FVS Frequently Asked Questions (FAQs)

Ask the question. Maybe we have the answer. The FVS staff has summarized some of the questions that are most commonly asked regarding FVS and related software: their installation, use, and interpretation. Browse this list of questions and answers to see if your question has already been answered.

General Questions

How much hard disk space does the FVS setup package require?
The size varies from 15 to 30 MBs, depending on the Region. When you consider you will be using your own data and probably make multiple runs, the size requirements increase rapidly. We suggest there should be at least 100 MBs for project data and run results, but this could vary on the size and scope of the project (specific stand versus a landscape analysis) and the number of runs performed. Also remember the Windows operating system (Windows 9x) needs a minimum of 200 MBs on your C:\ drive to run efficiently.

Is FVS compatible with Windows 2000?
Yes it is. However, you will have to be logged in with Administrator privileges to install the software.

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FVS Interface-Suppose

How do you configure Suppose to start in the folder where your data resides, not with the \Fvsbin folder?
Go to the Create or Change a Suppose Shortcut page for a detailed explanation of how to create or change the Suppose Windows shortcut.

What do you do when you get the following error message when you click the Select Simulation Stands command button from the main Suppose window: "Suppose cannot open locations file: suppose.loc"?
Go to the Create or Change a Suppose Shortcut page for a detailed explanation of how to create or change the Suppose Windows shortcut.

How can I modify an existing simulation file, but keep a copy of the original?
With the Suppose interface program running, from the File menu, select Open. Open the desired simulation file. Again, from the File menu, but this time, select Save As. Give the simulation a new name. Modifications will be made to the new file only. The original file will be left unchanged.

How do I get an existing simulation file back into the Suppose program?
Simulation files are saved in files with the .key extension. With the Suppose interface program running, from the File menu, select Open. Find the filename of the simulation you would like to open. You may need to navigate to a different directory if the file was saved in a directory other than the current one. Highlight the desired filename and click the appropriate button to open it.

Can I use an existing simulation with a new stand?
Yes, as long as the new stand uses the same geographic variant as the current stand(s). Open the existing simulation in the Suppose interface program. Click the Select Simulation Stands button. If the current stand(s) are not needed, click the Delete Stand button, delete the currently included stand(s) and close the Delete Stand window. Now, include the new stand. From the File menu, select Save As to give the new simulation a name different than the existing simulation.

If the stand you intend to use is set up to use a different geographic variant than the current stand(s) you will see the warning message "stand(s) were not processed because the variants they require are either not available or are blocked from use due to prior selections." That stand, as currently configured, will not be able to be used with the existing simulation.

Can I modify one part of an existing simulation without rebuilding the entire thing?
Yes. With the existing simulation open in the Suppose interface program click the Edit Simulation File button. Highlight the component that you would like to change and click the Edit Selection button. That component will open in the same window that was originally used to create it, with the same values displayed. Change the desired parameters and click OK. If you need to delete a component, highlight it and click the Delete button. If you need to add new components use the Management Actions or Use FVS Keywords buttons instead of the Edit Simulation File button.

Why do I get a warning when I am trying to add a stand to a simulation?
When using the Suppose interface program, the keywords are invisibly labeled with an indicator of the geographic variant that was being used when they were included in the simulation. The geographic variant is determined when a stand is included in the simulation. Variant information is read from the stand list file.

When the warning message "stand(s) were not processed because the variants they require are either not available or are blocked from use due to prior selections" is displayed, it means that the stand that is to be added to the simulation uses a different geographic variant than the current simulation. There are two ways that this happens. The first is that a simulation was created with a stand from one geographic variant, and now a stand from a different variant is being added. The second is that a simulation was created without selecting any stand at all, and now a stand is being added. In this second case, the Suppose program doesn't know which variant to use while building the simulation since no stand was selected. It uses the default variant, which is usually the Northern Idaho variant. Stands from any other variant may not be added. To avoid this second situation, always include the stand(s) first, before adding anything else to the simulation.

