Diversity of diagnostic horizons in soils of the contiguous USA: A case study

作者：Bockheim James G^*

来源：Catena, 2018, 168: 5-13.

DOI：10.1016/j.catena.2017.10.016

• Pedodiversity
• Diagnostic soil horizons
• MLRAs
• Laurentide Great Lakes

Many previous studies of pedodiversity have emphasized the lateral variability of soils. In this study, the vertical distribution of diagnostic horizons is examined at the soil-series level. Unlike genetic horizons, diagnostic soil horizons are based on quantitatively defined morphological and analytical properties; and they form the basis of modem soil classification systems. An examination of 1600 soil series in 63 representative (out of 226) Major Land Resource Areas (MLRAs) in contiguous USA revealed that they contain from one to seven diagnostic soil horizons, with an average of 2.6 +/- 1.2. About 20% of the soil series contain 4 or more diagnostic horizons; 80% of these soil series are in seven great groups: the Glossudalfs, Haplorthods, Fragiorthods, Endoaquods, Epiaquods, Fraglossudalfs, and Glossaqualfs. The Laurentide Great Lakes region contains a discordant number (57%) of soils with 4 or more diagnostic horizons, the most common being ochric (100%), albic (91%), argillic (85%), glossic (69%), spodic (51%), and a fragipan (19%). Several factors appear to contribute to the diversity of diagnostic horizons, including proximity to the Great Lakes where abundant snowfall precludes soil freezing and enables water to percolate rapidly through the soil in a short interval during the spring, the prevalence of stratified glacial deposits often containing a lithologic discontinuity, and a fluctuating water table, all of which enable specific weathering products to accumulate at different depths.

• 出版日期2018-9