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United States Department of Agriculture

FVS Models & Event Monitor Files

Hemlock Wooly Adelgid Event Monitor Addfiles

What is it?

The Hemlock Woolly Adelgid Event Monitor is a program that simulates the effects of the hemlock woolly adelgid (Adelges tsugae) within the confines of the Forest Vegetation Simulator (FVS). Infestation date is provided by the user, based on knowledge of the stand, and published estimates of population movement and projected infestation date. Once infestation occurs, mortality is leveled against eastern and Carolina hemlock species at the end of the FVS cycle. Hemlock woolly adelgid induced tree mortality is determined by the intensity of the initial infestation and the subsequent adelgid population cycles. Impact is also mediated by the geographic location of the stand, with relative impact on hemlock mortality increasing for southern hemlock stands.

This is a strategic model that demonstrates the potential loss of hemlock timber and habitat due to hemlock decline and mortality. The user can proactively reduce the risk posed by the hemlock woolly adelgid by scheduling appropriate management actions within FVS such as thinning to remove hemlock. Once an event is scheduled by the Hemlock Woolly Adelgid Event Monitor there are no reactive measures the user can take to prevent the loss of hemlocks or remove infestations.

Users of the Hemlock Woolly Adelgid Event Monitor should also be aware that, due to the limitations in FVS’s growth and mortality equations, the inter-tree variability normally seen in response to infestation by the hemlock woolly adelgid cannot be adequately modeled. Because of this limitation, the user is cautioned that this Event Monitor is best suited for evaluating relative differences in adelgid infestation at the stand level, rather than absolute responses for specific stands.

Who Can benefit from the Hemlock Woolly Adelgid Event Monitor?

Potential users of the Hemlock Woolly Adelgid Event Monitor include, but are not limited to, forest planners conducting large-scale, program-level assessments of forest development, silviculturists, prescriptionists, and wildlife habitat managers conducting project level analyses for forest management, and forest health professionals, commercial foresters, and private land owners seeking to minimize the impacts of the hemlock woolly adelgid. It is intended for use by those familiar with the proper use and execution of the Forest Vegetation Simulator. It is recommended that the user be well versed in interpretation of standard FVS output. Standard FVS output and variables specific to the Event Monitor (such as: HM_BA, EH_BA, OUTBREAK, PER_HBA) can be exported to spreadsheet programs for further analyses.

How do I use it?

The desired Hemlock Woolly Adelgid Event Monitor must be added to the simulation, preferably after one or more stands have been selected for use within FVS. From the Selections window in the Suppose interface:

  1. Click the “Edit Simulation File” button.
  2. Click the “Insert from file” button.
  3. Navigate to the location where you placed the Hemlock Woolly Adelgid Event Monitor File(s). Select the geographically appropriate Event Monitor file from the Insert component from file: window.
  4. Note: Double-clicking the correct filename will automatically add the Event Monitor to the selected stand(s) in question. Single-click selection requires the user to then hit the “Open” button to add the Event Monitor to the simulation.
  5. Note that the addfile now is associated with the stand(s) in question.
  6. “Close” the Edit Simulation window.
  7. Choose the post-processor that best fits your needs and run your simulation after giving it an appropriate name.

Which Hemlock Wooly Adelgid Event Monitor Files do I use?

There are two types of hemlock woolly adelgid keyword component (.kcp) addfiles appropriate for use with both the North East (NE) and Southern (SN) variants of FVS. Users who wish to simulate the effects of the hemlock woolly adelgid should use HWA_NE.kcp or HWA_SN.kcp addfiles, dependent upon stand location and the associated FVS variant. These addfiles utilize custom variables not available with the base FVS model. Users who wish to view these custom variables for simulations that do not include impacts by the hemlock woolly adelgid (i.e., uninfested stands) for comparison purposes should use x_HWA_NE.kcp or x_HWA_SN.kcp.

As the hemlock woolly adelgid impacts only species in the genus Tsuga, the Hemlock Woolly Adelgid Event Monitor is most meaningfully applied in forest types with a significant hemlock component. The user is strongly urged to apply the correct Event Monitor file to the appropriate stands. This is best achieved by creating geographically homogenous FVS simulations through creative use of FVS grouping codes.


Hemlock Wooly Adelgid Event Monitor (HWA_em.exe, 130 KB)

hemlock woolly adelgid damage

hemlock woolly adelgid (Adelges tsugae) Annand, 1924. Photo by Jason Van Driesche.