Why do my simulation results not change when I replace a keyword with one that has different values entered?
Often, the problem is that the keyword has not been replaced, but rather another keyword has simply been added to the simulation file. FVS will attempt to execute all of the keywords in the simulation file. For example, a ThinBTA keyword leaves a residual of 100 trees per acre, and a ThinBTA is added with the intent of leaving a residual of 120 trees per acre. In this case the first ThinBTA will result in 100 trees per acre being left, and the second ThinBTA will be cancelled since there are not enough trees remaining to leave 120. The result is no different than before the second ThinBTA was added.

If a keyword is actually to be replaced by a different keyword, it must be deleted from the simulation. This is done by clicking on the Edit Simulation File button, highlighting the keyword, and clicking the Delete button. A new keyword or management action is then added to the simulation in the usual way. If the same keyword is to be used but the parameters need to be changed, then that keyword does not need to be replaced. It just needs to be edited. Click the Edit Simulation button, highlight the keyword, and click the Edit Selection button. Change the desired parameters and click OK. It is a good practice to look for duplicate keywords in the Edit Simulation window.

What's the difference between "Management Actions" and "Keywords"?
Management Actions in the Suppose interface program are simply special uses of regular keywords in disguise. They were developed to be more intuitive and allow for easy use of sets of keywords. The selection links for the Management Actions were written in more "plain English" and do not require as much knowledge of what the keywords do. Anything that is done with a Management Action can also be done with the correct combination of keywords. The keywords that the Suppose program uses to accomplish the management can be seen in the main FVS output file in the "Options Selected by Input" section.

How do I change the default editor in Suppose?
Right-click on the Suppose desktop icon, click on "Properties". Add to the Target window the editor and pathname. For example Target: C:\fvsbin\suppose.exe -editor=C:\Progra~1\Window~1\Access~1\wordpad.exe. If a folder name is greater than 8 characters it must be shortened to first 6 letters and a "~1" must be added.

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Variants and Extensions

You recently downloaded a new FVS Model Extension (fire or pest) and the Extension does not show up in "Use FVS Keywords" window in the left text box under Extensions. Why?
Make sure that once you have downloaded the program off the Web that you also unzipped the file. To unzip, double click on the downloaded file. You can check to see whether the file was unzipped by confirming that the new Base Model or Model Extension is located in your \Fvsbin folder (e.g., ni.exe, nifm.exe).

If the Extension has been unzipped into your \Fvsbin folder, the other possibility is that you need to update the Suppose program. When new Model Extensions are created, the Suppose parameter file also needs to be updated. Consequently, you may have the latest version of the Suppose program with an outdated parameter file. To update Suppose (which includes the updated parameter file), go to the Software page on the FVS website. From there, follow the Suppose link.

How do you update a geographic Variant if you already have FVS on your PC?
To update a Variant, go to the Software link on the FVS website. From there, go to the Variant Files page. Download the desired Variant. Once downloaded, unzip it by clicking on it twice. It will overwrite the old variant executable in the \Fvsbin folder.

How can you find out which Variants support which Extensions?
Go to the FVS Variant Key and Included Extensions page on the FVS website.

Why can't I find the regeneration keywords in the "Use FVS Keywords" window?
FVS keywords belong to different extensions. Extensions are software components that perform a specific function. The default set of keywords that are displayed in the FVS Keywords window of the Suppose interface program are associated with the Base Model extension. To see the keywords that are associated with other extensions the user must highlight the appropriate extension in the left-hand pane of that window. To see the regeneration keywords, the user must highlight either "Full Establishment Model" or "Partial Establishment Model", depending on the geographic variant being used.

How do I determine which geographic variant to use with my data?
If the data files have already been correctly produced, Suppose will read the geographic variant information from the Stand List File when a stand is added to the simulation. That variant will be used for the entire simulation.

If you are producing the data files you will need to specify in the Stand List File which variant you want to use. The Variants page contains a map of the approximate geographic areas covered by the different variants. If you need more specific information look at the descriptions of the individual variants. If your area falls near the boundary between several variants you may need to experiment with each to see which most realistically represents your area.

In my keyword set my keywords and parameters seem to be correctly aligned in the correct columns/fields but FVS doesn't seem to run certain keywords.
Check to see if you have used tabs instead of spaces in the keyword set. To check this open the keyword file in Word. Go to 'Tools' in the main menu, click on 'Options', click on 'View', add 'Formatting Marks.' This will show you how the file is formatted and if you used tabs.

