利用137Cs示踪和孢粉分析法对喀斯特峰丛草地洼地泥沙沉积及侵蚀环境的研究

在贵州省茂兰喀斯特峰丛草地洼地联合运用137 Cs示踪和孢粉分析的方法,对洼地沉积泥沙剖面进行了研究.草地洼地泥沙剖面的137Cs垂直分布显示了泥沙沉积特征,以地层孢粉为主的孢粉组成显示了洼底泥沙主要来源于由碳酸盐岩石风化成土后随水流侵蚀搬运的坡地土壤颗粒.从沉积泥沙剖面的137Cs含量、土壤颗粒结构、孢粉总浓度的垂直变化说明洼地土壤侵蚀经历了一个相对的轻微侵蚀-剧烈侵蚀-侵蚀显著减缓的变化过程；沉积泥沙剖面样品中的现代孢粉组成出现从蕨类、草本、乔木(松)孢粉占优势到以适应喀斯特石生环境的蕨类孢粉和草本孢粉占优势的变化,指示了洼地环境植被出现从含稀疏常绿落叶松的草丛退化为草丛的变化.喀斯特峰丛草地洼地的泥沙沉积过程与洼地植被演变和洼地侵蚀环境变化具有密切联系.

Sediment Deposition and Erosion Environment in a Karst Peak-Cluster Grassland Depression Studied by 137Cs Tracing Technology and Pollen Analysis

¹³⁷Cs tracing technology and pollen analysis were jointly used to study sediment profile in a karstpeak-cluster grassland depression in Maolan,Guizhou Province.Vertical variations of ¹³⁷Cs,soil particlestructure and pollen composition in the profile showed that soil erosion in the grassland depression occurredin a relatively varied process from slight erosion to intensive erosion and then to rapidly decreased erosion.Those modern pollen of deposited sediment samples in the profile showed that the plant constitution dominated by fern seed,herb seed and tree seed changed to that dominated by fern seed and herb seed which adaptedto the karst rocky habitation.This means that herbosa including sparse Pinus plants degraded to herbosa inthe depression.Sediment deposition process is closely associated with plant regression and erosion environment change in the karst peak-cluster grassland depression.