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Forest Resources & Practices


Region II-III Reforestation Review

Annotated Bibliography

Auguat 30, 2016
Contents 
Introduction 2
Section 1 – General background 5
Section 2 - Silvics 9
Section 3 - Reforestation methods, results, and stocking standards 39
Section 4 - Site preparation, competition control, and soils 72
Section 5 - Fire and regeneration 93
Section 6 – Wildlife-reforestation interactions and adaptive

Management 122


Section 7 - Insects and disease effects on reforestation 187
Section 8 - Non-native and invasive species 213

Section 9 - Climate change and assisted migration 237


Section 10 - Reforestation modeling 280
Section 11 - Regeneration assessment and technology 286
Index 288

Introduction


The Region II and III Forest Practices Reforestation Science and Technical Committee Literature Review and Annotated Bibliography compile documents relevant to reforestation of commercial timber harvest areas in the boreal and transitional forests of southcentral and interior Alaska (see Fig. 1).

Figure 1. Map of Alaska Forest Resources and Practices Act regions.

Region II covers the boreal and transitional forests of south-central Alaska; Region III covers the boreal forests of interior Alaska.

The Alaska Forest Resources and Practices Act (FRPA, AS 41.17) governs commercial forestry operations on state, municipal, and private land. The Act is designed to protect fish habitat and water quality and ensure adequate reforestation while establishing management standards that are workable for landowners and operators. The current FRPA regulations in 11 AAC 95.375-.390 set standards for reforestation and site preparation statewide.


In 2014, the Department of Natural Resources Division of Forestry and Department of Fish and Game Habitat Division, under the aegis of the Alaska Board of Forestry, began a review of the reforestation standards for Regions II and III. The departments convened an interdisciplinary committee to do the science and technical review. The committee included scientists and experienced resource managers with extensive knowledge about forest and wildlife management, forest ecology and silviculture, fire science, entomology, and climate change. This group, the Region II and III Reforestation Science & Technical Committee (S&TC) was charged with compiling and synthesizing the best available information regarding reforestation in these regions, reviewing the existing standards, and where needed, recommending changes to the standards to the Alaska Board of Forestry.
The Committee compiled information for the following categories:

  • General background

  • Silvics

  • Reforestation methods, results, and stocking standards

  • Site preparation, competition control, and soils

  • Fire and regeneration

  • Wildlife-reforestation interactions
  • Insects and disease effects on reforestation


  • Non-native and invasive species

  • Climate change and assisted migration

  • Reforestation modeling

  • Regeneration assessment and technology

References for publications relevant to conditions in Region II and III were collected and cited, and an introduction compiled for each section. The bibliography and introductions were submitted to the full committee for review and editing. This document compiles the eleven review topics.


The following people contributed to the compilation and/or synthesis of this information:

  • Valerie Barber, University of Alaska Fairbanks, School of Natural Resources & Extension

  • Elizabeth Bella, US Fish and Wildlife Service, Kenai National Wildlife Refuge

  • Scott Brainerd, Alaska Department of Fish and Game, Division of Wildlife Conservation

  • Roger Burnside, Alaska Department of Natural Resources, Division of Forestry, retired

  • Jeremy Douse, Tanana Chiefs Conference, Forestry Program

  • Jim Durst, Alaska Department of Fish and Game, Division of Habitat

  • Marty Freeman, Alaska Department of Natural Resources, Division of Forestry

  • Nancy Fresco, University of Alaska Fairbanks, Scenarios Network for Alaska and Arctic Planning

  • Julie Hagelin, Alaska Department of Fish and Game, Division of Wildlife Conservation

  • Doug Hanson, Alaska Department of Natural Resources, Division of Forestry

  • Teresa Hollingsworth, US Forest Service, Boreal Ecology Cooperative Research Unit/University of Alaska Fairbanks

  • Jill Johnstone, University of Saskatchewan, Department of Biology
  • Glenn Juday, University of Alaska Fairbanks, School of Natural Resources & Extension


