Vegetation dynamics in response to climate change from the wetlands of Western Himalaya, India: Holocene Indian summer monsoon variability

Abstract

India’s agricultural output, economy and societal well-being are strappingly dependent on the stability of the southwest summer monsoon precipitation, its variability and extremes. Deviations in the Indian summer monsoon (ISM) precipitation may profoundly impact the agricultural productivity and gross domestic product (GDP) of the country. Understanding the spatiotemporal dynamics of the ISM precipitation during the Holocene is significant in many respects, particularly in terms of human development and establishment of centres of civilisations. Here, pollen records of the variability in ISM precipitation and their interpretation in terms of vegetation and climate change from two wetlands (Gharana and Nanga; Ramsar sites) of the Western Himalaya (India) is presented. The results suggest that between ~8536 and 5296 cal yr BP, mixed conifer/broad-leaved forests occurred in the Jammu region (Gharana Wetland sediment profile) under a cool and dry climate, probably indicating decreased monsoon precipitation. Subsequently, they were succeeded by mixed broad-leaved/conifer forests between ~5296 and 2776 cal yr BP under a warm and humid climate with increased monsoon precipitation, partly corresponding to the Holocene Climate Optimum (HCO). Between ~2776 and 1376 cal yr BP, with more expansion of broad-leaved forest elements in response to a warm and more humid climate the dense mixed broad-leaved/conifer forests came into existence in the region, indicating a further increase in monsoon precipitation. From ~1376 cal yr BP to present, the climate deteriorated, as manifested by the replacement of dense mixed broad-leaved/conifer forests by mixed conifer/broad-leaved forests in the region. The palaeoclimatic inferences drawn from the Nanga Wetland sediment profile of Samba District match with the Gharana Wetland sediment profile of Jammu District for the late-Holocene. This study provides insights into the vegetation dynamics, associated climate change and the ISM variability from the poorly understood wetland ecosystems of Southeast Asia during the Holocene.

New evidence of mid- to late- Holocene vegetation and climate change from a Neolithic settlement in western fringe of Central Ganga Plain: Implications for Neolithic to Historic phases

“…The palynological study of a Himalayan peat bog suggests a cool and moist climate between ~2032 cal BP and 1158 cal BP (Rawat et al, 2015), where prolific increase of coniferous taxa and relative decline of broad leaved and meadow taxa was observed (refer Figure 7g). Similar trend was observed from Gharana wetland in northwest Himalaya revealing expansion of broad-leaved plants and a simultaneous reduction in coniferous elements from ~2776 cal BP to 1336 cal BP (Qamar, 2019) and results from Bhujbasa, Gangotri (Kar et al, 2002) during ~2500 cal BP and 1700 cal BP are suggestive of an increase in monsoon precipitation, unlike HPT Zone-III. (Yadava and Ramesh, 2005), (d) δ 18 O values of planktonic foraminifera, namely, Gs.…”

Floristic and climatic reconstruction in the Indo-Burma region for the last 13,000 cal. yr: A palynological interpretation from the endangered wetlands of Assam, northeast India

“…However, pollen records in western Himalaya, India shows the advent of HCO between ~5296 and 2776 cal. yr BP under increased monsoon precipitation (Quamar, 2019).…”

The modern pollen–vegetation relationship in Jammu, India: a comparative appraisal

“…The palynomorphs were counted under a transmitted light microscope (Olympus BX50) with a 40× objective at the Quaternary Palynology Laboratory of the Birbal Sahni Institute of Palaeosciences (BSIP), Lucknow, India. Pollen and spores were identified by comparing their morphological characters with pollen and spores in published literature (Nair, 1965;Gupta and Sharma, 1987;Nayar, 1990;Quamar and Srivastava, 2013;Quamar, 2019;Quamar and Stivrins, 2021) and the pollen reference collection at the sporothek of the BSIP Herbarium. The samples were not very productive, though we tried to reach total pollen counts of ~300 per sample.…”