| Siberian elm | Silver maple | ||
| NDVI | SPAD readings | NDVI | SPAD readings |
SAP | 0.002** | 0.000*** | 0.001** | 0.000*** |
Watering frequency | 0.000*** | 0.060 | 0.011* | 0.420 |
SAP × watering frequency | 0.001*** | 0.550 | 0.506 | 0.473 |