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Growth Model Users Group

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

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Growth Model Users Group

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

  2. Growth Model Run-OffObjectives • 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. Growth Model Run-OffMethods • 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.

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

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

  6. Growth Model Run-OffResults • 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.

  7. Stand 1 • 30 Years Old (from planting) • Site Index 115 • TPA: 230 • BA: 106 ft2 • QMD: 9.2 inches • 95% Douglas-fir, 5% western hemlock

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  20. Stand 2 • 40 Years Old (natural stand origin). • Site Index 99 • TPA: 235 • BA: 113 ft2 • QMD: 9.4 inches • 100% Douglas-fir

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  32. Stand 3 • 30 Years Old (from planting) • Site Index 124 • TPA: 239 • BA: 95 ft2 • QMD: 8.5 inches • 89% Douglas-fir, 11% western hemlock

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  45. Model Projections at Age 60

  46. Model Projections at Age 60

  47. Model Projections at Age 60

  48. Model Projections at Age 60

  49. Model Projections at Age 60 The models appear to conform with Eichorn’s Rule.

  50. Growth Model Run-OffObservations • “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.

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