西北干旱区艾比湖典型区域蒸发盐动态变化特征及其对风蚀的响应初探

Dynamic variation of evaporated salt and its response to wind erosion in the playa of Ebinur Lake,arid northwest China

为了解干涸湖底不同区域风蚀作用下蒸发盐动态变化的分异特征,选择西北干旱区艾比湖干涸湖底为研究区,选取西北部间歇性干涸湖底(S1)、湖滨沙丘(S2)、东南部历史时期干涸湖底(S3)3个典型区域,对干涸湖底不同区域沉积物蒸发盐总盐含量的变化特征及其对风蚀的响应分异进行了研究。实验结果表明:①不同区域蒸发盐含量差别较大。三个研究区中S1表层蒸发盐含量最高,可达101.0 g·kg^(-1);S3含量次之,表层最高时为47.3 g·kg^(-1);而S2表层含量最高仅为40.0g·kg^(-1)。②S1、S2、S3三个研究区蒸发盐含量随时间变化表现出相同的特征。6月份含量最高,随季节的变化趋势为从6—10月份逐渐降低。在不同的季节随着深度增加,含量均呈现降低的趋势,即不同地点不同时间0~50 cm各层含量均表现出降低趋势。③蒸发盐含量对风蚀的响应特征具有明显的区域差异和复杂性。在风蚀作用下,S1研究区未覆盖区域蒸发盐含量明显高于覆盖区域,S2研究区的含量对风蚀的响应特征比较复杂,而S3未覆盖区域含量低于覆盖区域,与S1研究区对风蚀的响应特征相反。不同区域不同的地下水埋深、沉积物质地、植被特征及迥异的风蚀机理是造成蒸发盐含量差别及不同风蚀响应特征的主要因素。

In order to understand the salinity variation characteristic in the process of wind erosion, lacustrine sediment were sampled from three typical positions of Ebinur Lake （S1, intermittently dry lake bed; S2, lakeside; S3, permanently dry lake bed） to reveal changes of salt content and response characteristics to wind erosion, which dominated by bare desert, Phragmites australis, Haloxylon ammodendron and Halocnemum strobilaceum, respectively. The results showed that evaporated salt content in different locations of Ebinur Lake dry lakebed were quite different. The highest content among the three study areas appeared in S1 at the northwest intermittent dry lakebed, up to 101.00 g·kg^-1, followed by S3, which salt content was 47.3 g·kg^-1, the S2 had the lowest 40.0 g·kg^-1 at the surface. Evaporated salt content varied in time and space at different locations of dry lakebed, and the highest content occurred in June and gradually reduced with the seasonal changes from June to October; salt content showed a decreasing trend in different seasons with increasing depth, that is, evaporated salt content of five layers from 0 cm to 50 cm showed a downward trend at different times and different locations. Take wind erosion into consideration, the response characteristics of salt content to wind erosion showed significant regional differences. Salt content of sediment that was not covered in S1 was significantly higher than the covered area. The relationship between the covered and uncovered sediment in S2 was complex. However, response characteristic of S3 to wind erosion was just the reverse of that of S1. All above information indicated the regional difference and complexity of variation and response to wind erosion of evaporated salt content. Different groundwater table, sediment texture, vegetation characteristics and soil erosion mechanism are the main factors that result in different evaporation salt content and different wind response characteristic.