A B S T R A C T To better understand long-term drought variations in the central Himalaya, we dev... more A B S T R A C T To better understand long-term drought variations in the central Himalaya, we developed new tree-ring width chronologies of Himalayan spruce (Picea smithiana (Wall.) Boiss.) from three sites in the northwestern Nepal. The local site chronologies showed high cross correlations and similar growth-climate responses to regional spring drought variability. We thus combined all site chronologies into a regional composite (RC) standard chronology that spans 516 years (1498–2013 CE). The RC chronology showed significant positive (negative) correlations with spring (March–May) precipitation (temperature) variability. Meanwhile, RC chronology showed the highest correlation with spring self-calibrating Palmer drought severity index (scPDSI, r = 0.652, p < 0.001), indicating that radial growth of P. smithiana is strongly limited by spring moisture availability. Using RC chronology, we reconstructed the spring drought variability for the period 1725–2013, which explained 42.5% variance of the actual scPDSI during the calibration period 1957–2012. Our reconstructed spring drought variability in the central Himalaya showed consistent wet-dry episodes with other regional drought and precipitation reconstructions from the Himalaya and nearby regions. Spectral peaks and spatial correlation analysis indicate that spring drought variability in the central Himalaya may be linked to large scale climatic drivers, mainly Atlantic Multidecadal Oscillation activities due to sea surface temperatures variation in the Atlantic Ocean. Our reconstruction revealed a continuous shift toward drier conditions in the central Himalaya since early 1980s that coincide with continental-scale warming and reduced spring precipitation in the central Himalaya.
Wood anatomical features may be visible on the microscopic as well as on the macroscopic scale. W... more Wood anatomical features may be visible on the microscopic as well as on the macroscopic scale. While the former can often be quantified by detailed wood anatomical analyses, the latter are often treated as qualitative features or as binary variables (present/absent). Macroscopic tree-ring features can be quantified in terms of frequency, intensity, or classified according to their position within a tree ring, like intra-annual density variations (IADFs) in conifers or frost rings in earlywood or latewood. Although some of these tree-ring features, like e.g. missing rings or IADFs are often seen as anomalies, hampering dendrochronologists to perform proper crossdating of tree-ring series, many of these properties are formed under extreme environmental stress or heavy impact, and could mark these extreme events by the manifestation in the wood anatomical structures throughout the lifespan of trees. The described tree-ring features form discrete time-series of extreme events. For example, flood rings may be marked by lunar-shaped earlywood vessels or enlarged latewood vessels in ring-porous oaks. White earlywood rings and light rings indicate reduced cell wall thickness and lignification occurring in very cold years. Frost rings result from cambial cell death during abrupt cooling events in the growing season. Missing rings and IADFs are mainly caused by drought events. Characteristic variations in earlywood vessel size, shape, or number in ring-porous oak species are markers for flood events, defoliation, heat stress, or drought. Traumatic resin ducts may be triggered by a range of biotic or environmental stressors, including wounding, fires or mechanical factors. Reaction wood is indicative of mechanical stress, often related to geomorphic events. In many cases anatomical responses are unspecific and may be caused by different stressors or extreme events. Additionally, the sensitivity of trees to form such features may vary between species, or between life stages within one species. We critically evaluate the indicative value of different wood anatomical tree-ring features for environmental reconstructions.
