The Decline of the Clearcut: 26 Years of Change in Silvicultural Practices and Implications in Minnesota M.A

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Journal of Forestry, 2020, 244–259 doi:10.1093/jofore/fvaa007 Research Article - silviculture Received July 26, 2019; Accepted February 7, 2020 Advance Access publication March 27, 2020

Research Article - silviculture Downloaded from https://academic.oup.com/jof/article-abstract/118/3/244/5812992 by The University of Vermont Libraries user on 28 July 2020 The Decline of the Clearcut: 26 Years of Change in Silvicultural Practices and Implications in Minnesota M.A. Windmuller-Campione, M.B. Russell , E. Sagor, A.W. D’Amato , A.R. Ek, K.J. Puettmann, and M.G. Rodman

M. A. Windmuller-Campione ([email protected]), M. B. Russell ([email protected]), E. Sagor ([email protected]), and A. R. Ek ([email protected]), Department of Forest Resources, University of Minnesota, St. Paul, MN. E. Sagor (esagor@ umn.edu) and M. G. Rodman ([email protected]), Minnesota Sea Grant, University of Minnesota, Duluth, MN. A. W. D’Amato ([email protected]), Rubenstein School of Environment and Natural Resources, University of Vermont, Burlington, VT. K. J. Puettmann ([email protected]), Department of Forest Ecosystems & Society, Oregon State University, Corvallis, OR.

Abstract Silvicultural decisions and forest-management practices in Minnesota represent the collaboration and partnership between forest managers from multiple organizations and forest researchers. To better understand current practices, trends, needs, and opportunities, Minnesota has invested in the collection of quantitative data on the application of silvicultural systems and forest-management activities in 1991, 1996, 2008, and 2017. Drawing on those data, the goal of our study is to summarize 26 years of data to characterize and quantify trends in forest-management practices. During this period of time, timberland ownership (acres) has increased, whereas harvested volume has decreased (cords). Across state, federal, county, forest industry, and tribal forest lands, which collect- ively represent the majority of timberlands in Minnesota, the clearcut system decreased from 91% of the harvested area in 1991 to 72 percent in 2017. In contrast, the proportion of total harvested area as part of shelterwood, seed tree, selection, and thinning treatments all more than doubled from 1991 to 2017. Factors influencing the changes relate to forest health and diseases, shifts in ownership structure, and shifts in organizational policy and/or goals. The factors identified mirror many of the trends forest managers are experiencing in other regions, nationally and internationally.

Keywords: silviculture, even-aged systems, uneven-aged systems, regeneration, tending, forest health

The application of silviculture practices is continu- practices changes over time and what may influence ally changing, adapting, and responding to shifts these changes (D’Amato et al. 2018b). Over the last in societal goals and values, technologies, markets, 26 years, the state of Minnesota has made a great disturbances (e.g., fire, invasive species), and ad- investment to understand how landowners manage vances in forest science (Puettmann et al. 2009, forest land in terms of the silviculture practices Nyland 2016). Academic research often explores they choose as they reflect the goals, values, and de- how different silviculture treatments can be imple- sired outcomes (Jaako-Pöyry 1992, Puettmann et al. mented to meet various goals and objectives. It is less 1998, Puettmann and Ek 1999, D’Amato et al. 2009, common to study how the application of silvicultural Windmuller-Campione et al. 2019).

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Management and Policy Implications

Changes in forest management and silvicultural systems can reflect broader societal values, attitudes, and perceptions of forest management related to social, environmental, and economic goods and services. In aggregate, the silvicultural treatments applied across the landscape influence future wildlife habitat, wood-production possibilities, and silvicultural options. Understanding how treatments have changed over decades can give land managers, industry, policymakers, and researchers important context about the condition of surrounding forest Downloaded from https://academic.oup.com/jof/article-abstract/118/3/244/5812992 by The University of Vermont Libraries user on 28 July 2020 lands now and in the future. This understanding is critical to our ability to forecast not only future production opportunities, but also the relations between forest-management treatments today and conditions tomorrow. Forest-management organizations have a deep knowledge of the practices and decisions applied on their own land. However, disturbances, wildlife populations, and impacts from climate change do not honor ownership boundaries. By collecting data across all major landowners and several decades, researchers can offer land managers important insights that are not otherwise available. The research presented in this article summarizes trends in silvicultural practices from Minnesota. However, data from Minnesota can be used to compare and contrast forest management at local, regional, and national levels.

The impetus to develop and administer the first modified to reflect changes in topics of public concern. silvicultural practices survey in Minnesota was to ad- For example, new topics explored in later surveys in- dress growing public concern during the late 1980s re- cluded biomass harvesting, silvicultural practices for garding forest management, specifically the statewide forest insects and diseases, and the influence and im- timber harvest, available timber supply, and the po- plementation of best management practices (Table 1). tential negative impacts on wildlife, water, and other Although survey data are limited to Minnesota, general ecosystem services (Jaakko Pöyry Consulting, Inc. trends likely reflect overarching national and global 1994). The first survey of silvicultural practices was a drivers (e.g., the housing bubble and Great Recession, small part of a broader Generic Environmental Impact invasive species, changing ownership structures on pri- Statement that included detailed work on quantifying vate industrial lands, and climate change) that influ- the environmental, economic, and social impacts of ence how silviculture is practiced in a given region. different harvest levels on Minnesota’s forest (Jaako- Pöyry 1992). Since 1991, three additional surveys were implemented in 1996, 2008, and 2017 (Puettmann Minnesota’s Forest: Historical and et al. 1998, Puettmann and Ek 1999, D’Amato et al. Current Management 2009, Windmuller-Campione et al. 2019). Just as Minnesota’s forests have a long history of anthropo- silvicultural practices, markets, technology, and soci- genic use by numerous cultures (Stearns 1997). As etal values continue to change, the surveys have been documented by Daniel Greysolon in 1679 and by earlier

