JAAKKO POVRV JAAKKO POYRY CONSULTING, INC. Forest Health -....\. Technical Paper for a Generic Environmental Impact Statement on Tinlber Harvesting and Forest Management in Minnesota Prepared for: Minnesota Environmental Quality Board 658 Cedar Street St. Paul, Minnesota 55155 October 1992 Prepared by: Jaakko Poyry Consulting 560 White Plains Road Tarrytown, NY 10591 TEL: 914-332-4000 FAX: 914-332-4411 "'AAKKD pfiVAV JMKKO POYRY CONSULTING. INC. I November 6, 1992 Dr. Michael Kilgore GElS Project Manager Minnesota Planning Office 300 Centennial Office Building 658 Cedar Street St. Paul, MN 55155 Dear Dr. Kilgore: Pursuant to the State of Minnesota's GElS contract (No. 30000-18408-01) with Jaakko Poyry Consulting, Inc., as formally executed on May 15, 1991, and amended with Supplement No.1 on July 10, 1991, and Supplement No.2 on July 27, 1992, the sixth task included preparation of technical papers. One of these papers, Forest Health, is hereby submitted for review and approval. The material contained in this document is presented in accordance with the terms . outlined in Attachment A to the base contract, Section III, Subsection F. We look forward to a favorable review and approval of this work product in due course. Respectfully yours, James A. McNutt Executive Vice President and GElS Project Manager cc: Art Veverka Bob Dunn Doug Parsonson Alan Ek 5510 Six Forks Road • Raleigh. NC 27609 • Telephone: (919) 847-6842 • TeIefax: (919) 847·2902 Jaakko Pom Consulting. Inc .• Minnesota GBIS. Forest Health Technical Paper SUMMARY AND CONCLUSIONS Forests are presumed to be healthy when biotic and abiotic influences do not threaten the attainment of either current or future management objectives. Although specific aspects of forest condition can be quantified and measured objectively, assessing forest health depends in part on subjective evaluations and value judgements. Insects and diseases are important components of the forest ecosystem; they are fundamental agents of change impacting long-lived communities. The effects of insects and diseases on forests in the Lake States include tree mortality, tip dieback or top-kill, loss of reproduction and regeneration, loss of tree form and reduced resistance to other stresses. These effects can be translated into impacts on human uses of the forest such as loss of productivity due to mortality, decay, reduced growth rates and increased risk to fire. In addition, insects and disease can impact the recreational and aesthetic aspect of forest resources. Pests and diseases can also affect wildlife habitat values. Fungal decay provides habitat by creating hollows in trees, and insect pest larvae are a source of food for many species. However, widespread pest outbreaks leading to high levels of tree mortality may also reduce the habitat values for other wildlife species. This is a particular problem where natural checks and balances controlling a pest population cease to function, or where a new pest is introduced and there are no natural controls to check its growth. The risk to a forest stand of a pest attack or infestation (susceptibility) and the likelihood of damage if an attack occurs (vulnerability) are frequently related to stand age. Typically, as stands get older they become more susceptible to damage and are at greater risk of infestation. However, there are exceptions to this generalization where seedlings and young trees are preferentially attacked. Harvesting that requires multiple entries into a stand may also increase risk. For example, if care is not exercised, harvesting can damage residual trees, leaving them open to attack by both insects and diseases. Finally, atmospheric pollutants can weaken or stress trees, potentially increasing both their susceptibility and vulnerability. The amount of damage incurred during outbreaks of insects or disease is generally related to stand attributes and environmental conditions. In some cases, especially for insects, pest populations can be regulated by the activities of biological control organisms including predators, parasites and pathogens. Stand and site-related factors associated with severe impacts vary substantially with the nature of the health problem. However, low vigor trees, particularly those stressed by drought, are most likely to be severely affected by insects and diseases. Species and age-class diversity within and Jaakko Payry Consulting. Inc., Minnesota GElS. Forest Health Technical Paper among stands may reduce impacts relative to large, continuous areas of similarly-aged host trees. The purpose of this Technical Paper is to determine the possible effects of . an increase in timber harvesting and associated management practices on forest health in Minnesota. To make this assessment, emphasis was placed