山地灾害和人类活动干扰下九寨沟下季节海的沉积变化

Environmental Change Revealed by Lake Sedimentation in Jiuzhaigou National Reserve,Sichuan,China

九寨沟是我国旅游强度最大的山地旅游地之一,山地灾害是其旅游发展过程中面临的主要挑战。为了探讨山地灾害和人类活动对湖泊生态系统的影响,以下季节海湖泊沉积物为研究对象,利用137Cs和210Pb建立年代标尺,对沉积物粒度进行了分析1。37Cs和210Pb定年法确定湖底下38.5 cm处为1952年的沉积物,50 cm处为1848年的;沉积物粒度分析结果显示,剖面内中值粒径平均值偏大,沉积速率和粗颗粒含量在1952年之后呈明显增大趋势。结果表明,沉积物来源主要是泥石流等山地灾害造成的泥砂入湖、旅游开发过程中道路等基础设施建设带来的颗粒物质;湖泊沉积对流域内的山地灾害,如泥石流等有较好的响应;森林采伐和旅游开发在一定程度上促进了湖泊沉积。

Jiuzhaigou is one of the most popular mountain tourist destinations in China.Fast increasing visitors,geological and mountain hazards and human activities like logging and construction of roads are recognized as the main challenges in sustainable tourism development.Grain size of sediments of the lower Seasonal Lake in Jiuzhaigou was studied in order to understand the responses of sedimentation to geological events,mountain hazards and human activities like earthquake,logging and road construction.137Cs and 210Pb dating identified the 38.5 cm of the profile to be the year 1952,and 50 cm 1848.Grain size analysis revealed that the average value of the profile was somewhat coarse and that the deposition rate and percentage of sand after 1952 were considerably increased.Occurrence of geological events in the region such as earthquakes and local mountain hazards like landslides and debris flows were well represented in the sediments.Construction of infrastructure,like roads,walk boards and other service facilities,has contributed to the present composition of grains of different sizes.Logging in the late 1960s to the mid-1970s has also contributed to high percentage of coarse grains in the sediments.This study suggests that good planning and implementation of appropriate measures are important to reduce risks of mountain hazards in tourism development in mountainous regions.