• ANJUM FAROOQUI

Articles written in Journal of Earth System Science

• Vegetation history and salinity gradient during the last 3700 years in Pichavaram estuary, India

Palaeoclimate, palaeoecological and palaeoshoreline studies were carried out for a 2.5 m deep sediment core deposited since ∼3700 yrs BP in the central part of Pichavaram mangrove wetland, Cauvery river delta. Presently, the study area is dominated by Avicennia officinalis, A. marina and Suaeda sp. with fringes of Rhizophora sp. along the backwater channel. Based on sedimentology, palynological and thecamoebian analysis, it is inferred that since 2100 yrs BP the climate amelioration took place from warm and humid with strengthened monsoon to a dry and arid climate coupled with weakened monsoon condition inducing changes in ecology vulnerable for mangroves. Consequently, the vegetation too evolved from moist deciduous/evergreen forest to mixed deciduous forest and a reduction in mangrove diversity. The qualitative and quantitative study show a decline in the mangroves since the last millennium which may be attributed to the increased salinity along with enhanced anthropogenic activities in Pichavaram estuary. This is reflected by the dominance of salt tolerant mangrove associates since the last millennium.

• Impact of climate on the evolution of vegetation in tectonically active Karewa basin, Kashmir Himalayas

The rise of the Himalayas governed the Indian Summer Monsoon in Karewa basin during Plio-Pleistocene. A palynological study is presented to delineate the climate-vegetation relationship using an 8.5-m thick fluvio-lacustrine sequence of the Hirpur Formation (2.4–2.1 Ma). Our results suggest that the sediment sequence is mainly comprised of two units, namely, Unit 1 and Unit 2. Unit 1 shows the dominance of sub-tropical to broad-leaf temperate vegetation when mean annual temperature (MAT) was ${\sim}$ 17$^{\circ}$ C and mean annual precipitation (MAP) was 1025 mm. The subsequent increase in sand followed by a thin lignite layer with Trapa, megafossil (fruits) demarcates fluvial adjustments, suggesting a low altitude fluvio-lacustrine ecosystem. Conversely, Unit 2 shows a decline in rainforest pollen with a steady increase in conifers. The abrupt dominance of diatom species Tetracyclus lacustris and related species with MAT and MAP reducing to 10$^{\circ}$ C and 770 mm reveal a colder climate with the lacustrine ecosystem. This change of tropical to cool temperate vegetation could be attributed to the altitudinal rise of the Pir Panjal Mountains and consequent obstruction of the south-west monsoon, which resulted in lower precipitation and temperature during ${\sim}$ 2.4–2.1 Ma. Hence, the relic tropical flora of Palaeogene/Neogene transformed to Himalayan temperate flora sometime ${\sim}$ 2.1 Ma.

$\bf{Highlights}$

$\bullet$ Climate–vegetation relationship is established through a palynological record.

$\bullet$ Unit 1 comprises subtropical to broad-leaf temperate vegetation with warmer mean annual temperature and higher mean annual precipitation.

$\bullet$ Unit 2 comprises colder diatom species and is following cooler mean annual temperature and lower mean annual precipitation.

$\bullet$ A shift of tropical to cool temperate vegetation is related to the rise of the Pir Panjal Mountains, obstructing monsoon.

• # Journal of Earth System Science

Volume 130, 2021
All articles
Continuous Article Publishing mode

• # Editorial Note on Continuous Article Publication

Posted on July 25, 2019