Modern Pollen Rain Studies at the Forest Steppe Ecotone in the Lake Dayan Region, Mongolian Altai

Abstract

This paper presents the results of study on the relationship between vegetation and modern pollen rain in the Lake Dayan region of the Mongolian Altai, western Mongolia. Within the Joint Mongolian-German research project from 2010 to 2017 we collected dominating plants from six sites in Sagsai district, Bayan-Ulgii province. Geobotany records were made and collected about 173 species of 90 genera, 34 families. A vegetation survey carried out in 18 plots showing the species composition in the forest, forest edge and steppe differ markedly. Pollen traps were placed in the same vegetation plots to gain the pollen rain in the forest, forest edge and steppe for one year 2017-2018. The Larix forest and steppe are well reflected in the pollen rain. Pollen of Larix sibirica, Betula rotundifolia, Poaceae, Cyperaceae, Chenopodium and Artemisia were abundant in the forest and at the forest edge. In the steppe, pollen deposition of Larix sibirica, Betula rotundifolia were low, while that of Poaceae, Caryophyllaceae, Artemisia, Cyperaceae and Cichoroideae were high. The comparison of modern pollen rain with the surrounding vegetation for each site of the ecotone reveals that only different plant taxonomic levels can reflect the plant diversity patterns in the region. The vegetation cover was estimated by proportions of forest in 100 m and 500 m radius around the pollen trap, indicating that forest is less represented than steppe vegetation in the pollen rain. Environmental changes caused by human impact, such as grazing and deforestation are also reflected the modern pollen rain. Comparison of similarities of plant species in three sites, forest edge, forest interior and steppe, is performed, which were more similar between the forest edge and forest interior due to habitat similarity.