@article{BrunelloAndermannHelleetal.2019,
  author    = {Brunello, Camilla Francesca and Andermann, Christoff and Helle, Gerhard and Comiti, Francesco and Tonon, Giustino and Tiwari, Achyut and Hovius, Niels},
  title     = {Hydroclimatic seasonality recorded by tree ring delta O-18 signature across a Himalayan altitudinal transect},
  series = {Earth \& planetary science letters},
  volume    = {518},
  journal   = {Earth \& planetary science letters},
  editor    = {Vance, D.},
  publisher = {Elsevier},
  address   = {Amsterdam},
  issn      = {0012-821X},
  doi       = {10.1016/j.epsl.2019.04.030},
  pages     = {148 -- 159},
  year      = {2019},
  abstract  = {Water stable isotope ratios of tropical precipitation predominantly reflect moisture source and precipitation intensity. Trees can incorporate the isotopic signals into annual tree-ring cellulose records, permitting reconstruction of the temporal changes of hydroclimate over decades to millennia. This is especially valuable in the Himalayas where the understanding of monsoon dynamics is limited by the lack of a dense and representative observational network. We have analyzed tree ring delta O-18 records from two distinct physiographic sites along the upper Kali Gandaki valley in the central Nepal Himalayas, representing the wet High-Himalayas and the Trans-Himalayan dryland to the north. Empirical correlations and regression analyses were compared to an in-situ calibrated oxygen isotope fractionation model, exploring the relationships between tree ring delta O-18 and seasonal-mean variability of hydroclimatic forcing at the different locations. For this purpose, gridded precipitation data from the Asian rain gauge dataset APHRODITE, as well as high resolution onsite observations (relative humidity, air temperature, delta O-18 of precipitation and radial tree growth) were used. We found that two distinct sets of meteorological values, reflecting pre-monsoon and monsoon conditions, are needed to reproduce the measured tree ring delta O-18 values from the High-Himalayan site, but that a single set of monsoonal values performs best for the Trans-Himalayan site. We conclude that Trans-Himalayan trees capture long-term changes in strength of the Indian summer monsoon. In contrast, High-Himalayan tree ring delta(18)Orecords a more complex hydro-climatic signal reflecting both pre-monsoon and monsoon seasons with very contrasting isotopic signatures of precipitation. This difference in the two hydroclimatic proxy records offers an opportunity to reconstruct first-order hydroclimate conditions, such as local precipitation rates, and to gain new insights into monsoon timing and seasonal water source determination across the Himalayan orographic region. (C) 2019 Elsevier B.V. All rights reserved.},
  language  = {en}
}
@article{LiangHeinrichSimardetal.2013,
  author    = {Liang, Wei and Heinrich, Ingo and Simard, Sonia and Helle, Gerhard and Linan, Isabel Dorado and Heinken, Thilo},
  title     = {Climate signals derived from cell anatomy of Scots pine in NE Germany},
  series = {Tree physiology},
  volume    = {33},
  journal   = {Tree physiology},
  number    = {8},
  publisher = {Oxford Univ. Press},
  address   = {Oxford},
  issn      = {0829-318X},
  doi       = {10.1093/treephys/tpt059},
  pages     = {833 -- 844},
  year      = {2013},
  abstract  = {Tree-ring chronologies of Pinus sylvestris L. from latitudinal and altitudinal limits of the species distribution have been widely used for climate reconstructions, but there are many sites within the temperate climate zone, as is the case in northeastern Germany, at which there is little evidence of a clear climate signal in the chronologies. In this study, we developed long chronologies of several cell structure variables (e. g., average lumen area and cell wall thickness) from P. sylvestris growing in northeastern Germany and investigated the influence of climate on ring widths and cell structure variables. We found significant correlations between cell structure variables and temperature, and between tree-ring width and relative humidity and vapor pressure, respectively, enabling the development of robust reconstructions from temperate sites that have not yet been realized. Moreover, it has been shown that it may not be necessary to detrend chronologies of cell structure variables and thus low-frequency climate signals may be retrieved from longer cell structure chronologies. The relatively extensive resource of archaeological material of P. sylvestris covering approximately the last millennium may now be useful for climate reconstructions in northeastern Germany and other sites in the temperate climate zone.},
  language  = {en}
}