## 3 Results

Table 3: Significance tests and probability levels of the GAM models predicting plant production (peak NDVI), fitted separately for each vegetation type. Only the predictor variables included in the “best” model are shown. “Adjusted-R squared” and “Deviance explained” refer to the results of the full model, including all variables (i.e., those with significant and with non-significant effects). The responses of the different vegetation types to rainfall showed a common pattern, i.e., an asymmetric, concave downward function, whose maximum was situated at medium or relatively high values of rainfall. However, the location of the maximum and the strength of the response (i.e., the slope of the upward and downward parts of the curve) varied strongly among vegetation types (Figure 3). Saltmarsh production showed a pronounced increase at low rainfall levels, which started to saturate at ca. 400 mm, reached its maximum at 510 mm, and decreased moderately above it. Bulrush marsh production increased moderately at low rainfall, started to saturate around 600 mm, reached a maximum at 685 mm, and decreased slightly above it. Shrubland production showed a weak response, which increased slightly until reaching a maximum at 593 mm and decreased slightly after it. Grassland production showed a fairly symmetrical concavity that increased strongly until reaching a maximum at 511 mm and decreased strongly at higher levels of rainfall. The association between the production of the different vegetation types and their phenology (time of phenological peak) also showed a common pattern, albeit with considerable differences in the intensity and shape of the response curve (Figure 3). Responses range from a linear decrease in shrubland, to an inverted sigmoid curve in bulrush marsh, to asymmetric concave curves (with early peaks followed by a prolonged decrease) in saltmarsh and grassland. As a consequence, production peaks take place at the lowest phenology value registered (ca. days 87 and 210, respectively) in the shrubland and bulrush marsh, and close to day 150 for the saltmarsh and grassland. (These days correspond to early December, April, and February, respectively.) The effect of rainfall and phenology was not merely additive (i.e., there was a significant interaction effect in the selected models) for three vegetation types: saltmarsh, bulrush marsh, and grassland (Figure A3, Appendix A). The interaction effects add to the separate effects of both variables showing (i) declines in production at both low rainfall + late phenology and high rainfall + early phenology, for saltmarsh; (ii) a decline in production at low rainfall + early phenology, but an increase at high rainfall + late phenology, for bulrush; and (iii) an additional decline in production at the lowest rainfall levels, which coincide with early phenologies, for grassland. The density of domestic ungulates showed linear, negative effects on vegetation production (Figure 3). Cattle density showed a strong effect on bulrush marsh production, a moderate effect on grassland production, and non-significant effects on saltmarsh and scrubland production. Horse density showed a strong effect on saltmarsh production, a moderate effect on grassland production, and not-significant effects on bulrush marsh and scrubland production.