Final Environmental Impact Statement

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Vestal Final Environmental Impact Statement Chapter 3 management area, per the 2009 Black Hills Monitoring and Evaluation Report (USDA Forest Service 2010). Based on this data the objective is currently exceeded in MAs 4.1 and 5.1 and is near achievement in MA 5.4. Table 17. Existing Percentages of Very Large Sized Pine Acres by Management Area Forest-Wide MA Objective MA 4.1 - Existing MA 5.1 - Existing MA 5.4 - Existing 36 10% 20% 13% 9% The Vestal project area contributes to these forest-wide percentages. Currently, there are approximately 974 acres of SS4 pine which have an average tree size of very large in the Vestal project area. These stands are located in all three of these management areas. There are approximately 50, 208 and 716 acres of pine stands with an average tree size of very large in MAs 4.1, 5.1 and 5.4, respectively. Late Succession Late succession, or structural stage (SS) 5, is defined in the Forest Plan glossary as follows: “This structural stage is characterized by very large trees (16+ inches dbh). Trees are at least 160 years in age….Late succession ponderosa pine may occur in dense stands, but may also grow in the open or in park-like stands” (Mehl 1992). Forest Plan direction for SS5 is included in the management area objectives, as discussed earlier. The Vestal project area contains approximately 107 acres of identified late succession (SS5) pine forest in the project area and contributes to the existing forest-wide percentages for MA’s 4.1, 5.1 and 5.4. Late succession forest is at high risk for MPB infestation and a very high fire hazard rating. Currently there are approximately 10,267 acres of SS4B and approximately 2,700 acres of 4C in the project area; these stands would be available to grow into older, denser late successional stands. These stands would also be susceptible to morality from MPB infestation and wildfire. An additional 1,270 acres of SS3B (low MPB risk) would also be available to grow into SS5 stands in the future as additional replacement stands. Mountain Pine Beetle There is currently a mountain pine beetle epidemic occurring within the project area (USDA Forest Service 2011b, also Appendix H). All measures of beetle activity indicate a rapidly exploding beetle situation with a significant increase in tree mortality over the past three years (Allen 2011a). Stand conditions across the project area are largely (61%) at high risk to increasing mountain pine beetle caused mortality (Table 18). Combine the high stand hazard with the high risk of a large resident beetle population in place would indicate that tree mortality is going to keep increasing and likely increase at a rapid level. For a dramatic depiction of how quickly MPB caused mortality is occurring in this project area refer to the two pictures on page 2, Chapter 1, which dramatically display changes over a two year period. Tree mortality from mountain pine beetle is most evident in the northern and western portions of the project area, at this time. Field surveys completed in the fall of 2011 indicate that approximately six trees were infested by MPB in 2011 for every single tree
Vestal Final Environmental Impact Statement Chapter 3 attacked by MPB in 2010. These conditions signify a rapidly growing outbreak in this area (Allen 2011a). Refer to Map 11 in Appendix A for a depiction of the progression of this epidemic since 2005. Map 11 was generated from aerial surveying. The risk of mountain pine beetle infestation is predicted from pine structural stages. The Black Hills National Forest Insect Rating Guide (revised August, 2011) identifies risk as either High or Low, as summarized in Table 20. Table 18. MPB Risk Rating by Pine Structural Stage Structural Insect Stage Rating 1 Low 2 Low 3A Low 3B Low 3C High 4A Low 4B High 4C High 5 High Based on this guide, currently, there are approximately 14,373 acres of ponderosa pine at high risk for mountain pine beetle infestation in the Vestal project area (See Map 12 in Appendix A). This is about 61% of the pine stands in the project area. High-risk pine stands are at a greater potential for increased MPB activity. Most of the mortality is in trees that are greater than 7-inches in diameter, with lesser amounts in smaller trees. Mortality is also typically concentrated in stands where tree density is highest, typically over 100 basal area (Allen 2011a). Stands above 60 ft²/ac of basal area or higher (generally SS 3C, 4B, 4C and higher density 4A stands) are considered to be at high risk. Table 19 displays existing MPB risk ratings. Hardwoods Table 19. Current MPB Risk Rating for Ponderosa Pine in Vestal Mountain Pine Beetle Risk Acres Percentage Low 9,320 39% High 14,373 61% There are 431 acres (~2%) of designated aspen stands within the analysis area. These stands are scattered throughout the project area, but mainly occur in the northern and eastern portions (see Map 3 in Appendix A). Hardwoods, mainly aspen, can also be found growing as inclusions within some conifer stands in the project area. Aspen is often out competed by intruding conifers. Spruce White spruce is shade tolerant; enabling regeneration and growth under closed forest canopies and grows slower than ponderosa pine (Sheppard & Battaglia 2002). In the absence of stand replacing events (e.g., fire, insects) and vegetative treatment, there is potential for spruce communities to increase. However, due to its thin bark and low 37
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Final Environmental Impact Statement

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