Establishment of chronofunctions for dark loessial soil on the central Loess Plateau based on soil chronosequences

Abstract

The process of soil development can be studied quantitatively by analyzing the chronofunctions of soil based on its physical and chemical characteristics, which provide a basis for establishing soil development models. In this paper, the physical and chemical characteristics as well as the 14C age of Holocene dark loessial soil profiles found in Luochuan and Yanchang areas on the central Loess Plateau were analyzed to establish soil chronosequences. Then, linear functions, logarithmic functions, and third-order polynomials were used to fit the soil chronosequences to establish the soil’s chronofunctions, which were verified both theoretically and empirically. In the two soil profiles, third-order polynomials could best fit the age of clay (<0.002 mm), silt (0.002–0.02 mm), and sand (0.02–2 mm), and their trends reflected the characteristics of dark loessial soil layers. The changes of soil organic carbon and pH in relation to soil age could be fitted by logarithmic functions. Lastly, third-order polynomials could best fit changes in the soil’s CaCO3 content and Fe/Zr, K/Zr, P/Zr, Na/Zr and Mg/Zr ratios with soil age, which represented the migration processes of CaCO3 and various elements in the soil.