  • Susan Klein, Alaska Resources Library and Information Services

  • Nick Lisuzzo, US Forest Service, State & Private Forestry

  • Mitch Michaud, Natural Resources Conservation Service, Alaska Office

  • Stephen Nickel, Alaska Department of Natural Resources, Division of Forestry

  • Tom Paragi, Alaska Department of Fish and Game, Division of Wildlife Conservation

  • Will Putman, Tanana Chiefs Conference, Forestry Program

  • Amanda Robertson, US Fish & Wildlife Service, Northwest Boreal Landscape Conservation Cooperative

  • Celia Rozen, Alaska Resources Library and Information Services

  • Michael Shephard, US Department of the Interior, National Park Service

  • Rob DeVelice, US Forest Service, Chugach National Forest

  • John Winters, Alaska Department of Natural Resources, Division of Forestry

  • Trish Wurtz, US Forest Service, State & Private Forestry

  • John Yarie, University of Alaska Fairbanks, School of Natural Resources & Extension

  • Brian Young, Landmark College

Questions about this document may be directed to Marty Freeman, DNR Division of Forestry, 555 W 7th Avenue, Anchorage, AK 99501 (907-269-8467) or Jim Durst, ADF&G Habitat Division, 1300 College Road, Fairbanks, AK 99701 (907-459-7254).


Section 1

GENERAL BACKGROUND


Summary

Marty Freeman, Alaska Department of Natural Resources, Division of Forestry

This section includes references that provide general background on the forest resources present in southcentral Alaska (Barrett and Christensen, 2011) and planting history in Alaska (Graham and Joyner, 2011). Magoun and Dean (2000) is an extensive literature review focused on Interior Alaska floodplain forest dynamics. Ott (2005) lists ongoing forest research activity, including reforestation research in Alaska, and Puettmann and Ammer (2007) provide an overview of regeneration research trends in North American and Europe. Kneeshaw et al. (2000) discusses indicators of forest sustainability, include forest productivity from regeneration. Walters and Holling (1990) review methods to develop, screen, and evaluate forest management alternatives. Kerr (1999) emphasizes the importance of considering economic factors in determining reforestation standards.


References
Barrett, T. M. and G.A. Christensen, eds. 2011. Forests of southeast and south-central Alaska, 2004–2008: five-year forest inventory and analysis report. Gen. Tech. Rep. PNW-GTR-835. Portland, OR: U.S. Department of Agriculture, Forest Service, Pacific Northwest Research Station. 156 p.
Author abstract. This report highlights key findings from the most recent (2004–2008) data collected by the Forest Inventory and Analysis program across all ownerships in southeast and south-central Alaska. We present basic resource information such as forest area, ownership, volume, biomass, carbon sequestration, growth, and mortality; structure, and function topics such as vegetation and lichen diversity and forest age distribution; disturbance topics such as insects and diseases, yellow-cedar decline, fire, and invasive plants; and information about the forest products industry in Alaska, the potential of young growth for timber supply, biofuels, and nontimber forest products. The appendixes describe inventory methods and design in detail and provide summary tables of data and statistical error for the forest characteristics sampled.
Graham, J.S., and P.A. Joyner. 2011. Tree planting in Alaska. Tree Planters Notes. 54(2):4-11

Author abstract. Tree planting for reforestation in Alaska has been modest compared with other timber-producing States and has never exceeded 1 million trees a year. Most timber harvest occurs in southeast Alaska, where natural regeneration is usually prolific and logistical costs are very high. Tree planting has been more suited to the boreal forest, where white spruce (Picea glauca (Moench) Voss) regeneration is sought and natural regeneration can be problematic. In the 1990s, a large spruce bark beetle (Dendroctonus rufipennis Kirby) epidemic on the Kenai Peninsula stimulated tree planting. Planting for poplars (Populus spp.) may develop near rural communities as biomass energy develops. Tree planting by homeowners and communities has been growing, which has resulted in the development of several community tree inventory programs and management plans. In 2010, approximately 1,600 trees were planted on municipal property or in public rights-of-way in Anchorage, and a much higher number is estimated to have been planted on private and other public land.