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Post-Processors

I included a post processor in my simulation. Why is the output file blank?
Most of the post processors require output that is produced by including a specific keyword in the simulation. Without the correct keyword included the output from the post processor is not created, and the editor opens a blank document. For example, in order for theAverage Summary Table post processor to work, the EchoSum keyword must be included in the simulation. The keywords required by the post processors are listed in the Description/Notes box at the bottom of the post processor selection window of the Suppose interface program. For additional information refer to the document User's Guide to the Post Processors for the Forest Vegetation Simulator.

What is the difference between the "FVSSTAND Alone" post processor and the "Stand and Stock Tables" post processor?
Both post processors produce stand and stock tables for live tree, harvest tree, and mortality tree components by tree species by diameter class. The FVSSTAND Alone post processor has the added capability of displaying growth data as well as past and present information arrayed side-by-side for the live tree component. FVSSTAND provides subtotals by size class for easy summarization. FVSSTAND Alone produces associated yield files that can be imported into spreadsheets or databases for further processing. Both post processors can run through the Suppose program or run interactively from a DOS prompt or program icon. FVSSTAND Alone is a Windows-based program. The Stand and Stock Table post processor is a DOS based program. Both post processors produce stand tables for individual stands or plots. FVSSTAND Alone has the added feature of providing composite stand tables for many stands or plots. FVSSTAND Alone can also create SVS tree input files for each projection cycle stand table.

Are there any additional options for the post processors, like changing the diameter classes in the Stand and Stock Tables, or averaging computed variables by stand acreage?
Many of the post processors have some additional options, but these are not available through the Suppose interface program. Most of the post processors are small stand-alone programs. To make use of the additional options they must be run from a DOS or AIX command line. The names of the programs are listed in the Description/Notes box at the bottom of the post processor selection window of Suppose. Refer to the document User's Guide to the Post Processors for the Forest Vegetation Simulator for more detailed instructions.

Why doesn't SVS work, even though I have included a TreeList keyword in my simulation?
In the summer of 2000 there was a major upgrade to the process of calling the Stand Visualization System (SVS) as a post processor to FVS. A new FVS keyword called SVS was developed. It produces the SVS treelist files directly. The SVS keyword is now required instead of the TreeList keyword. Since the SVS treelist files are already created, there is no need for the old DOS program FVS2SVS to run, so SVS launches directly. The SVS keyword must be included in addition to having the SVS post processor selected.

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FVS Mechanics

How many growth sample trees does FVS need for local stand/plot calibration?
If increment data is provided within the FVS Input Tree file, then the large tree diameter model and/or the small tree height model can be scaled to reflect local conditions relative to regional growth trends. In order to compute scale factors, there must be five or more observations supplied per tree species. Diameter increment is accepted for tree greater than a designated threshold diameter whereas height increment is accepted for trees less than a designated threshold diameter. The threshold diameters vary by Variant, but it is generally 3-inches for large tree diameter growth and 5-inches for small tree height growth. Consult the Variant Overview for the definition of the threshold limits.

In addition, at least 3 height observations are required to calibrate the height-diameter relationship for any species.

I am using Variants in Region 5 and 6 and I notice growth and mortality are not what I expected, or the stand is growing too much volume. Why?
Check the default maximum Stand Density Index (SDI) that FVS is using. For many of these Variants, Ecoclass determines the SDI maximum. In some cases, the default SDI maximum based on Ecoclass is too high or too low. The SDI maximum determines the rate of density related mortality; therefore you could have exaggerated mortality or growth depending on the default SDI maximum. SDI maximum can be reset using the SDIMAX keyword.

Why are the residual trees per acre or basal area higher than the value I set on the harvest keyword?
The residual targets specified with the harvest keywords are not stand residuals, but are rather for specific ranges of diameter and height, and in some cases for particular species. Anything not within the specified range is not even considered for removal by that keyword. The stand residual will be the sum of the residual from the harvest keyword and all of the trees not within the range specified on the keyword. Refer to the description of a particular harvest keyword in the document Keyword Reference Guide for the Forest Vegetation Simulator for more detail.

