How reliable are non-pollen palynomorphs in tracing vegetation changes and grazing activities? Study from the Darjeeling Himalaya, India

Abstract

In spite of their demonstrated implications as ecological indicators, modern analogue studies of non-pollen palynomorphs (NPPs) from the mountainous regions are still meagre. We present here the results of a study on modern NPP assemblages recovered from surface samples (soils, sediments from lake surface and bog etc.) along a c. 130–3600m a.s.l. elevation gradient in the Darjeeling, eastern Himalaya to test their efficacy in distinguishing different vegetation zones and correlating grazing activities. We also used these data to check which of the variables i.e., elevation, vegetation type and grazing pressure, is/are most influential for deposition of NPPs and to obtain a NPP modern-analogue model that may assist future regional paleoecological interpretations. We subjected frequency data of 69 NPPs (consisting of algal, fungal and zoological remains each identified up to a certain taxonomic rank) and some other plant remains (like phytoclasts, hair bases and wood elements etc.) to multivariate statistical methods like Discriminant (DA) and Redundancy (RDA) analyses to assess their ecological indicative values. DA results showed that NPPs might be efficient predictors that correctly classified 72.6% of the samples to their correct vegetation zones along the elevation. RDA results further proved elevation and grazing pressure as the most significant variables influencing NPP deposition in the Darjeeling Himalaya. Considering the ecological requirements of the studied NPPs, this study also links some NPPs to their corresponding vegetation zones along the rising elevation as well as different grazing pressure and emphasizes the use of modern analogue studies in palaeoecological interpretations.