Characteristics of Soils under the Forest Steppe in Mongolia

Abstract

The forest steppe in Mongolia lies between the taiga forests and the steppe grasslands, in moister conditions than steppe grasslands. Forest steppe encompasses both coniferous forests and grasslands, each with a unique distribution pattern. This geographical diversity supports biodiversity, giving the forest steppe great value. Although there are many studies of the vegetation of forest steppe, few studies relate vegetation to soil properties. The objective of this study was to clarify the characteristics of soils under the forest steppe in Mongolia. The study was carried out at four sites in Gorkhi-Terelj National Park. We investigated the soil profiles under grassland on a south-facing slope (TER-G) and on a ridge (TER-T), under forest on a north-facing slope (TER-F1) and under dense forest on a north-facing slope (TER-F2). We analyzed soil organic carbon, total nitrogen, pH (H₂O, KCl), exchangeable bases, CEC and humic substances. Two soil-vegetation associations were identified. On Phaeozems characterized by a high C content and high base saturation ratio, the A horizon became thicker, the humic C to fulvic C ratio increased, and the ratio of humic acid to humic + fulvic acids increased as the vegetation changed from forest to grassland. In contrast, Umbrisol was characterized by a low C content, a high C/N ratio and a low base saturation ratio.