Log Volume Forecast Calculator

This model projects merchantable log throughput - the volume of roundwood a harvesting or milling operation handles per month, expressed in cubic meters, green tons, or board feet. It uses geometric rather than linear growth because the drivers of throughput (standing inventory, crew and machine capacity, market share) tend to scale proportionally rather than by a fixed increment. The annual rate is divided by 12 and compounded over the forecast horizon, then multiplied by a seasonal factor. For growth, forest mensuration offers a physical anchor: mean annual increment for managed stands commonly falls between 3 and 12 cubic meters per hectare per year depending on species and site index, which caps what sustained-yield harvesting can support. The seasonal factor captures predictable operating constraints rather than demand alone. Spring thaw restrictions on haul roads in northern regions, wet-season shutdowns in the tropics, and frost-dependent access to soft ground routinely swing monthly volume by 20 to 30 percent, so factors of 0.7 to 1.3 are realistic. Two limitations deserve emphasis. The variance band is a judgment interval, not a statistical prediction interval, and it does not widen with the forecast horizon the way real forecast error does, so 36- and 60-month projections should be treated as scenarios. Board-foot totals also depend on which log rule is applied, since Doyle, Scribner, and International quarter-inch scaling give materially different volumes for the same log.

Forecasting log volume rests on first being able to measure it. Cubic-content formulas from early nineteenth-century German forest mensuration - Huber's mid-diameter formula and Smalian's end-area average - remain the standard way to compute the volume of an individual log. North America instead developed board-foot log rules aimed at estimating recoverable lumber: the Doyle rule appeared around 1825, J. M. Scribner published his diagram rule in 1846, and Judson Clark introduced the International quarter-inch rule in 1906 to correct the systematic bias the older rules showed on small logs. These competing scales are the reason a volume forecast is meaningless unless the scaling rule is stated. Systematic projection came with sustained-yield management. German foresters formalized the normal forest and rotation concepts in the eighteenth and nineteenth centuries, and Martin Faustmann published his land-expectation formula for optimal rotation age in 1849. In the United States, the McSweeney-McNary Forest Research Act of 1928 authorized the nationwide survey that became the Forest Service Forest Inventory and Analysis program, which has produced repeated field measurements ever since. The FAO began its Global Forest Resources Assessment in 1948 and now reports on a five-year cycle. Empirical growth-and-yield simulators followed, notably Albert Stage's Prognosis model of 1973, which grew into the Forest Vegetation Simulator used for stand-level projection today.