Search

Accelerated glacier mass loss is primarily attributed to greenhouse-induced global warming. Land–climate interactions have increasingly been recognized as an important forcing at the regional-local scale, but the related effects on the Himalayan glaciers are less explored and thought to be an important factor regulating spatial heterogeneity. The aim of the present study is a multi-decadal approximation of glacier—hydroclimate interaction over the western region of the central Himalaya (WCH). Multi-species, highly coherent, tree-ring cellulose δ18O chronologies from three sites across the WCH were used to derive atmospheric humidity (Atmospheric Moisture Content: AMC) record of the last four centuries. Annual-scale AMC reconstruction implies a decreasing regional atmospheric moisture since the mid-19th century and a sharp decline in recent decades (1960s). Coherency analyses between regional AMC and glacier mass balance (GMB) indicate an abrupt phase-shift in the relationship after the 1960s within a common record of the last 273 years. To ascertain the cause of this phase-shift, annual AMC was disintegrated into seasonal-scale, utilizing ∼200 years of δ18O record of a deciduous tree species. Seasonal (winter: October–March; summer: April–September) AMC reconstructions and disaggregation results indicate higher sensitivity of regional ice-mass variability to winter moisture dynamics than summer.Winter season AMC reconstruction confirms a revival of winter westerlies-driven moisture influx in the region since the 1970 s. Meanwhile, the record for the summer season AMC indicates a gradual decline in moisture influx from the beginning of the 20th century. Interestingly, despite a prominent decline in Indian summer monsoon (ISM) precipitation after the mid-20th century, the summer season AMC—GMB relation remained stable. We hypothesize that decadal-scale greening, and consequently increased evapotranspiration and pre-monsoon precipitation might have been recycled through the summer season, to compensate for the ISM part of precipitation. However, isotope-enabled ecophysiological models and measurements would strengthen this hypothesis. In addition, high-resolution radiative forcing and long-term vegetation greening trends point towards a probable influence of valley greening on GMB. Our results indicate that attribution of ice mass to large-scale dynamics is likely to be modulated by local vegetation changes. This study contributes to the understanding of long-term hydroclimate—ice mass variability in the central Himalaya, where predictions are crucial for managing water resources and ecosystems.

Supplemental material, sj-docx-3-hol-10.1177_09596836221138352 for Inter-annual and intra-annual tree-ring oxygen isotope signals in response to monsoon rainfall in northwestern Thailand by Sineenart Preechamart, Nathsuda Pumijumnong, Achim Bräuning, Chotika Muangsong, Binggui Cai and Supaporn Buajan in The Holocene

Supplemental material, sj-docx-2-hol-10.1177_09596836221138352 for Inter-annual and intra-annual tree-ring oxygen isotope signals in response to monsoon rainfall in northwestern Thailand by Sineenart Preechamart, Nathsuda Pumijumnong, Achim Bräuning, Chotika Muangsong, Binggui Cai and Supaporn Buajan in The Holocene

Supplemental material, sj-docx-3-hol-10.1177_09596836221138352 for Inter-annual and intra-annual tree-ring oxygen isotope signals in response to monsoon rainfall in northwestern Thailand by Sineenart Preechamart, Nathsuda Pumijumnong, Achim Bräuning, Chotika Muangsong, Binggui Cai and Supaporn Buajan in The Holocene

Supplemental material, sj-docx-2-hol-10.1177_09596836221138352 for Inter-annual and intra-annual tree-ring oxygen isotope signals in response to monsoon rainfall in northwestern Thailand by Sineenart Preechamart, Nathsuda Pumijumnong, Achim Bräuning, Chotika Muangsong, Binggui Cai and Supaporn Buajan in The Holocene

Stem radial variations of Corsican Black pine (Pinus nigra Arnold subsp. laricio Maire) and Maritime pine (Pinus pinaster Aiton) were monitored to quantify the impact of two meteorologically contrasting consecutive years. On the French island of Corsica, in the western Mediterranean basin, the year 2017 was extremely dry, while 2018 was exceptionally wet. We attached electric band dendrometers to 36 pines along an east–west transect, spanning the central mountain range, and set up automated weather stations at all five sites, ranging from 10 m asl to 1600 m asl. Stem radial variations (SRV) were separated into irreversible growth (GRO) and tree water deficit (TWD) periods. During the drought of 2017, the most severe tree water deficits occurred in the western part of the island, whereas trees at higher elevations were more affected than at lower elevations. A prolonged decrease of SRV, even close to the tree line, suggests bimodal growth and reveals high plasticity of growth patterns in both Corsican pines. Stem radial variations correlated significantly with precipitation and temperature. The positive correlations of GRO with precipitation and the negative correlations of TWD with temperature imply that high evapotranspiration led to the intense period of TWD in 2017. A novel approach was used to further investigate the growth/climate relationship by including synoptic-scale pressure situations. This revealed that an elevation gradient in GRO per weather pattern was only present in the wet year and that even rarely occurring weather patterns can have a substantial impact on tree growth. This novel approach provides a more comprehensive insight into meteorological drivers of tree growth patterns by incorporating different scales of the climatic system.