Table 1. Topics covered by each survey period and number of respondents by year. Year 2017 2008 1996 1991

Number of respondents n = 22 n = 26 n = 25 n = N/A Types of questions asked Broad organizational questions (i.e., timberland managed) X X X X Nonindustrial private landowner management X Regeneration methods X X X X Herbivory protection X Site preparation X X X X Forest health X X Other silvicultural activities (i.e., burning, pruning, salvage harvest) X X X Residuals after harvest X X Site-level guidelines X X Changes in silvicultural practices X X Open-ended question on any additional information to be shared X X X 246 Journal of Forestry, 2020, Vol. 118, No. 3 indigenous oral histories, the areas surrounding the Great multiple public, private industrial, tribal governments, Lakes of now Minnesota and Wisconsin were used by and family forest landowners. There is a relatively the Dakota, Ojibwe, Assiniboine, and Cree people. For even split between private (51 percent) and public (49 example, reconstructions using dendrochronological percent) timberlands (Miles et al. 2017). Roughly 34 methods on tree species such as red pine (Pinus resinosa percent of private forestland is owned by an estimated Soland.) highlight the use of fire and culturally modified 114,000 family forest owners (Butler et al. 2016). Downloaded from https://academic.oup.com/jof/article-abstract/118/3/244/5812992 by The University of Vermont Libraries user on 28 July 2020 trees for trade, transportation, and land management in Other private ownership includes tribal governments northern Minnesota by the Ojibwe people (Johnson and and industrial private landowners. The primary public Kipfmueller 2016, Larson et al. 2019). land-management agencies are the state, which man- In the early 1800s, Minnesota’s approximately ages 22 percent of the timberland, counties and munici- 31.5 million acres of forests were described as mostly palities, which manage 15 percent of timberlands, and dominated by conifer species. However, expansive the National Forest System, which manage 12 percent European settlement and destructive logging practices of the timberlands. Timberlands provided a sustain- between 1880 and 1910 selectively removed eastern able source of revenue for the state’s forested counties. white pine (Pinus strobus L.), red pine, and northern For example, the St. Louis County Land and Minerals white cedar (Thuja occidentalis L.), which was fol- Department manages approximately 900,000 acres of lowed by the harvest of spruce (Picea spp.) and hard- forested lands and is one of 12 counties with active woods (Stearns 1997). In fact, logging was often a first forestry divisions. The State of Minnesota is the lar- step in clearing land for settlement. These harvesting gest public landowner, and designated parcels of forest practices were often followed by intense slash fires that (“school trust”) supplied US$3.19 million to school destroyed seed sources and shifted dominance in large systems during the 2017 fiscal year (Zieman 2018). areas to sprouting hardwood species, mainly trembling Minnesota’s current forest composition is a legacy aspen (Populus tremuloides Michx.) and bigtooth aspen of past harvesting and reforestation practices, which (P. grandidentata Michx.) (Schulte et al. 2007). As a in turn influences future decisions and forest compos- consequence of these destructive fires, associated prop- ition. The silvicultural treatments applied in aggre- erty damage, and livestock and human deaths, several gate across Minnesota will set the direction for future conservation and sustainable forestry efforts were ini- forest productivity, health, and resilience to disturb- tiated in the early 20th century at the local (e.g estab- ances. Future forest planners need information about lishment of the Minnesota State Forestry Board in 1900 not only forest inventories, but expected trajectories of followed by the establishment of a state nursery) and na- stand development, which are informed by an under- tional levels (e.g., the creation of the Superior National standing of the silvicultural treatments implemented Forest in 1909). During the period between 1910 and today. For example, the type of silvicultural system 1940, it was common that much of the forests that were used can favor very different species, which can in- converted to farms were not productive for agriculture. fluence forest products, wildlife habitat, and aesthetic These marginal lands were consequently abandoned values. Longitudinal data across all ownerships and and then transferred to state ownership. This resulted several decades can link past and current inventory in a substantial increase in forest land ownership by the data in ways that are otherwise only speculative. state of Minnesota. A large portion of this forest land is now administered by county governments in northern Minnesota. By the mid-1930s, Minnesota’s forest area Objectives had been reduced to less than 20 million acres and was The overarching goal of our study was to summarize dominated by young stands including several million 26 years of silvicultural survey data to characterize acres of brushlands (Flanary et al. 2016). and quantify trends in forest-management practices Over the next several decades, the amount of forest in Minnesota. Our first objective was to document land gradually increased. The USDA Forest Service trends in silviculture systems over the past 26 years Forest Inventory and Analysis (FIA) program database including regeneration, tending/intermediate treat- currently estimates approximately 16 million acres of ments, and harvest types. The second objective was timberland with an additional 1.8 million acres of forest to relate trends to forest health concerns with im- land in reserves in Minnesota (Miles et al. 2017). The plications on future directions in silvicultural prac- majority of this timberland is in central and northern tices. From these two objectives, we have quantitative Minnesota (Figure 1). Forest ownership is split among data to elucidate how social, economic, political, and Journal of Forestry, 2020, Vol. 118, No. 3 247 Downloaded from https://academic.oup.com/jof/article-abstract/118/3/244/5812992 by The University of Vermont Libraries user on 28 July 2020

