Abstract
The understanding of airborne pollen transportation is crucial for the reconstruction of the paleoenvironment. Under favorable conditions, a considerable amount of long-distance-transported pollen can be deposited far from its place of origin. In extreme arid regions, in most cases, such situations occur and increase the difficulty to interpret fossil pollen records. In this study, three sets of Cour airborne pollen trap were installed on the northern slope of Tianshan Mountains to collect airborne Picea schrenkiana (spruce) pollen grains from July 2001 to July 2006. The results indicate that Picea pollen disperses extensively and transports widely in the lower atmosphere far away from spruce forest. The airborne Picea pollen dispersal period is mainly concentrated between mid-May and July. In desert area, weekly Picea pollen began to increase and peaked suddenly in concentration. Also, annual pollen indices do not decline even when the distance increased was probably related to the strong wind may pick up the deposited pollen grains from the topsoil into the air stream, leading to an increase of pollen concentration in the air that is irrelevant to the normal and natural course of pollen transport and deposition. This, in turn, may lead to erroneous interpretations of the pollen data in the arid region. This study provided insight into the shift in the Picea pollen season regarding climate change in arid areas. It is recorded that the pollen pollination period starts earlier and the duration became longer. The results also showed that the temperature of May and June was positively correlated with the Picea pollen production. Furthermore, the transport of airborne Picea pollen data is useful for interpreting fossil pollen records from extreme arid regions.
Highlights
The genus Picea is one of the dominant tree species in boreal and cold-temperate evergreen coniferous forests, consisting of 35 species
The angle at which the maximum weeks arrived from was noted, and this angle varied, in general, it corresponded to an N–NW direction that hinders the airborne Picea pollen transported from Tianshan spruce forest to the desert region
There are about 55 km between Tianchi and Fukang, and 70 km of Beishawo, but we find that the highest quantities of pollen did not decline even as the distance increased, as the dispersal of airborne pollen grains depend both on the weather conditions and on the micro and macro topography
Summary
The genus Picea is one of the dominant tree species in boreal and cold-temperate evergreen coniferous forests, consisting of 35 species. Picea pollen appeared in samples of the low mountain area of eastern, central, western, and southern China, even on plains during the Quaternary period, especially during the last glaciation. Because of its origin, transportation and deposition of Picea pollen are still unclear Such descriptive or quasi-quantitative studies could not reflect the quantitative relationships between pollen surface samples and vegetation, especially in regions around the Tianshan Mountains, where various vegetation types and a unique topography existed. The study area is situated in the northern slopes of Tianshan Mountains in Xinjiang and displays a clear vertical distribution of vegetation types The vertical zones can be described as follow: From the higher to the lower elevated areas, vegetation includes alpine cushion, alpine and subalpine meadow, Tianshan spruce forest, steppe and desert-steppe, semidesert (Artemisia desert), and typical desert zones Small half-arbors composed of Halaxylon persicum, H. ammodendron, and other desert plants are developed widely
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