| Regression formula | Pattern of explanatory variables | |
| 1 | X1 | Crown area |
| 2 | X1 | Crown surface |
| 3 | X1 | Crown volume |
| 4 | X1 X2 | Crown area Tree height |
| 5 | X1 X2 | Crown surface Tree height |
| 6 | X1 X2 | Crown volume Tree height |
| 7 | X1 X2 | Crown area Crown length |
| 8 | X1 X2 | Crown area Crown length ratio |
| 9 | X1 X2 X3 | Crown area Tree height Crown length |
| 10 | X1 X2 X3 | Crown area Tree height Crown length ratio |