Causes of soil boundaries in an arid region: II. Dissection, moisture and faunal activity

TitleCauses of soil boundaries in an arid region: II. Dissection, moisture and faunal activity
Publication TypeJournal Article
Year of Publication1975
AuthorsGile L.H
JournalSoil Science Society of America Proceedings
Date Published1975
Call Number00504
Keywordsarticle, articles, geomorphology, also SEE <SOIL>, journal, journals, soil, argillic horizon, soil, boundaries, soil, calcic horizon, soil, cambic horizon, soil, classification, soil, petrocalcic horizon
AbstractStudies of soils in arid regions show similar boundaries between many soils. This paper illustrates some of the boundaries caused by differences in landscape dissection, soil moisture, and faunal activity. Some of the boundaries are apparent at the land surface and others are not. In dissected terrains a change from Argids to Orthids has been caused by slow, long-continued soil truncation associated with the dissection. The boundary occurs as a gradual, lateral change from a noncalcareous, reddish-brown, and red argillic horizon to a calcareous, brown cambic horizon. Differences in moisture movement in the past have caused soil differences resulting in boundaries between Typic Haplargids and Petrocalcic Paleargids. During Pleistocene pluvials, soil moisture moved deeply into reddish-brown pipes (preventing carbonate accumulation) but not in adjacent petrocalcic horizons. Typic Haplargids occur in the pipes whereas Petocalcic Paleargids occur adjacent to the pipes. Soil boundaries have also been caused by differences in moisture movement at present. Runoff from fan-piedmonts increases vegetation and organic carbon in and along margins of basin floors. This and associated increases in clay commonly result in a boundary between Typic Haplargids on the fan-piedmont and Ustollic Haplargids on the basin floors and adjacent toeslopes. In places, soil fauna have obliterated argillic horizons by mixing A and B horizons. This causes a boundary between Argids and Orthids.