Maximum latewood density (MXD) measurements from long-lived Black pines (Pinus nigra spp. laricio) growing at the upper treeline in Corsica are one of the few archives to reconstruct southern European summer temperatures at annual resolution back into medieval times. Here, we present a compilation of five MXD chronologies from Corsican pines that contain high-to-low frequency variability between 1168 and 2016 CE and correlate significantly (p &lt, 0.01) with the instrumental April–July and September–October mean temperatures from 1901 to 1980 CE (r = 0.52−0.64). The growth–climate correlations, however, dropped to −0.13 to 0.02 afterward, and scaling the MXD data resulted in a divergence of &gt, 1.5 °C between the colder reconstructed and warmer measured temperatures in the early-21st century. Our findings suggest a warming-induced shift from initially temperature-controlled to drought-prone MXD formation, and therefore question the suitability of using Corsican pine MXD data for climate reconstruction.

Langlebige Bäume können langfristige Klimaänderungen, aber auch kurzfristige Witterungsextreme in Form ihres Zuwachses und ihrer holzanatomischen Struktur archivieren. Die Variationen der Jahrringbreite und anderer Holzparameter reagieren dabei art- und standortsspezifisch auf unterschiedliche Klimafaktoren. An kalt-humiden Gebirgsstandorten ist die Jahrringbreite oft mit den Temperaturen der Wintermonate vor der Wachstumsphase oder mit der mittleren Temperatur über die Vegetationsperiode korreliert, während an semiariden Gebirgsstandorten der Zuwachs eher durch die verfügbare Feuchtigkeit während der Wachstumsperiode limitiert wird. Die maximale Spätholzdichte ist ein guter Indikator für die Sommertemperatur, während Isotopenverhältnisse des Sauerstoffs und des Kohlenstoffs in der Zellulose des Holzes sensitiv auf hydroklimatische Klimaparameter und Verdunstung reagieren. Quantitative Analysen der holzanatomischen Struktur ermöglichen eine extrem hohe zeitliche Auflösung der gespeicherten Klimainformation bis auf wenige Tage. Durch Kombinationen mehrerer Holzparameter mit unterschiedlicher saisonaler Sensitivität kann eine umfassende Rekonstruktion des Klimageschehens im Jahreslauf durchgeführt werden. Somit können Jahrringdaten auch mit anderen Klimaproxies wie Eisbohrkernen, Seesedimenten oder Abflussdaten verglichen werden, bieten dabei aber eine exakte, jahrgenaue Datierung. Im Hochgebirge bieten sich dadurch Möglichkeiten, landschaftsdynamische Prozesse wie Gletscherschwankungen und geomorphologische Ereignisse anhand von Jahrringdaten zu analysieren. Mit Hilfe langlebiger Straucharten können Jahrringanalysen auch in die alpine Region jenseits der Baumgrenze ausgeweitet werden. Which environmental factors can be analyzed using tree rings? Long-living trees can archive long-term climate changes, but also short-term weather extremes by their growth responses and adjustment in wood anatomical structure. The variations in the width of tree rings and other wood parameters react differently to various environmental factors, depending on species and location. At cold-humid high-elevation sites, tree-ring width is often correlated with temperatures during the winter months before the growth phase, or with the mean temperature during the vegetation period. In contrast, tree growth in semi-arid mountainous environments is mainly limited by the available moisture conditions during the growing season. The maximum late wood density is a good indicator to reconstruct summer temperatures, while the isotopic variations of oxygen and carbon in tree-ring cellulose are sensitive to hydroclimatic climate parameters and evaporation. Quantitative analyses of the wood anatomical structure allow an extremely high temporal resolution of the stored climate information down to a few days. By combining several wood parameters with different seasonal sensitivities, a comprehensive reconstruction of the climate during the course of the year can be accomplished. Thus, tree-ring data can also be compared with other climate proxies, such as ice cores, lake sediments or runoff data, but additionally offer the advantage of an exact, year-accurate dating. In high mountain areas, this offers the opportunity to analyze landscape dynamic processes such as glacier fluctuations and geomorphological events using tree-ring data. With the help of long-living shrub species, tree-ring analyses can be extended into the alpine region above the tree-line

The Himalayan region has already witnessed profound climate changes detectable in the cryosphere and the hydrological cycle, already resulting in drastic socio-economic impacts. We developed a 619-yea-long tree-ring-width chronology from the central Nepal Himalaya, spanning the period 1399−2017 CE. However, due to low replication of the early part of the chronology, only the section after 1600 CE was used for climate reconstruction. Proxy climate relationships indicate that temperature conditions during spring (March−May) are the main forcing factor for tree growth of Tsuga dumosa at the study site. We developed a robust climate reconstruction model and reconstructed spring temperatures for the period 1600−2017 CE. Our reconstruction showed cooler conditions during 1658−1681 CE, 1705−1722 CE, 1753−1773 CE, 1796−1874 CE, 1900−1936 CE, and 1973 CE. Periods with comparably warmer conditions occurred in 1600−1625 CE, 1633−1657 CE, 1682−1704 CE, 1740−1752 CE, 1779−1795 CE, 1936−1945 CE, 1956−1972 CE, and at the beginning of the 21st century. Tropical volcanic eruptions showed only a sporadic impact on the reconstructed temperature. Also, no consistent temperature trend was evident since 1600 CE. Our temperature reconstruction showed positive teleconnections with March−May averaged gridded temperature data for far west Nepal and adjacent areas in Northwest India and on the Southwest Tibetan plateau. We found spectral periodicities of 2.75−4 and 40−65 years frequencies in our temperature reconstruction, indicating that past climate variability in central Nepal might have been influenced by large-scale climate modes, like the Atlantic Multi-decadal Oscillation, the North Atlantic Oscillation, and the El Niño-Southern Oscillation.