Why is there regeneration in the simulation even though I did not schedule any?
Most of the geographic variants include regeneration from roots or stumps. Whenever trees of species that exhibit this behavior are cut, several stems will regenerate from each cut tree. This type of regeneration can be suppressed using the NOSPROUT keyword.

A few of the geographic variants (AK, CI, EM, KT and NI) also have the capability to include regeneration automatically after some types of harvests or after periods during which no regeneration was scheduled by the user. Refer to the document User's Guide to Version 2 of the Regeneration Establishment Model: Part of the Prognosis Model for details. The easiest way to suppress this type of regeneration is with the NOAUTOES keyword.

What causes the Summary Statistics table in the main FVS output file to be filled with all zeros?
When the Summary Statistics table is filled with zeros (or when the first cycle values are all zeros) it means that there were too few live tree records in the input tree data file. The Options Selected By Input section of the main output file will contain the warning:

******** SPS08 WARNING: TOO FEW PROJECTABLE TREE RECORDS

There are two main causes of this problem. The first is that the tree data file is not in the correct format. The second is that the "A" record of the stand list file contains the name of a file that is blank or does not exist. This is often due to a misspelling of the filename or an incorrect directory being specified. Refer to the FVS File Format page for a discussion of proper formatting.

I have included to CFVOLEQU (or BFVOLEQU) keywords, however my volumes have not changed.
Make sure you included the VOLUME (or BFVOLUME) keyword and indicated that you were using your own equation in field 7. Also if you want FVS to calculate volumes with your equation for the first cycle you must put a zero in field 1 (year), if you use the inventory year FVS will use the default equations for the first cycle and your equation for the rest of the cycles.

What does the merchantable cubic feet volume column include in the Summary Statistics Table in the Eastern variants (LS, SN, NE, SE, CS)?

The merchantable cubic feet volume column in the Summary Statistics Table includes pulpwood (to minimum merchantability specifications) plus sawlog volume. If you just wanted to know the total amount of pulpwood volume that did not include the sawlog volume. You would subtract sawlog ft3 volume from merchantable ft3 volume. However if you are using the Event Monitor to calculate volume, BTCUFT refers to the merchantable ft3 volume column in the Summary Statistics table and BMCUFT refers to the sawlog ft3 column in the Summary Statistics Table.

Does tree value class affect volume?
Not when you use the default National Volume Estimator Library Equations. However for FVS variants based on TWIGS (LS,CS,NE), if you use the regional volume equations, it will not calculate volumes for trees with a value class of 3, and will not calculate sawlog volume for trees with a value class of 2.

What damage codes are valid in the base version of FVS?

Top damage: 96=missing/broken top, 97=dead top.
Dwarf mistletoe: 30-34, with severity ratings of 0-6.
Special tree status: 55, with a severity rating of 1-99.
Percent volume defect: 25=defect for merchantable cubic and board foot volume, 26= defect for only merchantable cubic foot volume, 27= defect for only board foot volume, with severity ratings for all three being 1-99.

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Warnings/Error Messages

What is wrong when you get this error message in the FVS output when using the Southern Variant?

*****WARNING, INVALID FOREST TYPE WAS INPUT BY USER, DEFAULT INITIAL FOREST TYPE WILL BE CALCULATED BY MODEL

The Southern Variant calculates an FIA forest type based on stand species composition, stocking, and tree size information. The forest type is used to set a default maximum Stand Density Index (SDI) which is used in the mortality calculations. There are 3 ways to control forest type in the SN variant using the MODTYPE keyword, Field 3:

If an invalid forest type, or no forest type, or no MODTYPE keyword is entered, a warning message will be printed and the model will recalculate the forest type each cycle. The maximum SDI will be reset when the forest type changes;
If a valid forest type code is entered, the model will use that forest type to set the maximum SDI for the first cycle only. After the first cycle, the forest type will be recalculated each cycle and the maximum SDI will be reset when the forest type changes;
If a non-zero integer is entered in front of the forest type code on the MODTYPE keyword (e.g.,. the code 1103 is input for the Eastern white pine forest type (FIA code = 103) the forest type (and corresponding maximum SDI value) will be locked at FIA code 103 for the entire simulation. Please refer to the SDIMAX keyword for methods to override the forest type control of the maximum Stand Density Index during simulations.

