Slope aspect modulates canopy cover and elevation effects on soil quality in semiarid oak forests: Implications for soil management

Abstract

Forest ecosystems, covering approximately 30% of the world's land surface, play a crucial role in global environmental processes. Although the relationship between forest canopy cover and soil properties is recognized as complex and interdependent, the simultaneous direct and indirect effects of topography and canopy cover on soil quality remain poorly understood in semi‑arid mountain forests. To address this knowledge gap and inform effective land management, a comprehensive analysis of soil physical, chemical, and hydrological characteristics is required. Accordingly, this study uses structural equation modeling (SEM) to assess the direct and indirect effects of topography and canopy cover on soil properties and quality in the semi‐arid Zagros forests of western Iran. Soil samples were collected from 60 locations in the Zagros region (Mount Shalam, western Iran) using a systematic random sampling design, covering a range of canopy cover densities (open vs. closed), two slope aspects (north‐ and south‐facing), and three elevation classes (1750–1850, 1850–1950, and 1950–2050 m above sea level). A soil quality index was calculated based on the chemical, physical, and hydrological properties. The effects of canopy cover, slope aspect, and elevation on soil properties were analyzed using three‐way analysis of variance framework, followed by Duncan's multiple range test. SEM was subsequently evaluated on how topography, canopy cover, and soil properties influence soil quality. The results showed that soil properties were significantly influenced by canopy cover, elevation, and slope aspect. Soil quality was highest (0.86) under closed‐canopy conditions at mid‐elevation on north‐facing slopes and lowest (0.69) at upper elevation on south‐facing slopes with an open canopy. Significant differences were detected across all elevation classes and canopy types. Importantly, SEM revealed that canopy cover positively impacted soil quality through enhancing chemical and hydrological properties, while elevation had a negative effect on soil quality across both slope aspects. Collectively, these findings highlight the critical role of physiographic features and canopy cover in determining soil quality, providing valuable insights for the conservation, management, and restoration of soils in semi‐arid mountainous forests.