Supplementary Information Interplay between Livestock Grazing and Aridity on the Ecological and Nutritional Value of Forage in Semi-arid Mediterranean Rangelands (NE Spain)

Fig. S1 Location of study plots in the Middle Ebro Valley (Spain). See Table 1 for further details. Fig. S2 A) Number of sheep droppings (mean ± SE) per m2 for each grazing intensity and location. Different letters indicate significant differences among grazing intensities (post-hoc Tukey HSD test; p < 0.05). Significance of differences was tested by fitting a generalized linear mixed model (GLMM) in which grazing intensity and location were set as fixed factors, and study plot was set as a random intercept effect. A negative binomial distribution of errors was specified in the model to deal with overdispersion. B) Schematic representation of study plots and sampling quadrats. Table S1 Mean (± SE) for the variables of interest at the plot level. See Materials and Methods section for further details. Fig. S3 Initial path diagram with the hypothesized causal relationships among variables. Grazing intensity and aridity level are exogenous variables, while woody index, diversity, plant cover, production, plant C:N ratio and fiber index are endogenous variables. A total of four path diagrams were generated, one for each final variable (i.e., plant cover, forage production, forage C:N ratio and forage fiber index). Directions of the arrows indicate the causal relationships between variables. Dashed arrow indicates a non-hypothesized missing path added during the evaluation of the overall models fit. See Materials and Methods section for further details. Fig. S4 Spearman correlation coefficients among all variables included in the SEM analysis. Blue and red colors indicate positive and negative correlations respectively, with more intense colors denoting higher correlation values. Visual representation of the correlation matrix was created with the GGally package in R 4.0.3. Fig. S5 Direct (dark colors) and indirect (light colors) effects of grazing intensity (solid bars) and aridity (dashed bars) on community plant cover, forage production, C:N ratio and fiber index, community structure and diversity at A) p < 0.05 and B) p < 0.1. Red bars indicate negative effects. Blue bars indicate positive effects. See Materials and Methods section for further details. Table S2 List of plant species found at the study plot level, their labels, forage value (FV) and plant cover (%).