Modern pollen distribution across Mizoram,northeastern India,impacted by regional climate and anthropogenic activities

Abstract

Modern pollen-rain analysis was carried out for the first time across central, western and eastern regions of Mizoram, encompassing different regional climatic zones. The vegetation experiences massive ecological pressure as a consequence of environmental factors, including the monsoon winds from the Bay of Bengal, high temperature, precipitation conditions, and varied topography. Additionally, intense human activities in the state of Mizoram impact the forest landscape in the remote northeastern part of India. These include agricultural activities such as shifting cultivation (Jhum), commercial crop plantations such as banana, rubber, oil palm, tea, etc., pastoral activities and others. We collected moss cushion samples across transects in the central, western and eastern regions of Mizoram, to comprehend the impact of natural and anthropogenic factors on the modern vegetation and resultant pollen taxa on the surface deposits. The modern pollen data were analyzed statistically, including constrained redundancy analysis (RDA). The RDA analysis revealed the impact of bioclimatic variables on the pollen record, such as isothermality, precipitation in the warmest quarter and annual precipitation. The most significant variable was isothermality (bio_3) which indicated the dominance of anthropogenically impacted sites on the species distribution. Here, we identified that an interplay of climate- and anthropogenic-driven forcing were primarily controlling the modern vegetation and pollen-rain across Mizoram. The anthropogenic indicator pollen, such Poaceae (>50 µm), Caryophylaceae, Asteroideae, Cannabaceae, and Palmae at various sites reveal the impact of anthropogenic activities on the modern vegetation. The results reveal the impact of climatic zones, altitude gradients, anthropogenic activities and vegetation distribution on the pollen yield from the surface deposits.