Climatic correlations in the stable isotope records of silver fir (Abies pindrow) trees from Kashmir, India

Abstract

A high degree of coherence in the annual stable isotopic records along different radial directions of a silver fir tree and between two members of this species from the Kashmir Valley has recently been reported by us. Since such a common pattern of isotopic variability is most likely due to the climatic fluctuations in the site, we have compared the mean δD, δ¹³C and δ¹⁸O records of these trees with instrumentally measured climatic parameters recorded in a nearby weather station to identify the climatic parameters predominantly influencing the isotopic record. A multiple regression analysis of the two records for the period 1903-1932 yields the following: (1) δD is most sensitive to the amount of growing season precipitation, followed by mean maximum temperature. Tree cellulose shows an amount effect analogous to precipitation samples. The temperature coefficient for δ D is in good agreement with earlier estimates based on spatial correlations. (2) δ¹³C is significantly related to humidity and cloud amount. The signs of the regression coefficients are consistent with the recent model of Francey and Farquhar for ¹³C/¹²C fractionation in C₃ plants. (3) δ¹⁸O of cellulose appears to be controlled significantly by relative humidity. ¹⁸O shows less overall correlation with climatic parameters than δD and δ¹³C. (4) δD of carbon bound hydrogen and δ¹⁸O of tree cellulose are linearly related with a slope of 7.9±0.3, suggesting evaporative enrichment in leaf water.