Changes in Soil Carbon and Nitrogen Along a 3-m Vertical Profile and Environmental Regulation in Alpine Grassland on the Tibetan Plateau

Abstract

Much attention has been given to the distribution of soil organic carbon and nitrogen in alpine grasslands, but the important role of the deep soil layers has been understudied. In this study, the soil organic carbon and nitrogen contents in the shallow (0–30 cm), middle (30–100 cm) and deep (100–300 cm) layers were examined, and the effects of climatic, soil and vegetation factors were investigated along a climatic gradient on the Tibetan Plateau. We found that although soil organic carbon and nitrogen on the Tibetan Plateau declined logarithmically with depth, the total soil organic carbon and nitrogen in the middle and deep layers accounted for more than two-thirds of the total carbon and nitrogen in the 3-m depth soil profile. Carbon to nitrogen ratio increased with soil depth in 1 m soil, but it remained consistent in 1–3 m soil. The surface carbon and nitrogen contents were positively correlated with precipitation. The comprehensive research has revealed that soil carbon and nitrogen contents are mainly influenced by the local humid climate, vegetation productivity, and soil properties, which strongly depend on soil depth. Therefore, more attention should be given to the changes in carbon and nitrogen in deep soils in alpine regions.