Kerr. C.L. 1999. Levels of growing stock and economic returns. Pp. 19-21 in: Proc. of the Alaska Reforestation Council April 29, 1999 Workshop. Anchorage, AK. Univ. of Alaska Fairbanks Agric. & For. Exp. Sta. Misc. Publ. 99-8. 85 pp.
Author abstract. Current biological and social conditions on the Kenai Peninsula are putting significant negative economic pressure on private landowners. Biological and social (legal) conditions are driving most of the reforestation activity on private lands, but those who write regulations must also understand economic conditions. A guiding premise for the Alaska Forest Practice Act (FPA) is that economic criteria must be considered on at least an equal basis with other FPA concerns. This discussion provides preliminary information about the economic concerns of forest management in south-central Alaska.
Kneeshaw, D.D., Leduc, A., Drapeau, P., Gauthier, S., Pare, D., Carignan, R., Doucet, R., Bouthillier, L., Messier, C., 2000. Development of integrated ecological standards of sustainable forest management at an operational scale. For. Chron. 76, 481-493.

Author abstract. Within Canada, and internationally, an increasing demand that forests be managed to maintain all resources has led to the development of criteria and indicators of sustainable forest management. There is, however, a lack of understanding, at an operational scale, how to evaluate and compare forest management activities to ensure the sustainability of all resources. For example, nationally, many of the existing indicators are too broad to be used directly at a local scale of forest management; provincially, regulations are often too prescriptive and rigid to allow for adaptive management; and forest certification programs, often based largely on public or stakeholder opinion instead of scientific understanding, may be too local in nature to permit a comparison of operations across a biome. At an operational scale indicators must be relevant to forest activities and ecologically integrated. In order to aid decision-makers in the adaptive management necessary for sustainable forest management, two types of indicators are identified: those that are prescriptive to aid in planning forest management and those that are evaluative to be used in monitoring and suggesting improvements. An integrated approach to developing standards based on an ecosystem management paradigm is outlined for the boreal forest where the variability inherent in natural systems is used to define the limits within which forest management is ecologically sustainable. Sustainability thresholds are thus defined by ecosystem response after natural disturbances. For this exercise, standards are proposed for biodiversity, forest productivity via regeneration, soil conservation and aquatic resources. For each of these standards, planning indicators are developed for managing forest conditions while forest values are evaluated by environmental indicators, thus leading to a continuous cycle of improvement. Approaches to developing critical thresholds and corresponding prescriptions are also outlined. In all cases, the scale of evaluation is clearly related to the landscape (or FMU) level while the stand level is used for measurement purposes. In this view the forest should be managed as a whole even though forest interventions are usually undertaken at the stand level.

Magoun, A.J., and F.C. Dean. 2000. Floodplain forests along the Tanana River, interior Alaska: Terrestrial ecosystem dynamics and management considerations. Miscellaneous Publication 2000-3, Agricultural and Forestry Experiment Station, University of Alaska, Fairbanks. 139 p. [H]
Compiler abstract. This extensive and detailed literature review introduces the geomorphology and vegetation of the floodplain before characterizing forest succession, decomposition, wildlife ecology and habitat use, timber harvesting, and research needs. Although it focused on floodplain white spruce because these high volume stands were of interest during international export markets in the 1990s, the review includes substantial information on upland forest structure and processes for comparison and contrast. It serves as an excellent reference through 1999 on vegetation and wildlife.
Ott, R.A. 2005a. Summaries of management and research activities related to Alaska’s boreal forests. 2nd ed. Alaska Northern Forest Cooperative. Unpublished. 119 pp.
Compiler abstract. This document compiles summaries of published and unpublished management and research activities including information in the following categories:


  • Climate variability and forests

  • Fire management

  • Forest community classification,

  • Forest health,

  • Forest inventory

  • Site index

  • Tree regeneration

  • Tree thinning

  • Tree volume equations

  • Wildlife

Puettmann, K.J., and C. Ammer, 2007. Trends in North American and European regeneration research under the ecosystem management paradigm. Eur. J. For. Res. 126, 1-9.

