Abstract: Few studies are available on the relationship between modern pollen rain and climatic factors in the tropical and subtropical regions of low latitude in China. In this study, surface sediments of 43 water bodies (lakes, reservoirs, and ponds) were analyzed to explore the characteristics of modern pollen rain and its relationship to climatic factors in the Honghe region of southern Yunnan. Pollen analysis of surface sediments showed that pollen spectra of surface sediments from water bodies were characterized by abundant pollen and high arboreal pollen percentages. Arboreal pollen were dominated by Pinus, Alnus, and Fagaceae, while herbaceous pollen mainly included Poaceae, Asteraceae, and Cyperaceae. Pollen spectra also contained some fern spores (such as triletes) and algae (such as Pediastrum). Meanwhile, modern meteorological data of these water bodies were obtained by linear interpolation of 1961 to 2010 (50-year) from 13 meteorological stations in the Honghe region of southern Yunnan. Redundant analysis of modern pollen and climate data was used to examine the effects of climate factors on the spatial pattern of modern pollen rain. The results of redundancy analysis showed that the six climatic factors controlling modern pollen rain are mean annual precipitation and temperature, precipitation in spring and dry season, and temperature in July and rainy season. An increase in temperature resulted in vegetation dominated by evergreen broadleaved forest, and a decrease in precipitation caused an expansion of pine forest. Our results provide theoretical support for paleoclimate reconstruction using fossil pollen record.

Key words: open-path infrared gas analyzer, surface heating effect, Burba correction., optical path temperature, fine-wire thermocouple