in Eurasia shows a persistent increase in growing season NDVI over a broad contiguous swath of land from central Europe through Siberia to the Aldan plateau, where almost 58% (7.3×10 6 km 2 ) is forests and woodlands; North America, in comparison, shows a fragmented pattern of change in smaller areas notable only in the forests of the southeast and grasslands of the upper Midwest, (2) A larger increase in growing season NDVI magnitude (12% versus 8%) and a longer active growing season (18 versus 12 days) brought about by an early spring and delayed autumn are observed in Eurasia relative to North America, (3) NDVI decreases are observed in parts of Alaska, boreal Canada, and northeastern Asia, possibly due to temperature‐induced drought as these regions experienced pronounced warming without a concurrent increase in rainfall [ Barber et al ., 2000]. We argue that these changes in NDVI reflect changes in biological activity. Statistical analyses indicate that there is a statistically meaningful relation between changes in NDVI and land surface temperature for vegetated areas between 40°N and 70°N. That is, the temporal changes and continental differences in NDVI are consistent with ground‐based measurements of temperature, an important determinant of biological activity. Together, these results suggest a photosynthetically vigorous Eurasia relative to North America during the past 2 decades, possibly driven by temperature and precipitation patterns. Our results are in broad agreement with a recent comparative analysis of 1980s and 1990s boreal and temperate forest inventory data [ United Nations , 2000].

Continental-scale temperature variability during the past two millennia

2013-04-19

Moinuddin Ahmed , Kevin J. Anchukaitis , Asfawossen Asrat +7 more

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A dendrochronology program library in R (dplR)

2008-07-19

Andrew G. Bunn

Climate over past millennia

2004-05-05

P. D. Jones , Michael Mann

We review evidence for climate change over the past several millennia from instrumental and high‐resolution climate “proxy” data sources and climate modeling studies. We focus on changes over the past … We review evidence for climate change over the past several millennia from instrumental and high‐resolution climate “proxy” data sources and climate modeling studies. We focus on changes over the past 1 to 2 millennia. We assess reconstructions and modeling studies analyzing a number of different climate fields, including atmospheric circulation diagnostics, precipitation, and drought. We devote particular attention to proxy‐based reconstructions of temperature patterns in past centuries, which place recent large‐scale warming in an appropriate longer‐term context. Our assessment affirms the conclusion that late 20th century warmth is unprecedented at hemispheric and, likely, global scales. There is more tentative evidence that particular modes of climate variability, such as the El Niño/Southern Oscillation and the North Atlantic Oscillation, may have exhibited late 20th century behavior that is anomalous in a long‐term context. Regional conclusions, particularly for the Southern Hemisphere and parts of the tropics where high‐resolution proxy data are sparse, are more circumspect. The dramatic differences between regional and hemispheric/global past trends, and the distinction between changes in surface temperature and precipitation/drought fields, underscore the limited utility in the use of terms such as the “Little Ice Age” and “Medieval Warm Period” for describing past climate epochs during the last millennium. Comparison of empirical evidence with proxy‐based reconstructions demonstrates that natural factors appear to explain relatively well the major surface temperature changes of the past millennium through the 19th century (including hemispheric means and some spatial patterns). Only anthropogenic forcing of climate, however, can explain the recent anomalous warming in the late 20th century.

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Cultural Responses to Climate Change During the Late Holocene

2001-04-27

Peter B deMenocal

Modern complex societies exhibit marked resilience to interannual-to- decadal droughts, but cultural responses to multidecadal-to-multicentury droughts can only be addressed by integrating detailed archaeological and paleoclimatic records. Four case studies … Modern complex societies exhibit marked resilience to interannual-to- decadal droughts, but cultural responses to multidecadal-to-multicentury droughts can only be addressed by integrating detailed archaeological and paleoclimatic records. Four case studies drawn from New and Old World civilizations document societal responses to prolonged drought, including population dislocations, urban abandonment, and state collapse. Further study of past cultural adaptations to persistent climate change may provide valuable perspective on possible responses of modern societies to future climate change.

