The desica model is a simple implementation of a soil-plant-atmosphere water transport model, specifically designed to model the dynamics of the desiccation of plants to mortality.
When soil water uptake does not meet demand by the plant (which includes an important minimum conductance term), water is drawn from reserves held in the stem and leaves. When the water potential of the stem is low enough, the plant dies.
Open the script example_run.R, and follow instructions within. You should be able to run that script as is.