Author abstract. Forest management on many ownerships in North America and Europe has shifted toward the ecosystem management paradigm. The associated shift toward multiple management objectives and focus on natural development patterns should also be reflected in regeneration research efforts. As new information needs arise, research questions and approaches should be evaluated whether they are still appropriate. Specifically, spatial and temporal scales of research studies need to be expanded to accommodate complex sets of management objectives and constraints, rather than being focused on optimal tree regeneration. At the same time, silviculturists are asked to utilize natural trends as a guide for management, but most natural disturbance studies have focused on stand structures and not the regeneration processes. Criteria commonly used to describe disturbance regimes need to be modified to better guide regeneration research efforts under the ecosystem management paradigm.
Walters, C.J. and C.S. Holling. 1990. Large-scale management experiments and learning by doing. Ecology 71:2060-2068.
Author abstract. Even unmanaged ecosystems are characterized by combinations of stability and instability and by unexpected shifts in behavior from both internal and external causes. That is even more true for ecosystems managed for the production of food or fiber. Data are sparse, knowledge of processes limited, and the act of management changes the system being managed. Surprise and change is inevitable. Here we review methods to develop, screen, and evaluate alternatives in a process where management itself becomes partner with the science by designing probes that produce updated understanding as well as economic product.

Section 2



SILVICS

Summary


John Yarie, School of Natural Resources & Extension, University of Alaska Fairbanks

Glenn Juday, School of Natural Resources & Extension, University of Alaska Fairbanks
The term “silvics” has been defined as “the study of the life history and general characteristics of forest trees and stands with particular reference to environmental factors, as a basis for the practice of silviculture” (SAF 1998).
Fox (1999) suggested that the general public will start to see a more realistic view of the sustainability of forest values. This will be enhanced by the increased demand for fuel wood now and in the future. Tree reproduction will start to become a much more important issue followed by the natural growth rates that will occur in the future tied to climate change dynamics. All of these factors will be closely tied to the “silvics” of the species that are currently present on the landscape and the potential exotic species that might be established in the future all tied to climate change dynamics.

Seedling establishment and regeneration. Environmental factors that influence natural regeneration are seed production, dispersal, germination and seedling establishment basically for all boreal species but differences in these processes can dictate the species composition of the new forest — pure spruce to pure hardwoods to various levels of mixed-wood stands. Regeneration following disturbance tied to the changing climate will be a key factor to control vegetation dynamics across the boreal forest. The regeneration dynamics will depend on the type and severity of the disturbance. Bare mineral soil is considered to be the best substrate for seed regeneration of the species currently present in interior Alaska. However insect and disease mortality results in very little disturbance to the forest floor and seed regeneration has drastically lower potential compared to stump and root sprouting by both birch and aspen, respectively.

Seed availability is an important factor tied to regeneration dynamics. Most of the interior Alaska species show variability in the time of good seed crops. Birch has shown good seed production with high viability about every other year, aspen about every 4 to 5 years, white spruce every 6 to 10 years. High levels of black spruce seed production occur about every 4 to 8 years, but due to the serotinous cones high quantities of viable seed may be present in the tree crowns. Black spruce cone production usually starts about year 30 but seed quality is relatively low till about age 50. This suggests that you need approximately a 50-year fire return interval for black spruce ecosystems to suggest a return of black spruce to the same site.
Black spruce cone production did not decrease over a latitudinal gradient but seeds/cone, percentage of filled seeds and germination percentage did decrease in a northward trend. Black spruce seed production was found to be limited close to tree line by climate characteristics and the possibility of a poor seedbed (lack of frequent fire). It was also reported that there was an inconsistency in seed production cycles across the landscape at distances greater than three kilometers.

