1. Growth Model Users Group Growth Model Run-Off January 2002

2. Growth Model Run-Off Objectives Compare the projections of three “typical” stands of predominately Douglas-fir using GMUG member growth models. Evaluate the repeatability of projections by the same model among users. Evaluate the consistency of projections among models.

3. Each GMUG member was provided with a dbh-class based tree list for each stand with heights, crown ratios and expansion factors. Site Index (King’s Douglas-fir) and total age were provided. Each member to project stands in 10-year increments to age 60. Growth Model Run-Off Methods

4. 16 members responded. 7 models used. –CRYPTOS –DFSIM –FPS –FVS –ORGANON –SPS –TADAM (as TASS-derived model) 11 model versions. Growth Model Run-Off Results

5. –FPS Oregon region - 5 Washington region - 1 –FVS Pacific NW Coast - 2 West Cascades - 1 –TADAM - 1 –CRYPTOS - 1 Growth Model Run-Off Model Versions –ORGANON SMC - 6 Assisi - 1 –SPS 4.1h - 1 Pacific NW Region (2.HT) - 1 –DFSIM - 1

6. Problems/comments: –No location information given. –Site index was not consistent with some stands’ exhibited height. –Stand treatment history had to be assumed. –Maximum SDI not specified. –Some models (DFSIM, TADAM, CRYPTOS) do not know about western hemlock. –Clumpiness and plot-level information not provided. Growth Model Run-Off Results

7. Stand 1 30 Years Old (from planting) Site Index 115 TPA: 230 BA: 106 ft 2 QMD: 9.2 inches 95% Douglas-fir, 5% western hemlock

8. Stand 1

20. Stand 2 40 Years Old (natural stand origin). Site Index 99 TPA: 235 BA: 113 ft 2 QMD: 9.4 inches 100% Douglas-fir

21. Stand 2

32. Stand 3 30 Years Old (from planting) Site Index 124 TPA: 239 BA: 95 ft 2 QMD: 8.5 inches 89% Douglas-fir, 11% western hemlock

33. Stand 3

45. Model Projections at Age 60

49. The models appear to conform with Eichorn’s Rule.

50. Growth Model Run-Off Observations “Region” effects are very large. FVS in particular can more than double volume between regions. There was variation among users running the same model and version. All models maintain a remarkably consistent relationship between stand height and volume. CRYPTOS projections were very similar to northern growth models.