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Earthworms and termites, as soil engineers, play a major role in the regulation of biogeochemical processes and the provision of ecosystem services. They create biogenic aggregates on the soil surface, e.g., earthworm casts and termite sheetings, which can influence soil erosion and the downward transfer of fertility. We assessed the effect of the micro-relief generated by earthworms and termites on soil hydrodynamic properties, and soil and nutrient losses. Eighteen 1 m × 1 m plots were established for rainfall simulation experiments (2 runs of 40 min rain, intensity 90 mm h −1 ) in a steep slope fallow in Northern Vietnam. The soil surface of the micro-plots differed in the proportions of earthworm casts and termite sheetings. The results confirmed the importance of soil biostructures in the regulation of pedohydrological properties of soils. Although globular water-stable earthworm casts promote water infiltration in soil and decrease soil and nutrient losses, the unstable termite sheetings break-down rapidly and generate structural crusts which foster water runoff and soil detachment. No relation was observed between the abundance or biomass of earthworms or termites and the pedohydrological properties measured during the rainfall simulations. This therefore suggests that soil engineers can have greater impact on ecosystem functioning through their biogenic structures rather than as a result of their own abundance or biomass.

Vegetation stripes were described in arid areas of Africa, Australia and Mexico. They depend on the local concentration of rain water after runoff. In Mexico, we described the soil surface characteristics of vegetation stripes and performed rainfall simulations to analyze its hydrodynamic behaviour. Simulations were performed on plots characterized by the four soil surface features represented in the stripes. Four types of surface crusts were found in the stripes, erosion, sedimentation, and two types of structural crusts. The less vegetated plots had relatively impervious crusts with low preponding rains and high constant runoff rates. On the contrary, the highly vegetated plot had a thin crust and abundant litter which allowed a high infiltration rate. Runoff rates were positively related to rainfall intensity. Those relationships between surface characteristics and runoff determine the fate of rain water and may allow the prediction of the amount of runoff for a specific rain on a given plot.

In arid climates, plant growth and survival depend primarily upon the amount of soil water available at the roots. Variation in soil water content at the individual plant level must then be taken into account to analyse the production and dynamics of vegetation cover. The plant itself modifies local water availability through rainfall interception and stemflow. Rainfall interception and stemflow was studied for a shrub, Flourensia cernua, a dominant species of vegetation stripes in the Chihuahuan Desert, Mexico, in order to determine to what extent it could influence soil water recharge. Simulated rainfalls were applied at two intensifies on six 1 m2 plots centered around each shrub. Shrub cover was determined from vertical photographs. Experimental clipping from three shrubs allowed observations on the decrease in stemflow according to cover and measurement of the dry biomass of leaves and twigs. An experimental design enabled measurements to be made on throughfall, runoff from the base of the shrub, and to deduce stemflow and infiltration. Stemflow accounted for 4-45 per cent of the rainfall in our study plots and was significantly correlated with shrub cover. It was higher for the lower rainfall intensity. Stemflow, together with a high soil permeability, resulted in a greater soil water recharge under the shrub.