Succession. Ecosystem structural dynamics can be very different dependent upon the disturbance dynamics that have taken place. An ecosystem affected by fire will be structurally different than an ecosystem affected by insects or disease. In both cases two types of successional pathways are possible. One, canopy-dominant tree species replace themselves resulting in a relatively unchanging forest. This pattern can be termed as self-replacement. A different pathway called species-dominance relay involves simultaneous post-fire establishment of multiple tree species followed by canopy dominance shifts controlled by the autecology of the species present. It has been suggested that as climate change occurs species-dominance relay will decrease. Based on successional studies it has been suggested that fire should be used for site preparation of white spruce ecosystems if a self-replacement sequence is desired for a fast return to a white spruce ecosystem

In a study dealing with climate change dynamics and tree line advance (Wilmking 2003) it was suggested that this process will not be straight forward. Tree line advance will be dependent on the elevation and latitude of the current tree line and the spring weather events under climate change
Growth and forest ecosystem management. It has been suggested that as a result of climate change spruce growth will decline in eastern interior Alaska and increase in western interior Alaska. These differences are suggested as a result of potential precipitation differences that could occur in the future. If a species dominance pathway is present, then species competition will play a large role in ecosystem dynamics. It has been found that overtopping or shading significantly decreased growth of white spruce seedlings. Mortality was not indicated as increasing but slower growth was present. Looking at the light requirements of white spruce it was found that approximately 40% of full sunlight was required to maximize the growth of understory white spruce. Levels above did not show an increase in growth. However the competition canopy structure may play a major role in determine the amount of sunlight that is reaching the understory. Height growth in an aspen understory for white spruce was equal to what was found in open grown clearcut areas in west-central Alberta.

Management of white spruce ecosystems can range from an even-aged structure to an uneven-aged structure depending on the overall goals of the landowner. This can be tied to the objectives of the land owner and their potential vision for combining stand-level and landscape-level management. Stand level management and landscape level management can lead to different overall landscape structure. At the stand level, managers may concentrate on the even-aged management direction while at the landscape perspective more variability in ecosystem structure may bring in a larger number of uneven-aged stands.

Uneven-aged stands may result in low ingrowth (regeneration) of spruce in the existing stand (P. abies in Sweden) after harvesting, but overall tree mortality in the stand may also be low so there is sufficient survival to maintain the overall uneven-aged stand structure.
Regeneration management in interior Alaska was thought to require planting seedlings within 10 years of cutting. However recent studies have suggested that natural regeneration overwhelmed the density of planted seedlings. The one major difference was the distribution of trees across the area. In the planting procedure seedlings were equally spaced across the entire cutover area while using natural regeneration the seedling distribution was somewhat clumped.
Finally the presence of old-growth forest ecosystems across the landscape may be a key component for maintenance of biodiversity at the landscape level. The old-growth stage is characterized by small-scale disturbances that engender gap dynamics. This could lead to uneven-aged stands and an increase in landscape biodiversity. Major disturbances will cause an elimination of old-growth in various areas but in interior Alaska are a natural part of the landscape ecosystem dynamics.

REFERENCES
Adams, P.C. 1999. The dynamics of white spruce populations on a boreal river floodplain. Unpubl. PhD Thesis, Duke University. 178 pp.