Stable isotopes of tree rings are frequently used as proxies in climate change studies. However, species-specific relationships between climate and tree-ring stable isotopes have not yet been studied in riparian forests in the savannas of West Africa. Four cross-dated discs, each of Afzelia africana Sm. (evergreen) and Anogeissus leiocarpus (DC.) Guill. &amp, Perr. (deciduous) in the humid (HSZ) and dry (DSZ) savanna zones of the Volta basin in Ghana were selected from a larger tree-ring dataset to assess the relationships between the tree-ring carbon isotope composition (&delta, 13C values) and climatic parameters. The atmospherically corrected &delta, 13C values of both studied species showed that A. africana was enriched in 13C compared to A. leiocarpus. Strong correlations were found between &delta, 13C values of A. africana and A. leiocarpus with temperature, but weak correlations with precipitation. Spatial correlation analysis revealed significant relationships between &delta, 13C values of both tree species and Sea Surface Temperatures in the Gulf of Guinea in the southern Atlantic Ocean. The results suggest that the carbon isotope composition of riparian trees in the Volta river basin has a potential to reconstruct climate variability and to assess tree ecological responses to climate change.

Xylem hydraulic adjustment to global climatic changes was reported from temperate, boreal, and Mediterranean tree species. Yet, the long-term hydraulic adjustment in tropical tree species has not been studied so far. Here we developed the first standard chronologies of three hydraulic trait variables for three South Asian moist forest tree species to analyze their long-term hydraulic responses to changing climate. Based on wood anatomical measurements, we calculated Hagen–Poiseuille hydraulically weighted vessel diameter (DH), potential specific hydraulic conductivity (KS), and vulnerability index (VX) and developed standard chronologies of these variables for Chukrasia tabularis, Toona ciliata, and Lagerstroemia speciosa which are different in their xylem structure, wood density, shade tolerance, growth rates, and habitat preferences. Bootstrap correlation analysis revealed that vapor pressure deficit (VPD) strongly positively influenced the xylem water transport capacity in C. tabularis, whereas T. ciliata was affected by both temperature and precipitation. The hydraulic conductivity of L. speciosa was mainly affected by temperature. Different adjustment strategies were observed among the species, probably due to the differences in life history strategies and xylem properties. No positive relationship of conductivity and radial growth was found, but a trade-off between hydraulic safety and efficiency was observed in all studied species.

Atmospheric circulations influence local and regional weather conditions and, thus, tree growth. To identify summer weather types relevant for tree growth, and their associated synoptic-scale circulation patterns, an atmospheric circulation tree ring index (ACTI) dataset, derived from 414 tree-ring sites across Asia spanning the period 1871–2010, was created. Modes of common variability in the ACTI dataset were compared with leading modes of observed summertime 500-hPa geopotential height. The first four ACTI modes (explaining 88% of the total variance) were associated with pressure centers over Eurasia, the tropics, and the Pacific Ocean. The high spatiotemporal resemblance between the leading circulation modes, derived from both tree rings and 500-hPa geopotential height fields, indicates a strong potential for reconstructing large-scale circulation patterns from tree rings in Asia. This would allow investigations of natural atmospheric circulation variability prior to anthropogenic climate change and provide a means to validate model simulations of climate predictions.

Tree rings are natural archives of climate and environmental information with a yearly resolution. Indeed, wood anatomical, chemical, and other properties of tree rings are a synthesis of several intrinsic and external factors, and their interaction during tree growth. In particular, Intra-Annual Density Fluctuations (IADFs) can be considered as tree-ring anomalies that can be used to better understand tree growth and to reconstruct past climate conditions with intra-annual resolution. However, the ecophysiological processes behind IADF formation, as well as their functional impact, remain unclear. Are IADFs resulting from a prompt adjustment to fluctuations in environmental conditions to avoid stressful conditions and/or to take advantage from favorable conditions? In this paper we discuss: (1) the influence of climatic factors on the formation of IADFs (2) the occurrence of IADFs in different species and environments (3) the potential of new approaches to study IADFs and identify their triggering factors. Our final aim is to underscore the advantages offered by network analyses of data and the importance of high-resolution measurements to gain insight into IADFs formation processes and their relations with climatic conditions, including extreme weather events.

