关键词: 内陆盐沼, 人工林, 团聚体稳定性, 土壤胞外聚合物, 影响因素

Abstract: Soil water-stable aggregates and extracellular polymeric substances (EPS) strongly affect soil processes and functions, serving as important indicators of soil structure and quality. However, the changing patterns and internal correlations of both factors under artificial vegetation restoration are not well understood. In Qinwangchuan National Wetland Park of central Gansu Province, we measured soil aggregate composition and EPS content in the 0-20 cm layer across Tamarix chinensis plantations of different restoration years (3-, 7-, and 11-year-old) and an adjacent piece of secondary bare land (CK), and assessed the effects of T. chinensis plantation restoration on soil aggregate stability and EPS. The results showed that 1) planting T. chinensis generally improved soil aggregate structure and stability. Compared to the CK, the content of >0.25 mm water-stable aggregates, mean weight diameter (MWD), and geometric mean diameter (GMD) were all significantly increased in the plantation soils, showing a trend of initial increase followed by a decrease with stand age and peaking in the 7-year-old plantation. 2) Extracellular polysaccharide and protein contents increased consistently with restoration years, being 10.7 and 4.6 times higher in the 11-year plantation than in the CK, respectively. This result indicated that artificial vegetation restoration effectively promoted microbial metabolic activities. 3) MWD and GMD showed significantly positive correlations with the contents of >1 mm aggregates, 0.5-1 mm aggregates, extracellular polysaccharides, extracellular proteins, soil organic carbon (SOC), and litter biomass, but were negatively correlated with soil pH and electrical conductivity (EC). The EPS contents were significantly positively correlated with SOC, litter biomass, and cation exchange capacity, while were significantly negatively correlated with soil pH and EC. 4) Redundancy analysis showed that the contents of >1 mm aggregates, 0.5-1 mm aggregates, SOC, and EC were the core factors influencing soil aggregate stability (69.1% explanation), while EC and pH were the key environmental variables regulating EPS content (57.8% explanation). This study elucidated the evolutionary patterns and influencing factors of soil aggregate stability and EPS during the restoration of T. chinensis plantations, and thereby provided a scientific basis for restoring degraded salt marshes in arid and semi-arid China.

Key words: inland salt marsh, plantation, aggregate stability, soil extracellular polymeric substance, influencing factor