Topsoil moisture patterns on arid hillsides – Micro-scale mapping by thermal infrared images

SummaryIn arid hillsides the topsoil moisture is a key factor in understanding environmental processes such as overland flow generation and soil–plant interactions. The reported research focused on the effects of hillside aspect and micro-topography on the spatial distribution of topsoil moisture on the shrub microenvironment scale, and on the diminution pattern of the moisture content after rain events. Data were acquired by close-range thermal infrared (TIR) imaging and processed with a model in which spatially consecutive TIR data are converted into soil moisture values and high-resolution maps. The results indicate a dynamic pattern of topsoil moisture in shrub microenvironments on arid hillsides. The pattern consists of a moist patch that is spatially associated with the shrub canopy projection. The changes in the spatial characteristics over time depend upon the micro-topography and the hillside aspect, north (N) or south (S). The main differences are in the soil moisture content (N > S), its rates of change (S > N), the size of the moist patch relative to the shrub canopy projection (N > S), and in the displacement of the moist patch relative to the shrub canopy projection (downslope on N and upslope on S). The results may provide a better understanding of the time variation of surface water resources on the shrub scale, and also of surface water redistribution during rainfall.