on identifying the circumstances likely to change the proportion of susceptible/vulnerable age classes, and the circumstances that require multiple entry harvesting operations. For each covertype, a 10 percent change in susceptible or vulnerable area by age class (0 to 40, 40 to 50, 50 to 60, 60 to 70, >70 yrs), was established as the threshold to determine the minimum change needed to significantly affect susceptibility or vulnerability to most forest diseases. This percentage is also considered to be the minimum level of change that is detectable above naturally occurring variation. The data from the second harvest scenarios described in the Maintaining Productivity and Forest Resource Base technical paper (Jaakko Piiyry Consulting, Inc. 1992a) were used as a basis for determining changes in age class structure and associated changes to the state's forests susceptibility and vulnerability to insect pests and diseases. In general, increased harvesting will tend to shift the age-class distribution of forest stands toward younger ages. When compared with the older stands they replace, younger stands are usually more vigorous and are typically more resistant to attack and are better able to recover following an attack. Increased harvesting will tend to reduce incidence of many insect pests and diseases that are favored by older forests. Insect sp~ies in this category include spruce and jack pine budworm and two-lined chestnut borers. In addition, diseases such as white trunk rot of aspen are also likely to be reduced. Other diseases will probably decrease in the short-term, but may ultimately increase as a result of increased intensity of timber harvesting, including cankers and decay of upland hardwoods and oak wilt. In contrast, the incidence of some insect pests, such as white pine weevil, are likely to increase as a consequence of increased harvest levels. This is due to an increase in acreage of susceptible younger stands. The incidence of some diseases are also likely to increase, including Diplodia shoot blight and canker, and Scleroderris canker of red pine. Some of the predicted increases in susceptibility and vulnerability are based on the assumptions that an increase in timber harvesting would substitute young, more susceptible stands of pine species to replace older stands that have been cut; changed management objectives including longer rotations and hence more susceptible/vulnerable age classes of other forest types; and increased use of thinning and selection harvests that will increase the risk of damage to retained trees. ii Jaakko POyry Consulting. Inc •• Minnesota GBIS. Forest Hea11h Technical Paper Mitigation alternatives focused on developing strategies to prevent pest buildups, to monitor and plan responses, and to apply stand level mitigations. Strategies discussed include: • monitoring and, if required, manipulating age class distributions of forest type groups to manage changes in susceptibility and vulnerability associated with changes in age class; • promote operator training and introduction of equipment that will reduce the level of damage to trees retained after thinning or selective cutting of a stand; • more ownerships should be involved in monitoring pest populations; • Integrated Pest Management Strategies for the major pests should be developed; and • strategies to increase the use of MNDNR guidelines for pest management should be implemented. iii Jaakko POm Consulting. Inc .. Minnesota GBIS. Forest Health Technical Paper TABLE OF CONTENTS .UST OF FI:GURFS • • • • • • • • • • • • • • • • • • • • • • • • • • • • • •• vi UST OF TAB~ ••••••••••••••••••••••••••••••• viii UST OF PR:EPAKERS •••••••••••••••••••••••••••• ix" 1 IN1'RODUCTION .............................. 1 1.1 Description ................................ 1 1.2 Sources of Data . .. 3 2 EXISTING ENVIRONMENT .... .. 4 2.1 Introduction . .. 4 2.2 Current Productivity Losses Due to Forest Health Factors ... 4 2.3 Forest Health Management in Minnesota .............. 7 2.3.1 Monitoring............................ 7 2.3.2 Management Guidelines .................... 7 2.3.3 Pest and Disease Management in Minnesota ........ 9 2.4 Pests and Underlying Forest Health Factors ........... 10 2.4.1 Aspen-Birch .......................... 11 2.4.2 Black Spruce. .. 13 2.4.3 Lowland Conifers . .. 13 2.4.4 Lowland Hardwoods ..................... 13 2.4.5 Pine ............................... 14 2.4.6 Spruce-Fir ........................... 17 2.4.7 Upland Hardwoods ............ .. 18 3 ME1BODS FOR ASSESSMENT OF IMPACTS .......... 21 3.1 Pests Potentially Affected by Changes in the Level of Timber Harvesting ........................... 21 3.1.1 Insects.............................. 21 3.1.2 Diseases............................. 22 3.2 Assessment