Figure 1. Current distribution of forested land in Minnesota, excerpted from Riemann et al. 2018. ecological drivers influence forest-management prac- manage their respective lands (Butler et al. 2016). tices across the state and within forest-management However, without this assumption, comparisons organizations across time. among years would not be possible, since a statewide number is derived from an expansion factor related Methods to harvest levels (see paragraph below for additional detail on calculation). The harvest levels include both Silvicultural Surveys public and private lands. Although imperfect, this ap- Survey Design, Strengths, and Limitations proach and the broad diversity in management prac- One questionnaire was administered to each major tices among respondents support the assumption that forest management organization including public, on average, management of lands excluded from the private industrial, and tribal governments in 1991, survey would be adequately represented, in aggregate, 1996, 2008, and 2017. Because of limited resources, by survey responses. family forest landowners were not surveyed (see Puettmann et al. 1999 for discussion). The 1991 and To standardize results from the different survey 1996 survey data represent 50 percent of all tim- years, statewide estimates were derived by multiplying berland, and the amount of timberland surveyed in- the respondent silvicultural system acreages by an ex- creased to 64 percent and 66 percent, respectively, in pansion factor. This factor was calculated as the re- 2008 and 2017. ported statewide harvest level in the survey year divided Given the large number and the difficulties in sur- by the sum of the respondent reported harvests. For veying silvicultural practices from individual family example, in 2017, this approach expanded respondent forest landowners, we have made the assumption that acreages in silvicultural systems using an expansion silvicultural practices on these lands followed the same factor 1.61, which is the ratio between the reported trends as on the other, surveyed ownerships. This as- statewide harvest levels (2,514,286 cords) and the sumption simplifies the complex reasons that family harvest level reported by survey respondent harvests forest landowners own and choose to manage or not (1,559,921 cords) (Hillard et al. 2019). The expansion 248 Journal of Forestry, 2020, Vol. 118, No. 3 to the statewide level allowed for comparison across participated in the survey. Additional details on the the various surveys, since the amount of acreage man- survey and specific results from the 1991 study can be aged by the survey respondents varied among years. found in Jaako-Pöyry Consulting, Inc. (1992). In addition to the assumption that similar silvicultural systems and harvest intensities are used on surveyed The 1996 Survey and nonsurveyed lands, we also assumed that the same Building from the framework of the 1991 survey with Downloaded from https://academic.oup.com/jof/article-abstract/118/3/244/5812992 by The University of Vermont Libraries user on 28 July 2020 management infrastructure (e.g., logging firms and modifications and additions, a questionnaire was dis- equipment and seedling availability) operates on all tributed to forest-management organizations to follow types of ownerships, and statewide guidelines are im- up on silvicultural practices in 1996 (Table 1). The plemented (Minnesota Forest Resources Council 2013, questionnaire was mailed to the same organizations Rossman et al. 2016, Blinn et al. 2019). However, as for the 1991 survey and resulted in similar land statewide numbers should be viewed as estimates, as coverage, i.e., less than 1 percent difference in re- neither of the surveys resulted in a statewide census. ported acreage between 1991 and 1996 (Puettmann The general consistency in the types of questions and et al. 1999). In total, 25 organizations responded to the organizations that participated consistently over the questionnaire (Table 1). This was a participation the 26 years provides insight into broad-scale trends in rate of 83 percent. Modifications included additional forest-management practices in Minnesota (Table 1). questions on residual tree retention after regener- Another limitation is related to silviculture ter- ation harvesting, other silvicultural activities including minology used in the survey. Although each survey burning, slash disposal, and timing of harvesting, and had a list of definitions as supplementary material, open-ended questions related to silvicultural practices. respondents had to reference the definitions in their Additional details and results from the 1996 study can answers. Additionally, each silvicultural prescription be found in Puettmann et al. (1998). was classified by the practicing foresters, and his or her use of terminology may vary depending on edu- The 2008 Survey cation, organization, and regional history. Consistency During the spring of 2009, the third survey on silvicul- in vocabulary such as timber stand improvement (TSI) tural practices was distributed to forest-management was maintained among surveys across years. The term organizations to summarize data from the 2008 fed- clearcut used here commonly includes coppice systems eral fiscal year. The majority of questions asked in the (e.g., aspen) in the region. Key terms are defined in the 1991 and 1996 survey were repeated; some questions Results section and can be found in the Supplemental may have been reworded but maintained the main Material. Finally, there is ongoing discussion regarding theme to allow for comparisons across years (Table 1). silvicultural terminology as used in multiple textbooks Additional questions were added to assess new forest- (e.g., Nyland 2016, Aston and Kelty 2018) and up- management issues under discussion during that time dates of silviculture definitions in The Dictionary of including biomass harvesting, the use of site-level Forestry (Helms 1998, Deal 2019) during the survey Timber Harvest and Forest Management Guidelines period. We accounted for these issues in the interpret- (MN Forest Resources Council 2013), forest health ation of our data as much as possible. issues, and open-ended questions related to current forest-management practices, future management The 1991 Survey practices, and regeneration issues. In total, 26 organ- The 1991 survey was implemented and summarized izations completed the questionnaire, a response rate by Jaako-Pöyry Consulting, Inc. to provide important of 96 percent (Table 1). Additional details on the 2008 information as part of the Generic Environmental survey and its results can be found in D’Amato et al. Impact Statement report for the management of tim- (2009). berland in Minnesota (Table 1). The survey requested a broad summary of ownership and practices, and more The 2017 Survey detailed questions related to silvicultural systems, re- The fourth survey was implemented in fall of 2017 to generation practices, site preparation, and TSI. The capture changes in forest-management practices with exact number of forest organizations that participated special attention to forest-health concerns and trends is not available. However, it was noted that 100 per- in silvicultural practices. Forest-health issues were es- cent of state, national forest, forest industry, and tribal pecially emphasized because of increased concerns on organizations and 95 percent of county organizations how exotic and native insects and diseases influence Journal of Forestry, 2020, Vol. 118, No. 3 249 forests and thus forest management. The majority of and acres harvested by silviculture systems. Because questions have been repeated across all four surveys of differences among the survey period, statistical tests to enable comparisons, including basic information on of differences were not preformed. Instead, we empha- the usage of silvicultural systems, regeneration prac- sized general trends over time, i.e., how silvicultural tices, site preparation, and TSI (Table 1). Additional practices changed in the whole state and within indi- questions related to forest health, herbivory, and chan- vidual organizations. Downloaded from https://academic.oup.com/jof/article-abstract/118/3/244/5812992 by The University of Vermont Libraries user on 28 July 2020 ging environmental conditions were included. Open- The survey also included open-ended questions. ended questions were maintained from the 2008 Responses to open-ended questions were categorized survey. In total, 22 forest management organizations based on the theme and the importance (i.e., this is our responded, a response rate of 75 percent. Additional main concern). Responses were then summarized to details on the 2017 survey and specific results can be identify issues and concepts mentioned commonly or found in Windmuller-Campione et al. (2019). indicated as particularly high priorities by respondents.