Proxy-based reconstructions of hemispheric and global surface temperature variations over the past two millennia

2008-09-03

Michael Mann , Zhihua Zhang , Malcolm K. Hughes +4 more

Following the suggestions of a recent National Research Council report [NRC (National Research Council) (2006) Surface Temperature Reconstructions for the Last 2,000 Years (Natl Acad Press, Washington, DC).], we reconstruct … Following the suggestions of a recent National Research Council report [NRC (National Research Council) (2006) Surface Temperature Reconstructions for the Last 2,000 Years (Natl Acad Press, Washington, DC).], we reconstruct surface temperature at hemispheric and global scale for much of the last 2,000 years using a greatly expanded set of proxy data for decadal-to-centennial climate changes, recently updated instrumental data, and complementary methods that have been thoroughly tested and validated with model simulation experiments. Our results extend previous conclusions that recent Northern Hemisphere surface temperature increases are likely anomalous in a long-term context. Recent warmth appears anomalous for at least the past 1,300 years whether or not tree-ring data are used. If tree-ring data are used, the conclusion can be extended to at least the past 1,700 years, but with additional strong caveats. The reconstructed amplitude of change over past centuries is greater than hitherto reported, with somewhat greater Medieval warmth in the Northern Hemisphere, albeit still not reaching recent levels.

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Some statistics useful in regional frequency analysis

1993-02-01

J. R. M. Hosking , James R. Wallis

Regional frequency analysis uses data from a number of measuring sites. A “region” is a group of sites each of which is assumed to have data drawn from the same … Regional frequency analysis uses data from a number of measuring sites. A “region” is a group of sites each of which is assumed to have data drawn from the same frequency distribution. The analysis involves the assignment of sites to regions, testing whether the proposed regions are indeed homogeneous, and choice of suitable distributions to fit to each region's data. This paper describes three statistics useful in regional frequency analysis: a discordancy measure, for identifying unusual sites in a region; a heterogeneity measure, for assessing whether a proposed region is homogeneous; and a goodness‐of‐fit measure, for assessing whether a candidate distribution provides an adequate fit to the data. Tests based on the statistics provide objective backing for the decisions involved in regional frequency analysis. The statistics are based on the L moments [ Hosking , 1990] of the at‐site data.

2500 Years of European Climate Variability and Human Susceptibility

2011-01-14

Ulf Büntgen , Willy Tegel , Kurt Nicolussi +7 more

Variability of central European temperature and precipitation shows correlations with some major historical changes. Variability of central European temperature and precipitation shows correlations with some major historical changes.

A new scenario for the Quaternary history of European beech populations: palaeobotanical evidence and genetic consequences

2006-05-17

Donatella Magri , Giovanni G. Vendramin , Bernard Comps +7 more

• Here, palaeobotanical and genetic data for common beech (Fagus sylvatica) in Europe are used to evaluate the genetic consequences of long-term survival in refuge areas and postglacial spread. • … • Here, palaeobotanical and genetic data for common beech (Fagus sylvatica) in Europe are used to evaluate the genetic consequences of long-term survival in refuge areas and postglacial spread. • Four large datasets are presented, including over 400 fossil-pollen sites, 80 plant-macrofossil sites, and 450 and 600 modern beech populations for chloroplast and nuclear markers, respectively. • The largely complementary palaeobotanical and genetic data indicate that: (i) beech survived the last glacial period in multiple refuge areas; (ii) the central European refugia were separated from the Mediterranean refugia; (iii) the Mediterranean refuges did not contribute to the colonization of central and northern Europe; (iv) some populations expanded considerably during the postglacial period, while others experienced only a limited expansion; (v) the mountain chains were not geographical barriers for beech but rather facilitated its diffusion; and (vi) the modern genetic diversity was shaped over multiple glacial–interglacial cycles. • This scenario differs from many recent treatments of tree phylogeography in Europe that largely focus on the last ice age and the postglacial period to interpret genetic structure and argue that the southern peninsulas (Iberian, Italian and Balkan) were the main source areas for trees in central and northern Europe.

