Effects of meteorological factors and air mass

Image: Air pollen proportions in the birch wetland of Ebinur from September 2012 to August 2015. Different seasons are categorized by dashed lines.
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Photo credit: © Science China Press

As an important part of modern pollen research, monitoring contemporary air pollen compared to surface pollen can not only detect immediate responses to climate change, but also detect changes in species and vegetation on longer time scales. Airborne pollen concentrations were observed by monitoring birch wetlands in Ebinur Lake National Wetland Nature Reserve (44 ° 34’15.6 “N, 8344’43.4” E) with a Cour sampler at a height of 1.48 m.

The results showed that pollen from herbaceous taxa such as Artemisia and Chenopodiaceae, each year the pollen association dominated, while the arboreal pollen taxa were dominated by Betula and Picea (Fig.1). Betula Pollen come predominantly from Betula microphyllathat dominated the birch wetlands, and pollen grains emitted by aquatic plants in the birch forests. Based on the vegetation distribution in the Ebinur wetland, the airborne pollen composition in our study corresponded to the local vegetation with the exception of the spruce pollen. The airborne pollen accumulations thus coincided with the growth of local plants and can reflect pollen taxa that have been transported far.

A comprehensive analysis of the relationships between airborne pollen and meteorological factors showed that the peak season of atmospheric pollen corresponded to the flowering period and varied with meteorological variables in different years. The comparison between meteorological data and airborne pollen data showed that seasonal patterns of airborne pollen varied with meteorological factors, in particular temperature, precipitation, wind speed and wind direction. The annual fluctuations in the total pollen concentration in the air in the wetlands first increased and then decreased from September 2012 to August 2015 (Figure 2).

According to modern backward trajectory analysis (HYSPLIT model) (Fig. 3) additionally Picea Pollen was brought in from the Tianshan Mountains, which resulted in the highest concentrations of arbor pollen from September 2012 to August 2013; the Ebinur wetland and the Central Asian desert region had the highest concentrations of pollen. Between September 2014 and August 2015, the lowest pollen concentrations were associated with lower xerophyte pollen content, which originated in the Kazakh hills in late autumn.

A comparison between surface and air pollen in Xinjiang showed that Betula Pollen provided a suitable reference to modern vegetation and thus reflected the local plant communities. The relationship between pollen and vegetation is key to reconstructing the “real face” of paleovegetation and paleoclimate using fossil pollen data. Betula Pollen was moderately represented in the total pollen of the study area, which indicates birch growth; These results can improve the accuracy and reliability of vegetation and climate reconstructions based on pollen data.

This research was funded by the National Natural Science Foundation of China (Nos. 41971121 & 41572331).

See the article:

L. Chen, Y. Zhang, Z. Kong. Pollen patterns in the air and their relationship to meteorological factors in the Betula microphylla dominated wetland of Lake Ebinur, Xinjiang, China. SCIENCE CHINA Geosciences, 2021, 64 (10): 1746-1760. https://doi.org/10.1007/s11430-020-9801-7

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