侵蚀性花岗岩坡地不同地貌部位土壤剖面风化特征研究
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国家自然科学基金项目(41471221)资助


Soil Profile Weathering Feature of Eroded Weathering Granite Slope at Different Sections
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Supported by the National Natural Science Foundation of China (No.41471221)

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    摘要:

    为揭示发育于侵蚀性风化花岗岩坡地上不同地貌部位土壤剖面的风化发育特征,在浙江省选择了典型的风化花岗岩坡地:浙江省嵊州市水土保持监测站为研究区,在监测站同一坡面不同侵蚀强度的坡顶、坡中、坡底选取3个典型的土壤剖面(140 cm),从下至上等距离(20 cm)采集土壤样品,共采集21个土样。进行了各层土壤基本理化特性和化学全量的分析,并分别计算了3个剖面不同层次的主要化学风化系数及总的风化强度,结果表明:(1)在强烈侵蚀的花岗岩风化残积坡地发育的土壤,总体发育成熟过程较弱,其进一步的发育与典型的地带性土壤的发育有很大的差异,侵蚀过程严重地影响了土壤的进一步成熟,侵蚀强度越大,则土壤发育越差。(2)土壤剖面总的风化强度不大,上下层的递变差异很小,脱硅富铝化过程随着剖面深度的增加风化程度越来越弱。(3)土壤剖面的化学分层不明显,各种风化指标均在60 cm左右形成了一个分界层,其上受水力侵蚀影响明显,其下呈现出的特性以继承残积母质为主。(4)不同地貌部位的风化发育程度排序为:坡底<坡中<坡顶,其与采样坡面的侵蚀强度排序正好相反。(5)风化程度与有机质和黏粒含量具有较为明显的正比关系,在侵蚀环境下,土壤的物理特性对风化的影响明显,在沉积环境下土壤有机质的影响大于黏粒含量的影响。总之,由于受侵蚀的影响,坡地土壤剖面的淀积层不发育,剖面呈现出的假淀积层不是由淋溶作用形成的,而是具有一定风化程度的风化残积层,结果导致发育于山地丘陵侵蚀性坡地的土壤层次划分不同于常规的土壤层次划分。

    Abstract:

    【Objective】Strong soil erosion affects profoundly soil development on slopes. On slopes the same in parent material, but different in erosion intensity, soil varies sharply in weathering development degree. In the granite hill and mountain areas of Southeast China, the soil developed on weathering residual slopes suffers severe water erosion, and differs distinctly from other zonal soils in soil weathering development profile. 【Method】 This study in oriented to characterize weathering development of soil profiles at different landform positions of an eroded weathering granite slope. A typical weathering granite slope was selected in Shengzhou, Zhejiang province for monitoring of soil erosion with the help of the Shengzhou Soil and Water Conservation Monitoring Station. On the slope where the station sits, three typical soil profiles (140 cm in depth) were selected at sites different in erosion intensity along the slope from top to bottom, and soil samples were collected 20 cm apart from bottom to top in each soil profile. So a total of 21 soil samples were gathered for analysis of basic physicochemical properties and chemical total contents in various soil layers. On such a basis, calculation was done of main chemical weathering coefficients of the soil layers and total weathering intensity of the soil profiles, separately. As the zonal soil of the studied is red soil, of which the main chemical weathering processes are enrichment of iron and aluminum and leaching of dissolved salts. Therefore, the chemical weathering indices selected in this study were dominantly those that may reflect enrichment of iron and aluminum and leaching of dissolved salts, they are ① Al2O3/SiO2, ② Fe2O3/SiO2 ③ R2O3/SiO2, ④ Al2O3/(RO+R2O) and ⑤ R2O3/(RO+R2O). In order to analyze weathering intensity of each soil layer relative to the bottom layer in the same soil profile and facilitate comparison between the soil layers in weathering intensity, further calculation was performed of relative weathering intensity (I relative) of each soil layer relative to the bottom one. 【Result】The following conclusions were drawn from the analysis and calculation:(1)The soil of the profile at the site of severely eroded weathering residual granite slope is on the whole rather slow in soil developing and maturing process, and differs sharply from the typical zonal soil in further development, and severe erosion greatly hinders maturing processes of the soil; and the severer the erosion, the poorer the soil developed;(2)The soil profile as a whole is not very high in weathering intensity; the variation in weathering intensity between soil layers in the soil profile is very gentle; the peak of weathering intensity appears in the 40~60cm soil layer, instead of the surface soil layer; the processes of desilication and aluminum enrichment weaken with profile depth and intensifying weathering degree; and the decreasing trends of Al2O3/SiO2 ,Fe2O3/SiO2 and R2O3/SiO2 are quite obvious in all the three soil profiles, which demonstrate that soil weathering degree lowers with profile depth;(3)Chemical stratification of the soil profiles is not distinct, with all the weathering indices forming a boundary layer at about 60cm in depth; the layers above it are obviously affected by water erosion and those below mainly inherit the properties of the residual soil parent material;(4)In terms of weathering intensity, the three soil profiles display an order of bottom profile < mid profile < top profile, which is just the reverse of that in terms of erosion intensity; (5)Weathering degree is significantly and positively related to the contents of organic matter and clay, and also to physical properties of the soil under erosion; However, the influence of organic matter content is greater than that of clay content in the soil in deposition environment. 【Conclusion】Affected by erosion, the illuvial horizon of soil profile does not develop on slopes, the false illuvial horizon is a certain weathering degree weathering residual layer, but is not formed by eluviations, which leads to the division of soil layer developed from hill and mountain areas differs from conventional method.

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陈儒章,张丽萍,邱陆旸,邬燕虹.侵蚀性花岗岩坡地不同地貌部位土壤剖面风化特征研究[J].土壤学报,2016,53(6):1380-1388. DOI:10.11766/trxb201603240644 CHEN Ruzhang, ZHANG Liping, QIU Luyang, WU Yanhong. Soil Profile Weathering Feature of Eroded Weathering Granite Slope at Different Sections[J]. Acta Pedologica Sinica,2016,53(6):1380-1388.

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  • 收稿日期:2015-12-25
  • 最后修改日期:2016-07-05
  • 录用日期:2016-07-19
  • 在线发布日期: 2016-08-30
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