Rock fragment content alters spatiotemporal patterns of soil water content and temperature: Evidence from a field experiment

Soil water and temperature play a crucial role on hydrological and heat cycling in terrestrial ecosystems, yet rock fragment content in affecting soil water content, temperature, and their relationship is still poorly understood, particularly in dynamic water-heat environments in stony region. In this study, we conducted a field experiment with rock fragment content ranging from 0% to 75%, and investigated soil water content and soil temperature across soil profiles from 2018 to 2022. Soil water content and temperature showed apparent spatiotemporal dynamics under varying rock fragment content. Increased rock fragment content significantly decreased soil water content, but the effect in wet season was stronger than that in dry season. Soil water content increased first and then decreased with increasing soil depths in the conditions of 0% and 25% rock fragment content, but monotonically increased in soils with 50% and 75% rock fragment content. Presence of rock fragment raised annual mean soil temperature, and rock fragment content posed various impacts on soil temperature which depended on seasons and soil layers. Among the rock fragment content gradient, 25% rock fragment content posed a consecutive warming effect on soils in each season. Negative correlation between soil water content with soil temperature was observed both in 10 cm and 30 cm soil layers during wet season, while positive correlation in 30 cm soil layer during dry season. These results indicated that rock fragment content can drive the change in spatiotemporal patterns of soil water content and temperature, and presence of rock fragment strengthened coupling relationship between soil water content and temperature during the wet period.