Data Analysis Although similar questions were asked in all four Results surveys, changes to the wording and structuring of Overall Forest Areas and Harvest Operations the questions occurred, mainly based on participant Over the 26 years covered by the surveys, timber- feedback. Additionally, new questions were added, or land acreage in Minnesota has increased from ap- questions were subdivided or combined. To maintain proximately 14.7 million acres in 1991 and 1996 privacy, trends have been summarized at the owner- to 15.8 million acres in 2017 (Table 2). However, ship level or across ownerships. For the same reason, during this same time, the harvested wood volume information on specific forest types was not collected, declined. Statewide estimates of harvested volume as this would have provided spatial references that across all ownerships were 2.51 million cords in 2017 could have been used to identify specific landowners. (Table 2), approximately 14 percent lower than the Statewide estimates were calculated using the ex- reported harvest volume in 2008 (2.92 million cords) pansion factor for each survey period for timberland and about 34 percent below the 3.81 million cords ownership, volume harvested, total acres harvested, reported in 1996.

Table 2. Statewide estimates by year for all forest management organizations related to overall ownership, forest-management activities, and silvicultural systems implemented. Statewide estimate*

Variable 2017 2008 1996 1991

Ownership, harvesting, and regeneration Timberland ownership (acres) 15,815,400 14,988,700 14,723,200 14,723,200 Total volume harvested (cords) 2,514,286 2,924,500 3,810,000 3,530,333 Cords harvested/acre timberland 0.15 0.20 0.25 N/A Cords harvested/acre timber sale 20.8 15.8 19.8 Harvesting operations (acres) 145,894 134,209 192,514 171,155 Average clearcut size (acres) 17 29 24 N/A Regeneration (acres) 119,564 130,257 166,380 161,400 Acres by silvicultural system and thinning (percentage of total acres in parentheses) Clearcut† 105,746 (72) 128,167 (78) 163,956 (86) 152,328 (91) Strip clearcut 40 (0) 0 (0) 454 (0) 1711 (1) Seed tree 3957 (3) 3002 (2) 2629 (1) 0 (0) Shelterwood 3041 (2) 4303 (2) 1530 (1) 0 (0) Selection (group and single-tree) 8504 (6) 7164 (4) 1981 (1) 3422 (2) Thinning (commercial) 24,606 (16) 27,044 (14) 20,555 (11) 10,270 (6)

Note: Some summary data are not available for 1991 and are noted as N/A. *Statewide estimates were calculated using the expansion factor for each survey period. †Clearcut definition can be found in supplemental material. 250 Journal of Forestry, 2020, Vol. 118, No. 3

Harvest intensity also varied over the 26-year survey these combined systems only accounted for 5 percent of period in terms of volume removed per acre, total acres the acres harvested in 2017 (Table 2; Figure 2). In add- harvested, and average size of a clearcut. The amount ition, application of these silvicultural systems varied of cords harvested per timber sale acre and total acres considerably among organizations. For example, in harvested was the lowest in the 2008 survey with 15.8 2017, the National Forest System had the highest use cords/ac and 134,209 acres, respectively (Table 2). of these systems (15 percent of acres harvested). In con- Downloaded from https://academic.oup.com/jof/article-abstract/118/3/244/5812992 by The University of Vermont Libraries user on 28 July 2020 The 2017 survey saw the highest level of cords har- trast, forest industry and Tribal governments reported vested per timber sale acre, 20.8 cords/ac, which is no acres harvested with the seed tree or shelterwood slightly greater than the 1996 estimate of 19.8 cords/ system (0 percent). All organizations except for forest ac. However, the total area harvested was greatest in industry have increased the percentage of acres treated 1996 with 192,512 acres (Table 2). The 2008 survey with thinnings across the survey periods (Figure 2). period had the largest clearcut size with an average of 29 acres; the average clearcut size had decreased to 17 Regeneration, Site Preparation, and TSI acres in the 2017 survey period (Table 2). The number of acres regenerated during a given survey period closely tracked the number of acres Regeneration Harvest Systems harvested (Table 3). Pre- and postregeneration activ- Although clearcutting was the predominant silvicul- ities, such as site preparation and TSI treatments, de- tural system in Minnesota across all survey periods, creased steadily over time. Site-preparation methods its use has declined across all organizations (Table 2; are treatments designed to improve the site for regen- Figure 2). Across all respondents, the percentage of har- eration and include prescribed burning, disking, herbi- vested acres treated with the clearcut system declined cide treatments, and other methods. For this study, from 91 percent in 1991 to 72 percent in 2017 (Table 2; TSI methods are treatments designed to increase the Figure 2). The National Forest system had the most growth or value of trees before a commercial timber drastic reduction in clearcutting during the four survey harvest and include pruning, precommercial thinning, periods from a high of 96 percent of acres harvested in and other methods. In 2017, less than 20,000 acres 1991 to 42 percent of acres in 2017 (Figure 2). were treated with site preparation or TSI methods, Although aggregate results showed a steady increase about one-half of the over 40,000 acres reported in in application of the seed tree and shelterwood systems, the 1991 survey (Table 3).

