东祁连山南坡现代花粉雨与植被

Modern pollen precipitation in the southern slope of the Eastern Qilian Mountains and its relationship to vegetation

东祁连山南坡位于青藏高原、黄土高原和西北干旱区的过渡地带 ,植被类型具有多样性、复杂性和过渡性的特点 ,植被垂直分异十分明显 .以该区主要植被类型下的表土花粉百分含量为数据源 ,采用DCA排序方法定量研究表土花粉的组合特征及其与环境的关系 .结果表明 :主要的植被类型可以由他们的表土花粉谱区分开来———杨桦林、云杉林、高寒灌丛、高寒草甸 .花粉谱的变化也反映了植被随海拔高度和温度的变化 .但杨桦花粉在林中的代表性有待进一步研究 ;氧化作用对花粉的破坏作用最大 ,花粉浓度随pH值升高呈指数递减 ,pH值 7 6以上 ,花粉浓度迅速降低 .

This paper aims is to investigate pollen-vegetation relationship in the Qilian Mountains. Located in the transition zone of the Tibetan Plateau,the Loess Plateau and the arid area of Northwest China, the Qilian Mountains is sensitive to global environmental change. A total of 13 surface pollen samples from main vegetation were collected. Pollen percentages were calculated in all samples. The soil samples were collected, Detrended Correspondence Analysis(DCA)ordination method was employed on the pollen data. The results show that dominant vegetation types can be recognized by their pollen spectra: Picea crassifolia forest, alpine shrub and alpine meadow. It is altitude and temperature that determine the distribution of the surface pollen and the vegetation. The good agreement between modern vegetation and modern surface samples across this area provides a measure of the reliability of using pollen data to reconstruct paleoenvironment and paleovegetation pattern in this or other similar regions. While the loss of Betula pollen in forest needs further investigation. Pollen oxidation is the most important factor that contributes to the damage of modern pollen in the study area. Pollen concentrations decrease with the increase of pH values of soil, and decrease sharply as the pH is over 7 6.