Classing the Soil Skeleton (Greater than Two Millimeters): Proposed Approach and Procedure

Abstract

In soil science, analytical procedures apply almost exclusively to the fine earth (<2 mm). Rock fragments or skeleton (>2 mm) are regarded as inert and discarded during sieving; however, we have found that the clasts display physical and chemical properties that can equal or surpass those of the fine earth. These properties depend largely on the degree of alteration of the clasts. In light of these findings, we developed a method to separate the rock fragments into weathering classes. This method has been applied to five European skeleton‐rich soils derived from different parent materials. Color intensity, roughness and irregularities of the surfaces, cracks, and surface features of the exposed minerals were considered reliable criteria for the separation of the clasts. We noticed also that the degree of alteration of the clasts corresponds to size: as size decreased, weathering increased. Consequently, sieving could be used for separating the weathering classes. On the basis of these criteria, clasts were differentiated into highly, moderately, and slightly altered. There are statistically significant differences among the weathering classes in terms of bulk density, porosity, organic C, total N, and cation‐exchange capacity. There are no statistically significant differences in pH. The results confirm that the procedure separates relatively homogeneous and different classes of rock fragments. We also compared the characteristics of the soil skeleton to those of the fine earth and fresh rock. We concluded that not characterizing the skeleton of the soils may provide distorted information on the capability of these substrata.

Pedogenesis in the sorted patterned ground of Devon Plateau, Devon Island, Nunavut, Canada

“…Soil samples collected on a volume basis were ovendried at 105°C and the bulk density (D b ) was calculated according to Corti et al (1998). The other soil samples were left to air-dry and sieved at 2 mm so as to separate fine earth and skeleton.…”

Effects of gravel on soil and vegetation properties of alpine grassland on the Qinghai-Tibetan plateau

“…Thirdly, the gravel-dependent changes in soil moisture and temperature may influence soil enzyme activity (Wu et al, 2011), which is an important mediator for organic matter degradation, mineralization and nutrient recycling (Huang et al, 2013;Tripathy et al, 2014). Studies by Corti et al (1998Corti et al ( , 2002 found that rock fragments (skeleton or gravel) in stony soil with alteration contained substantial amount of organic carbon. However, SOC in the rock fragments (skeleton or gravel) was often neglected in the calculation of total soil C and N due to soil nutrition analysis mainly focused on the fine earth fraction (less than 2 mm).…”

Mineralogy and pore space characteristics of traprocks from Central Siberia, Russia: Prerequisite of weathering trends and soil formation

“…A higher porosity of hard rock in the case of Pit Е-5/8 indicates more altered rock (Corti et al, 1998), probably due to differences in the porosity of the original source rock, which seems to be a prerequisite of a more pronounced step of rock disintegration and the formation of a deeper and mature profile.…”