艾比湖干涸湖底6种景观类型不同深度富盐沉积物粒径的分形特征

Fractal Characteristics of Particle Size Distribution in Salt-rich Sediments from Different Depths under Six Different Types of Landscapes in the Playa of the Ebinur Lake

干旱区干涸湖底在强烈的风蚀作用下成为盐碱尘暴的重要来源之一。为研究干涸湖底不同景观类型的抗风蚀效应,选择新疆准噶尔盆地西部艾比湖干涸湖底6种不同景观类型下的富盐沉积物为研究对象,基于沉积物样品的体积粒径分布数据,运用单重、多重分形理论和典范对应分析(CCA)排序方法,重点探讨艾比湖干涸湖底不同景观类型下富盐沉积物粒径分布分维值的分异特征。结果显示:胡杨林带(L1)、乔本结合带(L2)、草本结合带(L3)、芦苇荒漠带(L4)、梭梭荒漠带(L5)、无植被覆盖(L6)6种景观类型0～30cm和30～60cm的富盐沉积物分维值分别存在显著性差异。各景观0～30cm分维值介于1.94～2.40,30～60cm分维值介于1.92～2.53,总体均处于低位水平。0～30cm平均分维值依次为L5>L1>L6>L4>L2>L3,30～60cm平均分维值为L5=L1>L4>L6>L2>L3。富盐沉积物粒径分布分维值与粒径小于73.63μm的体积含量呈显著正相关。研究表明多重分形维数和CCA排序方法可以有效的揭示干涸湖底自然植被条件下不同深度富盐沉积物粒径分布的均匀性特征。指出干涸湖底风蚀控制研究方向应集中在根据湖区的富盐沉积物-植物特征,对富盐沉积物性状进行改良,提高原生物种幼苗存活率,通过生态修复防治盐尘暴。

Dry lakebed has become one of the main sources of saline-alkali dust storms in arid areas due to strong wind erosion. In order to study the anti-erosion effects of different types of landscapes, salt-rich sedi- ments were collected under six different types of landscapes in the playa of the Ebinur Lake. Using the methods of single and multi-fractal dimension and Canonical Correspondence Analysis （CCA）, the spatial distribution characteristics of erosion intensity were discussed with the particle size data of salt-rich sediments. The results showed that fractal dimension of the particle size distribution （PSD） had significant differences between two sediment samples from the depth of 0--30 cm and 30--60 cm under six kinds of landscapes. The fractal dimension values of the PSD ranged from 1.94 to 2.40 in the sediments from the depth of 0--30 cm and decreased in the order of zone dominated by Haloxyton ammodendron （L5）〉 by Populus euphratica （L1）〉 by bare desert （L6）〉 by Phragmites australis （L4）〉 by other trees（L2）〉 by herbs （L3）, but the other ranged from 1.92 to 2.53 from the depth of 30--60 cm and followed the order of L5= LI〉〉L4〉L6〉L2〉L3. The fractal dimension of the PSD was significantly positively correlated with the particle volume-size fraction （〉73.63 μm）. Thus, the multifractal dimension and CCA analysis can provide useful methods for analyzing the uniformity characteristics of the PSD from different depths of salt-rich sedi- ments in natural vegetation. According to studies of the salt-rich sediments and plant in the Ebinur Lake, establishing of native vegetation is one method of stabilizing shifting soil and minimizing saline dust pollution from dry lakebeds. It is suggested that the future research should focus more on ecological restoration for preventing saline dust storms.