Figure 2. Percentage of acres harvested reported for each survey year by regeneration method and commercial thinning. Clearcut regeneration harvests includes clearcut with and without residuals and patch clearcuts. Selection harvests includes single-tree, group selection, and partial harvests. Commercial thinnings do not include timber stand improvement activities. Journal of Forestry, 2020, Vol. 118, No. 3 251

Table 3. Forest-management activities reported during each survey period. 2017* 2008† 1996‡ 1991‡

Regeneration 74,180 95,513 86,143 84,991 Site preparation 8689 12,632 13,950 15,206 Timber stand improvement 9525 17,782 15,107 25,428

Harvesting operations 74,180 102,380 85,786 84,991 Downloaded from https://academic.oup.com/jof/article-abstract/118/3/244/5812992 by The University of Vermont Libraries user on 28 July 2020

Note: Questions on these four aspects have been consistent over the four survey periods. *Acreage represents 66 percent of all timberland in Minnesota. †Acreage represents 64 percent of all timberland in Minnesota. ‡Acreage represents 50 percent of all timberland in Minnesota.

Forest Health and Disturbance on a subset of public lands in Minnesota and Wisconsin The 2008 and 2017 surveys included questions on between 2010 and 2014 (Russell et al. 2017). silvicultural practices related to forest health and dis- New questions about herbivory were added in turbances (Table 1). Forest organizations are using dif- 2017 (Table 1). Respondents reported using herbivory ferent silvicultural treatments to manage for 15 forest protection on 27,265 acres during 2017. Budcapping insects and diseases, four of which are exotic (Table 4). was the primary method of herbivory protection on However, overall usage of treatments for insect and 20,296 acres. Budcapping is a common tool used in disease was relatively low (less than 20 percent of the the Lake States, mostly on conifer species where the respondent organizations; Table 4). terminal bud is protected by stapling a piece of paper When treatments were used in response to forest- around it (Palik and Johnson 2007). Respondents re- health threats, the three most common were clearcutting, ported that a minimum of 897 acres were replanted the promotion of mixed species, and the use of partial for various reasons including impacts from herbivory. or complete salvage harvesting. Clearcutting was re- However, 897 acres should be seen as a minimum, ported in both 2008 and 2017 as a management tool since several respondents reported that the amount for eastern larch beetle (ELB) (Dendroctonus simplex of replanting or reasons for replanting could not be LeConte), spruce budworm (Choristoneura fumiferana easily tracked. Clemens.), shoot diseases including Diplodia pinea and Sirococcus strobilinus, eastern spruce dwarf mistletoe Qualitative Perceptions (Arceuthobium pusillum), bark beetles, and other in- In 2008 and 2017, the survey included open-ended sects and diseases (Table 4). Of those organizations questions on how silvicultural practices have changed managing for the threat of emerald ash borer (EAB) in the past 5 years (Table 1). Important themes identi- (Agrilus planipennis Fairmaire), more than 20 per- fied in 2008 were the promotion of increased structural cent of them in 2017 used clearcutting to manage ash and compositional diversity including shifting single stands. Respondents reported the promotion of mixed species stands to mixed-species stands, increasing the species to reduce the impact of seven different insects use of gaps and residual trees in both even and uneven- and diseases in both 2008 and 2017, including all four aged systems, and increasing resilience to current and of the exotic species (Table 4). Species diversity was in- future forest health threats. Additionally, respondents creasingly promoted and identified as a management noted the broadening of goals and values, suggesting tool in 2017 as compared to 2008. For example, almost that timber production may have become a lower pri- 30 percent of organizations were promoting mixed spe- ority. However, this was not the case for forest industry. cies for EAB in 2017 compared to 12 percent of organ- Instead, they reported increased scrutiny of the return izations in 2008. The use of partial or complete salvage on investment for silvicultural treatments. harvests was reported for spruce budworm, ELB, two- The same questions were asked in 2017. Several lined chestnut borer (Agrilus bilineatus Weber), and similarities remained, e.g., the increasing focus on silvi- other species in 2008 and 2017 (Table 4). The amount cultural practices to meet nontimber goals and object- of salvage operations was considerably higher in 2017 ives. In addition, many respondents noted that future (5,852 acres) than in 2008 (210 acres). Data on salvage (EAB) and current forest health threats have changed operations were not collected in 1996 or 1991, but sal- and will change their management. Many respond- vaged timber provided 10 percent of all wood volume ents also noted the focus on managing for resilience. 252 Journal of Forestry, 2020, Vol. 118, No. 3

Table 4. Percentage of forest-management organizations that have used different silvicultural practices to address the impacts and threats from native and invasive insects. 2008 2017

Percentage Percentage of of respond-

Treatment respondents using Treatment ents using Downloaded from https://academic.oup.com/jof/article-abstract/118/3/244/5812992 by The University of Vermont Libraries user on 28 July 2020

