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Fit a vulnerability curve

Fit a xylem vulnerability curve to get P50, the slope at P50, and the maximum conductance. See Plant hydraulics models.

Inputs

A water potential column, plus either:

  • percent loss of conductivity (PLC; a 0–1 fraction is recognized), or
  • a conductance column (K, Kleaf, Kstem, Kroot, conductance, and similar).

Steps

examples/vulnerability.csv has PLC for three stems:

pk fit hydraulics examples/vulnerability.csv --model vulnerability --group-by stem

examples/vulnerability_k.csv has leaf conductance instead:

pk fit hydraulics examples/vulnerability_k.csv --model vulnerability

With PLC, conductance is relative, so Kmax is close to 1. With a conductance column, Kmax is in the same units as that column.

If you leave out --model, the hydraulics tool tries vulnerability first, then pvcurve, and uses the first that can read the file.