Average basal area growth (in cm2) by species for four-year period before and after topping for Pennsylvania study area.
| Topped trees | Control trees | |||
|---|---|---|---|---|
| Species | 1969-1972 | 1972-1976 | 1967-1971 | 1972-1976 |
| Oak, chestnut | 80 | 80 | 70 | 70 |
| Oak, northern red | 120 | 110 | 120 | 130 |
| Yellow-poplar | 240 | 210 | 220 | 180 |
| Average | 170 | 130 | 130 | 130 |