Temperature variations for the last 2000 years by tree-ring chronologies from Polar and Upper Mountain tree line in Siberia

Sukachev Institute of Forest, SB RAS, Krasnoyarsk

Head of the Institute:

Eugene A.Vaganov, Academician of the RAS
Academgorodok, Krasnoyarsk, 660036, Russia
Tel.: (7)(3912)431429, (7) (3912) 433686
Fax: (7)(3912)433686
email: ifor@krsk.infotel.ru

Principal researchers:

E.A.Vaganov, Academician
M.M.Naurzbaev, Senior Researcher
V.V.Shishov, Researcher
A.V.Kirdyanov, Researcher
D.V.Ovchinnikov, Post-graduate student

Project objectives

The comparative analysis of summer temperature variations in high latitudes and South Siberia Mountains reconstructed by supralong (up to 2 millennia) tree-ring chronologies makes it possible to find out common for the vast territory of Siberia long-term and short-term temperature changes, to correlate them with the other indirect data of temperature variations in North Hemisphere; it sufficiently enriches International and Russian data base on the Holocene climate change; allows to create models of forest growth response to climate changes; to evaluate the range of polar and upper tree line movement during the last millennia.

In the project the greatest attention will be paid to quantitative reconstruction of summer temperature on the basis of several indices of tree-ring chronologies: annual tree-ring width variability, wood density, cell sizes and cell wall thickness. The analysis of these characteristics in complex allows to increase greatly time scale resolution of dendroclimatic reconstructions obtaining data not only for year but for seasons separately.

Background and significance of objectives

At present there are two directions of intensive Earth climate history researchers in the Holocene with the help of indirect information sources. First, this is a creation of net and data base on the terrestrial globe with long rows of measurements (instrumental records, tree-rings, lake sediments, ice cores, coral growth layers etc.) to reconstruct spatial-temporal temperature and precipitation variability (Mann et al., Nature, 1998, 392:779-782). Secondly, this is comparison of quantitative climate reconstruction with high temporal resolution (year, season) for selected regions obtained from various indirect sources (Briffa et al., Nature, 1998, 391:678-682; Jones et al., Holocene, 1998, 1998, 8(4):455-471).

Creation of supra-long (several millennia) tree-ring chronologies in key regions of Siberia for evaluation of natural North Hemisphere climate changes is of most importance in these works. Reconstruction obtained with their help allow not only to find out and evaluate climate fluctuations, but to be used to calibrate and to date other indirect sources with low temporal resolution or being problematic in absolute dating.

Laboratory of Dendrochronology of V.N.Sukachev Institute of Forest SB RAS has great experience in creation of long-term chronologies as well as in revealing and analysis of climatic components of tree growth changes. A net of dendroclimatic stations was created on the whole territory of Siberia for the last decade (Fig. 1), which made it possible to carry out spatial-temporal reconstruction of temperature changes and to make up maps of summer temperature anomalies for the Siberian Subarctic since 1610 up to 1990 (Vaganov et al, 1996). On the territories where well-preserved wood remains and subfossil wood from alluvial deposits were found the works on creation of millennium chronologies started (Fig. 2) (Vaganov et al., 1997, 1999; Naurzbaev, Vaganov, 1999). A lot of preserved wood remains in continental regions of Siberia (close to glaciers in the Altai and upper forest border in Stanovoye Upland) are found as well. With the help of equipment of densitometrical laboratory and image system for cell wood structure of tree-rings the measurements of annual tree-ring characteristics additional to tree-ring width made which allowed to obtain information of intra-annual changes of climatic variables. For this purpose special, original simulation models were worked out, there are also worked out models of reconstruction of temperature and precipitation during growth season by annual tree-ring structure characteristics (by wood density profile, by cell lumen and cell wall thickness) (Vaganov et al., 1994, 1996). The created dendroclimatic data base for Siberia is constantly being widened.

Research plan: approaches and methods

The investigation methods include a set of experimental measurements, traditional for dendrochronology and dendroclimatology and widely used in world chief laboratories, and statistical approaches (site selection and material collection, annual tree-ring characteristics measurements by automatic devices and in densitometrical laboratory, cross-dating procedure, standardization of raw measurements and climatic signal discharge, estimation of climatic functions, creation of simple and multiple regression models of leading climatic factors reconstruction, spectral analysis of long-term temporal chronologies etc.) as well as worked out unique methods of annual tree-ring measurements and computer programs of raw data processing (automatic systems usage and systems for image analysis to measure cell structure of annual tree-rings, usage of simulation models of annual tree-ring formation by daily temperature, moisture and solar radiation changes, statistical multiple methods to reconstruct intraseasonal variability of climatic factors inferred from characteristics of annual tree-ring structure etc.) (Fig. 3). The latter are not only pioneer but also define priorities of Laboratory of Dendrochronology of Institute of Forest SB RAS in world dendroclimatology.

Expected results

Obtaining and dendroclimatic analysis of 2-millennia tree-ring chronologies by variations of width and structure of annual rings for two regions of subarctic territory (eastern Taymir and the lower Indigirka River) and continental part of Siberia (the Altai, Stanovoye Upland):

Revealing of coincident long-term and high frequency variations of temperature in subarctic area and continental part of Siberia for 2 millennia by methods of principal component analysis and spectral analysis:

Usage of tree-ring chronologies and climatic reconstruction to calibrate the other indirect climatic data and to compare with climatic reconstruction based on ice core, lake sediment, pollen and other paleobotany data:

List of publications of participants related to the project

 

Fig. 1. A network of stations for dendroclimatic monitoring of the boreal forests of Siberia (large circles stand for where supralong chronologies are created)).

Fig. 2. Remains of larch trunks on the surface (A) and semi-fossil timber in alluvial sediments (B).

Fig. 3. Cellular structure of tree-rings (A) and fragments (B) of chronologies with respect to cell size (1) and cell wall thickness (2).