Tree rings are natural archives of climate and environmental information with a yearly resolution. Indeed, wood anatomical, chemical, and other properties of tree rings are a synthesis of several intrinsic and external factors, and their interaction during tree growth. In particular, Intra-Annual Density Fluctuations (IADFs) can be considered as tree-ring anomalies that can be used to better understand tree growth and to reconstruct past climate conditions with intra-annual resolution. However, the ecophysiological processes behind IADF formation, as well as their functional impact, remain unclear. Are IADFs resulting from a prompt adjustment to fluctuations in environmental conditions to avoid stressful conditions and/or to take advantage from favorable conditions? In this paper we discuss: (1) the influence of climatic factors on the formation of IADFs; (2) the occurrence of IADFs in different species and environments; (3) the potential of new approaches to study IADFs and identify their triggering factors. Our final aim is to underscore the advantages offered by network analyses of data and the importance of high-resolution measurements to gain insight into IADFs formation processes and their relations with climatic conditions, including extreme weather events.

Tree rings are natural archives of climate and environmental information with a yearly resolution. Indeed, wood anatomical, chemical, and other properties of tree rings are a synthesis of several intrinsic and external factors, and their interaction during tree growth. In particular, Intra-Annual Density Fluctuations (IADFs) can be considered as tree-ring anomalies that can be used to better understand tree growth and to reconstruct past climate conditions with intra-annual resolution. However, the ecophysiological processes behind IADF formation, as well as their functional impact, remain unclear. Are IADFs resulting from a prompt adjustment to fluctuations in environmental conditions to avoid stressful conditions and/or to take advantage from favorable conditions? In this paper we discuss: (1) the influence of climatic factors on the formation of IADFs; (2) the occurrence of IADFs in different species and environments; (3) the potential of new approaches to study IADFs and identify their triggering factors. Our final aim is to underscore the advantages offered by network analyses of data and the importance of high-resolution measurements to gain insight into IADFs formation processes and their relations with climatic conditions, including extreme weather events.

Regarding woody plant responses on higher atmospheric inputs of the macronutrients nitrogen (N) and phosphorous (P) on tropical forests in the future, an adaptive modification of wood anatomical traits on the cellular level of woody plants is expected. As part of an interdisciplinary nutrient manipulation experiment (NUMEX) carried out in Southern Ecuador, we present here the first descriptive and quantitative wood anatomical analysis of the tropical evergreen tree species Alchornea lojaensis (Euphorbiaceae). We sampled branch wood of nine individual trees belonging to treatments with N fertilization, N+P fertilization, and a control group, respectively. Quantitative evaluations of eleven different vessel parameters were conducted. The results showed that this endemic tree species will be able to adapt well to the future effects of climate change and higher nutrient deposition. This was firstly implied by an increase in vessel diameter and consequently a higher theo. area-specific hydraulic conductivity with higher nutrient availability. Secondly, the percentage of small vessels (0–20 μm diameter) strongly increased with fertilization. Thirdly, the vessel arrangement (solitary vessels vs. multiple vessel groupings) changed toward a lower percentage of solitary vessel fraction (VS), and concurrently toward a higher total vessel grouping index (VG) and a higher mean group size of non-solitary vessels (VM) after N and N+P addition. We conclude that higher nutrient availability of N and N+P triggered higher foliage amount and water demand, leading to higher cavitation risk in larger vessels. This is counteracted by a stronger grouping of vessels with smaller risk of cavitation to ensure water supply during drier periods that are expected to occur in higher frequency in the near future.

The seasonal climate drivers of the carbon cycle in tropical forests remain poorly known, although these forests account for more carbon assimilation and storage than any other terrestrial ecosystem. Based on a unique combination of seasonal pan-tropical data sets from 89 experimental sites (68 include aboveground wood productivity measurements and 35 litter productivity measurements), their associate canopy photosynthetic capacity (enhanced vegetation index, EVI) and climate, we ask how carbon assimilation and aboveground allocation are related to climate seasonality in tropical forests and how they interact in the seasonal carbon cycle. We found that canopy photosynthetic capacity seasonality responds positively to precipitation when rainfall is < 2000 mm.yr−1 (water-limited forests) and to radiation otherwise (light-limited forests); on the other hand, independent of climate limitations, wood productivity and litterfall are driven by seasonal variation in precipitation and evapotranspiration respectively. Consequently, light-limited forests present an asynchronism between canopy photosynthetic capacity and wood productivity. Precipitation first-order control indicates an overall decrease in tropical forest productivity in a drier climate.

Systematic investigations of the upper forest line (UFL) primarily concentrate on mid and high latitudes of the Northern Hemisphere, whereas studies of Neotropical UFLs are still fragmentary. This article outlines the extraordinary high tree diversity at the UFL within the Andean Depression and unravels the links between the comparatively low position of the local UFL, high tree-species diversity, and climate. On the basis of Gentry′s rapid inventory methodology for the tropics, vegetation sampling was conducted at 12 UFL sites, and local climate (temperature, wind, precipitation, and soil moisture) was investigated at six sites. Monotypic forests dominated by Polylepis were only found at the higher located margins of the Andean Depression while the lower situated core areas were characterized by a species-rich forest, which lacked the elsewhere dominant tree-species Polylepis. In total, a remarkably high tree-species number of 255 tree species of 40 different plant families was found. Beta-diversity was also high with more than two complete species turnovers. A non-linear relationship between the floristic similarity of the investigated study sites and elevation was detected. Temperatures at the investigated study sites clearly exceeded 5.5°C, the postulated threshold value for the upper tree growth limit in the tropics. Instead, quasi-permanent trade winds, high precipitation amounts, and high soil water contents affect the local position of the UFL in a negative way. Interestingly, most of the above-mentioned factors are also contributing to the high species richness. The result is a combination of a clearly marked upper forest line depression combined with an extraordinary forest line complexity, which was an almost unknown paradox.