Author abstract. Studies of forest development on river floodplains in interior Alaska have asserted that succession is linear and directional. Beginning with the invasion of willows on newly formed silt bars, subsequent fluvial depositional builds terraces of increasing height and distance from the river on which successive communities of alder, balsam poplar, white spruce, and eventually black spruce develop. This classical model assumes that primary succession is a deterministic autogenic process in which early successional species facilitate the establishment of late successional species through environmental modification. I focused on the dynamics of white spruce establishment and growth in this successional environment. My primary objective was to describe boreal floodplain white spruce forests and the major environmental and biotic constraints on their development. I examined factors affecting the age, growth and spatial structure of white spruce populations across successional sere. Ecosystem processes on the Tanana River floodplain are closely linked to fluvial processes, and these in turn are directed by climate. Patterns of deposition and erosion resulting in the building and removal of successional terraces are functions of the climate controlled river discharge fluctuations, and are neither continuous nor directional. White spruce occurs as seedlings, saplings, and seed-producing trees throughout the primary successional sequence, and its age structure reflects past variation in recruitment and mortality rates. Successful seedling establishment is episodic and correlated with a combination of interacting environmental and biotic factors, including silt deposition accompanying floods, seed production and dispersal, and herbivory of seedlings by snowshoe hares. Both herbivory and low light under canopies reduce seedling height growth. The relative influence of some of these factors changes through succession because of interactions with the developing vegetation. Radial growth patterns of mature floodplain white spruce trees differ from those of nearby upland trees in their reduced sensitivity to climate variability because of the high water table on the floodplain. Although elements of the classic facilitation model of succession are consistent with some of my results, much of the spatial and temporal variability in patterns of white spruce establishment and growth can be attributed to episodic environmental and biotic factors throughout the succession.
Brassard, B.W., Chen, H.Y.H. 2006. Stand structural dynamics of North American boreal forests. Crit. Rev. Plant Sci. 25, 115-137.
Author abstract. Stand structure, the arrangement and interrelationships of live and dead trees, has been linked to forest regeneration, nutrient cycling, wildlife habitat, and climate regulation. The objective of this review was to synthesize literature on stand structural dynamics of North American boreal forests, addressing both live tree and coarse woody debris (CWD) characteristics under different disturbance mechanisms (fire, clearcut, wind, and spruce budworm), while identifying regional differences based on climate and surficial deposit variability. In fire origin stands, both live tree and CWD attributes are influenced initially largely by the characteristics of the stand replacing fire and later increasingly by autogenic processes. Differences in stand structure have also been observed between various stand cover types. Blowdown and insect outbreaks are two significant non-stand replacing disturbances that can alter forest stand structure through removing canopy trees, freeing up available growing space, and creating microsites for new trees to establish. Climate and surficial deposits are highly variable in the boreal forest due to its extensive geographic range, influencing stand and landscape structure by affecting tree colonization, stand composition, successional trajectories, CWD dynamics, and disturbance regimes including regional fire cycles. Further, predicted climate change scenarios are likely to cause regional-specific alterations in stand and landscape structure, with the implications on ecosystem components including wildlife, biodiversity, and carbon balance still unclear. Some stand structural attributes are found to be similar between clearcut and fire origin stands, but others appear to be quite different. Future research shall focus on examining structural variability under both disturbance regimes and management alternatives emulating both stand replacing and nonstand replacing natural disturbances.
Brown, K. R., D.B. Zobel, and J.C. Zasada. 1988. Seed dispersal, seedling emergence, and early survival of Larix laricina (DuRoi) K. Koch in the Tanana Valley, Alaska. Canadian Journal of Forest Research 1988, v. 18, no. 2 (Mar. 1988) pp. 306-314.

Author abstract. The seasonal and spatial patterns of seed release, germling emergence, and early survival of Larix laricina (DuRoi) K. Koch were studied in 1980–1981 near Fairbanks, Alaska. Dispersal was studied on one wetland site. Seedling emergence and 1-year survival were studied on three wetland microsite types (troughs, feathermoss, and tussock tops, located at increasing elevations above permafrost) and in mineral soil and undisturbed feathermoss seedbeds in a mature Picea glauca stand of alluvial origin. Approximately 95% of the viable Larix seed from the 1980 cone crop fell by November 1980. Spatial distribution of seed away from the stand was erratic because of variable winds and the presence of a single Larix away from the stand edge. Average dispersal distances were less than those reported for other coniferous species. Emergence and early survival in both site types were affected by seedbed type. In the alluvial stand, germination and 1-year survival were greater on mineral seedbeds than on feathermoss. Emergence began in mid-July, well after minimum temperatures required for germination had been reached; timing appeared to be related to differences in volumetric moisture contents of the two seedbed types. Although cumulative totals of emergence and mortality did not differ between microsite types in the wetland, seasonal patterns of each differed with microsite. Emergence in troughs was delayed until early July by cold seedbed temperatures; increased precipitation in mid to late July raised the water table and flooded newly emerged seedlings in trough microsites but moistened feathermoss sufficiently to promote germination. Variation in emergence and mortality was high within a given microsite type.

