With the aim of studying the effects of different vegetation zones on soil aggregate stability and its stoichiometric characteristics, the soils under Robinia pseudoacacia plantations located within different vegetation zones on the Loess Plateau were selected as the research object. Indicators including the content, stoichiometry, and stability of different aggregate fractions were analyzed. The results showed that the content of >2 mm and 0.25-2 mm, the mean diameter (EMWD), and the geometric mean diameter (EGMD) of aggregate fractions were in the order of forest zone > forest-steppe zone > grassland zone. However, the stability proxies of aggregate fractions across the three vegetation zones indicated that the content and erodibility (K factor) of 0.053-0.25 mm exhibited an opposite trend. The overall trend of the soil organic carbon and total nitrogen of aggregate fractions among the three vegetation zones was that the forest zone significantly overtopped the forest-steppe zone and grassland zone, while the content of total phosphorus showed no significant differences among the three vegetation zones. Additionally, the content of soil organic carbon and total nitrogen of < 0.053 mm and 0.25-2 mm was the highest among the different fractions in the grassland zone, while that of 0.053-0.25 mm and 0.25-2 mm was the highest in the forest-steppe zone. In contrast, there were no significant differences in the content of organic carbon and total nitrogen in the forest zone among the different aggregate fractions. The total phosphorus content topped in < 0.053 mm fractions in the grassland zone and the forest-steppe zone, while that in the forest zone had no significant differences among the different aggregate fractions. Besides, the C:N ratios of < 0.053 mm and 0.053-0.25 mm in the steppe zone and the forest-steppe zone were higher than that in the forest zone, while that of 0.25-2 mm and >2 mm had insignificant differences among the three vegetation zones. The C:P and N:P ratios of fractions in the forest zone were significantly higher than that in the forest-steppe zone and steppe zone. Overall, the stability and stoichiometry of soil aggregate fractions exhibited relatively significant differences among the three vegetation zones. Additionally, the stability, soil organic carbon, and total nitrogen content of aggregate fractions in the forest zone were generally higher than those in the forest-steppe zone and grassland zone.
Keywords: Loess Plateau; latitude; soil aggregate stability; vegetation zones.