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On the Average Value of Correlated Time Series, with Applications in Dendroclimatology and Hydrometeorology

1984-02-01

T. M. L. Wigley , Keith R. Briffa , P. D. Jones

In a number of areas of applied climatology, time series are either averaged to enhance a common underlying signal or combined to produce area averages. How well, then, does the … In a number of areas of applied climatology, time series are either averaged to enhance a common underlying signal or combined to produce area averages. How well, then, does the average of a finite number (N) of time series represent the population average, and how well will a subset of series represent the N-series average? We have answered these questions by deriving formulas for 1) the correlation coefficient between the average of N time series and the average of n such series (where n is an arbitrary subset of N) and 2) the correlation between the N-series average and the population. We refer to these mean correlations as the subsample signal strength (SSS) and the expressed population signal (EPS). They may be expressed in terms of the mean inter-series correlation coefficient r̄ as R̄n,N2nNr̄NNr̄ R̄N2Nr̄Nr̄ Similar formulas are given relating these mean correlations to the fractional common variance which arises as a parameter in analysis of variance. These results are applied to determine the increased uncertainty in a tree-ring chronology which results when the number of cores used to produce the chronology is reduced. Such uncertainty will accrue to any climate reconstruction equation that is calibrated using the most recent part of the chronology. The method presented can be used to define the useful length of tree-ring chronologies for climate reconstruction work. A second application considers the accuracy of area-average precipitation estimates derived from a limited network of raingage sites. The uncertainty is given in absolute terms as the standard error of estimate of the area-average expressed as a function of the number of gage sites and the mean inter-site correlation.

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The smoothing spline : a new approach to standardizing forest interior tree-ring width series for dendroclimatic studies

1981-01-01

Edward R. Cook , Kenneth E. Peters

A new approach to removing the non -climatic variance of forest interior tree -ring width series, using the smoothing spline, is described. This method is superior to orthogonal polynomials because … A new approach to removing the non -climatic variance of forest interior tree -ring width series, using the smoothing spline, is described. This method is superior to orthogonal polynomials because it makes no assumptions about the shape of the curve to be used for standardization. Also, because the curve can range continuously from a linear least squares fit to cubic interpolation through the data, it is far more flexible than polynomials and provides a more natural fit. For computing the spline, we found that specifying the Lagrange multiplier p which appears in the calculus of variation solution rather than the residual variance as suggested by Reinsche was both practical and more efficient. In effect, the smoothing is a one -parameter family of low -pass filters defined by p. We describe the general characteristics of these filters in the time and frequency domains and compute the response functions for several of them. The smoothing is an excellent tree -ring standardization method because its filtering characteristics are well defined. Its utility for dendroclimatology should be considerable since, outside of semiarid environments, sites similar to forest interiors predominate. Es wird ein neuer Ansatz zur Beseitigung der nicht -klimatisch bedingten Varianz aus den Jahrringfolgen von Baumen aus dem Bestandesinneren mit Hilfe von Ausgleichs -Splines beschrieben. Dieses Verfahren ist der Berechnung von orthogonalen Polynomen uberlegen, da es keine Annahmen uber die zur Standardisierung benotigte Kurvenform macht. Da die Spline -Kurve kontinuierlich von einem linearen Ausgleich auf der Grundlage der kleinsten Abweichungsquadrate bis zu einer kubischen Interpolation reichen kann, ist sie weitaus flexibler als Polynome und fuhrt zu einer naturlichen Anpassung. Wir haben herausgefunden, das die Vorgabe des LagrangeMultiplikators p, der bei der Losung der Variation vorkommt, zur Berechnung des Spline praktikabler und wirksamer ist als die Vorgabe der Restvarianz, wie Reinsche vorschlagt. In der Tat ist der Ausgleichsspline eine Familie von Einparameter -Tiefpassfiltern, die durch p definiert werden. Wir beschreiben die allgemeinen Eigenschaften dieser Filter im Zeit und Frequenzbereich und berechnen fur einige von ihnen die ResponseFunktionen. Der Ausgleichsspline ist ein sehr gutes Verfahren zur Standardisierung von Jahrringen, da seine Filtereigenschaften gut definiert sind. Seine Einsatzmoglichkeit in der Dendroklimatologie durfte betrachtlich sein, da auserhalb der semiariden Standorte solche dominieren, die dem Bestandesinneren ahnlich sind. Une nouvelle approche destinee a oter la variance non climatique contenue dans les series dendrochronologiques provenant de l'interieur de zones forestieres par l'utilisation de fonctions spline est decrite. Cette methode est superieure a celle basee sur les fonctions polynomials orthogonales parce qu'elle ne fait aucune hypothese concernant la forme de la courbe qui doit etre utilisee pour la standardisation. De plus, la courbe d'approximation engendree par une fonction peut varier continuellement depuis un lissage lineaire calcule par les moindres carres jusqu'a une interpolation cubique au travers des donnees. De ce fait, cette equation est bien plus souple que les polynomiales et procure des approximations plus naturelles . Pour calculer la fonction spline, nous avons trouve que specifier le multiplicateur p de LAGRANGE plutot que la variance residuelle comme le propose REINSCHE est a la fois pratique et plus efficace. En effet, le de lissage est une famille a un parametre de filtres passe -bas defini par p. Nous decrivons les caracteres generaux de

