Overview

The initial development of SIMPPLLE was done for the two Region One geographic zones: west and east of the Continental Divide. Thus, there is more documentation of the system knowledge than with some of the other geographic areas. Both of these original geographic zones were developed for single life form description of the vegetation.

Discussion on System Knowledge

Mountain Pine Beetle in Lodgepole Pine

The logic for mountain pine beetle probability in lodgepole is built upon the hazard rating system in General Technical Report INT-36, “Guidelines for reducing losses of lodgepole pine to the mountain pine beetle in unmanaged stands in the Rocky Mountains”. The interpretation of a combination of a hazard ratings and past processes are based on analyses by silviculturists using the system on sample landscapes. The stand level data used in these hazard rating systems must be replaced by other information that is consistent with the level of available vegetation information. For example, basal area of lodgepole pine is replaced by whether the plant community is only lodgepole pine, or it contains one other species, or two other species. Elevation of the plant community is replaced by the habitat type group assigned. Probabilities are assigned to combinations of hazard ratings and past processes in both the vegetation unit being evaluated and its neighbors. These probabilities are based on analyses by silviculturists using the system on sample landscapes. The user-interface provides the means to change the probabilities, but not the combination of attributes of hazard, past insect and fire activity.

 Mountain Pine Beetle in Ponderosa Pine

The basis for the probability of mountain pine beetle in ponderosa pine starts with the determination of a hazard. This hazard is based on the research work documented in “Risk Rating Guide for Mountain Pine beetle in Black Hills Ponderosa Pine” (Stevens et al. 1980). This work uses the number of stories, basal area of ponderosa pine and the ponderosa pine quadratic mean diameter (qmd) to develop a risk of low, moderate, or high. Within SIMPPLLE, the single story, two story, and multi-story designation easily provides the information of one story, two stories, or more than two. The diameter definitions for the size classes used in SIMPPLLE provide the information that we use for the quadratic mean diameter (qmd). The levels of ponderosa pine basal area used in the Risk Rating Guide could not be used directly with SIMPPLLE since we do not carry basal area information. In its place we used a combination of the size-class and canopy-coverage class. The following figures display the logic used within SIMPPLLE.

In the user interface, we do not display the logic that results in the hazard, only the combination of the hazard and other attributes that are used to assign a probability. Included in the logic is an interaction with mpb in lodgepole pine. These figures are not currently available through the user interface.

Mountain pine beetle is a process that has a spread component to it. That is, it can occur in a plant community without having to have originated in it if one of its neighbors has the disturbance process. Included in the probability logic is an interaction between mountain pine beetle in lodgepole pine and ponderosa pine.

Mountain Pine Beetle in White Pine

The default relationships and probabilities are the result of workshops with silviculturists, ecologists, and pathologists. The logic for mountain pine beetle in whitebark pine is based on the degree of whitebark pine in the community, the size-class/structure, density, and past fire processes.

Blister Rust in White Pine

Blister rust is not identified as a separate process within SIMPPLLE. During the course of our workshops in the Region, the decision was made that it was so common that it should be included within the succession pathways.

From whatever pathway state an existing stand may currently be in, the progression is to lose density until we eventually have a nonstocked condition.

Separate pathways have been developed for rust-resistant white pine (rrwp) to allow for it to be planted in treatments. The presence of blister rust in the pathways for both white pine and whitebark pine presents a problem when the user wants to make long-term simulations to recreate historical conditions. Before these simulations can be made we must recreate the white pine pathways by taking out blister rust. To a certain extent this is already done. Simply change the rust resistance white pine (rrwp) back to white pine (wp) and save these as historic pathways.

Douglas Fir Beetle

The logic for Douglas-fir beetle was derived through a series of workshops with silviculturists,
ecologist, and entomologists in the Region. The logic uses a combination of the abundance of Douglas-fir, size-class/structure, density and the occurrence of a past light or mixed severity fire.

No spread logic has been incorporated with this disturbance process.

Spruce Beetle

The relationships and probabilities are the result of workshops with silviculturists, ecologists, and pathologists. The logic is based on habitat type groups, degree of presence of susceptible species, size-class and if a past light- or mixed-severity fire has occurred.

Western Spruce Budworm

The hazard rating system developed by Carlson and Wulf in the Spruce Budworms Handbook contains attributes of individual plant communities that were generalized to the landscape scale for use in the SIMPPLLE modeling system. One factor within the hazard rating is a measure of the surrounding suitable host forest. Within SIMPPLLE, this factor is expanded to include not just the adjacent communities, but also the percent of the landscape that is in contiguous, suitable host forest conditions. This is an example where some detail is given up in stand level attributes, but other components are gained in relation to landscape level attributes.

We compute a susceptibility-index as is done in the research work. This index consists of:

•  Percent-host-index
• Percent-climax-host-index
• Density-index
• Structure-index
• Stand-vigor-index
• Maturity-index
• Site-climate-index
• Character-of-adjacent-index

Root Disease

Most of the existing research for root disease requires a level of inventory information that is not consistent with what is available at landscape scales. Monitoring on long-term measurement for areas in the Region can provide rates of change due to root disease and other disturbance process. These values have been used in transition matrices in other models but we do not want to lock these values within SIMPPLLE. They should serve as comparisons to what SIMPPLLE produces on similar landscapes through multiple stochastic simulations. Future analysis should be done to compare these values to the ranges that result from multiple simulations.

The relationships and probabilities are the result of workshops with silviculturists, ecologists, and pathologists. The logic is based on habitat type groups, degree of presence of susceptible species and if past partial harvest has been done.

Invasive Species - Eastside Only

Research from Lisa J. Rew, Bruce Maxwell, and Richard Aspinall, Land Resources and Environmental Science Department, Montana State University has been incorporated into version 2.5. Their research on “Predicting the Occurrence of Non-indigenous Species Using Environmental and Remotely Sensed Data” uses a log-odds equation with the following variables:

Conifer Encroachment - Eastside Only

This system knowledge component was developed before many of the current regeneration features were in the system. The purpose is to account for ecological stratifications, certain habitat types in Region One, that are classified as non-forest, but with the absence of fire certain adjacent conifer species will encroach. The logic screen accounts for the concept that the larger the plant community of non forest habitat type, the longer it must be free of fire before the encroachment can occur. The code that identifies considered habitat type groups is not accessible. However, it can be seen by looking at the pathways for the non-forest habitat type groups. Those pathways have Douglas-fir, Ponderosa Pine, and Limber Pine present. Thus, if a seed source is present in an adjacent plant community it is possible in the absence of fire to get regeneration of the species.