Abstract
The picturesque and high conservation value thermal landscapes of the Valley of Geysers feature endothermal (heated by endogenous fluids) soils which support endangered and unique species. ...However, such soils have not been distinguished as a separate taxon within most classification systems. In this study, we described the soil morphology at macro-, meso- and micro-scales, chemistry, mineralogy and vegetation of these landscapes as they are affected by the steam-heated acid-sulfate waters. The studied catenary sequence from exothermal (non-heated) to endothermal soils was characterized by decreasing contents of soil organic carbon, sand fraction, essential nutrients (Ca, K, Mg, Mn and Si), increasing soil acidity, amounts of fine particle-size fractions and contents of trace elements (Al, As, Co, Cr, Cu, Fe, Pb, Ti and V) as well as the development of sodium-sulfate salinity, kaolinization and ferrugination. In phytocenoses supported by endothermal soils, species of order
Rosales
and
Asparagales
were overrepresented among obligate and facultative thermophytes respectively, and species of order
Poales
were underrepresented among facultative thermophytes in relation to the flora of the Valley of Geysers. Phytocenoses on the non-heated Andosols were enriched in
Polypodiopsida
species. The results of our comparative analysis of the thermally-induced variability in the soils and vegetation contribute to the general understanding of mineralogical, bio-abiotic and biological systems affected by steam-heated acid-sulfate waters. We hope that our findings will provide a basis for future transdisciplinary studies of the influence of steam-heated waters of a hot spring on the thermal landscapes.
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In this paper, we analyze diagnostics of volcanic ash soils in soil classification systems applied in the United States, Russia, New Zealand, and in the international WRB system. In the Russian ...soil classification system, classification of soils, the diagnostic criterion for full-profile volcanic soils is the presence of a specific BAN horizon with a bulk density of less than 1 g/cm
3
, intra-aggregate thixotropy, fine granular (caviar-like) structure, and the high contents of humus and oxalate-soluble Al (10–15%), Fe (2–6%), and Si (4–7%). According to the WRB and
Soil Taxonomy
systems, volcanic soils (Andosols and Andisols, respectively) are diagnosed by the presence of a high content of allophane or organomineral complexes with Al and Fe (short-range-order materials), as well as a low bulk density (<0.9 g/cm
3
) and a high phosphate retention. In the New Zealand soil classification, volcanic soils (at the highest hierarchical level—Allophane and Pumice soils) are the soils forming on igneous rocks and having a low bulk density, a high content of volcanic sand and gravels, and a high phosphate retention. In the field, reliable diagnostics of volcanic ash soils can be achieved on the basis of the Russian and New Zealand soil classification systems. The WRB system and
Soil Taxonomy
require additional laboratory diagnostics. Direct correlation of the names of volcanic soils is possible only at the highest hierarchical level from the New Zealand and Russian schemes into the WRB and
Soil Taxonomy
systems, and between the WRB and
Soil Taxonomy
systems. Although, it is necessary to have morphological descriptions of soil profiles and analytical results due to the differences in the threshold values used in the considered classification systems.
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