Table 1. Summary of plot-level attributes (mean and standard deviation) for each region in the study.
| Region | Number of observations | Mean age (years) | Max age (years) | Site index (m)1 | Basal area (m2) | ||
| Public forest land | |||||||
| Northeast | 243 | 67 | 169 | 19.1 | (5.8) | 27.2 | (14.3) |
| North Central | 463 | 64 | 222 | 18.0 | (4.8) | 23.4 | (29.8) |
| South | 644 | 46 | 160 | 24.8 | (6.2) | 17.4 | (15.3) |
| Intermountain West | 644 | 110 | 460 | 12.7 | (4.6) | 21.8 | (17.2) |
| Pacific Northwest | 10075 | 109 | 900 | 21.6 | (7.7) | 32.1 | (29.1) |
| Private forest land | |||||||
| Northeast | 1001 | 59 | 139 | 18.9 | (5.5) | 24.7 | (13.1) |
| North Central | 840 | 57 | 200 | 18.9 | (5.0) | 21.9 | (14.9) |
| South | 7449 | 36 | 550 | 25.2 | (5.9) | 12.6 | (32.1) |
| Intermountain West | 244 | 86 | 367 | 12.8 | (4.6) | 16.5 | (14.4) |
| Pacific Northwest | 6248 | 56 | 600 | 25.8 | (7.9) | 26.1 | (99.6) |
1
Only site index estimates with a base age 50 years were used in this estimate.