## 3 Results and Discussion
### Changes in Soil Chemical Properties  
Several soil chemical properties were analyzed to support a mechanistic explanation of changes in Cu bioavailability and potential leaching after 6 months of soil incubation under climatic stress. In figures and tables, the values of soils before incubation are also reported but they were not included in the comparison between treatments with ANOVA (with the exception of Table 2). The two-way ANOVA resulted in a significant interaction between soil type and soil management for all variables, except for soil DOC where only the soil type (calcareous vs. acid) and not the soil management (conventional vs. organic) showed a statistical difference (Table S1). For this reason, further analyses (one-way ANOVA, also see Table S2) were conducted on each soil type and management, focusing on the effect of the imposed stress (temperature, moisture, or their combination). \begin{table}
\begin{tabular}{l c c c c} \hline
**Soil Type** & \multicolumn{2}{c}{**Acid Soils**} & \multicolumn{2}{c}{**Calcareous Soils**} \\ \cline{2-5}
**Soil Management** & **Conventional** & **Organic** & **Conventional** & **Organic** \\ \hline pH & 5.1 \(\pm\) 0.1 & 5.7 \(\pm\) 0.1 & 7.5 \(\pm\) 0.1 & 7.4 \(\pm\) 0.1 \\ Carbonates (mg kg\({}^{-1}\)) & \textless{}d.l. 1 & \textless{}d.l. & 36 & 118 \\ Cu total (mg kg\({}^{-1}\)) & 143.3 \(\pm\) 1.6 & 131.5 \(\pm\) 4.9 & 105.3 \(\pm\) 0.4 & 132.4 \(\pm\) 2.3 \\ TOC (g kg\({}^{-1}\)) & 17.7 \(\pm\) 0.3 & 24.6 \(\pm\) 0.6 & 22.8 \(\pm\) 1.6 & 20.3 \(\pm\) 0.7 \\ TN (g kg\({}^{-1}\)) & 1.9 \(\pm\) 0.1 & 2.9 \(\pm\) 0.1 & 2.6 \(\pm\) 0.2 & 1.8 \(\pm\) 0.1 \\ C:N & 9.1 \(\pm\) 0.2 & 8.5 \(\pm\) 0.1 & 8.6 \(\pm\) 0.3 & 11.4 \(\pm\) 0.8 \\ DOC (mg kg\({}^{-1}\)) & 161.1 \(\pm\) 12.7 & 110.4 \(\pm\) 3.4 & 164.1 \(\pm\) 5.8 & 187.2 \(\pm\) 10.9 \\ Olsen P (mg kg\({}^{-1}\)) & 75.4 \(\pm\) 31.0 & 118.0 \(\pm\) 0.5 & 8.3 \(\pm\) 0.4 & 98.4 \(\pm\) 8.8 \\ N-NH\({}_{4}\)\({}^{+}\) (mg kg\({}^{-1}\)) & 15.9 \(\pm\) 1.5 & 15.1 \(\pm\) 3.2 & 15.5 \(\pm\) 4.1 & 37.1 \(\pm\) 4.0 \\ N-NO\({}_{3}\)\({}^{-}\) (mg kg\({}^{-1}\)) & 48.5 \(\pm\) 10.5 & 64.4 \(\pm\) 2.1 & 8.7 \(\pm\) 0.9 & 55.9 \(\pm\) 10.8 \\ \hline Texture category & Loam & Sandy Loam & Silty Clay Loam & Silty Clay Loam \\ Sand (\%) & 51 & 74 & 19 & 17 \\ Slit (\%) & 35 & 18 & 53 & 58 \\ Clay (\%) & 14 & 8 & 28 & 25 \\ \hline \end{tabular} \({}^{1}\) <d.l.: below detection limit.  
\end{table} 
Table 1: Main physicochemical properties of soils. Soil pH showed a different behavior between acid and calcareous soils (Figure 1a,b): acid conventional soil showed a significant decrease caused by temperature stress, slightly mitigated by moisture stress at elevated temperatures, while it did not change under moisture stress at 19 \({}^{\circ}\)C. On the contrary, the acid organic soil showed a tiny but significant increase either under temperature or moisture stress. Calcareous soils behaved similarly: temperature stress caused a slight increase of pH in conventional soil only, but moisture stress caused a significant decrease of pH in both soils. Figure 1: Soil pH, total organic carbon (TOC), total nitrogen (TN), C/N ratio, and dissolved organic carbon (DOC) in soils before and after 6 months’ incubation under no stress (19 \({}^{\circ}\)C and 40% WHC), moisture (19 \({}^{\circ}\)C and 10% WHC), temperature (29 \({}^{\circ}\)C and 40% WHC), and combined stresses (29 \({}^{\circ}\)C and 10% WHC). Different letters denote significant differences between treatments within each soil type and management, according to [PERSON]’s multiple comparison test (\(p<0.05\)). Similar to most chemical or biochemical reactions, the decomposition of organic matter in soil is inherently temperature-sensitive, and rates of decomposition can increase with increasing temperature according to Arrhenius kinetics [26]. Therefore, our initial hypothesis was that soil exposed to higher temperature would decrease the amount of soil organic matter, measured either as total organic carbon (TOC) or as dissolved organic carbon (DOC).