Spek, 1993 and Spek, 1996 showed a correlation between loam content and the presence or absence of Carbic Podzols (humus podzol) and Umbric Podzols (brown podzol soils). Sandy soils with a loam content of less than 10% are susceptible to podzolization, the natural process in which Umbric Podzols will develop into Carbic Podzols. When the loam content is 10–25%, the soils may podzolize as a consequence of human actions, such as land management that Riluzole is causing a process of increased acidification. With a loam content of more than 25%, podzolization never occurs (Fig. 2). A critique to the model is that the distinction between 0% and 10% loam and 10%–25% loam may be less relevant if there are no data of specific clay % and the mean diameter of the sand fraction. In this study more grain size parameters have been tested also to evaluate the soil degradation model of Spek, 1993 and Spek, 1996.
Fig. 2. Diagram of soil degradation (based on Spek, 1996) and the transformation of Umbric Podzols with 10–20 vol% loam to Carbic Podzols during the Holocene. In this diagram, the podzolization process is hypothesized to accelerate during the Late Bronze Age to Early Iron Age (1650 BC–500 BC).Figure optionsDownload full-size imageDownload as PowerPoint slide