Tipping elements and thresholds for extreme climate events in the Indian Summer Monsoon (ISM) realm (TISUR) IP3: Ecological regime shifts in response to monsoon dynamics and anthropogenic activities
Final Report Abstract
Ecosystems, rainfed agriculture, and economic prosperity of the densely populated Indian subcontinent critically depend on the amount and distribution of annual monsoon precipitation. Several factors influencing monsoon activity on intraseasonal and interannual timescales have been identified for recent decades. Palaeoclimate data indicate that such factors can persist regionally for decades or centuries, leading to hydrological changes, extreme climate events, and ecological regime shifts. Given uncertainties in future projections of the Indian summer monsoon (ISM) under a global warming scenario, a thorough understanding of past vegetation and climate dynamics—and their drivers—is essential. This DFG-funded project focused on the data-poor and ecologically sensitive NW Himalaya. As part of a multidisciplinary study, a Holocene sediment profile from Lake Manasbal (MB) was analyzed palynologically. Throughout the study period, tree pollen proportions ranged from 30–80%, with the lowest values observed before the Holocene and between 6.2 and 4 ka BP. Persistent mixed coniferous-broadleaf forests are mainly indicated by 10–25% Pinus pollen, accompanied by temperate deciduous trees such as Ulmus, Quercus, Juglans, Celtis, and Corylus. Over the past four millennia, increased proportions of Platanus, Juglans, Morus, and Sorbus-type pollen point to human cultivation of these species. The continued presence of open habitats is reflected in the abundance of Artemisia, Poaceae, and other open-ground taxa. In line with archaeological findings, clear evidence of local and regional human impact (HI) is indicated by Cerealia, Cannabis, and Plantago lanceolata pollen from 2 ka BCE onwards. However, landscape opening and increased HI indicators beginning around 4.2 ka BCE suggest earlier agricultural practices than those currently confirmed by archaeology. Beyond palynomorph frequencies, PFT (Plant Functional Type) diversity analysis was used to gain further insights into ecosystem changes and functional biodiversity. Overall PFT diversity steadily increased during the Holocene, with an acceleration linked to significant human influence. Climate-driven changes are most apparent in woody PFT patterns supporting a dominantly humid early Holocene, followed by drier mid to late Holocene. Notably, the mega-drought between 7 and 6 ka BP, identified by geochemical data, had only minor or delayed rather than immediate effects on PFT patterns of zonal vegetation. From 6.2 ka BP onward, the PFT diversity pattern appears clearly overprinted by HI. Overall, PFT diversity charts underscore that biodiversity and ecosystem functioning are shaped by complex interactions among climate, landscape dynamics, and human activities, rather than by environmental conditions alone. Combined with geochemical and sedimentological proxies, the new pollen data enable detailed reconstructions of environmental changes and extreme climate events in the Kashmir valley.
Publications
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Holocene vegetation dynamics and biodiversity changes in the realm of the Indian Summer Monsoon - a case study on the Lonar Crater Lake pollen. European Palaeobotany and Palynology Conference 2022, Stockholm
Utescher, T., Stebich, M., Prasad, S. & Riedel, N.
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Middle to late Holocene changes of vegetation, climate and land use in Northern India based lacustrine sediments of the MB lake (Kashmir valley). European Palaeobotany and Palynology Conference 2022, Stockholm
Stebich, M., Utescher, T., Gaye, B. & Prasad, S.
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Diversity patterns of plant functional types in the Holocene of Central India: A case study on the Lonar Crater Lake pollen record. The Holocene, 33(5), 491-504.
Utescher, Torsten; Prasad, Sushma; Riedel, Nils & Stebich, Martina
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Holocene changes of vegetation, climate and land use in Northern India based lacustrine sediments of the MB lake (Kashmir valley). NECLIME annual conference 2023, Matsudo/Chiba, Japan - hybrid, August 30 to September 6, 2023
Stebich, M., Utescher, T., Khan, S., Gaye, B., Prasad, S. & Jehangir, A.
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Holocene dynamics of vegetation and pft-diversity reflected in lacustrine sediments of Central India and Kashmir valley. International Conference on Tropical Biodiversity and Geofactors, March 10-11, 2023, Jaipur; invited keynote lecture
Stebich, M., Riedel, N., Utescher, T., Sarkar, S., Sachse, D., Prasad, S., Basavaiah, N., Vijay Pal Meena, A. Anoop, P.K. Mishra, A. Jehangir & B. Gaye
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Archives and proxies: potential and limitations. II. Indian Quaternary Congress, IIser Mohali, 3-5 JUNE 2024
Ambili, A., Jehangir, A., Laskar, P., Menzel, P.K., Mishra, P.K., Priya, P., Riedel, N., Sarkar, S., Basavaiah, N., Gaye, B., Krishnan , R., Marwan, N., Meena, V.P., Prasad, S., Plessen, B., Sachse, D., Stebich, M. & Yousuf A.R.
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Holocene changes of vegetation, climate and land use in Northern India based lacustrine sediments of the MB lake (Kashmir valley). II. Indian Quaternary Congress, IIser Mohali, 3-5 JUNE 2024
Stebich, M., Utescher, T., Khan, S., Prasad, S., Jehangir, A., Ambili, A., Mishra, P.K. & Gaye, B.
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Reconstruction of Holocene Vegetation in NW Himalayan Ecozones: A Palynological study of MB Lake Sediments. XV. International Palynological Congress (IPC) XI. International Organisation of Palaeobotany Conference (IOPC) Prague, Czech Republic May 27-31, 2024
Khan, S., Stebich, M., Utescher, T., Gaye, B., Prasad, S., Ambili, A., Jehangir, A. & Mishra P.K.