Tree-ring chronologies underpin the majority of annually-resolved reconstructions of Common Era climate. However, they are derived using different datasets and techniques, the ramifications of which have hitherto been little explored. Here, we report the results of a double-blind experiment that yielded 15 Northern Hemisphere summer temperature reconstructions from a common network of regional tree-ring width datasets. Taken together as an ensemble, the Common Era reconstruction mean correlates with instrumental temperatures from 1794-2016 CE at 0.79 (p < 0.001), reveals summer cooling in the years following large volcanic eruptions, and exhibits strong warming since the 1980s. Differing in their mean, variance, amplitude, sensitivity, and persistence, the ensemble members demonstrate the influence of subjectivity in the reconstruction process. We therefore recommend the routine use of ensemble reconstruction approaches to provide a more consensual picture of past climate variability.

Tree-ring chronologies underpin the majority of annually-resolved reconstructions of Common Era climate. However, they are derived using different datasets and techniques, the ramifications of which have hitherto been little explored. Here, we report the results of a double-blind experiment that yielded 15 Northern Hemisphere summer temperature reconstructions from a common network of regional tree-ring width datasets. Taken together as an ensemble, the Common Era reconstruction mean correlates with instrumental temperatures from 1794-2016 CE at 0.79 (p

Tree-ring chronologies underpin the majority of annually-resolved reconstructions of Common Era climate. However, they are derived using different datasets and techniques, the ramifications of which have hitherto been little explored. Here, we report the results of a double-blind experiment that yielded 15 Northern Hemisphere summer temperature reconstructions from a common network of regional tree-ring width datasets. Taken together as an ensemble, the Common Era reconstruction mean correlates with instrumental temperatures from 1794–2016 CE at 0.79 (p, Tree rings are a crucial archive for Common Era climate reconstructions, but the degree to which methodological decisions influence outcomes is not well known. Here, the authors show how different approaches taken by 15 different groups influence the ensemble temperature reconstruction from the same data.

Significance The variability of the Asian summer monsoon (ASM) is important for the functioning of ecological and societal systems at regional to continental scales, but the long-term evolution and interannual variability of this system is not well understood. Here, we present a stable isotope–based reconstruction of ASM variability covering 4680 BCE to 2011 CE. Superimposed on a gradual drying trend, a rapid drop in mean annual precipitation (>40%) toward persistently drier conditions occurred in ∼1675 BCE. This megadrought caused regional forest deterioration and enhanced aeolian activity affecting Chinese ecosystems. We argue that this abrupt aridification starting ∼2000 BCE triggered waves of human migration and societal transformation in northern China, which contributed to the alteration of spatial pattern of ancient civilizations., Asian summer monsoon (ASM) variability and its long-term ecological and societal impacts extending back to Neolithic times are poorly understood due to a lack of high-resolution climate proxy data. Here, we present a precisely dated and well-calibrated tree-ring stable isotope chronology from the Tibetan Plateau with 1- to 5-y resolution that reflects high- to low-frequency ASM variability from 4680 BCE to 2011 CE. Superimposed on a persistent drying trend since the mid-Holocene, a rapid decrease in moisture availability between ∼2000 and ∼1500 BCE caused a dry hydroclimatic regime from ∼1675 to ∼1185 BCE, with mean precipitation estimated at 42 ± 4% and 5 ± 2% lower than during the mid-Holocene and the instrumental period, respectively. This second-millennium–BCE megadrought marks the mid-to late Holocene transition, during which regional forests declined and enhanced aeolian activity affected northern Chinese ecosystems. We argue that this abrupt aridification starting ∼2000 BCE contributed to the shift of Neolithic cultures in northern China and likely triggered human migration and societal transformation.

