1. General Model Information

Name: Generalized Growth and Yield Model

Acronym: GENGYM

Main medium: terrestrial
Main subject: biogeochemistry
Organization level: biocoenosis
Type of model: not specified
Main application:
Keywords: forest, conifer pine, ponderosa pine, deterministic, growthprojections


Carleton B. Edminister
Rocky Mountain Forest and Range Experiment Station
240 W. Prospect Fort Collins
CO 80526-2098
Phone: 970 498-1264
Fax : 970 498-1010



GENGYM (Generalized Growth and Yield Model) is a deterministic regression type model that predicts growth of mixed conifer and ponderosa pine stands in the southwest United States. Tree growth is projected in 1-inch wide diameter classes (d.b.h.). Growth projections are given in ten-year increments. The model was developed by Edminister and was validated using an error propagation mixing and data splitting technique (Edminister et al., 1991).

Model data input requirements include:

The model provides information about the future distributions of each d.b.h class, height of trees in each d.b.h class, and age distributions. The temporal scale of the model is 10 years, with the spatial scale at the stand level. The model is written in Microsoft FORTRAN in the DOS environment.

Author of the abstract:


II. Technical Information

II.1 Executables:

Operating System(s): DOS

II.2 Source-code:

Programming Language(s): FORTRAN 77

II.3 Manuals:

II.4 Data:

III. Mathematical Information

III.1 Mathematics

III.2 Quantities

III.2.1 Input

Model Input Data Requirements: Number of driving variables (or % live crown). Stemdiameter (.10 Inches). Number of stems per acre by diameter class, site index, species.

III.2.2 Output

Model Output Data: Tabular ASCII formatted future distributions of each d.b.h class, height oftrees in each d.b.h class, and age distributions.
Temporal Scale: Can be 10 year growth projects. One rotation length.
Spatial Scale: Stand level.

IV. References

Edminister, C.B., H.T. Mowrer, R.L. Mathiasen, T.M. Schuler, W.K.Olsen and F.G. Hawksworth. 1991. GENGYM: a variable density stand tableprojection system calibrated for mixed conifer and ponderosa pine standsin the Southwest. USDA-FS Research Paper RM-297, Rocky Mountain Forestand Range Experimental Station, Ft. Collins, Colorado.

V. Further information in the World-Wide-Web

VI. Additional remarks

Global change implications: GENGYM is a model that can be used forglobal change research. It provides longterm information on conifer forestage and size structure. It could be an important model to understand thepotential affects of climate change on the over 10 million acres of conifersin Southwest.

Last review of this document by: T. Gabele : 17. Sep 1997

Status of the document:
last modified by Tobias Gabele Wed Aug 21 21:44:43 CEST 2002

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