Table 2.
Chemical characteristics of clusters of soil samples introduced in the study.
| Variable | Kruskal–Wallis p value | Tree clusters | Saline site | |||
|---|---|---|---|---|---|---|
| Cluster forest 1 | Cluster forest 2 | Cluster urban 3 | Cluster urban 4 | Inowrocław-Mątwy45 | ||
| Salinity | ||||||
| C-org (%) | Ns1 | 1.7 ± 0.55 | 2.3 ± 0.76 | 2.2 ± 0.32 | 2.1 ± 0.42 | |
| Major nutrients | ||||||
| N-NH4 (mg/l) | Ns | 9.2 ± 3.4 | 6.6 ± 3.1 | 7.3 ± 1.2 | 12 ± 2.1 | |
| N-NO3 (mg/l) | 0.011 | 21 ± 15 b | 52 ± 14 a | 24 ± 5.4 b | 21 ± 4.7 b | |
| P (mg/l) | 0.0016 | 5.0 ± 0.0 c | 17 ± 8.3 bc | 44 ± 12 a | 34 ± 11 ab | |
| K+ (mg/l) | 0.018 | 44 ± 24 b | 46 ± 48 b | 81 ± 19 ab | 132 ± 39 a | 34 ± 1.0 |
| Na+ (mg/l) | 0.0015 | 23 ± 3.4 b | 27 ± 11 b | 74 ± 48 ab | 439 ± 230 a | 280 ± 7.4 |
| Cl− (mg/l) | 0.0065 | 26 ± 4.2 b | 28 ± 11 b | 38 ± 12 ab | 154 ± 81 a | 590 ± 12 |
| Mg2+ (mg/l) | 0.00081 | 24 ± 9.0 b | 67 ± 20 ab | 136 ± 9.3 a | 78 ± 18 ab | 14 ± 0.5 |
| Acidity | ||||||
| Ca2+ (mg/l) | 0.0045 | 221 ± 96 b | 1241 ± 560 ab | 1877 ± 269 a | 1561 ± 687 a | 90 ± 3.5 |
| pHH2O | 0.0032 | 4.6 ± 0.63 b | 6.5 ± 1.0 ab | 7.5 ± 0.19 a | 7.8 ± 1.0 a | |
| Fe2+ (mg/l) | 0.0056 | 279 ± 50 a | 102 ± 54 ab | 56 ± 35 b | 95 ± 72 ab | |
| Mn (mg/l) | Ns | 36 ± 30 | 5.1 ± 6.8 | 4.3 ± 1.9 | 3.0 ± 1.2 | |
| Heavy metals | ||||||
| Zn (mg/l) | 0.0015 | 2.9 ± 1.2 b | 13 ± 8.2 ab | 20 ± 3.9 a | 47 ± 21 a | |
| Cu (mg/l) | 0.0012 | 1.2 ± 0.39 b | 1.1 ± 0.35 b | 5.5 ± 1.6 a | 12 ± 3.4 a | |
| Pb (mg/kg) | 0.013 | 28 ± 15 ab | 20 ± 7.9 b | 33 ± 9.1 ab | 70 ± 47 a | |
| Cd (mg/kg) | 0.0067 | 0.15 ± 0.06 b | 0.41 ± 0.29 ab | 0.34 ± 0.18 ab | 0.94 ± 0.57 a | |
| Geo-accumulation index | ||||||
| Zn (Igeo) | Not performed | − 4.6 ± 0.61 | − 2.5 ± 0.94 | − 1.8 ± 0.28 | − 0.6 ± 0.64 | |
| Cu (Igeo) | Not performed | − 4.3 ± 0.46 | − 4.5 ± 0.45 | − 2.2 ± 0.41 | − 1.1 ± 0.42 | |
| Pb (Igeo) | Not performed | − 0.093 ± 0.79 | − 0.56 ± 0.56 | 0.14 ± 0.4 | 1.2 ± 0.96 | |
| Cd (Igeo) | Not performed | − 0.010 ± 0.61 | 1.5 ± 1.0 | 1.2 ± 0.79 | 2.7 ± 0.88 | |
Means and standard deviations of selected chemical properties and pH of soil samples within each cluster of trees. Results of the Kruskal–Wallis test for the differences between the concentrations of each of the chemical components with the homogenous groups of clusters. The geo-accumulation index values85 were computed for the HM in each cluster (the Kruskal–Wallis test was not performed in that case) in comparison to the geochemical background46.
Ns non-significant.