Micromorphological features of old cultivated and modern soil in guanzhong areas of Shaanxi Province, North China

Chino. 通过对土壤微形态研究试图阐明陕西关中地区现代土壤的发育过程和微形态标志。用偏光显微镜对LGT剖面不同发生层的薄片进行了观察和影像定量分析。不同发生层的矿物组合十分相似，石英（Q）和长石（Pl）占绝对优势，但C/F15andmicro;m值、不同矿物间的比例、颗粒形态等有明显差异。土壤形成物主要是粘土矿物、方解石和无定形Fe，Ap层中有大量针状方解石微晶、次生粘土和蚯蚓粪粒，BC层方解石数量多且形态最复杂，Bt1和Bt2层方解石很少，但有大量粘土亚胶膜。所谓的“堆垫土”实际上由两部分组成，下部BC主要是全新世晚期堆积的风积物，表层Ap是2000年以来人类不断施加土粪、风尘堆积和农耕活动的综合产物。

Inglés. Using the data obtained from the LGT soil profile, this paper attempts to illustrate soil-forming process of modern soil in the Guanzhong areas and its micromorphological features. Micromorphology was observed under a petrographic microscope, and its image was quantitatively measured by LEICAL Qwin software. Micromorphological observations of the thin sections show that the minerals assemblage of different horizons very similar, which is mainly composed of Q and Pl. However, there are obvious differences in C/F15andmicro;m ratio, mineral content, and coarse features. Pedofeatures mainly consist of clay, calcite, and amorphous Fe. Ap horizon is characterized by abundant needleshaped secondary-calcite, secondary-clay, and earthworm fecal pellet. BC horizon is characterized by the secondary-calcite of large quantity with various shapes. Bt1 and Bt2 horizons are characterized by abundant clay hyopcoatings and a small quantity of secondary-calcite. All the results of this research suggest that Earth-cumulic Orthic Anthrosols consist of both the upper Ap horizon, which cause loessal dung and eolian dust deposition, and cultivation occurs simultaneously during the process of Ap horizon-formation, and the lower BC horizon, which is aeolian sedimentary at the time of relative aridity during late Holocene.