Rhizosphere Characteristic of Available Trace Elements During the Succession on Abandoned Croplands in the Loess Plateau, China

Abstract

The different chemical and biological properties of the rhizosphere affect metal speciation in the soil, which in turn affects metal bioavailability. Changes in the rhizosphere accumulation of trace elements by plants may affect natural succession. This study investigated the effects of rhizosphere and bulk soils over time on available trace element (Mn, Fe, Cu, and Zn) concentrations in abandoned croplands at the Dunshan watershed in the Loess Plateau. Results showed that trace element accumulation depends on plant species, soil condition, and successional stage. The trace elements exhibited different responses to plant root presence. During the succession on the abandoned croplands in the Loess Plateau, organic C, total N, and available Zn concentrations in the rhizospheres increased compared with those in the bulk soil, whereas the pH and available Mn concentration decreased. The dominant species showed higher rhizosphere organic C, total N, available Mn, available Fe, and available Zn concentrations than the companion species. The concentrations of available Mn, Fe, and Zn in the rhizosphere of the early successional species Artemisia capillaries Thunb showed no detectable age-related tendency. In contrast, the concentrations of available Cu, Fe, and Zn in the rhizosphere of the later species Artemisia sacrorum Ledeb increased with years since abandonment. Correlation and regression analyses indicated that trace element accumulation is closely associated with organic C and total N concentrations for the later successional species, and increased organic C and total N concentrations can enhance its absorption of the trace elements.