Ecohydrological adaptation of soils following land abandonment in a semi-arid environment

Representative land use types were selected in southeast Spain to investigate the redistribution of soil water in relation to vegetation development and land abandonment.
Simulated rainfall experiments were performed during 2 days on each of the four selected surfaces: ploughed, a 3-year fallow field, a 12-year abandoned field with shrubs and a semi-natural field with Stipa tenacissima tussocks. Each experiment consisted of five runs of artificial rain. Soil moisture dynamics were measured by time domain reflectometry (TDR), as well as runoff and ponding on the plot surface. Also the movement of the wetting front was measured after each run.
On the ploughed field, ponding and local runoff were less important with shallow and homogeneous wetting fronts. The other land uses showed increased heterogeneity in wetting front development, with soil water pockets under the plants that moved down at greater velocities than under the bare inter-spaces. It is hypothesized that S. tenacissima and possibly Artemisia herba-alba adapt their environment by capturing water through stem-root flow systems to divert water to deeper soil layers to reduce evaporation. Furthermore it is suggested that during vegetation development soil heterogeneity increases, as expressed by the water infiltration patterns observed, and that the bare inter-patches are important in the infiltration process.