Phytolith spectra of some eastern Himalayan pteridophytes: Assessing potential for distinguishing different vegetation–climate zones along the elevation gradient

Abstract

To understand the relationship of phytolith production patterns in regional pteridophytes with elevation dependent climatic variables, and their potential to differentiate vegetation zones of the eastern Himalayan Mountain, we have studied phytolith spectra of 58 pteridophytic species of 22 families from tropical–temperate vegetation belts of Darjeeling, Sikkim and Arunachal Pradesh. Nineteen major phytolith types recovered from foliages and shoots of the pteridophytes are assessed for their potential to distinguish different vegetation zones, if any. Combined data suggest that epidermal polygonal (EP), jig saw plate (JSP), cast of epidermal cells (CEC), globular folded (GF), polyhedral bodies (PB), hair cell base (HCB) and silicified tracheids (TR) are the most significant phytolith morphotypes produced along the tropical‒temperate vegetation belts. Of these, CEC and GF could successfully discriminate tropical and sub-tropical from temperate vegetation. PB may be used as indicator of sub-tropical/lower-temperate vegetation and climate, and HCB as indicator of sub-tropical‒temperate vegetation and climate. Cluster analysis (CA) applied on the pteridophyte phytolith data shows morphotype signal for different vegetation zones. Discriminant analysis (DA), detrended correspondence analysis (DCA) and redundancy analysis (RDA) have arranged pteridophytic phytolith assemblages along the evapotranspiration and moisture availability gradients, approximating the actual distribution of vegetation along the rising elevation. DA has classified 75% of the taxa into their correct vegetation zones. Misclassification by DA may be attributed to the redundancy of the phytolith morphotypes among the studied taxa and indicating that caution should be taken when applying them in the fossil phytolith assemblages. The study infers a combined influence of climate–energy and moisture availability on the elevational distribution of the pteridophytic phytoliths in the eastern Himalaya. This study indicates that pteridophytic phytoliths have the potential to record regional forest zones despite steep environmental gradients and may be used in interpreting regional fossil pteridophytic phytolith spectra during palaeoclimate reconstructions.