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Free keywords:
Tree rings; Stable carbon isotopes; Maximum latewood density; Eastern Siberia; Permafrost; Dendroclimatology
DDC:
550 - Earth sciences
Abstract:
We present the first and longest (413 years) dataset on stable carbon isotope ratios in tree-ring cellulose (δ13C), tree-ring width (TRW), and maximum latewood density (MXD) obtained from larch trees growing on permafrost under continental climate in the Suntar Khayata mountain ridge in Eastern Siberia (Russia). With this first study we calibrate tree-ring parameters against climate quantities, and based on these results assess the potential added value of MXD and especially of δ13C complementing TRW analysis for future climate reconstruction purposes. δ13C chronologies were corrected for human induced changes in atmospheric CO2 since AD 1800. Two different approaches were compared i) a correction referring merely to the decline in atmospheric δ13C (δ13Catm) and ii) a correction additionally accounting for the increase in atmospheric partial pressure of CO2. δ13C chronologies are characterized by strong signal strength with only 4 trees representing the population signal at the site (mean inter-series correlation = 0.71 and EPS = 0.90). δ13C variation shows low similarity to TRW and MXD, while correlation between TRW and MXD is highly significant. Correlation analysis of tree-ring parameters with gridded instrumental data (Climate Research Unit, CRU TS 2.1) over the AD 1929–2000 calibration period demonstrates that TRW and MXD react as reported from other sites at cold and humid northern latitudes: precipitation plays no significant role, but strong dependencies on monthly mean, maximum and minimum temperatures, particularly of the current summer (June to August), are found (up to r = 0.60, p < 0.001). Combining instrumental data to a summer season mean (JJA) and TRW and MXD to a growth parameter mean (TRW + MXD), clearly shows the importance of the number of frost days and minimum temperatures during summer (r = 0.67, p < 0.001) to dominate tree growth and highlights the potential for climate reconstruction. Carbon isotope fixation in tree rings is obviously less controlled by temperature variables. In particular, the frost days and minimum temperature have a much smaller influence on δ13C than on tree growth. δ13C strongly reacts to current-year July precipitation (r = − 0.44, p < 0.05) and June–July maximum temperature (r = 0.46, p < 0.001). All significant (p < 0.05) correlation coefficients are higher when using the corrected δ13C chronology considering an additional plant physiological response on increasing atmospheric CO2 concentration, than using the chronology corrected for δ13Catm changes alone. Spatial distribution of correlations between tree-ring data and climate variables for Eastern Siberia indicates that the summer temperature regime in the studied region is mostly influenced by Arctic air masses, but precipitation in July seems to be brought out from the Pacific region. Both the combined TRW + MXD record and the δ13С record revealed a high reconstruction potential for summer temperature and precipitation, respectively, particularly on decadal and longer-term scales.
