Forest ecosystems can be characterized by a set of catenas arranged along the slope in mountainous areas as these affect microhabitat features, which in turn influence soil properties. Heretofore, few studies have examined how topographic variables affect soil properties and quality in semiarid regions. This study aimed to provide important insights into how catena position and shape influence soil properties, soil quality, and their interrelationships in a semiarid protected oak forest in western Iran. Basic soil properties were measured in the laboratory. In addition, the soil quality index (SQI) was calculated at different topographic positions along both convex (Λ-shaped) and concave (V-shaped) catenas at two soil depths (0–15 and 15–30 cm). The findings indicated that soil organic carbon and total nitrogen declined in the lower depth in both V- and Λ-shaped catenas and at all catena positions. The lowest porosity was observed in the lower depth at toeslope positions (TS) of both catenas. Substrate-induced respiration (SIR), microbial biomass carbon (MBC), and basal respiration (BR) were higher in the upper depths at TS positions on V-shaped catenas than on Λ-shaped catenas. These biological indices were consistently higher in the upper depths than in the lower depths across all positions of both catenas. SQI had the highest values at TS positions on both catenas and in the upper depths across all positions. Pearson correlations between soil properties indicated that SQI was most strongly and positively correlated with biological properties in both catenas. The nutrient levels, microbial activity, and soil porosity in both catena shapes and at both soil depths displayed a relatively downward trend with increasing elevation from toeslope to summit positions. The results showed that catena topographic sequence shape and position affected most of the soil properties, providing evidence of the important role of topography in creating pedodiversity in oak forest ecosystems.