Wälder stellen wichtige Ökosystemleistungen und -güter bereit und tragen damit maßgeblich zur Lebensgrundlage der Menschen bei. Sie unterliegen jedoch vielseitigen Bedrohungen, welche die volle Funktionsfähigkeit des Ökosystems gefährden und deren Entwicklung beeinträchtigen. Inwiefern sich diese auf die Funktionsweise und die Walddynamik in Kasachstan äußert, ist aufgrund der wenigen durchgeführten dendroklimatischen Untersuchungen im Detail unklar. Hinzu kommt, dass für die qualitative Bewertung der Klima-Wachstums-Beziehungen diese Studien in ihrer räumlichen und zeitlichen Abdeckung unzureichend sind. Zu den bereits verfügbaren Informationen fehlen zur Einschätzung gemeinsamer Muster und Unterschiede hinsichtlich der Reaktion des Baumwachstums auf das Klima qualitative Analysen. Hierfür wurden alle verfügbaren Publikationen zu den dendroklimatischen Untersuchungen in Kasachstan analysiert. Diese Analyse ermöglichte nicht nur die Zusammenfassung der verfügbaren Informationen zu den Beziehungen zwischen Klima und Wachstum, sondern lieferte zudem konkrete Informationen zu vorhandenen Forschungslücken. Einige dieser Lücken wurden durch die Untersuchungen der variierenden Klima-Wachstums-Beziehungen der Schrenks Fichte im Einzugsgebiet des Ile-Flusses geschlossen. Die durchgeführte Studie verdeutlicht unterschiedliche Reaktion von Früh-, Spätholz und Gesamtringbreite auf den Klimawandel. Der starke Einfluss des Klimawandels wurde durch die Abnahme des Temperatursignals um die 1970er-Jahre beobachtet. Eine erkennbare Periodizität bei Schwankungen der Baumringindizes lässt auf einen Einfluss bestimmter Klimaindizes, z. B. der Nordatlantischen Oszillation u. a. schließen. Die im Rahmen dieser Dissertation durchgeführten Untersuchungen tragen zur Entwicklung eines Baumring-Netzwerkes in Kasachstan bei. Die erhoben Daten sind für die Bewertung möglicher Auswirkungen des Klimawandels auf die Wälder der Schrenks Fichte in Kasachstan hilfreich. Forests are very important for people’s livelihood. They provide important ecosystem services and goods. However there are many threats that interfere with the normal functioning and development of forest ecosystems. The influence of climate change processes on functioning and dynamics of forests in Kazakhstan is understudied, and is observed in the relatively small number of dendroclimatic studies. Additional limitations in understanding of climate-growth relationships arise from insufficient spatial and temporal coverage of those studies and the absence of a qualitative analysis of already available information for identification of common patterns and differences in the impacts of tree growth on climate. The main research goal of this thesis was accordingly to address these limitations. An analysis of all available publications on dendroclimatic studies in Kazakhstan was performed. This analysis not only summarized the available information on climate-growth relationships, but also provided certain information about existed research gaps. Some of those gaps were addressed by an investigation of variation of climate-growth relationships of Schrenk spruce in the Ile River basin. The study revealed certain differences in reaction of earlywood, latewood and total ring width on climate in four mountain ranges of the Ile River basin. The strong influence of climate change was observed in a decreasing temperature signal around the 1970s. Revealed periodicities in the fluctuation of tree-ring indices suggested an influence of certain climate indices such as North Atlantic Oscillation and the Tropospheric Biennial Oscillations. Collectively, the analysis in this dissertation contributes to development of the tree-ting network of Kazakhstan. Obtained information should help in assessment of possible impacts of climate change on Schrenk spruce forests in Kazakhstan.

Under current climate change scenarios, validation of drought indices is of paramount importance, since the frequency and intensity of droughts are likely to increase. The thesis contributes a comprehensive comparison of drought indices, by validating them against various environmental datasets, such as tree ring, streamflow and carbon flux data on the European and regional scales. Furthermore, the potential of a satellite-based vegetation index to act as a proxy for drought studies was examined by linking it with tree ring data on a global scale. Unter den aktuellen Klimawandelszenarien ist die Validierung von Dürreindizes von größter Bedeutung, da Häufigkeit und Intensität von Dürren wahrscheinlich zunehmen werden. Diese Arbeit liefert einen umfassenden Vergleich von Dürreindizes, indem sie diese gegen verschiedene regionale und globale Umweltdatensätze wie Jahrringdaten von Bäumen, Daten zur Wasserführung von Flüssen und Kohlenstoff-Flüsse validiert. Darüber hinaus wurde das Potenzial eines satellitenbasierten Vegetationsindex als Proxy für Dürrestudien durch Verknüpfung mit Jahrringdaten auf globaler Ebene untersucht.

Tree rings are natural archives of climate and environmental information with a yearly resolution. Indeed, wood anatomical, chemical, and other properties of tree rings are a synthesis of several intrinsic and external factors, and their interaction during tree growth. In particular, Intra-Annual Density Fluctuations (IADFs) can be considered as tree-ring anomalies that can be used to better understand tree growth and to reconstruct past climate conditions with intra-annual resolution. However, the ecophysiological processes behind IADF formation, as well as their functional impact, remain unclear. Are IADFs resulting from a prompt adjustment to fluctuations in environmental conditions to avoid stressful conditions and/or to take advantage from favorable conditions? In this paper we discuss: (1) the influence of climatic factors on the formation of IADFs; (2) the occurrence of IADFs in different species and environments; (3) the potential of new approaches to study IADFs and identify their triggering factors. Our final aim is to underscore the advantages offered by network analyses of data and the importance of high-resolution measurements to gain insight into IADFs formation processes and their relations with climatic conditions, including extreme weather events. This research is linked to activities conducted within the COST FP1106 “STReESS” network. Collection of datasets used for this work was supported by the projects: – ELENA (CGL2012-31668) and CGL2015-69985-R funded by the Spanish Science and Innovation Ministry (MICINN) and FEDER funds. – PGIDIT06PXIB502262PR funded by Dirección Xeral de Investigación, Desenvolvemento e Innovación, Xunta de Galicia. – Slovenian Research Agency (program P4-0015). – Austrian Science Fund (FWF-TRP 122-B16). – Russian Science Foundation 14-14-00295. – POCI/CLI/58680/2004 and PTDC/AAC-AMB/111675/2009 funded by the Portuguese Foundation for Science and Technology (FCT) and the European Union (POCI 2010) SI

