PAI period is typically measured over what time frame?

• A. 1 year
• B. 5 years
• C. 10 years
• D. 5 or 10 years

Answer: (D)

Periodic Annual Increment refers to the average annual growth over a defined period, used to compare stands and guide management. The period needs to be long enough to smooth out year-to-year fluctuations caused by weather, pests, or measurement error, but not so long that it obscures changes in productivity or regime. A five-year window provides a clear mid-term view of growth trends, while a ten-year window extends that to longer-term productivity aligned with typical rotation and planning horizons. Shorter intervals, like one year, would be too noisy to be reliable. Thus, five or ten years are the typical choices for measuring PAI.