Burns, R.M. and B.H. Honkala, tech. coordinators. 1990. Silvics of North America: v.1. Conifers; v.2. Hardwoods. U.S. Forest Service, Washington, DC. Agric. Handbook 654. 877 p.



Author abstract. The silvical characteristics of about 200 forest tree species and varieties are described. Most are native to the 50 United States and Puerto Rico, but a few are introduced and naturalized. Information on habitat, life history, and genetics is given for 15 genera, 63 species, and 20 varieties of conifers and for 58 genera, 128 species, and 6 varieties of hardwoods. These represent most of the commercially important trees of the United States and Canada and some of those from Mexico and the Caribbean Islands, making this a reference for virtually all of North America. A special feature of this edition is the inclusion of 19 tropical and subtropical species. These additions are native and introduced trees of the southern border of the United States from Florida to Texas and California, and also from Hawaii and Puerto Rico.
Chrimes, D., 2004. Stand development and regeneration dynamics of managed uneven-aged Picea abies forests in boreal Sweden, Doctor’s Dissertation. Swedish University of Agricultural Sciences, Department of Silviculture. Umeå Sweden.

Author abstract. Volume increment and ingrowth are important aspects of stand development and regeneration dynamics for determining the effectiveness of uneven-aged silvicultural systems. The main objectives of this thesis were to establish the influence of standing volume on volume increment after different kinds of harvest regimes, the influence of overstorey density on height growth of advance regeneration, and the influence of bilberry (Vaccinium myrtillus L.) on spruce regeneration in managed uneven-aged Norway spruce (Picea abies (L.) Karst.) forests in boreal Sweden. Model simulations with 5-year growth iterations and three harvest regimes of diameter-limit, single-tree selection, and schematic harvests were used to investigate the influence of standing volume on volume increment. Additionally, field experiments at two sites, re-inventoried ten years after treatments that had a 3×2 factorial design of three thinning intensities (30, 60, 85% of pre-harvest standing volume) and two types of thinning (harvested larger or smaller trees), were used. The influence of overstorey density on height growth was established using one of the sites that measured height increments of seedlings, saplings, and small trees in the plots. A field investigation was carried out to establish the influence of bilberry on spruce saplings, which cut bilberry stems in 1 m2 circle plots around treated saplings and their height growth compared to the control saplings with uncut bilberry stems.

Volume increment increased with increasing standing volume, culminated, and eventually declined. The highest volume increment was found for diameter-limit harvests followed by single-tree selection and schematic harvests. For harvesting a residual stand to 50 m3ha-1, the schematic harvest showed increment losses equaling 25 years of growth. For the field experiments at both sites, standing volume was correlated significantly positively (p<0.05) with volume increment. Only for the more productive site, standing volume was correlated significantly negatively (p<0.05) with ingrowth. The height increments for all spruce advance regeneration were better correlated with canopy openness than with basal area or standing volume. Treated saplings decreased in height increment compared to the control during the first and second year after cutting bilberry.


In conclusion, volume increment increased with increasing standing volume and harvesting mostly the larger trees in a residual stand with large number of stems and large number of small trees yields high volume increments. At both sites the ingrowth of spruce regeneration was low, but higher than mortality and the number of trees removed, and thus it was sufficient to replace the harvested trees. The cutting of bilberry reduced the height growth of spruce regeneration.




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