The eastern Nyainqêntanglha Range is located at the southeastern fringe of the Tibetan Plateau, representing one of the major pathways of monsoonal moisture from the foreland to the plateau. Owing to the combination of a rugged high mountain topography and abundant moisture, more than 8000 km² of the eastern Nyainqêntanglha Range are covered by monsoonal temperate glaciers. Previous studies have shown that these glaciers are particularly sensitive to climate change. The eastern Nyainqêntanglha Range’s glaciers thus provide an important archive of past and present climate dynamics. The interplay of glaciers, topography and climate in this region is, however, hardly constrained to date. Furthermore, a consistent late Holocene glacial chronology, combining dating results with geomorphological and sedimentological evidence, is still lacking. The research synthesized in this dissertation aims to improve the understanding of spatial and temporal patterns of late Holocene glacier fluctuations in the eastern Nyainqêntanglha Range and to identify relevant climatic forcing mechanisms. In this context, focus was put on the Little Ice Age (LIA) because its maximum glacier advance represents the last major turning point from an advancing to a retreating glacier regime, implying a transient steady-state. Aiming to achieve a consistent and well-constrained overall result, the study was conducted by application of a multi-proxy approach including glaciological, geomorphological, sedimentological and dendrochronological methods, aided by optically stimulated luminescence and radiocarbon dating. Starting with remote sensing, 1964 glaciers were mapped from a Landsat ETM+ scene and subsequently parameterized by DEM-supported measurements. Analysis of the geomorphological evidence provided the basis to investigate patterns of modern glaciation and post-LIA changes quantitatively, which revealed substantial retreat. An evaluation of different methods to calculate equilibrium line altitudes (ELAs) showed that an optimized toe-to-ridge altitude method was more suitable than other methods in settings with complex topography, a lack of mass balance measurements, and adequate hypsographic data. The results of these studies provided insights into the complex topography–climate–glacier coupling and revealed the underlying patterns. These included a combination of distinct insolation effects, channeling of moisture by the valley system, foehn effects in lee positions, orographic precipitation in luv positions, and large-scale hygric and thermal gradients. Additionally, analysis of glacier length and ELA changes showed that the sensitivity of the glacier’s reaction to climatic changes is positively correlated to both size of the glacier and the grade of continentality. Field-work-based work focused on the creation of a consistent morphosequence. The results yielded similar configurations and numbers of moraines at all studied settings, implying that similar climatic events affected the whole region since the LIA. The geomorphological settings of the glacier forelands were, however, remarkably different, showing the substantial impact of the local topography-climate-glacier configurations. A critical evaluation of different relative and numerical dating methods provided constraints for a conceptual chronosequence. They suggest that the LIA comprised several distinct glacier advances, particularly an early advance before ∼1500 CE and a succession to the maximum advance from the mid-17th to mid-18th century. After the LIA maximum, continued retreat that was only interrupted by short phases of stability followed, as evidenced by 2–3 recessional moraines in the investigated settings.

Der bereits stattfindende Klimawandel mit ansteigenden Temperaturen, einer Zunahme von Trockenperioden und Hitzewellen während der Vegetationsperiode wird das Risiko von Trockenstress für Bäume und Sträucher erheblich erhöhen. Eine der Herausforderungen ist daher die erfolgreiche Etablierung von gesunden, langlebigen und an die spezifischen urbanen Standorte adaptierten Bäume, um die ökologischen und ökonomischen Wohlfahrtswirkungen städtischen Grüns auch in Zukunft zu gewährleisten. Das Ziel dieser Arbeit war es deshalb, sowohl die Eignung einiger häufig verwendeter Straßenbaumarten für stark versiegelte Straßenbaumstandorte als auch deren Toleranz gegenüber Trockenstress am Beispiel von Dresden zu identifizieren. Die Arbeit verfolgt einen dendrochronologischen und einen physiologischen Ansatz. Im dendrochronologischen Teil der Arbeit wurden die Jahrringzeitreihen von 16 Straßenbaum-Chronologien, 3 Einzelbaum-Chronologien im Stadtgebiet von Dresden und 4 Chronologien eines trockenen Waldstandortes in einem Naturschutzgebiet sowie 2 Chronologien frischer Waldstandorte analysiert. Auf Basis der trendbereinigten Zuwachszeitreihen wurden Klima-Zuwachs-Relationen, moving correlations, Weiserjahranalysen und superposed epoch analyses (SEA) durchgeführt. Im physiologischen Teil der Arbeit wurde in den Sommermonaten der Jahre 2009 und 2010 auf vier urbanen Straßenbaumstandorten der lichtgesättigte Gasaustausch von sechs Baumarten und das Blattwasserpotential von vier Baumarten ermittelt. Für die Messperioden und in ausgewählten Trockenperioden wurde die Wassernutzungseffizienz der Baumarten verglichen. Auf urbanen Straßenbaumstandorten reagieren die Arten Acer platanoides, Acer pseudoplatanus und Fagus sylvatica stark sensitiv auf Trockenheit. Im Gegensatz dazu können die Arten Platanus x hispanica, Quercus robur subsp. sessiliflora und Quercus rubra als weniger trockenheitsempfindlich betrachtet werden. Die dendrochronologischen und physiologischen Ergebnisse erlauben für Tilia cordata Mill., Tilia platyphyllos und Pyrus communis eine Einordnung in eine mittlere Eignung für versiegelte Flächen. Aus den dendrochronologischen und physiologischen Ergebnissen dieser Untersuchung lässt sich schließen, dass sich die höheren Temperaturen und die zunehmenden Trockenperioden für alle untersuchten Arten negativ auswirken können. Dennoch zeigen die Baumarten Platanus x hispanica, Quercus robur subsp. sessiliflora und Quercus rubra, dass sie den sich verändernden Klimabedingungen auf stark versiegelten urbanen Standorten gut widerstehen können und auch in Zukunft eine hohe Vitalität beibehalten werden.