Bark beetles Slash removal 38 Slash removal 5 Thinning 15 Thinning 45 Promotion of mixed 15 Promotion of mixed 5 species species Clearcutting 15 Clearcutting 9 Partial salvage harvest 14 Cankers on aspen Clearcutting 38 Clearcutting 50 Salvage harvest 8 Partial salvage harvest 5 Promotion of mixed 9 species Dwarf mistletoe (Arceuthobium Clearcutting 23 Clearcutting 36 pusillum) Sanitation cutting 12 Partial salvage harvest 5 Salvage harvest 18 Slash removal 5 Eastern larch beetle (Dendroctonus Clearcutting 15 Clearcutting 27 simplex) Salvage harvest 8 Partial salvage harvest 32 Promotion of mixed 9 species Emerald ash borer* (Agrilus Promotion of mixed 12 Promotion of mixed 27 planipennis) species species Thinning 8 Thinning 23 Clearcutting 23 Forest tent caterpillar (Malacosoma N/A Clearcutting 9 disstria) Promotion of mixed 9 species Gypsy moth* (Lymantria dispar) Promotion of mixed 15 Promotion of mixed 5 species species Thinning 4 Thinning 5 Larch case bearer (Coleophora N/A Salvage harvest 18 laricella) Clearcutting 9 Partial salvage harvest 9 Promotion of mixed 5 species Oak wilt* (Ceratocystis fagacearum)Promotion of mixed 4 Promotion of mixed 5 species species Sanitation cutting 4 Partial salvage harvest 5 Salvage harvest 9 Thinning 9 Root and butt rot Clearcutting 8 N/A Sanitation cutting 4 Promotion of mixed 4 species Slash removal 4 Reduced rotation age 4 Journal of Forestry, 2020, Vol. 118, No. 3 253

Table 4. Continued 2008 2017

Percentage Percentage of of respond- Treatment respondents using Treatment ents using Downloaded from https://academic.oup.com/jof/article-abstract/118/3/244/5812992 by The University of Vermont Libraries user on 28 July 2020 Shoot blights (Diplodia pinea Clearcutting 19 Clearcutting 14 and Sirococcus strobilinus) Promotion of mixed 8 Promotion of mixed 9 species species Improved growing stock 9 Pruning 5 Slash removal 5 Spruce budworm (Choristoneura Thinning 12 Thinning 5 fumiferana) Clearcutting 12 Clearcutting 23 Salvage harvest 8 Partial salvage harvest 18 Promotion of mixed 9 species Two-lined chestnut borer Salvage harvest 12 Salvage harvest 14 (Agrilus bilineatus) Thinning 8 Thinning 14 Promotion of mixed 8 Promotion of mixed 5 species species Partial salvage harvest 14 White pine blister rust* Promotion of mixed 19 Promotion of mixed 14 (Cronartium ribicola) species species Sanitation cutting 19 Partial salvage harvest 14 Improved growing stock 15 Improved growing stock 18 Pruning 45 Thinning 9 Slash removal 5 White pine weevil (Pissodes strobi) Promotion of mixed 4 Promotion of mixed 14 species species Partial salvage harvest 5 Pruning 14 Thinning 9

Note: *Invasive species.

Current and future markets and the need to work unique long-term data set documenting trends in silvi- across agencies were additional concerns in 2017. cultural practices. Over the 26-year period in Minnesota, timberland increased by approximately 1.1 million acres (Table 2). Discussion Our estimates of total forested acreage (15.8 million Harvest Intensity and Harvesting Systems acres) are very similar to estimates from FIA (16 mil- The impetus for the first silvicultural practices survey lion acres) (Miles et al. 2017). In contrast, harvest was the public concern regarding harvest levels and levels peaked in 1996 (3.8 million cords) and were the sustainability of forest-management activities in lower in 2008 and 2017 (Table 2). The long-term de- Minnesota (Jaako-Pöyry 1992). The first survey fo- cline in harvest levels likely reflects the weakening and cused on gathering data on the harvest intensity and slow recovery of the housing market and reduction types of silvicultural practices used. Subsequent sur- in certain paper markets. Compared to recent trends, veys continued to collect these data and expanded the housing starts were lowest during 2009–11 with only types of questions asked to explore additional aspects 554,000 reported nationally in 2009 (Woodall et al. such as forest health, herbivory, and the direction of 2011). From 2009 to 2016, mill capacity declined with silvicultural practices (Table 1). This has resulted in a more than 175 sawmills closing in Minnesota (MN 254 Journal of Forestry, 2020, Vol. 118, No. 3

