Characterizing anomalous climatic events (SPEI base)
To identify climatic anomalies, we chose the standardized precipitation-evapotranspiration index (SPEI, Vicente-Serrano et al. 2010). We compiled it for local monthly values at time scales ranging from 1 to 48 months and at the spatial resolution 5° x 5°. This means that, for a given month, it represents the cumulative water balance over the previous n months. Here, we used n = 3 months (SPEI-03), which presented the highest correlation with NDVI data. Based on the index values, we identified for each plot, from year 2000 to 2018, dry and wet events outside the normal range (-0.68 < SPEI < 0.68), as well as their intensity: extreme (SPEI > |1.27|) or moderate (|0.68| < SPEI < |1.27|) (Vicente-Serrano et al. 2010).