Slope and aspect controls on soil climate: Field documentation and implications for large‐scale simulation of critical zone processes

Abstract

Abstract Soil climate, as quantified by soil temperature (TS) and water content (θ), exerts important controls on critical zone processes. It may be sensitive to variations in local slope and aspect (SA), but this attribute remains poorly quantified at the local scale and unresolved in large‐scale models. Estimation of SA effects on soil climate across multiple scales may facilitated using topographically modified, incoming clear‐sky solar radiation (SR,CS,T). We established six paired automated soil climate monitoring stations on opposing north‐facing (NF) and south‐facing (SF) slopes (4 yr) and collected spatial TS and θ data within the hectare surrounding four stations (2 yr) to measure SA effects on soil climate. Results were compared with physically based simulations and evaluated in the context of SR,CS,T. Spatial θ data were more variable than Ts, and both were consistent with values from continuous monitoring stations. On average, the SF TS was much greater (4.7 °C) and the annual summer drought longer (36 d) than on the adjacent NF aspect. Seasonal variations of TS and θ were different from each other and also different from SR,CS,T. Local conditions, including snow cover, precipitation patterns, and soil properties, largely controlled seasonal variations of TS and θ, which cannot be predicted from SR,CS,T. This indicates that realistic simulation of many critical zone processes requires high‐resolution inputs. Simulations captured first‐order SA effects and could be useful for estimating SA effects in lieu of field monitoring.