Model Description

ORGANON is a computer model of individual tree growth for areas of the Pacific Northwest.

It is an individual tree growth model that uses a list of trees, each with exact measurements, as input data. The user can specify periods of growth, in five year increments, and management such as thinning, fertilizing, and pruning. For each of the requested activities, the individual trees are modified to reflect the effects of the actions. The program produces stand statistics at each step, and yield tables after final harvest of the stand.

Presently, the ORGANON model is applicable to four areas or stand structures: (1) the mixed species, even- and uneven-aged stands of Southwest Oregon with tree ages up to 350 years (SWO version), (2) young-growth (up to 120 years old) Douglas-fir and/or western hemlock even- and uneven-aged stands of Northwest Oregon (NWO version), (3) young growth even-aged stands of Douglas-fir and/or western hemlock in western Oregon, Washington and British Columbia (SMC version), and (4) young-growth even-aged plantations (upto 30 years old) of red alder in western Oregon and Washington (RAP version). Although it will project uneven-aged stands, the NWO version was developed primarily from data taken from even-aged stands.


ORGANON is composed of 13 different types of equations for predicting:
1. Maximum crown width of open grown trees
2. Largest crown width of stand growth trees
3. Crown profile
4. Bark thickness
5. Cubic-foot volume (total or merchantable)
6. Taper
7. Height-diameter
8. Height to crown base
9. Dominant height and site index
10. Height increment
11. Diameter increment
12. Crown recession rate
13. Mortality

Each equation has parameters that are specific for each version and for each of the species in the version. These parameters have been determined using the modeling data sets and linear and nonlinear regression techniques.

All of the equations in ORGANON are applicable to any possible stand structure (e.g., single and multi-storied even-aged stand structures, and uneven-aged stand structures). One reason for this flexibility is a result of the choice to not use stand (or tree) age in any of the equations. The only use of stand age in ORGANON is to label the output and calculate MAI for even-aged stands. Therefore, ORGANON makes the assumption that tree dynamics is a function of tree size rather than tree age.

Another reason that ORGANON can be applied to any possible stand structure is the choice to use crown ratio and both one sided and two sided competition variables in the equations. Finally, ORGANON's single-tree structure means that it is applicable to either pure or mixed species stands as long as there have been the necessary equations developed that are specific to each of the species of interest.


All data used to develop ORGANON came from research plots. The data for two versions (southwest Oregon and northwest Oregon) were collected using a grid of temporary plots installed in healthy stands with structures that potentially could be management targets (this included even and unevenaged stands with pure or mixed species composition). All trees 1.0 foot tall and taller were measured for dbh, total height, height to crown base, and trees that died in the past growth period were noted. Type and severity of damage were noted on all sample trees. All trees with dbh approximately 1.0 inches or larger were increment bored for past radial increment. Trees presenting a clear view of past height growth rate were measured directly with a height pole. A subsample of trees without a clear view of past height growth rate were felled and stem analysis used to determine past height growth rate.

The other two versions of ORGANON (Stand Management Cooperative and Red Alder Plantation) were developed from the best research installations available for the species. These installations were created to study a number of silvicultural practices involving thinning, fertilization, and/or planting density.


ORGANON has had more refereed publications written about its equations and architecture than any growth and yield model (public or private) available in the western United States. The refereed publication process is a critical element in the scientific process, which involves review by anonymous experts in the topic that examine and, if accepted for publication, approve of the data collection procedures, the statistical modeling procedures, and the equation forms used by the modeler/author. The resulting certification/verification of the model(s) is a substantial benefit that one gains by using ideas/models that have survived the crucible of that process.


Overview of the input data need to run ORGANON

The trees input to the program should have the following measurements:

Point/Plot number REQUIRED An integer between 1-999 showing what group the tree belongs to.
Species Code REQUIRED Each possible species has a code assigned.
Diameter REQUIRED Diameter outside bark, in inches, 4.5 feet above ground level (DBH).
Total Tree Height RECOMMENDED Total height of tree in feet.
Crown Ratio RECOMMENDED Height to live crown divided by total height.
Radial Growth OPTIONAL Radial growth inside bark in inches.

Use this data format:
-------  ------------------------------------------------
 Column  Variable
-------  ------------------------------------------------
  1- 3   Plot/Point Number (integer)
  5- 7   Species Code (integer)
  9-13   Diameter at Breast Height (inches) 
         (real-1 decimal place)
 15-19   Total Tree Height (feet) (real-1 decimal place)
 21-24   Crown Ratio (real-2 decimal places)
 26-31   Expansion Factor (per acre) (real-2 decimal places)
 33-37   5-year Radial Growth inside bark (inches)
 39-40   User Code (integer)
-------  ------------------------------------------------

Here is an example:

1 2 3 4 1234567890123456789012345678901234567890 ---------------------------------------- 10 202 27.5 134.9 .63 25.24 2.91 1 10 202 10.0 .0 .00 .00 .00 0 ----------------------------------------

All optional entries may be entered as zeros (as in the second tree above) and will be filled in by the program. For plots that have no trees, include a record with the plot number and zero for all other entries.

Species and Species Codes used by ORGANON

Species codes in ORGANON follow the USFS stand exam numeric codes. These are:

Code Species         SWO NWO SMC RAP
    015  White fir        Y   N   N   N      
    017  Grand fir        Y   Y   Y   N      
  081  Incense cedar    Y   N   N   N    
 117  Sugar pine       Y   N   N   N   
 122  Ponderosa pine   Y   N   N   N   
202  Douglas-fir      Y   Y   Y   Y  
 231  Pacific yew      Y   Y   Y   N   
242  West. Red Cedar  Y   Y   Y   Y  
    263  Western hemlock  Y   N   Y   Y      
312  Bigleaf maple    Y   Y   Y   Y  
351  Red Alder        Y   Y   Y   Y  
361  Pacific madrone  Y   Y   Y   N  
  431  Golden chinkapin Y   N   N   N    
492  Pacific dogwood  Y   Y   Y   Y  
631  Tanoak           Y   N   N   N  
805  Canyon live oak  Y   N   N   N  
815  Oregon white oak Y   Y   Y   N  
818  Calif. black oak Y   N   N   N  
920  Willow           Y   Y   Y   Y  

Project participants
ORGANON was developed by David W. Hann, Ph.D., professor of forest biometry. He was assisted by Arlene Hester, David Larsen, David Marshall, Doug Maguire, Martin Ritchie, John Scrivani, David Walters, and Chao-Huan Wang during development of the Southwest Oregon version. The SWO version was funded by The Forestry Intensified Research (FIR) Cooperative. Development of the Northwest Oregon (NWO) version was assisted by Arlene Hester, David Marshall, Martin Ritchie, Chao-Huan Wang, and Abdel Azim Zumrawi. It was funded by The College of Forestry Research Properties, Oregon State University. Development of the Stand Management Cooperative (SMC) version was assisted by David Marshall, Christina Olsen, Charles Aylworth, and Mark L. Hanus. It was funded by the Stand Management Cooperative, University of Washington, Seattle. Development of the Red Alder Plantation (RAP) version was assisted by Andrew Bluhm and David Hibbs. It was funded by the Hardwood Silviculture Cooperative, Oregon State University.
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