If an upland oak has a height of 70 ft at age 75, what is the site index?

If an upland oak has a height of 70 ft at age 75, what is the site index?

• A. 58
• B. 61
• C. 63
• D. 66

Answer: (B)

Site index is the height that dominant trees would be at a standard base age, typically 50 years for upland hardwoods. To translate a current height at a given age into a site index, foresters use growth curves that relate height at a certain age to the height expected at the base age. If an upland oak is 70 ft tall at age 75, those curves indicate a site index of about 61 ft. In other words, at age 50, a tree on this site would be expected to reach roughly 61 ft tall. The other values would imply noticeably different growth trajectories on the standard curves, whereas 61 ft best matches the observed height at 75.

Site index is the height that dominant trees would be at a standard base age, typically 50 years for upland hardwoods. To translate a current height at a given age into a site index, foresters use growth curves that relate height at a certain age to the height expected at the base age. If an upland oak is 70 ft tall at age 75, those curves indicate a site index of about 61 ft. In other words, at age 50, a tree on this site would be expected to reach roughly 61 ft tall. The other values would imply noticeably different growth trajectories on the standard curves, whereas 61 ft best matches the observed height at 75.