## 3 Results and Discussion
### Effect of Single or Combined Climatic Stress on Soils  
According to Hedges' g values (Figure 4), the soil properties most affected by the imposed treatments are TOC, TN, DOC, and mineral N forms (NH4\({}^{+}\) and NO3\({}^{-}\)). Temperature stress negatively affected soil organic matter indices (TOC and TN), which showed a Hedges' g value \(<-0.5\). On the contrary, the moisture stress (water deficit) tended to compensate the increase of temperature by reducing the respiration of microbial biomass and, therefore, the degradation of soil organic matter [71]. Similarly, dissolved organic C (DOC) showed a Hedges' g under temperature stress \(<-1\), whereas it increased by moisture stress, and also resulted positive under the combined climatic stresses.  
Ammonium N (N-NH4\({}^{+}\)) tended to be affected by moisture and by the combination of moisture and temperature stresses, whereas the increase of soil temperature did not affect its concentration. In fact, optimal ammonification ranged from 5 up to 30 \({}^{\circ}\)C. Nitrate N (N-NO3\({}^{-}\)) was affected by both temperature and moisture, but in the opposite direction. The interaction of the two stresses tended to be compensated (Figure 4c).  
Rather surprisingly, the tested stresses did not have significant effects on Cu bioavailability, mobility, and speciation when all four soils were considered collectively.  
However, drawing a PCA of main soil properties on the first two principal components (95.8% of variance explained), it is possible to notice that the first PC axis (83.4% of variance explained) is mainly described by Cu-related variables (Figure 5), with the exception of Cu Step 2, which mainly describes the second PC axis (12.4%). Therefore, despite the selected four soils representing very different vineyard situations, the behavior of Cu under climatic stress was rather homogeneous, probably as a result of common origin of Cu pollution.  
In addition, there is a clear separation of the four soils, either for their management (conventional vs. organic) or for their pH (acid vs. calcareous). Soil pH, in particular, well defines the calcareous and acidic groups. pH is, in fact, one of the main driving factors affecting most soil properties [49], and it consistently affects the ordination. It also explains why points related to the different imposed stress treatments but belonging to the same soil are closely located in the PCA.  
Figure 4: Changes of soil properties due to temperature stress (**a**), moisture stress (**b**), or their combination (**c**). Effect sizes (g) lower than 0.2 are considered not meaningful. Positive or negative mean effect sizes indicate an increase or a decrease of the soil property after the stress, respectively. Changes are shown using forest plots of mean effect sizes, based on Hedges’ g index.  
Figure 5: Principal component analysis of soil properties grouped by soil management type (organic vs. conventional) or soil pH (calcareous vs. acidic). The first two axes of the PCA explain 95.8% of the variance. Blue solid arrows are used for the ordination. Gray dashed arrows refer to descriptors (not influencing the ordination).