Methods of Dendrochronology, Applications in the Environmental Sciences

1991-02-01

David K. Yamaguchi , Edward R. Cook , Leonardas A. Kairiukstis

Some Historical Background on Dendrochronology.- Primary Data.- Data Analysis.- Methods of Calibration, Verification, and Reconstruction.- Tree-Ring/Environment Interactions and Their Assessment.- Tree Rings in the Study of Future Change. Some Historical Background on Dendrochronology.- Primary Data.- Data Analysis.- Methods of Calibration, Verification, and Reconstruction.- Tree-Ring/Environment Interactions and Their Assessment.- Tree Rings in the Study of Future Change.

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Physiological Ecology of the Alpine Timberline

1979-01-01

Walter Tranquillini

Methods of Dendrochronology

1990-01-01

E. R. Cook , L. Kairiūkštis

Tree Rings and Climate

1978-02-01

Raymond S. Bradley , Harold C. Fritts

Positive Interactions and Interdependence in Plant Communities

2007-01-01

Ragan M. Callaway

Winter-spring temperature reconstructed from tree-ring earlywood blue intensity in southern Anhui province of China

2025-06-21

Kunyu Peng , Keyan Fang , Feifei Zhou +4 more | Quaternary Science Reviews

Dinámica de la línea de árboles en el volcán Iztaccíhuatl, México

2025-06-20

Leopoldo Galicia , Itzel Guzmán-Vázquez | Investigaciones Geográficas Boletín del Instituto de Geografía

Los procesos que explican la dirección y la velocidad de la migración de la línea de árboles, particularmente en sistemas montañosos de altas altitudes, son aspectos escasamente estudiados. En el … Los procesos que explican la dirección y la velocidad de la migración de la línea de árboles, particularmente en sistemas montañosos de altas altitudes, son aspectos escasamente estudiados. En el volcán Iztaccíhuatl, perteneciente al Eje Neovolcánico Mexicano, la línea de árboles se presenta alrededor de los 4000 msnm, aunque existe evidencia de su avance, que no ha sido homogéneo, probablemente debido a las irregularidades topográficas inherentes de los sistemas montañosos. Este estudio evalúa el papel de las variaciones de temperatura, radiación y humedad del suelo derivadas de aspectos topográficos como la elevación, la pendiente, la orientación y la sombra orográfica en la dinámica de la línea de árboles. Los objetivos de esta investigación fueron: i) comparar la posición de la línea de árboles en el volcán Iztaccíhuatl durante el periodo comprendido entre 1995 y 2017, y ii) analizar el impacto de las condiciones topográficas y ambientales en los movimientos de la línea de árboles. Utilizamos imágenes satelitales Landsat y desarrollamos un modelo de clasificación supervisada para identificar la línea de árboles como el límite entre el bosque y el pastizal. Para analizar los factores que condicionan la dinámica de la línea de árboles, clasificamos los principales ambientes según características topográficas (elevación, pendiente, orientación y sombra orográfica) y variables ambientales (temperatura, radiación descendente, la radiación ascendente y el índice de humedad del suelo (SMI)). Identificamos siete tipos de ambientes basados en variables topográficas y ambientales. Nuestros resultados indican un avance generalizado en la línea de árboles hacia mayores altitudes (32 m en promedio hasta 2014), con retrocesos localizados en laderas empinadas noroeste (temperaturas bajas: 10.18 °C; humedad reducida: SMI 0.62). Por el contrario, los avances predominaron en pendientes suaves y orientaciones noreste, asociadas a temperaturas moderadas (16-18 °C) y mayor humedad (SMI: 1.26). La dinámica de la línea de árboles en este volcán responde a una combinación compleja entre condiciones térmicas y de humedad, moduladas por la topografía. Pendientes pronunciadas y orientaciones con escasa radicación solar promueven la mortalidad probablemente por congelamiento o desecación, mientras que áreas con microclimas más cálidos y húmedos favorecen el establecimiento y crecimiento de árboles. Esto sugiere que no solo el calentamiento global, sino que factores múltiples determinan la dirección y velocidad del límite de los árboles en las montañas.

