Micromorphology of Surface Crusts in the Knersvlakte,South Africa
Micromorphology of Surface Crusts in the Knersvlakte,South Africa作者机构：Department of Soil Science Stellenbosch UniversityStellenbosch South Africa Department of Environment and Soil Science University of LleidaRovira Roure 191 Lleida
出 版 物：《Journal of Mountain Science》 (山地科学学报（英文）)
年 卷 期：2009年第6卷第2期
页 面：189-196页
核心收录：
学科分类：09[农学] 0903[农学-农业资源与环境] 090301[农学-土壤学]
基 金：BIOTA Southern Africa (sponsored by the German Federal Ministry of Education and Research under promotion number 01 LC 0024A) the South African government (National Research Foundation, Mobility and Training Grant 2005/ GUN No: 2072287/ PUN No: 212778) for financial support
主 题：Infiltrability optical microscopy porosity air vesicles
摘 要：Soils in the Knersvlakte are particularly prone to crusting and have lower inherent infiltrability than other soils across western southern Africa. Micromorphological techniques were used to examine the structure and porosity of soil crusts in the Knersvlakte to ascertain why crusting is so intense in this region. Quantile regression using boundary lines was employed to examine the relationships between infiltrability and soil properties for all samples （n = 67）. This analysis showed that infiltrability is potentially maximal at low water- dispersible ＇clay plus silt＇ content and low silt content （r^2 = 0.72 and 0.64; respectively, n = 67） （Figure 2）. The strength of crusts, pH, EC, clay mineralogy, and water-dispersible clay, silt and ＇clay plus silt＇ content were compared, and a pore analysis using optical microscopy was undertaken on images of six soil thin sections （n = 6） （circular and parallel polarizers）. Pore analysis was further undertaken on five horizontal slices of equal dimensions taken through each soil thin section. The porosity samples with low infiltrability （〈 100 mm·hr^-1, n = 4） had greater crust strength, lower porosity （both total and in the least porous slice） and greater water-dispersible ＇day plus silt＇ and silt content than the porosity samples with high infiltrability （〉 100mm·hr^-1, n = 2）. The porosity samples with low infiltrability showed a trend of lower pH and greater water dispersible clay percentage. Porosity varied within the porosity samples due to the presence of dense clay/silt bands （〈 0.5 mm in width） with relatively few air vesicles. The porosity samples with horizontal slices of low porosity （but large numbers of air vesicles） had low infiltrability, while those without slices of low porosity （and relatively few air vesicles） had high infiltrability. We conclude that the intense crusting and resultant low infiltrability of soils in the Knersvlakte appears to be related to the formation of thin, dense clay/silt bands in the
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