Interpreting Climate Proxies from Tree-rings
Trees, as long living plants, are governed by environmental and/or climate changes within their habitat. Their growth rings record to a large extent the temporal dynamics of these changes either directly or through tree physiological reactions. They rende
- PDF / 3,208,393 Bytes
- 20 Pages / 439.37 x 666.142 pts Page_size
- 93 Downloads / 195 Views
Interpreting Climate Proxies from Tree-rings Gerhard Helle and Gerhard H. Schleser
8.1 Introduction Trees, as long living plants, are governed by environmental and/or climate changes within their habitat. Their growth rings record to a large extent the temporal dynamics of these changes either directly or through tree physiological reactions. They render the highest time resolution thus far possible for environmental or climate reconstructions of the past 10,000 years (exactly dated, annually resolved, see: [828], [994]). Trees are a substantial part of the human environment with a high socio-economic value. Their large geographical extension over various regions of the world, including those with greatest population densities but also marginal areas allows to gain unique informations about local and regional consequences of global climate change.
8.2 Climate Proxies from Tree-rings Most of our present knowledge about the Earth's climate variability over the last millennium is based on tree-ring studies using tree-ring-width and maximum late wood density (e.g., [953], [118], [117], [126], [116], [124], [510], [686], [688] [201], [184]). Data of both, ring-width and maximum late wood density are usually standardized to minimize non-climatic variances originating from tree aging, changing light conditions in the canopy and changes in the supply of soil nutrients. Usually, transfer functions are developed by applying uni-variate, linear regression models using relationships between standardized data series and measured climatic quantities. These transfer functions enable the reconstruction of climate quantities from proxy data series after they have been verified against independent data or climate data withheld from the training set [116]. Many articles have been written which describe the methods used by classical dendroclimatology (e.g., [1158], [38], [187], [182], [344], citeFRITTS91, [949], [951], [950], [477], [873], [1053], [124]) H. Fischer et al. (eds.), The Climate in Historical Times © Springer-Verlag Berlin Heidelberg 2004
130
Gerhard Helle and Gerhard H. Schleser
Tree-ring-width (RW) and maximum late wood density (MLD) variations have most successfully been used for climate reconstructions at sites where tree growth is limited by one dominant climatic factor (e.g., [655], [950], [117], [120], [126], [124], [512]). MLD gives significant correlations with temperature for cold and moist high-latitude and/or high-elevation sites, e.g. northern NAmerica or Siberia. In these regions an increase of temperature during summer or late summer prolongs the growing season and, thus, improves growth resulting in more dense late wood. A disadvantage of the use of MLD as climate proxy is its restricted applicability, namely to certain coniferous tree species only. It is less suitable for temperature reconstruction in regions where an increase of temperature is linked with increasing stress caused by drought, i.e. arid regions. In these areas, e.g. the southwestern part of the USA, ring-widt h studies revealed good
Data Loading...