Quantitative genetic variation in growth, cold tolerance and wood density of Corymbia citriodora subsp. variegata and Corymbia torelliana in Argentina

2025-06-20

Carla Anahi Gimenez , Juan Adolfo López , Carlos David Vera Bravo +2 more | New Forests

The Exposure of Prairie Soils to Millennia of Climate Variability and Change

2025-06-20

David J. Sauchyn , Mohammad Zare , Mary Vetter +3 more | Canadian Journal of Soil Science

The native grassland ecosystems of the Northern Great Plains (NGP) are adapted to millennia of climate variability. Field experiments have examined the response of native prairie to a range of … The native grassland ecosystems of the Northern Great Plains (NGP) are adapted to millennia of climate variability. Field experiments have examined the response of native prairie to a range of historical weather conditions that is unrepresentative of the full spectrum of hydroclimatic variability since grasslands became established on the NGP. We review existing paleo-environmental records of Holocene vegetation and climate and present a tree-ring reconstruction of the hydroclimate of the past millennium. Sedimentation rates and pollen in cores from prairie lakes reveal significant disturbance of native prairie under drought conditions, but also relatively rapid recovery of the grassland when the climate cycles back to wetter conditions. Tree-ring signals of prolonged and severe drought coincide with the reactivation of sand dune fields and indicators of reduced vegetation cover and soil erosion in the lake sediments. Climate model projections of future changes in the soil water balance suggest that prairie grasslands will be subject to drier conditions like those in the paleoclimate record from the mid-Holocene and more recent medieval warm period. The stability and resistance of prairie soils to wind and water erosion, as a function of the resilience of native grassland, contrast with the agroecosystems that have replaced most of the native prairie. By casting a unique paleo-environmental perspective on the resilience of native prairie as a protective soil cover, this paper provides a context and further support for agricultural practices that restore and maintain soil health.