DNR 2016). The general long-term trend of reduction (Table 2; Figure 2). The increased use of other silvicul- in mill capacity is also found in other regions. For ex- tural systems and commercial thinning operations may ample, the southern United States experienced a steady be due to a combination of several factors. Managers decline in mills between 1991 and 2009 (Hodges et al. are increasingly relying on natural regeneration when 2011). applying uneven-aged and other even-aged systems The loss of mill capacity and changing forest such as seed tree or shelterwood harvests to meet eco- Downloaded from https://academic.oup.com/jof/article-abstract/118/3/244/5812992 by The University of Vermont Libraries user on 28 July 2020 product markets are also two likely factors influencing logical and economic requirements (Palik and Zasada harvest intensity and the average harvest size. 2003). For example, eastern white pine has been a dif- Harvest intensity fluctuated over time, whereas the ficult species to regenerate in Minnesota and across the average clearcut size continued to decrease (Table 2). Lake States. The use of a shelterwood system on certain As mill capacity and mill requirements continue to sites can decrease costs by relying on natural regener- change, forest managers are becoming increasingly ation of eastern white pine instead of artificial regen- creative in “lumping” multiple stands into a single eration while concurrently meeting ecological goals sale to meet forest management goals. This can result (Krueger et al. 2007). Managers are exploring regener- in more smaller stands that produce higher volumes. ation systems other than clearcutting also in northern This would explain the smaller average clearcut size hardwood and oak (Quercus spp.) stands. In these but higher average volume harvested in 2017 than stands, uneven-aged systems and shelterwood systems in 2008. may, respectively, better fit those species’ silvics and at Just as the average clearcut size has decreased during the same time may accomplish other goals such as in- the survey period, the proportion of acres harvested creased species diversity (Bolton and D’Amato 2011). using the clearcut silvicultural system continued to de- Additionally, changes in harvest technology including cline from 91 percent of acres harvested in 1991 to 72 the more frequent use of cut-to-length systems pro- percent of acres harvest in 2017 (Table 2; Figure 2). vide more flexibility in applying regeneration methods. The steepest decline was within the National Forest For example, such use may allow for more partial System, with only 42 percent of acres harvested using harvesting, as damage to residual overstory trees is lower clearcutting in 2017. The steep decline on the National with the new harvesting technologies, even in uneven- Forest lands may be partially due to changes in termin- aged stands (Huyler and LeDoux 1999). Finally, there ology within the Forest Service. For example, “clearcut is an increased focus on silvicultural practices aimed to with residuals” appeared to be a general catchphrase for promote stand resilience, complexity, and heterogen- partial harvesting operations in the 1990s. Accordingly, eity, all widely viewed as important attributes to main- in the 2017 survey, the definition of clearcutting was tain forest health and resilience under changing climate updated to include “… clearcut stands may include re- conditions (D’Amato et al. 2010, D’Amato et al. 2011, serve or residual trees.” In contrast, the definition of Silver et al. 2013, Nagel et al. 2017). In addition, re- a clearcut used in previous survey did not include residual trees and uneven-aged systems can provide in- siduals (Supplemental Material). The definition used in creased structural and age class diversity important to the 2017 survey reflects current management practices selected wildlife species and other ecosystem services outlined in the Timber Harvest and Forest Management (Grinde et al. 2017). An increased emphasis on these Guidelines on leave tree retention and implementa- aspects by various landowners may also be responsible tion of clearcutting in Minnesota (Minnesota Forest for the trends in silvicultural systems. Resource Council 2013). The change in the definition The reduction in the total clearcut acreage and of clearcutting in Minnesota is just one example of the average clearcut size will result in changing vege- challenges in regard to silviculture terminology. These tation dynamics. If both trends continue, the most challenges will likely persist because of regional dif- common forest type (aspen) may transition through ferences, educational backgrounds of forestry profes- succession and stand dynamics to mixed-wood for- sional, landowners, forest workers, and the public, as ests containing aspen, spruce, balsam fir, and other well as because of the broadening of goals and values shade-tolerant hardwoods (Frelich 2002). Such in silviculture. changes will have implications for the future wood Organizations other than the Forest Service had a supply, but also for wildlife species, with posi- less dramatic decline in the clearcut systems. However, tive or negative changes depending on the species all organizations have seen an increase in uneven-aged (Frelich et al. 2012). Large-scale disturbances, such management and commercial thinning operations as clearcuts, are critical for bird species like ruffed Journal of Forestry, 2020, Vol. 118, No. 3 255 grouse (Bonasa umbellus Linnaeus) (Svoboda and Although organizations see value and invest in Gullion 1972) and neotropical migrants (Schulte herbivory protection methods, there has been a and Nieme 1998) that require early successional long-term reduction in application of site preparation habitat. For example, a large clearcut with residuals and TSI treatments (Table 3). This low level of invest- (640 acres) in northern Minnesota resulted in an in- ment is in part possible because one of the dominant creased number of disturbance-dependent bird spe- tree species (aspen) of the region regenerates through Downloaded from https://academic.oup.com/jof/article-abstract/118/3/244/5812992 by The University of Vermont Libraries user on 28 July 2020 cies, including the golden-winged warbler (Vermivora sexual and asexual methods after a clearcut or coppice chrysoptera Linnaeus) compared to preharvest con- harvest without the need for additional site prepar- ditions (Myers 2016). Additionally, variation in ation or TSI. Aspen is generally sold as a pulp spe- the size of clearcuts has important implications for cies on relatively short rotations (40–60 years). The small and large mammal species, including snow- decreasing investment in site preparation and TSI shoe hares (Lepus americanus) and moose (Alces may also reflect shifts in forest-management prac- acles Linnaeus) (Peek et al. 1976, Timmermann tices occurring nationally and globally during the last and McNicol 1988). In this context, several forest- three decades. Such trends are at least partially driven management strategies are currently being explored by ownership patterns, including ownerships having by the Minnesota Moose Habitat Collaborative to shifted from industrial private forest ownerships to improve moose habitat through harvesting (clearcut real estate investment trusts (REITs) or timber invest- and/or coppice) to create early successional habitat. ment management organizations (TIMOs) (Fernholz In addition, artificial regeneration of conifer species et al. 2007, Gunnoe et al. 2018). In 1994, the 10 lar- may be necessary for winter cover for these species gest private timberland owners were vertically inte- (www.nature.org). grated industrial private forests. By 2006, only two of these industrial private timberland owners remained Regeneration, Site Preparation, and TSI in the top 10; the other eight ownerships were TIMOs Regeneration by natural and/or artificial means is a or REITs (Bliss et al. 2010). Such shifts in Minnesota key aspect of any silvicultural system (Nyland 2016). forest ownership include, for example, Boise Cascade In Minnesota, there is nearly a one-to-one match be- (private industry) becoming Molpus, a TIMO, and tween the number of acres harvested and the number Potlatch being reorganized as an REIT. In contrast, of acres regenerated, naturally or artificially, in each Blandin Paper Company (now owned by UPM- survey period. Regenerated acres may be slightly Kymmene) divested its lands from its mill. UPM- higher or lower than harvested acres during a survey Kymmene then sold a conservation easement of its period for several reasons such as the use of supple- lands to the state of Minnesota, ensuring that the land mental or enrichment planting, planting occurring will still be managed by UPM-Kymmene to continue over more than 1 year after harvest because of various as a working forest that is open to the public (Hibbard site preparation methods, the inclusion of com- et al. 2011). The local, regional, and international mercial thinning where regeneration is not the goal shift in private forest industry lands to TIMOs and in total harvested acres, or the need for replanting REITs have changed the focus away from managing after regeneration failure occurs. Replanting may be forests with a direct focus on supplying specific mills necessary for several reasons, including herbivory, and managing for the future stand of a vertically inte- competition by other vegetation, drought, planting grated company. Instead, these new owners prioritize stock quality, or planting crew performance that short-term economic return or the highest and best leads to failure in initial plantings (Sauerman 1992, use of the real estate. This results in increased scru- Krueger and Puettmann 2004, Palik et al. 2007, and tiny of the economic efficiency of forest-management many others). All these factors may contribute to the activities and infrastructure investments. In many need for replanting, but herbivory impact on regen- cases, this has resulted in a concomitant decrease in eration is a common factor in regeneration failures investment in early, noncommercial stand treatments in various regions (Russell et al. 2001, Rooney et al. (D’Amato et al. 2018a). 2003, Patton et al. 2018), which necessitates investment in protective and expensive measures such as Disturbances and Forest Health budcapping. For example, over 25,000 acres of regen- Forest managers are increasingly concerned about the eration protection by budcapping was carried out in impacts and threats of native and exotic insects and Minnesota in 2017. diseases (Puettmann 2014), and accordingly they are 256 Journal of Forestry, 2020, Vol. 118, No. 3 applying multiple types of silvicultural practices to ad- Conclusions dress these concerns in Minnesota. In response to the Long-term data about silviculture practices in open-ended questions on how silvicultural practices Minnesota reflect how the forestry sector has re- will change in the future, numerous forest managers sponded to a variety of ecological, economic, and soci- noted that the arrival of EAB will change their man- etal issues. Although the data collected on silvicultural agement practices in 2017. Such concerns were not

