Hydraulic-related defoliation

Functions to calculate the proportion of crown defoliation due to hydraulic disconnection.

hydraulics_proportionDefoliationSigmoid(
  psiLeaf,
  P50,
  slope,
  PLC_crit = 0.88,
  P50_cv = 10
)

hydraulics_proportionDefoliationWeibull(
  psiLeaf,
  c,
  d,
  PLC_crit = 0.88,
  P50_cv = 10
)

Arguments

psiLeaf

Leaf water potential (in MPa).

P50, slope

Parameters of the Sigmoid function.

PLC_crit

Critical leaf PLC corresponding to defoliation

P50_cv

Coefficient of variation (in percent) of leaf P50, to describe the variability in hydraulic vulnerability across crown leaves.

c, d

Parameters of the Weibull function.

Value

The proportion of crown defoliation.

Details

The functions assume that crowns are made of a population of leaves whose hydraulic vulnerability (i.e. the water potential corresponding to 50 follows a Gaussian distribution centered on the input P50 and with a known coefficient of variation (P50_cv). The slope parameter (or the c exponent in the case of a Weibull function) is considered constant. Leaves are hydraulically disconnected, and shedded, when their embolism rate exceeds a critical value (PLC_crit).

See also

hydraulics_conductancefunctions

Author

Hervé Cochard, INRAE

Miquel De Cáceres Ainsa, CREAF