Methodological Innovations in the History of Climate and Society Studies

2025-06-19

Samuel S. White , Qing Pei , Lukáš Dolák | Environmental History

The history of climate and society (HCS)—or “climate history”—is the study of past climate and weather and their place in human affairs. HCS combines methods and perspectives from the natural … The history of climate and society (HCS)—or “climate history”—is the study of past climate and weather and their place in human affairs. HCS combines methods and perspectives from the natural and social sciences and humanities. It also comprises diverse approaches to research and publication, ranging from narrative histories in single-authored monographs to technical articles in scientific journals written by large interdisciplinary teams. Its main areas of research include (1) reconstruction of past climatic changes, variations, and extreme weather; (2) societal impacts and sources of vulnerability and resilience; (3) societal adaptations and responses; and (4) past knowledge and perceptions of climate and weather. HCS has brought new insights into history and perspectives on present global warming. Researchers have identified important and complex roles of climate change, climate variability, and extreme weather in past events, while challenging simple climate determinism. Nevertheless, the rapid growth and diversity of the field have brought challenges. Major issues include how to combine information from heterogeneous physical and written sources; how to integrate quantitative and qualitative data and methods; how to analyze causation; how to realize consilience across disciplines in the humanities, social, and natural sciences; and how to work across disparate spatial and temporal scales. This article presents works that have defined and advanced methods in HCS, especially recent works that have addressed these difficult issues. In addition to methodological studies and reviews, it includes case studies showcasing new approaches and concepts. In practice, methods from many disciplines can contribute to HSC research. These include special techniques in archaeology (radiocarbon dating, isotopic analysis, paleopathology, paleogenomics) and paleoclimatology (dendrochronology, speleology, glaciology, palynology) as well as the humanities and social sciences. However, these methods have their own specialized literatures, which are beyond the scope of this article. This bibliography focuses on innovations in historical climatology, or the reconstruction of past climates and weather from written and early instrumental (e.g., thermometer) records, and past climate–society interactions, particularly impacts of climate variability and extreme weather and sources of societal vulnerability, adaptation, and resilience. This bibliography aims to be representative, yet it is far from comprehensive. Bibliographies, databases, and journals are provided to help researchers keep up with the thousands of relevant publications and new research in the field.

The impacts of large-scale climate extremes on aboveground biomass in subtropical pine-dominant forests of Texas, USA: 20 years of monitoring

2025-06-19

Zhi-Ping Liu , Weimin Xi , Mukti Ram Subedi +2 more | Journal of Forestry Research

The Relationships Between Climate and Growth in Six Tree Species Align with Their Hydrological Niches

2025-06-19

J. Julio Camarero , José Antonio López Sáez , Álvaro Rubio‐Cuadrado +6 more | Forests

Understanding how regional and local climate variability drive radial growth in trees is necessary to assess the climate-warming mitigation potential of forests. However, tree species occurring in the same region … Understanding how regional and local climate variability drive radial growth in trees is necessary to assess the climate-warming mitigation potential of forests. However, tree species occurring in the same region differently respond to climate variability, including climate extremes such as droughts, depending on soil–moisture gradients (hydrological niche). We analyzed a tree-ring network built in a mountainous area (Sierra de Gredos, central Spain) to compare climate–growth responses between species and sites located along soil–moisture gradients. Tree-ring methods were applied to six tree species, and sampled in twelve sites, including conifers (Pinus pinaster) and broadleaves (Quercus pyrenaica, Quercus robur, Quercus ilex, Celtis australis, and Prunus lusitanica). Series of growth indices were correlated with climate variables and climate indices (NAO, North Atlantic Oscillation). The radial growth of most species was enhanced by high growing-season precipitation, linked to negative NAO phases. The influence of precipitation on growth variability strengthened as site elevation decreased, particularly in the case of C. australis and oak species. The topographical modulation of climate–growth couplings indicates that the hydrological niche drives species responses to water shortage. Tree-ring data could be used to refine time-dependent hydrological niches.

Recovery and Reconstructions of 18th Century Precipitation Records in Italy: Problems and Analyses

2025-06-19

Antonio della Valle , Francesca Becherini , Dario Camuffo | Climate

Precipitation is one of the main meteorological variables in climate research and long records provide a unique, long-term knowledge of climatic variability and extreme events. Moreover, they are a prerequisite … Precipitation is one of the main meteorological variables in climate research and long records provide a unique, long-term knowledge of climatic variability and extreme events. Moreover, they are a prerequisite for climate modeling and reanalyses. Like all meteorological observations, in the early period, every observer used a personal measuring protocol. Instruments and their locations were not standardized and not always specified in the observer’s metadata. The situation began to change in 1873 with the foundation of the International Meteorological Committee, though the complete standardization of protocols, instruments, and exposure was reached in 1950 with the World Meteorological Organization. The aim of this paper is to present and discuss the methodology needed to recover and reconstruct early precipitation records and to provide high-quality dataset of precipitation usable for climate studies. The main issues that have to be addresses are described and critically analyzed based on the longest Italian precipitation series to which the methodology was successfully applied.

