Himalayan Geology, Vol. 41 (2), 2020, pp. 202-207, Printed in India
Standardized Precipitation Index reconstruction during the last two centuries over western Himalaya, India: deduced by tree ring-width records
SOMARU RAM1*, RAMESH KUMAR YADAV1, H.N. SINGH1, MANOJ K. SRIVASTAVA2
1Indian Institute of Tropical Meteorology, Pune-411008, India
2Department of Geophysics, Banaras Hindu University, Varanasi-221005, India
*Email (Corresponding author): somaru@tropmet.res.in
Abstract: Tree-ring width index chronologies of three different species (Cedrus deodara, Abies pindrow and Picea smithiana) from the western Himalaya have been carried out in relation to understand the climate fluctuations. The first principal component developed based on the above species showed significant positive relationship with Standardized Precipitation Index (SPI) and negative with Heat Index (HI) during pre-monsoon month, but the highest correlation coefficients of tree growth with heat and SPI were observed during May, are -0.52 and 0.60 respectively, which are highly significant at 0.1% level. The results indicate that increasing heat index during May might lead to dry soil by accelerating the potential evapotranspiration which creates the moisture deficiency over the region. The significant positive relationship of tree growth with SPI indicates that tree growth of the western Himalaya is moisture sensitive, which enable us to extend SPI to monitor dry and wet periods before the instrumental period. The reconstructed SPI back to 1778 shows climate variability, on both inter-annual and inter-decadal time scale. The reconstruction showed increasing wetness in the twentieth century and recent few decades. Extreme and severe dry is noticed during 1921 (-2.4) and 1892 (-2.0) in the entire reconstruction has been associated with very low tree growth during the corresponding year over the western Himalaya.
Keywords: Western Himalaya, Conifers, Tree-ring, Standardized Precipitation Index, Heat Index.
