Drought reconstruction and related dendrogeomorphic time-series analysis from Kinnaur region of western Himalayas

Abstract

Moisture variability driven by climate change impacts soil moisture, affecting vegetation growth and cover, and enhances the morphodynamics, potentially increasing geohazard risks. Dendroclimatology and dendrogeomorphology techniques effectively quantifying the past moisture variability and geohazard episodes can be used to understand the climate-induced geohazard mechanisms in long-term. We reconstructed moisture variability and geohazard (rockfall) activity from the Kinnaur region in the Indian western Himalayas. The Western Disturbances (WDs) driven winter precipitation provides moisture crucial for tree growth during the spring and summer months. We developed a 463 year-long (1558–2021 CE) tree-ring width chronology (TRWC) of Cedrus deodara and performed correlation analysis with various climate variables. The significant positive correlation between TRWC and standardized precipitation evapotranspiration index (SPEI04) for the February-March-April months revealed the combined effect of winter and spring month's water balance on tree growth. The SPEI04 reconstruction for the past 356 years showed that the study region experienced moderate to severe wet spring years between 1725 and 1757 CE, teleconnected to westerly circulation patterns, falling in the Little Ice Age (LIA) time frame. The dry spring phase after 1757 CE significantly teleconnects with a tropical ocean warming during late 19th and 20th centuries. We assessed the impact of moisture changes on the geohazard frequency and found good correspondence between years with dry spring months and rockfall activity. We observed an increase in geohazard activity since the mid-20th century, indicating an increasing vulnerability of slopes to ground failure. The spring and summer months are becoming more critical for tree growth and ground stability due to unprecedented temperature rise during the last century. Our findings provide a suitable baseline for adapted forest management, sustainability and ground stability measures under ongoing climate warming.