Improving phenological event identification in trees using manually measured dendrometer data: conventional approaches vs. the novel two-stage threshold approach

2025-06-18

Przemysław A. Jankowski , Rafael Calama , Jorge Aldea +3 more | Frontiers in Forests and Global Change

Accurate detection of phenological events, such as growth onset, cessation, and seasonal transitions, is essential for understanding tree growth dynamics, particularly in Mediterranean forests where bimodal growth patterns are common. … Accurate detection of phenological events, such as growth onset, cessation, and seasonal transitions, is essential for understanding tree growth dynamics, particularly in Mediterranean forests where bimodal growth patterns are common. While microcore analysis remains the most precise method, its labor-intensive nature has led researchers to rely on dendrometer-based approaches. However, traditional methods using dendrometer data— such as parametric growth curve fitting with phenological events detected as relative thresholds—are often biased by hydration-related fluctuations and may fail to accurately capture complex growth patterns. In this study, we compared commonly used detection methods, including the Gompertz and Richards parametric functions, a generalized additive model (GAM), and the zero-growth (ZG) concept, with a novel approach: the two-stage threshold approach (2STA). Our results showed that the 2STA consistently outperformed existing methods in identifying spring onset, summer cessation, and autumn onset, exhibiting deviations within the expected measurement uncertainty (±7 days). The method’s reliance on direct growth rate transitions, rather than smoothed curves or arbitrary percentiles, reduced errors associated with hydration-related stem fluctuations. However, year cessation was best estimated using a 95% relative growth threshold derived from the Richards function. These findings highlight the potential of the 2STA as a robust and objective method for phenological event detection using manually collected band dendrometer data, particularly for species with complex intra-annual growth patterns. Future research should focus on refining climate-based thresholds for cambial activity and validating the method across a wider range of species and environmental conditions.

Climatic aridification and its driving mechanism in the Three-River Source Region over the past millennium

2025-06-18

Changrun Wu , Xiangzhong Li , Guangxin Liu +4 more | Quaternary Science Reviews

Hydrological conditions lead to asynchronised responses of alpine plant communities to temperature changes at the watershed scale

2025-06-17

Liyuan Ma , Wencong Lv , Jianqing Du +7 more | Plant and Soil

Patterns of Intra-Order Variation in Shoot Traits Are Order-Specific Along the Branch Basal Height Gradient of Larix principis-rupprechtii

2025-06-17

Yang Yu , Huayong Zhang , Zhongyu Wang +1 more | Forests

Intra-order trait variation is a key driver of aboveground shoot performance at different branch basal heights. Although the basic light exposure and nutrient supply to shoots vary with branch basal … Intra-order trait variation is a key driver of aboveground shoot performance at different branch basal heights. Although the basic light exposure and nutrient supply to shoots vary with branch basal height, most studies have focused on inter-order variation in shoot traits. However, how and to what extent shoot traits change with branch basal height, as well as whether a general intra-order pattern exists among different shoot orders, remain largely unclear. We compared intra-order variation in shoot diameter, length, specific stem length (SSL), and stem tissue density (STD) across four branching orders of Larix principis-rupprechtii along a vertical height gradient of 5.5–6.0 m. We tested (a) the degree of intra-order versus intra-order variation in shoot traits along the gradient and (b) whether intra-order trait patterns and their relationship with branch basal height were consistent across the four branching orders. Specifically, we hypothesized that within a branching order, shoot traits would undergo adjustments: shoots at higher positions would focus on growth (by increasing diameter and length), whereas shoots at lower positions would enhance resource acquisition (by increasing SSL) and protection (by increasing STD). Branching order explained most of the overall variation in shoot traits, including shoot diameter and length, but accounted for only a small portion of the variation in SSL and STD. Branch basal height explained only a small fraction of intra-order shoot trait variation, which was larger within than between basal heights. Moreover, the relationships between traits and branch basal height rarely aligned with our hypotheses and varied considerably across different shoot orders. Along the complex branch basal height gradient, where multiple traits change simultaneously, shoots of different shoot orders exhibit distinct patterns of variation, leading to specific intra-order trait variation. The lack of support for our hypothesis may result from the multifaceted interactions between light availability, spatial constraints, nutrient heterogeneity, and dynamic branch-order interactions. Our findings suggest that to better understand the impact of environmental variation on shoot performance, future research should integrate a more comprehensive analysis of shoot responses to change and measure a broader range of shoot traits and environmental variables.

