黄土高原中东部沙尘与非沙尘天气花粉组成及来源范围

通过黄土高原两个不同地区(浑源、洛川)沙尘与非沙尘天气花粉组合的对比来探讨主要花粉类型最大传播距离。结果表明：沙尘天气花粉汇集量明显高于非沙尘天气,特别是蒿属和藜科花粉,沙尘天气平均是非沙尘天气的3倍以上。随风速增大,花粉可能的最大源区范围明显增大。风速低于3.3 m/s时,蒿属和藜科花粉多来自100 km范围内,其他类型花粉来源范围不超过20 km;风速大于5.9 m/s时,蒿属和藜科花粉源区范围增至300 km以上;其他类型花粉不超过100 km。风速达到12.5 m/s时,蒿属及藜科最大花粉源区范围可达1000 km,其他类型花粉不超过300 km。浑源地区不论平均风速还是最大风速均明显高于洛川地区,因此,主要花粉类型可能的最大源区范围达200 km,大于洛川地区(低于100 km)。

Airborne pollen assemblages and maximum source area in dust and non-dust weather in the central and eastern Loess Plateau

The Loess Plateau landscape is partly affected by aeolian processes, and even during humid climate periods, wind has been a major component in pollen transfer. This paper presents the results of pollen trapping studies designed to quantify the pollen assemblages carried by the winds of the Loess Plateau in different vegetation compositions in dust and non-dust weather conditions in two regions (Luochuan and Hunyuan) in the Loess Plateau. The results show that the total pollen influxes in dust weather are obviously higher (more than two times) than that in the non-dust weather in the same site and similar period. The contrast of pollen assemblages in dust weather and non-dust weather shows that pollen percentages and influxes of most trees and shrubs varied irregularly in the dust weather and non-dust weather, while the pollen influxes of Artemisia and Chenopodiaceae which dominate herb pollen assemblages, are obviously higher (more than three times) in the dust weather than those in the non-dust weather, indicating that part of the Artemisia and Chenopodiaceae can be brought to the Loess Plateau together by strong wind with dust from long distance away. The maximum of pollen source radius will increase obviously with the increase of wind speed, especially for the smaller and lighter pollen taxa such as Artemisia and Chenopodiaceae. When the wind speed is lower than 3.3 m/s, Artemisia and Chenopodiaceae mainly come from within a 100-km range, whereas other types are within 20 km; When the wind speed is higher than 5.9 m/s, the maximum source radius of Artemisia and Chenopodiaceae pollen grains increase to 300 km in distance, Ephedra, Betula, and Populus etc. with midium size increase to 100 km and Ulmus and Quercus etc. with a bigger size increase to 50 km. When the wind speed is higher than 12.5 m/s, the maximum source radius of Artemisia and Chenopodiaceae pollen grains can reach 1000 km. Even in the same wind speed, the differences of the maximum pollen source radius for different taxa are obvious. In Hunyuan County, compared with in Luochuan County, not only the average and maximum wind speed are higher, but the prevailing wind direction is more consistent with the direction where dust comes. So, maximum the pollen source radiuses of major taxa are larger in Hunyuan than that in Luochuan. Apart from Artemisia and Chenopodiaceae, the majority of pollen taxa source radius are within 200 km in Hunyuan but only 100 km in Luochuan.