Allows calculating annual-based or monthly-based drought stress indices from spwb objects.
spwb.stress(x, index = "NDD", freq = "years", bySpecies = FALSE)An object of class spwb.
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 data frame with periods (e.g., years or months) in rows and plant cohorts (or species) in columns. Values are the calculated stress index.
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 C<U+00E1>ceres et al. (2015).
"NDD": Number of drought days, as defined in De C<U+00E1>ceres et al. (2015).
"WSI": Water stress integral, as defined in Myers (1988).
De C<U+00E1>ceres M, Mart<U+00ED>nez-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<U+2013>323 (doi: 10.1093/treephys/4.4.315)