Soil water dynamics in a rain shelter experiment

Water is the main control of biological processes in arid and semiarid sytems. A rain interception experiment was conducted in order to evaluate changes in water availability of the superficial soil in a grass steppe of the Dry Magellanic Steppe (South Patagonia, Argentina). Treatments included: 50% interception (dry year simulation), control and 50% more rain added through watering during summer (wet year simulation). Three replications were available in each treatement. Each plot had a MPS-6 soil matrix water potential and a ECRN-100 temperature probe. Rain was recorded using a Decagon device ECRN - 100 pluviometer. Data was recorded hourly using a Decagon EM50 logger. Grazing was excluded in all plots. The hypothesis was that watering during summer would prevent the soil from drying and that rain interception would generate a long and intense drought during summer. Results indicate that the soil remained humid most of the time in the watered treatment, but nevertheless some short dry periods were registered when plots did not receive rain pulses between watering events. As hypothesized, soils in the interception plots showed longer and more intense drought periods, but this happend only during fall. At the beggining of winter soils reached field capacity in all plots and remained so until spring. In this way, drought in the superficial soil occured in brief periods during the warm season and depended on summer rains.