重庆市紫色土系统分类高级单元划分研究

Higher Category Partition for Purple Soils in Chongqing in Chinese Soil Taxonomy

依据中国土壤系统分类的原则和方法,对重庆市境内的41个紫色土典型剖面进行鉴别、检索和分类定名,并与其发生分类进行参比。结果表明,41个紫色土典型剖面分别被划归为4个土纲(人为土、淋溶土、雏形土和新成土)、6个亚纲、12个土类和19个亚类等系统分类高级单元,被划归为雏形土土纲的剖面最多,其次为新成土土纲,仅有9个剖面被划归为紫色湿润雏形土或紫色正常新成土;雏形土土纲和新成土土纲均分别对应紫色土发生分类的3个亚类(酸性紫色土、中性紫色土和石灰性紫色土),而淋溶土土纲则仅与酸性紫色土1个亚类相对应;地形、海拔、母岩和人为活动与紫色土的土壤水分状况、剖面发育、颜色以及其他理化性质等关系密切,是影响重庆市紫色土系统分类高级单元划分的重要因素;针对多数紫色土个体达不到紫色砂、页岩岩性特征的色调标准以及铁质湿润雏形土的下设亚类不能充分反映紫色土属性(如石灰性、酸性等)差异等问题,建议适当放宽紫色砂、页岩岩性特征的颜色要求或增设石灰铁质湿润雏形土和酸性铁质湿润雏形土2个亚类。

【Objective】It seems that so far little has been done on classification of purple soils in Chongqing in line with the Chinese soil taxonomy. Therefore, a systematic study in this paper was conducted to attribute the purple soils in Chongqing in the Chinese Soil Taxonomy（CST） at the higher category level, and establish references between the Genetic Soil Classification of China（GSCC） and CST for the soils, in an attempt to promote development of quantitative classification for the soils, and provide certain scientific references for survey and mapping, resource evaluation, rational utilization and improvement of regional soils. 【Method】Field soil surveys were conducted to specify forty-one soil profiles of the purple soils in Chongqing, and obtain soil-forming conditions and soil morphological characteristics of the profiles. Soil samples were collected from the profiles by horizon for analysis of physical and chemical properties. According to the ＂Keys to Chinese Soil Taxonomy（3 rd ed.）＂, diagnostic horizons and diagnostic characteristics for the tested soils were determined, and the soils were attributed and named in CST level by level. The references between GSCC and CST were established for the purple soils at the subgroup level. 【Result】The forty-one purple soil profiles were sorted into 4 orders（Anthrosols, Argosols, Cambosols and Primosols）, 6 suborders（Orthic Anthrosols, Perudic Argosols, Udic Argosols, Perudic Cambosols, Udic Cambosols and Orthic Primosols）, 12 groups and 19 subgroups in CST. At the order level, most of the soil profiles were sorted into Cambosols, which was followed by Primosols. Cambosols or Promosols in CST corresponded to three subgroups（acid purple soil, neutral purple soil and calcareous purple soil） in GSCC, while Argosols in CST did to only one subgroup, namely, acid purple soil in GSCC. Among the 25 purple soil profiles sorted into the Udic Cambosols suborder in CST, only 5 could further be sorted into the Purpli-Udic Cambosols group, and most（or 15） into the subgroup of Red Ferri-Udic Cambosols under the Ferri-Udic Cambosols group, and into three purple soil subgroups in GSCC, separately. Topography, elevation and parent rock could obviously affect the diagnostic basis for classification of purple soils in CST at higher category levels. The first two affected mostly soil moisture regimes, while the latter did color, profile development, physical and chemical properties of purple soils. In addition, appropriate farming activities could turn purple soil into Fimi-Orthic Anthrosols. 【Conclusion】Compared with GSCC in classifying purple soils, CST is higher in capability of distinguishing the soils, identifying accurately typical individuals and providing reference information for utilization and amelioration of purple soil resource in Chongqing. Topography, elevation, parent rock, and human activities are the main factors influencing classification of purple soils in Chongqing in line with CST at higher category levels. In order to further perfect the CST, some suggestions are given for revising identification criterion of lithologic character（L. C.） of purplish sandstones and shales, and solving the problem that the subgroups set under the Ferri-Udic Cambosols group in CST fail to fully reflect the differences in soil properties between the purple soils in Chongqing.