Spatiotemporal patterns of soil moisture is important for understanding landscape hydrologic processes. While spatiotemporal characteristics of soil moisture content (θ) have been frequently studied, that of soil matric potential (ψ) remains sparse. We investigated the spatial variability and temporal stability of ψ at multiple depths (10-100 cm) across a 7.9-ha forested catchment and their relationships with soil type, terrain, and season. The results from a 5.5-yr database consisting of 62 sites clearly showed a downward parabolic trend in ψ spatial variability with decreasing spatial mean value of ψ (i.e., becoming drier) across all depths. The catchment’s overall spatial variability of ψ generally increased with soil depth and was relatively high during summer and fall. Sand and silt contents were significant factors (p<0.05) influencing ψ in surface layers (0 to 20 cm), while ψ at the subsurface (40 to 100 cm) were highly correlated with elevation. The temporal stability of ψ spatial pattern was generally higher in surface soil than that in the subsurface, but weaker in the spring as compared to other seasons. Moreover, relative dry areas tended to have less evident ψ temporal stability at each depth that is attributable to higher sensitivity of ψ to changes in θ when soil is dry. Finally, at least one of the representative sites of the catchment meanψ at each depth was found within a south-facing concave hillslope at the mid-elevation, which were different from the representative sites of the catchment mean θ. The results from this study have implications for upscaling soil water from point-based observations to the hillslope and catchment scales.
Yu, H., P. Yang, and H.S. Lin (2015): Spatiotemporal patterns of soil matric potential in the Shale Hills Critical Zone Observatory. Vadose Zone Journal, Vol 14, no. 7. DOI: 10.2136/vzj2014.11.0167