******** SPS08 WARNING: TOO FEW PROJECTABLE TREE RECORDS

Why do I get a warning message about too few tree records?
FVS requires at least two live tree records in your input data. The warning message:

******** SPS08 WARNING: TOO FEW PROJECTABLE TREE RECORDS

means that FVS has found less than two trees. There are two main causes of this problem. The first is that the tree data file is not in the correct format. The second is that the "A" record of the stand list file contains the name of a file that is blank or does not exist. This is often due to a misspelling of the filename or an incorrect directory being specified. Refer to the FVS File Format page for a discussion of proper formatting.

When the warning message "stand(s) were not processed because the variants they require are either not available or are blocked from use due to prior selections" is displayed it means that the stand that is to be added to the simulation uses a different geographic variant than the current simulation. There are two ways that this happens. The first is that a simulation was created with a stand from one geographic variant, and now a stand from a different variant is being added. The second is that a simulation was created without selecting any stand at all, and now a stand is being added. In this second case, the Suppose program doesn't know which variant to use while building the simulation since no stand was selected. It uses the default variant, which is usually the Northern Idaho variant. Stands from any other variant may not be added. To avoid this second situation, always include the stand(s) first, before adding anything else to the simulation.

What does the warning "Suppose does not insure correct keywords when you use this option" mean?
This warning message appears whenever Suppose is about to open its free-form editor. This editor is used where the Suppose interface program does not have a standard window with boxes to fill or and lists to pick from. It is usually used with the more advanced features of the model, like conditional scheduling, computing values, or using the Parms format on activity keywords. The free-form editor works much like a text editor. The warning means that, once in the editor, Suppose has no way of checking whether the things you type are valid FVS code. It is possible to write code that FVS cannot interpret, or that causes FVS to crash.

Why do I get an invalid treelist file warning when using SVS as a post-processor?
The warning message "Cannot open treelist file... Are you sure the file is an SVS tree list?" usually means that no SVS treelist files were created by FVS. This is usually because the SVS keyword was not included in the simulation file. In the summer of 2000 there was a major upgrade to the process of calling the Stand Visualization System (SVS) as a post processor to FVS. A new FVS keyword called SVS was developed. It produces the SVS treelist files directly. The old system of using the FVS treelist file has been replaced, and the SVS keyword is now required instead of the TreeList keyword.

What does the following error message mean?

******** WARNING: THIS LABEL SET IS SHORTER THAN THE ONE YOU SPECIFIED

This warning is usually nothing to worry about. It appears in the Options Selected by Input section of the main FVS output file. It directly follows the SPLabel keyword description. The things listed in the SPLabel keyword record are called Stand Policy Labels. The Suppose interface program reads these directly from the Grouping Codes contained in the Stand List File. The warning means that there were more grouping codes in that file than FVS can handle. Unless you are using stand management rules with the Event Monitor in FVS this warning is of no concern. Refer to the document User's Guide to the Event Monitor: Part of Prognosis Model Version 6 for more information.

What does the following warning message mean?

******** WARNING: INITIAL STAND STOCKING OF x TREES/ACRE IS MORE THAN 5% ABOVE THE UPPER LIMIT OF y TREES/ACRE. UPPER LIMIT IS BASE ON A SDI MAXIMUM OF z , AND AN UPPER BOUND OF xx % OF MAXIMUM. MAXIMUM SDI BEING RESET TO xxx FOR FURTHER PROCESSING.

In most variants, mortality is based on Stand Density Index (SDI). Stand density asymptotes at a certain percentage of the maximum SDI. This is generally 85% of maximum SDI, but a user can adjust that level. If the initial stand density is more than 5% above this asymptotic level, the model automatically adjusts the maximum SDI. This warning message indicates one of two things:

The maximum SDI values (either input by the user, or set by model defaults) are too low, or
There is an error in data input, and stand densities are too high.

In the first case, the solution is to raise the SDI values using the SDIMAX keyword. In the second case, you probably have an error on your DESIGN keyword specifications.

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Last modified: Friday, 02-Dec-2005 18:16:27 EST