摘要
本文仅就黄土高原的土壤和古土壤与环境变迁的轨迹,也就是从黄土沉积和黄土层性质的特殊性入手来剖析一下土壤性征所能反映的生物气候信息,提供一鳞半爪的事实,以期对当前某些学术观点的对立,有所缓和。主要内容:(1)特殊的沉降方式形成特殊的成土母质;(2)特殊的成土母质进行着特殊的成壤过程;(3)特殊的成壤过程形成特殊的土被结构;(4)特别强调土壤形成过程中的生物反馈作用以及提出对有机物的积累和腐解、矿化等方面的新见解,并用事实验证了黄土高原土壤中粘粒胶膜的出现既不是粘粒淋淀又不是土体原位风化而纯系植物尤其草木植物根系的原地腐解、矿化为简单的矿质后再在有利的条件下,经过一定的时段形成新的粘土矿物。
This paper, might provide some, perhaps fragmental, knowledge about the relation of soil (including paleosol) on the loess plateau to environmental variations. The authors are trying to enter into the nature and speciality of the loess deposition and loess layer and then annalyze the bidogy-climate information possibly contained in the soil characteristics. This approach might alleviate the antagonism and hence promote the cooperation between different scientific views. The authors suggests that:(1) Paticular settling modes let to particular mother material for the pedogenesis. It is just the prolonged falling accumulation and continuous alternative pedogenesis-lithification of this material of 'parasoil-pseudosoil' along the middle reach of the Yellow River that formed the loesspaleosol sequence as thick as 200 meters.(2) Particular pedogenetic process is going on parent material particularly. The pedogenesis process in loesspaleosol sequence is rather unique. Except the compaction effect. due to the biotic (such as the root growth) separating then coagulating process on the mother material which is contrary to normal pedogenesis, the uniqueness is also expressed in: a) the pedogenesis is not in harmony with the loess-body weathering; b) the big cycle of geology is inseparable with the small biotic cycle; and c) the soil formation surface is going upwards but combining with the tape-out of the pedogenesis intensity both down- and up-wards . The growth, disintegration, and mineralization of the root system form the material base for the coagulation film, and on the other hand form a certain barrier to the hydrolysis of the mineral grains in the natural state of the loess-body.(3) The particular soil cover structure is formed by the particular pedogenesis. After a comparison between the paleosol genetic profile and the modern soil in morphology, quality, composition of the clay granule and humus content, nature etc., it is discovered that except for the buried soil of Heilusoil type in Malan loess to the north of the Weibei plateau, all the other paleosols are similar to the cinnamon soil; and the section pattern is temporarily discribed as A—AB_((P))—B_(Ca)—BC—C profile. The A horizon contains about 1% humus, and displays a distinct granular structure, and it was formed from loose homogeneous loess by the biotic activities of insecting and pushing-pressing; the AB horizon is similar to A, but the humus content is lower, deeper colored (more reddened), rather compact, sometimes has a prismatic structure with the prisma beging able to section into small, fine angular nutty-structure, and as a matter of fact it is the most permeable horizon (p) with noncapillary micropores and fissures intensively developed; Bca is the calcareous illuvial horizon similar to loess in general, but the CaCO_3 content is as high as more than 16% which sometimes occurs as loess-doll; the BC is a transitional horizon between Bca to C; and the C is the rather pure, homogenous loess.(4) Finally, the authors point out the following points as a conclusion and for furture testing. a) The sequence of loess-paleosol, especially its formation due to the contradictory, reciprocal processes-peologensis and dust accumulation, should be much emphasized because it is the only trace of the biotic and climatic changes or even the global changes left on loess plateau. It is only the concept of the loess-paleosoi sequence that can leads us to the objective reality. b) The study on the essence of the pedogenesis in the loess accumulation background should go urgently into deeper. c) The biotic feedback should never be underestimated. Because much mineral material (such as Si, Fe, Al, Ca, K, Mn etc.) is relased after disintegration of the organic relics to directly form the clay fraction, which is much stronger and more important than the formation of the clay fraction through the weathering of the primary minerals. d) Attention should be paid to the accumulation, disintegration, humification and decompolition, and mineralization of the organic material. The es
出处
《土壤学报》
CAS
CSCD
北大核心
1992年第4期351-357,共7页
Acta Pedologica Sinica
关键词
土壤
黄土高原
发生过程
环境
Soil, Loess plateau, Pedogenesis, Soil cover structure, Heilusoil
