辽东山地冰缘地貌表层土壤粒度特征

Grain size characteristics of overlying soil onperiglacial landforms in mountainous region of eastern Liaoning

为探究辽东山区冰缘地貌表层土壤的质地特征及侵蚀强度,对48个典型冰缘地貌的土壤样品进行粒度测试分析,结果表明:研究区土壤级配良好,且径级跨度较大,质地以黏土质粉砂为主,粉砂其次,偶见砂质粉砂。土壤粒度整体较细(粒度参数平均粒径Mz的值约6.45),分选差(标准偏差σI约1.89),以正偏居多(约占58%),峰态多为很窄峰(约占83%);粒度频率分布包括单峰(25%)、双峰(50%)和多峰(25%);结合萨胡判据和南北坡土壤粒度不对称等特征,初步推测早期土壤沉积组分来自近源浅表风化和远源风成沉降,其混合组分经冰缘流水搬运改造后形成土壤沉积。根据分维值(约2.28)、级配比例及敏感组分的提取可知,沉积水动力不强,地表植被覆盖越优良,对流水侵蚀能力的消耗和抑制则越显著。供试样品的粒度特征反映流水侵蚀强度不大,植被覆盖发挥了重要的水土保持功能。

[Background] As typical and representative periglacial landforms in the Mr. Laotudingzi in the center of Nature Reserve in eastern Liaoning, the characteristics of the surface ground and the changes in the natural environment are concerned by the geographers. More researches associated with it were done. However, the specific research on the mechanical analysis of soil here has been rarely published. [Methods]In order to fill the blank of the research on this area and provide the reference data for the soil and water conservation specialist or forestry specialist, based on the investigation and fieldwork, the undisturbed soil samples were returned and pretreated, the grain size characteristics of the overlying soil in 48 sample plots were analyzed. [ Results] The most of the soil particles were fine （average on about φ value is 6.45）, and the soil texture was mainly dominated by clayey silt. Additionally, the soil texture also had other presentation by consisting of silt or sandy silt that was rarely discovered. The soil of the study area was mainly positive skew distribution （ about 58% ） , and the sorting feature of grain size was ＂ Not good＂ （σ1 about 1.89） , as for leptokurtosis, most of the soil samples were showed by ＂Very narrow＂ （83%）. The frequency curves of sediment-size distribution of 48 samples presented in 3 forms by test data showing： unimodal （25%）, bimodal （50%） and multimodal （25%）. The sedimentary environment was categorized as fluvial according to the calculation by Sahu discriminant. Considering the grain-size characteristic parameter, sediment-size frequency distribution and the asymmetrical sedimentary features in southern and northern slope, it was preliminarily inferred that the incipient sediment source should be including the weathered material of local rock fragments formed by frost weathering and the sand long-distance deposit by wind from the area of Yellow Sea and Bohai Sea in late glacial; and the multi-component removed and deposited by periglacial stream during a long process, and settled on the surface ground. The fraetal dimension of grain size was between 2. l 1 to 2.39 and average on about 2.28, taking the ratio of clay and fine silt into consideration, it could be deduced that the water dynamics here was not strong. [ Conclusions] And the fractal dimension, together with the environmentally sensitive grain size component, reflected that the better the land surface vegetation covered, the more significant the depletion and suppression of water erosion were. The characteristic of grain size here indicated that the intensity of water erosion was low and vegetation coverage played the vital role in the the water and soil conversation.