Linking black spruce xylem anatomy to local hydroclimate in two boreal fens

2025-06-15

Karisa Tyler , Myroslava Khomik , Daniele Castagneri +5 more | Trees

Heatwave dynamics in Türkiye: a long-term spatiotemporal analysis of frequency, duration, and intensity (1970–2022)

2025-06-14

Hasan Tatlı , Hıdır Serkendiz | Environmental Monitoring and Assessment

Fires and drought during the Euro-American settlement period (1850-1950) in the Nebraska Sand Hills

2025-06-14

James V. Benes , Paul R. Hanson , Sherilyn C. Fritz | The Holocene

The connections among human activity, fire, and drought are examined in this study of historic records and sediment cores collected from six lakes within the Nebraska Sand Hills. We use … The connections among human activity, fire, and drought are examined in this study of historic records and sediment cores collected from six lakes within the Nebraska Sand Hills. We use microscopic charcoal particles from lake sediment cores to reconstruct fire history from ~1800 to 1950 C.E. We also use historical documents and the dates of post office establishment to constrain Euro-American settlement patterns in the regions adjacent to the cored lakes and compare the fire histories with the historic record of regional droughts to understand the connections between environmental conditions and land-use change associated with Euro-American settlement. Fires in the Great Plains are commonly assumed to be controlled by fuel availability, and in many studies periods of higher biomass burning are attributed to greater fuel loads. While both periods of drought resulted in decreases in biomass burning, the early 20th century drought (Dust Bowl) resulted in the lowest levels of burning during our period of inquiry. However, in one site, we found that increases in biomass burning occurred during periods of late 19th and early 20th century droughts, and we attribute these anomalies to increased anthropogenic ignitions or a localized increase in fuel loads. Above average biomass burning is recorded at all but one of our study sites during the initial phases (ca. 1850–1875 C.E.) of Euro-American settlement. Afterward, the six sites become much more varied and regional trends are less coherent, most likely because of the low population density and temporal scale of inquiry.

Tree radial growth and vegetation dynamics in northern China and northern Patagonia regulated by ocean–atmosphere circulation

2025-06-13

Tiyuan Hou , Feng Chen , Xiaoen Zhao +7 more | Forest Ecology and Management

A new method for alpine timberline peaks extraction based on remote sensing and inverted digital elevation model

2025-06-12

Luguang Jiang , Ye Liu | Geo-spatial Information Science

Dynamics and Structural Changes in the Janj Mixed Old-Growth Mountain Forest: Continuing Decline of Conifers

2025-06-11

Srđan Bilić , Vojislav Dukić , Srđan Keren +1 more | Forests

Old-growth forests are rare in Europe, yet they play a critical role in biodiversity and carbon storage. This study examines the structural dynamics of the Janj old-growth forest in the … Old-growth forests are rare in Europe, yet they play a critical role in biodiversity and carbon storage. This study examines the structural dynamics of the Janj old-growth forest in the Dinaric Alps using repeated field measurements from 2011 and 2021 at 39 systematically arranged 12 m radius plots. All trees (DBH ≥ 7.5 cm), regeneration (10 cm height to 7.5 cm DBH), and coarse woody debris (CWD) were assessed. Results revealed that total basal area declined by 3.5 m2 ha−1 over the decade, primarily driven by significant reductions in stem density for silver fir (p = 0.001) and Norway spruce (p = 0.001). In contrast, European beech maintained a stable basal area throughout the study period. Moreover, silver fir exhibited a significant increase in mean diameter (p = 0.032) and a pronounced rise in regeneration individuals (t = 3.257, p = 0.002). These findings underscore a gradual compositional shift towards European beech dominance, with conifers facing higher mortality in larger diameter classes. The substantial volume of CWD (463 m3 ha−1) highlights advanced decay dynamics consistent with mature forest conditions. This study emphasizes the value of repeated measurements to capture subtle yet important successional changes in primeval forests, which is essential for conservation planning and sustainable forest management.