Holocene-aged basaltic lava flows offer a unique opportunity to study the initial stages of soil formation. In the cool, dry climate at Craters of the Moon National Monument and Preserve (CROM) in southern Idaho, organic soils (Histosols in Soil Taxonomy) are the dominant soil on recent lava surfaces. Unsaturated Histosols, or Folists (Folic Histosols in World Reference Base [WRB]), occupy crevices and depressions on the lava surface and support vegetation adapted for life in this harsh environment. These soils are comprised of either a thin fibric (Oi horizon) over a hemic (Oe horizon) or a single, relatively homogenous Oe horizon over relatively unweathered basalt bedrock. The parent material for organic soils is biologic rather than geologic in origin with parent vegetation growing in crevices supplying the necessary organic debris. Soil acidity is directly influenced by the type of vegetation growing in the soil, with more acidic leaf litter creating lower pH soils while more alkaline plant debris generates soil with more neutral pH. Within these shallow soils (12-35 cm), organic C content (mean 333 g kg-1) is proportional to fiber content and cation-exchange capacity (CEC) and inversely proportional to bulk density. Compared with Folists of wetter climates, those forming at CROM have substantially higher bulk densities with a mean of 0.41 g cm-3. The influence of loessial mineral material likely accounts for the increased mineral content and subsequent increase in bulk density. Knowledge of the morphological, physical, and chemical properties of Folists at CROM is essential to improve our understanding of the ecological significance of Folists and co-evolution of soils and plant communities in a cool, arid environment.
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机译：全新世的玄武岩熔岩流为研究土壤形成的初始阶段提供了独特的机会。在爱达荷州南部的月球环形山国家纪念碑和自然保护区（CROM）凉爽干燥的气候中，有机土壤（土壤分类学中的Histosols）是最近熔岩表面的主要土壤。不饱和的组织溶胶或泡沫（在世界参考库[WRB]中为叶类组织溶胶）占据了熔岩表面的缝隙和洼地，并为适应在这种恶劣环境中生活的植被提供了支持。这些土壤由半纤维（Oe层）上的薄纤维（Oi层）或相对未风化的玄武岩基岩上的单个相对均匀的Oe层组成。有机土壤的母体来源是生物而不是地质，母体植被生长在缝隙中，提供了必要的有机碎片。土壤的酸度直接受到土壤中生长的植被类型的影响，酸性较高的凋落物产生的pH值较低的土壤，而碱性较多的植物残渣产生的pH值则为中性。在这些浅层土壤（12-35厘米）中，有机碳含量（平均333 g kg-1）与纤维含量和阳离子交换容量（CEC）成正比，与堆积密度成反比。与潮湿气候的Folists相比，CROM上形成的那些具有更高的堆积密度，平均密度为0.41 g cm-3。黄土矿物材料的影响可能是矿物含量增加以及堆积密度随后增加的原因。对CROM上Folists的形态，物理和化学特性的了解对于增进我们对Folists的生态学意义以及在凉爽，干旱的环境中土壤和植物群落共同进化的理解至关重要。
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