沙漠根套的类型及其成因
首发时间:2006-10-11
摘要:在腾格里沙漠东南部发现三种不同淀积类型的管状砂结核,其胶结物分别是钙质和铁锰长石矿物。钙质砂结核在丘间洼地与风蚀墩、灌丛沙堆相伴分布,多呈散乱的地表蚀余堆积,有的则保留着由直立主根和水平支根构成的完整根系形状。在沙漠边缘的湖滩沙层中,风蚀裸露部位出现排列密集的管状铁锰砂结核,向上尖灭于分布广泛的顶部钙积层。这些管状砂结核主要是在植物蒸腾过程中,由质流作用导致土壤溶液中的矿质离子在根系周围沙体中富集,并经过脱水、氧化等反质流作用发生淀积、胶结而形成的根套。不同根套淀积类型的层序分布反映了该地区土壤环境的干、湿变化。
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The types and formation of root-crusts in desert
Abstract:Three types of cannular sand nodules have been found at southeastern of the Tengger Desert, and the main depositions are calcic mineral and ferrimanganic feldspathoid respectively. The calcic sand nodules distribute at the depression of the sand dunes, companied with wind erosion frusta and shrub-coppice dunes. Most of the calcic sand nodules disheveled distributed at the earth surface as erosion remaining-deposit, some kept the integrity root system composed by the standing taprootand the aclinic branch roots. In the sand-layers of lake beach at desert edge, cannular ferrimanganic feldspathoid dense arranged at exposed wind erosion area, and these feldspathoid disappeared at the top calcic layers which distributed broadly. These cannular sand nodes are root-crusts formed during the process of vegetable transpiration. Mineral flowing process caused the mineral hydronium of soil solution enriched around the root, after contra-mineral flow process such as dehydration and oxidization, the root-crusts formed by illuviation and cementation. The layers have different root-crusts types reflected the environmental changes between drought and wetness.
Keywords: Tengger Desert, calcic root-crust, Fe/Mn root crust, mineral characteristics
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