practices are from a single state, they reflect similar Downloaded from https://academic.oup.com/jof/article-abstract/118/3/244/5812992 by The University of Vermont Libraries user on 28 July 2020 considered during the first survey in 1991. trends that have been observed nationally and inter- EAB has already killed more than 10 million ash nationally (Woodall et al. 2011, D’Amato et al. 2018b). (Fraxinus spp.) since it was first identified in the mid- Although the exact drivers of the shifts in the silvi- 1990s in Detroit, Michigan (Kovacs et al. 2011). There cultural systems used in Minnesota cannot be assessed are estimated to be another 218 million ash trees with this survey, we can hypothesize that the decreasing greater than 5 in. in Minnesota, with the vast majority acreage in the clearcut system and increasing use of in the black ash forest type (Hillard 2018). Prior to uneven-aged systems are likely due to multiple fac- EAB, black ash forests were understudied and had tors, such as native and invasive forest health issues, limited active management because of access limita- forest-product supply and demand, and organizations (winter only harvests in wet areas) and limited tional structure and ownership. As managers promote markets (Erdman et al. 1987). However, in the past mixed-species stands for economic and ecological re- 10 years, there has been an increase in research and siliency to multiple threats, silvicultural practices will management efforts to regenerate black ash stands continue to change, and new threats in the future may to increase species diversity prior to EAB infestation push silvicultural practices in different directions. (D’Amato et al. 2018b). In 2017, managers applied Foresters and natural-resource managers will need to clearcut harvesting, thinning, and/or the promotion be increasingly flexible (Puettmann 2014, Shifley et al. of mixed-species stands, including nonhost species 2014, Shifley et al. 2016). This flexibility will require through artificial and natural regeneration (Table 4) to forest-management agencies to consider diversity: di- manage ash threatened by EAB. versity of age classes, diversity of species mixtures, Although EAB is one of the most prominent and a diversity of management approaches to buffer threats to forest managers in Minnesota, the im- against the impacts of climate change, invasive spe- pact of native and exotic species, especially insects cies, market variability, and many other factors. No and diseases, on forest management continues to one stand will be resistant or resilient to every threat, drive management decisions regionally, nation- provide habitat for every wildlife species, or produce ally, and internationally (Hulme 2009, Shifley et al. every forest product. However, when individual stands 2014, Ramsfield et al. 2016). Mountain pine beetle are compiled at a landscape scale and across owner- (Dendroctonus ponderosae Hopkins.) and spruce ships, a diversity of species mixtures, age classes, and beetle (Dendroctonus rufipennis Kirby), both na- management approaches will increase the potential for tive to western North America, have been at epi- ecological and economic resiliency to future changes. demic levels for over a decade (Negrón and Fettig 2014). Both beetle epidemics have been fueled by a combination of factors including changing climatic Supplementary Materials conditions, and forest composition and structure. Supplementary data are available at Journal of Forestry Mountain pine beetle is also expanding to higher online. elevations that traditionally have not been managed (Logan and Powell 2001) and to more eastern re- Acknowledgments gions, impacting jack pine and lodgepole-jack pine Funding for this research was provided by the Interagency hybrids (Cullingham et al. 2011). All four pine spe- Information Cooperative, University of Minnesota Department cies in Minnesota and the Lake States are suitable of Forest Resources, the University of Minnesota Extension, hosts (Rosenburger et al. 2017). In the Great Lakes, and the Minnesota Agricultural Experiment Station under the structure and composition of pine forests were projects MIN-42-063 and MIN-42-068. The authors wish rated as being of moderate to high susceptibility to thank the numerous agency personnel from county, fed- (Windmuller-Campione 2018). eral, industry, tribal, non-profit, and state organizations that Journal of Forestry, 2020, Vol. 118, No. 3 257 provided initial feedback on early drafts of the survey, as well Erdmann, G.G., T.R. Crow, M. Ralph Jr., and C.D. Wilson. as the time and effort that went into completing the survey. 1987. Managing black ash in the Lake States. USDA Forest Service Gen. Tech. Rep. NC-115, North Central Forest Experiment Station, St. Paul, MN. 115 p. Literature Cited Fernholz, K., J. Bowyer, and J. Howe. 2007. TIMOS & Ashton, M.S., and M.J. Kelty. 2018. The practice of silvicul- REITS: What, why, & how they might impact sustain-

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