Temporal dynamics and stability of spatial soil matric potential in two land use systems

The spatial variability of the soil water status and its temporal behavior are essential for hydrological modeling and agricultural management. Changes in atmospheric conditions such as precipitation usually cause large temporal dynamics in the soil water status, whereas inherent soil properties such as soil texture and topography maintain their spatial pattern with time. Our objective was to identify the relevant spatial and temporal processes underlying soil water behavior. Along a 48- by 3-m transect evenly distributed across two land use systems, i.e., cropland and grassland, the soil matric potential (Ψm) was measured on a weekly basis from May to October 2013 at 1-m intervals and at depths of 10, 30, 50, 70, 90, and 110 cm. The spatial variance of Ψm at the 10-cm depth decreased with weekly precipitation and the spatial median of ym in both land use systems, owing to the enhancement of lateral water redistribution by elevated soil wetness. Temporal dynamics in Ψm and its spatial variance diminished with soil depth. In contrast, the temporal stability of Ψm generally increased with soil depth because of the decreasing impact exerted by precipitation. According to Spearman’s rank correlation coefficients, the relative distribution of Ψm in space was more strongly correlated with relative elevation than with soil texture in the grassland. These results have direct implications for irrigation management.