Paleovegetation dynamics in an alternative stable states landscape in the montane Western Ghats, India

Prabhakaran Ramya Bala, Sarath Pullyottum Kavil, Ichiro Tayasu, Chikage Yoshimizu, Kaustubh Thirumalai, Krishnan Sajeev, Raman Sukumar

Research output: Contribution to journalArticlepeer-review

1 Scopus citations


Peat deposits (>50 ka) in the montane Nilgiris (Western Ghats, India), have been central to the reconstruction of late Quaternary paleoclimate using paleovegetation changes in the forest-grassland vegetation mosaic that coexist here. However, it is well-known that short-term disturbances can also cause vegetation switches when multiple stable vegetation states exist. We studied paleovegetation changes within the alternative stable states framework using stable carbon isotopes (relative abundance of C3-C4 vegetation) on the cellulose fraction from two high-resolution radiocarbon-dated peat cores ~170 m apart in the Sandynallah valley: Core 1 closer to the hillslope (32,000 years old) and Core 2 from the centre of the valley (45,000 years old). Core 1 is located in an ecotone showing shola-sedgeland dynamics with vegetation switching at c.22 ka from shola (possibly due to fire) to a prolonged unstable state until 13 ka sustained by low waterlogging. Following a hiatus c.13 ka, sedgeland dominates, with a shift into shola at 3.75 ka driven by increasing aridity. Core 2 shows a stable sedgeland mixed C3-C4 composition responding to temperature, enriched in C3-vegetation in the last glacial with C4-dominance beginning c.18.5 ka, indicative of deglacial warming. The distinctive vegetation states at corresponding times in Cores 1 and 2 within the same valley, responding independently to disturbances and climate, respectively, is the first paleo-record from an alternative stable states landscape in the montane tropics. Thus, short-term disturbances and site attributes need to be accounted for before ascribing vegetation change to changing climate in such vegetation mosaics.

Original languageEnglish (US)
Pages (from-to)297-307
Number of pages11
Issue number4
StatePublished - Apr 2022


  • C3-C4 mixed
  • Nilgiris
  • carbon isotope
  • deglacial warming
  • disturbance
  • late Quaternary
  • paleoclimate
  • resistivity survey
  • shola-grassland
  • tropical peat

ASJC Scopus subject areas

  • Global and Planetary Change
  • Archaeology
  • Ecology
  • Earth-Surface Processes
  • Palaeontology


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