蒙古国北部Gun Nuur湖表层沉积物花粉分布特征

Spatial characters of modern surface pollen assemblage of Lake Gun Nuur,northern Mongolia

蒙古国北部Gun Nuur湖20个表层沉积物孢粉组合与数量分析研究揭示,孢粉组合及浓度分布存在显著空间差异。结果表明:双束松型花粉百分含量由湖泊东南向西北降低,桦属、蒿属、藜科以及禾本科百分含量增加,湖泊东南侧赤松林是造成孢粉组合空间分异的主要原因。孢粉浓度分布与湖泊水深具有良好的对应关系,体现了湖水流对孢粉的二次搬运和富集作用。现代森林草原地带Gun Nuur湖表层孢粉组合中松属含量较高,具超代表性;受松属影响蒿属和藜科花粉含量较低,代表性较低。

The study on lake surface sediment pollen assemblage and flux is of important significance for paleoeco logical environment reconstruction because it provides the references such as the origin of pollen, pollen representa tive and environment significance. In order to study the relationship between the lake surface sediment pollen and the regional vegetation landscape, 20 sites are investigated along the southeastnorthwest, the southwestnortheast and the southnorth transections of the lake Gun Nuur, northern Mongolia, in hope that spatial distributional characters of pollen assemblage, pollen concentration and representation of main pollen genera could be disclosed. Specifical ly, pollen assemblage and total pollen concentrations of 20 sites were analyzed and the relationships between pollen assemblages and the regional vegetation pattern were multivariably and statistically discussed, the relationship between total pollen concentration and water depth were explored too. Firstly, pollen assemblage data shows the noticeable differentiations existed along southeastnorthwest direction, which is characterized by a decline in Pinus Diploxylon type pollen percentage and increases in Betula, Artemisia, Chenopodiaceae and Gramineae pol len percentages, and this differences might be attributed to the influences of the Scots pine forest developed to the east and south of Lake Gun Nuur, and this was also disclosed by the result of detrended correlation analysis （DCA） on those 20 lake surface sediment pollen assemblage, suggesting that sample sites could be distinguished by the en ginevalue of axis 1, maybe the axis 1 represent the distance between the sites and the Scots pine forest in the south and east. And overrepresentation of Scots pine pollen was disclosed or confirmed in the landscape of Scots pinedominated forest steppe, while underrepresentation of Artemisia and Chenopodiaceae were suggested and this might resulted from the compensationdecline effect （i.e., Fagerlind effect） of Scots pine pollen percentages. Furthermore, comparison between contour maps of total pollen concentration and the water depth may suggests a positive correlation existed, showing high total pollen concentration at deeper sites and vice versa, suggesting the suspension and redeposition by water flow was notable. The results of the study in this paper provide references to study the distribution of modern pollen and the reconstruction of the ancient environment. On the other hand, this study on pollen of lake surface deposition can be a reference in this research field in northern China.