Paleo-vegetation and climate variability during the last three millennia in the Ladakh, Himalaya

Abstract

Unlike other parts of the world, the high-resolution past climate (monsoonal) record of Northwestern Himalaya is limited and such paucity of data on climatic records hinders the past climatic understanding which further reduces the possibility of future prediction. In this study, high-resolution centennial to millennial-scale regional vegetation changes and associated climatic variability (Indian Summer Monsoon) is being reconstructed from a sedimentary profile of Shakti Wetland, Ladakh Northwestern Himalaya deposited during the Late Holocene. The reconstructed climate and vegetation record is based on a multi-proxy approach which are pollen, non-pollen palynomorphs (NPP), stable isotopes (δ13Corg, δ15Nbulk), total organic carbon (TOC), and total nitrogen (TN) derived from sedimentary profile spanning the last ∼ 3200 cal yr BP. A substantial variability in the ISM strengths was found throughout the profile covering the time span of ∼ 3230–740 cal yr BP. The peak warm and wet condition occurred during ∼ 2890 to 2630 cal yr BP, inferred from the rise in an alpine meadow, dry steppe, and marshy taxa. This interval is characterized by relatively lower δ15N suggesting increased nitrification. The first evidence of Cerealia pollen indicated that human settlement near the study area might have initiated around ∼ 2700 cal yr BP. Pollen data show a mixed forest type vegetation from ∼ 2630–2130 cal yr BP. The increase in alpine taxa suggests a wet phase from ∼ 1280 to 740 cal yr BP which globally corresponds to the Medieval Climate Anomaly (MCA). In addition, spectral analysis on the δ13C proxy shows multiple periodicities during the last ∼ 3200 cal yr BP reinforcing the idea of solar control on climate variability of Ladakh.