Variability in phytolith spectra of some Panicoid grasses from different soil salinity zones of the deltaic West Bengal, India: implications in understanding depositional environments

Abstract

Phytoliths are microscopic silica bodies deposited in and between plant cells. They are known to be important environment indicators and thus hold significant prospect for present and past ecological and environmental interpretations. We present here results of morphometric and assemblage analyses of phytoliths from five Panicoid grasses, i.e. Chrysopogon aciculatus, Imperata cylindrica, Oplismenus burmannii, Paspalum distichum, and Echinochloa crus-galli. Each was collected separately from mesophyte-dominated low saline and halophyte-rich high saline phytoecological zones of the lower Gangetic delta of West Bengal, India. Bilobate phytoliths with relatively longer shanks, and rondel and tower morphotypes were recovered in significantly higher frequencies from samples of high salinity zones, whereas cross, polylobate, and trapeziform morphotypes were found predominantly in grasses from mesophyte-dominated low salinity zones. The above-mentioned morphotypes were found to be strongly correlated with soil salinity. Phytolith data of the grasses from two different ecophysiological zones were further subjected to principal component analysis (PCA), which successfully distinguished the two salinity zones. The present investigation may serve as a basis to identify distinct phytoecological zones resulting from differences in salinity by using grass phytoliths. This study further explores the possibility of identifying different depositional environments when used during regional palaeovegetational and palaeoenvironmental reconstructions.