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Calculates plant drought stress indices, at different temporal scales, from simulation results.


droughtStress(x, index = "NDD", freq = "years", bySpecies = FALSE, draw = TRUE)



An object of class spwb, pwb, growth or fordyn.


A string with the index to be calculated, either "DI", "NDD", "ADS", "MDS" or "WSI" (see details).


Frequency of stress statistics (see cut.Date). Normally, either "years" or "months" for yearly-based or monthly-based indices.


Allows aggregating output by species.


A boolean flag to indicate that a plot should be returned.


A data frame with periods (e.g., years or months) in rows and plant cohorts (or species) in columns. Values are the calculated stress index. If draw=TRUE a ggplot is returned instead.


The currently available drought stress indices are:

  • "ADS": Average of daily drought stress values for the period considered.

  • "MDS": Maximum daily drought stress during the period considered.

  • "DI": Drought intensity, as defined in De Cáceres et al. (2015).

  • "NDD": Number of drought days, as defined in De Cáceres et al. (2015).

  • "WSI": Water stress integral, as defined in Myers (1988).


De Cáceres M, Martínez-Vilalta J, Coll L, Llorens P, Casals P, Poyatos R, Pausas JG, Brotons L. (2015) Coupling a water balance model with forest inventory data to predict drought stress: the role of forest structural changes vs. climate changes. Agricultural and Forest Meteorology 213: 77-90 (doi:10.1016/j.agrformet.2015.06.012).

Myers BJ (1988) Water stress integral - a link between short-term stress and long-term growth. Tree Physiology 4: 315–323 (doi: 10.1093/treephys/4.4.315)


Miquel De Cáceres Ainsa, CREAF