This volume is the result of the conference $\textit{Tree Rings in Archaeology, Climatology and Ecology}$ (TRACE) 2003, which took place from May 1st – 3rd 2003 at the Museum Catherijneconvent in Utrecht (NL) and was organized by Dr. E. Jansma of the Association for Tree-Ring Research (ATR). With the annual TRACE conference, the ATR intends to present the state of the art as well as new research perspectives in the field of dendrochronology, to actively stimulate further investigations and closer collaboration between different research groups, and to strengthen dendrochronological sciences in central European research. About 70 scientists and students from Austria, Belgium, England, Germany, the Netherlands, Poland, Spain and Switzerland attended the meeting. In total, 24 talks and 12 posters were presented, covering the topics (1) Geomorphology, (2) Ecology, (3) Climatology, (4) Palaeoenvironment, (5) Cultural Heritage, (6) Isotopes and Climate, and (7) New Applications. This volume contains 21 extended abstracts based on these presentations. We sincerely thank the participants of the meeting, who contributed to a lively and enthusiastic exchange of ideas, and Marjolein Mullen (Utrecht University), Elsemiek Anraets and Tamara Vernimmen (RING) for their practical help. TRACE 2003 was sponsored by (1) the National Service for Archaeological Heritage in the Netherlands (ROB, Amersfoort); (2) the Laboratory of Palaeobotany and Palynology (Department of Biology, Utrecht University), (3) Forschungszentrum Juelich GmbH (Juelich) and (4) the Netherlands Centre for Dendrochronology (RING Foundation; Amersfoort).

This publication is the outcome of the “Dendrosymposium 2002“, a tree-ring conference held from April 11th – 13th 2002 at the University of Bonn (Institute of Geography) and the Research Centre Jülich (Institute of Sedimentary Systems, ICG V). The aims of the German-language symposium were (i) to present the state of the art as well as new research perspectives in the different fields of dendrochronology, (ii) to stimulate further investigations and closer collaboration between different research groups and (iii) to strengthen dendrochronological sciences in central European research. About 50 scientists from Germany, Switzerland, Austria and The Netherlands attended the meeting. In total, 20 talks and 19 posters covering the topics (1) Archaeology, (2) Long Records, (3) Climatology, (4) Isotopes and Climate, (5) Isotopes and Plant Physiology, (6) Dendroecology, (7) Forest Dynamics at the Timberline and (8) Geomorphology were presented. The contributions clearly documented the topical and methodological progress that has been achieved in dendrochronology during the last years, including new approaches such as stable isotope analysis, dendrogeomorphology or ecophysiological aspects. The proceedings volume contains 21 extended abstracts. In order to give a comprehensive overview, shorter abstracts of participants, who did not submit a long version, are additionally included in their original language. Another important goal of the conference was the first meeting of the “Gesellschaft für Jahrringforschung” GJF (“Association of Tree Ring Research” ATR) founded in September 2001 in Davos. Gerhard Schleser (Research Centre Jülich) and Esther Jansma (National Service for Archaeological Heritage/The Netherlands) have been elected for a period of two years as the president and vice president of the Association, respectively. Considering his outstanding scientific and educational merits Fritz Schweingruber was assigned as honorary president. Members of the advisory council are Achim Bräuning (Stuttgart), Jan Esper (Birmensdorf), Holger Gärtner (Birmensdorf), Karl-Uwe Heussner (Berlin), Hans-Peter Kahle (Freiburg), Klaus-Felix Kaiser (Birmensdorf), Kurt Nicolussi (Innsbruck), Constantin Sander (Heidelberg), Matthias Saurer (Villingen), Burkhard Schmidt (Köln), Uwe Treter (Erlangen) and Matthias Winiger (Bonn). More detailed information is available on-line at the ATR-Homepage: $\textbf{www.tree-ring.org}$ Finally, sincere thanks are given to all the participants of the meeting, who made it a lively forum with much exchange of ideas, including the authors of the submitted papers and last but not least to the organizing team of the symposium Burkhard Neuwirth (Bonn), Holger Gärtner (Birmensdorf), Kerstin Treydte (Jülich), Gerd Helle (Jülich) and Jan Esper (Birmensdorf).