Neeshia Macanowicz-Soil Moisture in the Desert 7/24/2019

Neeshia Macanowicz, Restoration Ecologist at the Jornada Experimenta Range, reviews how to measure soil moisture. As part of a larger project, Neeshia is collecting soil moisture data on 36 plots located on the Jornada, within the Chihuahuan Desert. The 36 plots are distributed evenly with 12 plots each in black grama grassland, shrub-grass mix and shrubland ecological states. Neeshia and other researchers at the Jornada hope to learn whether there are detectable differences in soil moisture among the three different plant communities types (ecological states). Here, Neeshia explains how the soil moisture probes work and what they measure: how quickly water infiltrates to 10 cm (depth of the installed probes) after significant rain events, as well as how quickly the soil dries out once the rain stops. If there are detectable differences in soil moisture among the three plant community types, this could be one of the factors influencing their ability to grow grasses. Soil moisture affects seed germination and plant establishment. Soil must be moist at the surface long enough for new seeds to germinate. Then moisture within the upper 10 cm of the soil profile must be present long enough for seedlings to become established. The longer soil can retain moisture within the upper 30-50 cm the longer water is available for existing perennial grasses to utilize. The quicker water infiltrates and the faster the upper soil depths dry out, the harder it is for grass seeds to germinate and grass plants to become established. However, shrubs, such as honey mesquite, can easily utilize soil moisture at lower depths (such as below 50 cm, where grass roots are usually not found). The soil moisture data, alongside additional data, will provide a more robust understanding of the processes influencing the three vegetation states. The data collected by Neeshia and other scientists provide information on the potential of the 36 plots to grow plants, retain resources and resist erosion. These data include: soil profile descriptions (soil texture and other properties), infiltration rates, soil stability and plant cover by species. The Jornada also has weather stations monitoring wind speeds, precipitation, wind-borne sediments and other variables.