This publication is the outcome of the "Dendrosymposium 2002", a tree-ring conference held from A... more This publication is the outcome of the "Dendrosymposium 2002", a tree-ring conference held from April 11 th -13 th 2002 at the University of Bonn (Institute of Geography) and the Research Centre Jülich (Institute of Sedimentary Systems, ICG V). The aims of the Germanlanguage 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. : 40 Fossil pines from loamy slope sediments reflect Lateglacial climatic variations J. Esper 47 A millennium-long temperature reconstruction for the Tien Shan Mountains, Kirghizia (short Abstract) H.-P. Kahle and R. Unseld: 48 Analyse der raumzeitlichen Variationen des Radialzuwachses von Fichten in Südwestdeutschland (short Abstract) Th. Riemer: 49 Trendanalyse mit gemischten Modellen -Methodik, Software und Anwendung in der Dendroklimatologie (short Abstract)
A B S T R A C T To better understand long-term drought variations in the central Himalaya, we dev... more A B S T R A C T To better understand long-term drought variations in the central Himalaya, we developed new tree-ring width chronologies of Himalayan spruce (Picea smithiana (Wall.) Boiss.) from three sites in the northwestern Nepal. The local site chronologies showed high cross correlations and similar growth-climate responses to regional spring drought variability. We thus combined all site chronologies into a regional composite (RC) standard chronology that spans 516 years (1498–2013 CE). The RC chronology showed significant positive (negative) correlations with spring (March–May) precipitation (temperature) variability. Meanwhile, RC chronology showed the highest correlation with spring self-calibrating Palmer drought severity index (scPDSI, r = 0.652, p < 0.001), indicating that radial growth of P. smithiana is strongly limited by spring moisture availability. Using RC chronology, we reconstructed the spring drought variability for the period 1725–2013, which explained 42.5% variance of the actual scPDSI during the calibration period 1957–2012. Our reconstructed spring drought variability in the central Himalaya showed consistent wet-dry episodes with other regional drought and precipitation reconstructions from the Himalaya and nearby regions. Spectral peaks and spatial correlation analysis indicate that spring drought variability in the central Himalaya may be linked to large scale climatic drivers, mainly Atlantic Multidecadal Oscillation activities due to sea surface temperatures variation in the Atlantic Ocean. Our reconstruction revealed a continuous shift toward drier conditions in the central Himalaya since early 1980s that coincide with continental-scale warming and reduced spring precipitation in the central Himalaya.
Wood anatomical features may be visible on the microscopic as well as on the macroscopic scale. W... more Wood anatomical features may be visible on the microscopic as well as on the macroscopic scale. While the former can often be quantified by detailed wood anatomical analyses, the latter are often treated as qualitative features or as binary variables (present/absent). Macroscopic tree-ring features can be quantified in terms of frequency, intensity, or classified according to their position within a tree ring, like intra-annual density variations (IADFs) in conifers or frost rings in earlywood or latewood. Although some of these tree-ring features, like e.g. missing rings or IADFs are often seen as anomalies, hampering dendrochronologists to perform proper crossdating of tree-ring series, many of these properties are formed under extreme environmental stress or heavy impact, and could mark these extreme events by the manifestation in the wood anatomical structures throughout the lifespan of trees. The described tree-ring features form discrete time-series of extreme events. For example, flood rings may be marked by lunar-shaped earlywood vessels or enlarged latewood vessels in ring-porous oaks. White earlywood rings and light rings indicate reduced cell wall thickness and lignification occurring in very cold years. Frost rings result from cambial cell death during abrupt cooling events in the growing season. Missing rings and IADFs are mainly caused by drought events. Characteristic variations in earlywood vessel size, shape, or number in ring-porous oak species are markers for flood events, defoliation, heat stress, or drought. Traumatic resin ducts may be triggered by a range of biotic or environmental stressors, including wounding, fires or mechanical factors. Reaction wood is indicative of mechanical stress, often related to geomorphic events. In many cases anatomical responses are unspecific and may be caused by different stressors or extreme events. Additionally, the sensitivity of trees to form such features may vary between species, or between life stages within one species. We critically evaluate the indicative value of different wood anatomical tree-ring features for environmental reconstructions.
This publication is the outcome of the "Dendrosymposium 2002", a tree-ring conference held from A... more This publication is the outcome of the "Dendrosymposium 2002", a tree-ring conference held from April 11 th -13 th 2002 at the University of Bonn (Institute of Geography) and the Research Centre Jülich (Institute of Sedimentary Systems, ICG V). The aims of the Germanlanguage 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. : 40 Fossil pines from loamy slope sediments reflect Lateglacial climatic variations J. Esper 47 A millennium-long temperature reconstruction for the Tien Shan Mountains, Kirghizia (short Abstract) H.-P. Kahle and R. Unseld: 48 Analyse der raumzeitlichen Variationen des Radialzuwachses von Fichten in Südwestdeutschland (short Abstract) Th. Riemer: 49 Trendanalyse mit gemischten Modellen -Methodik, Software und Anwendung in der Dendroklimatologie (short Abstract)
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