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Tree-ring chronologies of ring width and stable carbon isotope ratios (δ13C) over the past 160 years were developed using living larch trees at two forest sites, each with different annual precipitation, in eastern Siberia: Spasskaya Pad (SP) (62°14′N, 129°37′E); and Elgeeii (EG) (60°0′N, 133°49′E). Intrinsic water-use efficiency (iWUE) was derived from tree-ring δ13C. The physiological responses of the larch trees to climate varied between these sites and over time. Ring widths correlated negatively with summer temperatures at SP, where summer precipitation is lower than at EG, probably due to temperature-induced water stress. Since the 1990s, however, the negative effect of warming has been more severe at EG, where the productivity of larch trees is higher than at SP. A greater reduction of larch tree growth and higher increase rate of iWUE at EG reflects greater temperature-induced water stress, which is incident to the larger forest biomass. Our results suggest that effect of increase in atmospheric CO2 on larch tree growth is not sufficient to compensate for temperature-induced water stress on larch growth in eastern Siberia and differences in precipitation and forest productivity largely affect the larch tree response to changing climate in eastern Siberia. [ABSTRACT FROM AUTHOR]

Abstract: We present a dendroclimatic reconstruction of Palmer Drought Severity Index (PDSI) in Yakutsk (62° 14′N, 129° 37′E), East Siberia using a larch tree-ring (latewood) δ13C chronology (1780–2008 AD). The correlation function analysis showed significant positive correlations between earlywood, latewood and total ring width and July PDSI of the previous summer. On the other hand, tree-ring δ13C from earlywood, latewood and total ring showed significant negative correlations with July PDSI in current summer, of which latewood δ13C showed highest correlation with PDSI. A moving-window correlation analysis demonstrated that the temporal stability in correlation between tree-ring variables and PDSI was highest when July PDSI was compared with latewood δ13C. Tree-ring δ13C values were corrected by taking account of both the changes in the isotope ratio of atmospheric CO2 (δ13Ca) and the plant physiological response to changes in atmospheric CO2 concentration (Ca). This correction significantly improved the sensitivity of larch tree-ring δ13C to PDSI, demonstrating that the correction is useful in building a reliable model to estimate past changes in PDSI. Our study shows that larch tree-ring δ13C has enough potential to reconstruct July PDSI series. Using a liner regression model, July PDSI was reconstructed from latewood δ13C over the last 229 years. The reconstruction showed an interannual to decadal wet/dry fluctuation with a decreasing trend from 1780 to 1960, suggesting that aridification progressed at least after the late Little Ice Age in East Siberia to the modern period of global warming. [Copyright &y& Elsevier]