Effects of land-use patterns on soil carbon and nitrogen variations along revegetated hillslopes in the Chinese Loess Plateau

Abstract

In water-limited areas, revegetation of abandoned croplands may lead to extensive land-use changes and considerable variations on soil carbon (C) and nitrogen (N). However, the impact of land-use patterns (i.e., the spatial combinations of different land-use types) on soil C and N variations following revegetation remains unclear. In this study, we measured soil organic carbon (SOC), total carbon (TC), and total nitrogen (TN) stocks to a depth of 200 cm in grassland (GL), shrubland (SL), young forestland (YF), and mature forestland (MF) under four land-use patterns in a catchment located in the Chinese Loess Plateau. The highest SOC, TC and TN stocks occurred in MF and the lowest was found in GL. Compared to every single land-use type, soil C and N stocks significantly increased under different land-use patterns. The highest SOC stock (6.51 kg m−2) was found in the GL-YF-SL pattern, and the highest TC stock (47.25 kg m−2) and TN stock (0.70 kg m−2) were both observed in the MF-YF pattern. SOC stocks showed significantly positive correlations with TC and TN stocks under different land-use patterns (p < 0.05), except for the GL-MF. The soil C-N interactions were stronger in the MF-SL and GL-YF-SL patterns compared to the GL-MF and MF-SL. Redundancy analysis indicated that the SOC, TC, and TN variations were well explained by aboveground biomass and land-use patterns, with accumulated variance of 41.6% and 54.2% in Axis 1 and Axis 2, respectively. The differences of soil C and N accumulation among land-use patterns were mostly related to different vegetation coverage and the intensity of soil erosion. This study indicates that creating proper spatial distribution of land-use types on hillslopes could benefit soil C and N sequestrations and ecosystem restoration in semi-arid environments.