Summary:

## Plant Hydraulic Stress (PHS) Routine

The PHS routine models water transport through vegetation based on a simple hydraulic framework following Darcy's Law for porous media flow. The key points are:

### Water Supply and Transpiration Demand
- Water supply is modeled according to the circuit analog shown in Figure 2.11.1.
- Transpiration demand is modeled relative to maximum transpiration using a transpiration loss function dependent on leaf water potential.

### Solving for Vegetation Water Potential
- The routine solves for the vegetation water potential that matches water supply with transpiration demand.

### Influences
- The PHS routine is influenced by the work of Bonan et al. (2014), Chuang et al. (2006), Sperry et al. (1998), Sperry and Love (2015), and Williams et al. (1996).

In summary, the PHS routine provides a detailed model of plant water transport and hydraulic stress, accounting for both water supply and transpiration demand to determine the vegetation water potential.