image: Airborne pollen percentages in the Ebinur birch wetland from September 2012 to August 2015. Different seasons have been categorized by dashed lines. view more
Credit: ©Science China Press
As an important part of modern pollen research, compared with surface pollen, the monitoring of contemporary airborne pollen can not only identify immediate responses to climate change, but also recognize changes in species and vegetation at longer time scales. Airborne pollen concentrations were observed by monitoring the birch wetland in the Ebinur Lake National Wetland Nature Reserve (44°34′15.6″N, 83°44′43.4″E) using a Cour sample collector at the height of 1.48 m.
Results showed that pollen from herbaceous taxa, such as Artemisia and Chenopodiaceae, dominated the pollen assemblage every year, whereas the arboreal pollen taxa were dominated by Betula and Picea (Fig.1). Betula pollen predominately originated from Betula microphylla, which dominated the birch wetland, and pollen grains emitted by aquatic plants within the birch forests. Based on the vegetation distribution in the Ebinur wetland, the airborne pollen composition in our study corresponded to the local vegetation, except for the spruce pollen. The airborne pollen assemblages were thus consistent with the growth of local plants and can reflect long-distance transported pollen taxa.
Comprehensive analysis of relationships between airborne pollen and meteorological factors showed that the peak seasons of atmospheric pollen corresponded to the flowering period and varied with the meteorological variables in different years. The comparison between meteorological data and airborne pollen data indicated that seasonal patterns of airborne pollen varied with meteorological factors, particularly temperature, precipitation, wind speed, and wind direction. Annual variations in the total airborne pollen concentration in the wetland first increased and then decreased during September 2012–August 2015 (Fig.2).
According to modern backward trajectory analysis (HYSPLIT model) (Fig.3), additional Picea pollen was brought over from the Tianshan Mountains, resulting in the highest concentrations of arbor pollen from September 2012 to August 2013. In the summer and autumn of September 2013 and August 2014, a large amount of exotic herbaceous pollen from the desert in the southwest of the Ebinur wetland and Central Asian desert region led to the highest pollen concentrations. Between September 2014 and August 2015, the lowest pollen concentrations were related to a lower xerophyte pollen content being sourced from the Kazakh hilly area during late autumn.
A comparison between surface and airborne pollen in Xinjiang demonstrated that Betula pollen presented a suitable indication of modern vegetation, thereby reflecting the local plant communities. The relationship between pollen and vegetation is the key to reconstructing the “true face”of paleovegetation and paleoclimate using fossil pollen data. Betula pollen was moderately represented in the total pollen of the study area, which indicated birch growth; these results can improve the accuracy and reliability of vegetation and climatic reconstructions based on pollen data.
This research was funded by National Natural Science Foundation of China (Nos. 41971121 & 41572331).
See the article:
L. Chen, Y. Zhang, Z. Kong. Airborne pollen patterns and their relationship with meteorological factors in the Betula microphylla-dominated wetland of Ebinur Lake, Xinjiang, China. SCIENCE CHINA Earth Sciences, 2021, 64(10): 1746-1760. https://doi.org/10.1007/s11430-020-9801-7
Journal
Science China Earth Sciences