Variation in dissolved organic matter characteristics of soil aggregates in slip deposition zone with natural succession on a semiarid region.

Abstract

Variations in soil properties of soil slips during vegetation restoration have been tentatively explored. This study explores the impact of successional age in soil slip deposition zones (depth <3 m) on the dissolved organic matter (DOM) characteristics of soil aggregates across different sizes and soil layers. The variation in DOM properties with successional age, soil depth, and aggregate size was examined using UV-visible and excited emission matrix spectral techniques. Overall, dissolved organic carbon (DOC) content in soil aggregates with three sizes increased with successional age, particularly in aggregates larger than 2 mm. The DOC content of soil aggregates was greater in top soil layer (TSL) (0-2 cm) (303.04 mg kg^-1) and middle soil layer (MSL) (2-20 cm) (217.81 mg kg^-1) than in the bottom soil layer (BSL) (20-50 cm) (75.81 mg kg^-1). The molecular weight and aromaticity of soil DOM were gradually increased with the successional age. Parallel factor analysis revealed a gradual increase in humic-like components and a decrease in protein-like components with the successional age. Notable layer differences were observed, with higher humic-like components in TSL (31 %) and MSL (32 %) compared to the BSL (28 %). Particularly, DOM in the TSL and MSL was primarily controlled by plant sources, whereas it was mainly affected by microbial sources for the DOM in the BSL. In this case, the autochthonous characteristics of soil aggregates in the TSL increased and after that decreased with successional age, while vice versa for the MSL and BSL.