1. Concepts of Forest Regeneration

2. Regeneration vs. Reproduction
Regeneration: the act of renewing tree cover by establishing young trees naturally or artificially (verb)
Reproduction: Seedlings or saplings existing in a stand (noun)

3. Artificial vs. natural regeneration
Natural Regeneration - stand establishment is from natural sources: natural seeding, sprouting, suckering, layering
Artificial Regeneration - stand establishment is from human intervention: planting seedlings or cuttings or by direct seeding.

4. Reforestation vs. afforestation
Reforestation: reestablishment of forest cover on areas where it once occurred
Afforestation: introduction of trees to sites that did not support forests or had no forest cover for a long period of time.

5. Concepts of Regeneration
Key goals of a regeneration strategy:
Make the results predictable
Control microenvironment
Ensure prompt replacement of the stand
Affect species composition
Match species to site and to objectives
Arrest succession
Many desirable species are early successional (oak and pine)

6. Concepts of Regeneration
Key goals of a regeneration strategy:
Appropriately stock the site with desirable species
Number and distribution
Set the stage for future management
Minimize poor or excessive stocking
Minimize remedial treatments (problems that require fixing)
Intermediate treatments should, where possible, be constructive
Minimize the chance of failure
Ensure adequate seed supply
Ensure proper seed bed for good germination and establishment
Take prompt remedial action if necessary

7. Concepts of Regeneration
Origin of reproduction
Seed vs. vegetative
New individual vs. clonal

8. Categories of Reproduction
New seedlings: originate following regeneration event
Advance reproduction: in place prior to regeneration event and released by event
Stump sprout: traditionally from stump >2” ground line diameter
Root suckering: sprouts from shallow lateral roots
Typically follows the severing of the parent stem and with direct sunlight to the forest floor
Examples: black locust, sweetgum, aspen

9. Stump Sprouting

10. Stump Sprouting Probability by Age and Species
Sprouting tends to decrease with size and age and varies by species
Stump Sprout
Probability
Tree Age

11. Regeneration Process
New forest communities establish whenever three conditions develop:
Presence of abundant viable seed or vegetative propagules
Soil and seedbed conditions enable germination of seed or help induce shoot development off parent trees
Environmental conditions foster the survival and growth of established trees

12. Regeneration Process Seed Supply Flowering and seed production
Influenced by species, genetics, climate
Can be cyclical and have high year-to-year variation
Example: masting species such as oaks

13. Regeneration Process Seed dispersal
Reproductively mature trees within dissemination range required for regeneration from seed
Vegetative or artificial regeneration required if seed is not available
Factors influencing seed dissemination (i.e., dispersal)
Height of release
Distance from source
Abundance of seed
Weight and aerodynamic structure
Activity of dispersing agent
Wind speed and direction, topography, numbers and movement of animals

14. Seed dispersal distance is species dependent

15. Regeneration Process Seed bank
Viability and germination stimuli various among species

16. Regeneration Process Seed Bed and Germination
Physical characteristics of forest floor affect germination
Litter depth and type
Some species (for example, many pines) require a mineral seedbed
Mineral seed beds can created by natural disturbances (i.e. fire) or site preparation treatments
Position of seed within the seedbed affect predation and germination rates
Light, temperature, and moisture affect seed viability and germination

17. Concepts of Regeneration
Generally,
Light wind-disseminated seeds require mineral seedbed
Large seeded species like oaks are aided by being buried under a litter layer as long is it is not too thick (5 cm)
Litter layer helps protect against predation, desiccation, and extreme temperatures

18. Species of the Central Hardwood Region
Seed Dissemination
Gravity
Animals
Wind
Yellow-poplar X
White oak
Chestnut oak
Black oak
Northern red oak
Scarlet oak
Sugar maple
Red maple
Pignut hickory
American beech

19. Regeneration Process Established Seedlings
Survival and growth of seedlings influenced by mitigating effects of forest canopy on light, temperature, and moisture in the understory
Species physiologic characteristics and shade tolerance affect their response to a given understory environment
Silvical characteristics of desired species must be considered in conjunction with those of competitor species to assess competitive dynamics of newly established seedlings.

20. Regeneration Process Established Seedlings and Shade Tolerance
Shade tolerant: Not only are they able to establish in the understory, but they are able to persist.
This doesn't necessarily mean they are putting on a lot of growth, but they are staying alive
Intermediate tolerance: Able to establish in the understory but they cannot survive for extended periods
Shade intolerant: May establish in the understory, but normally die out in dense shade
When released following extended periods of low light they respond with sluggish growth

21. Overview of Silvicultural Systems
Even-aged vs. Uneven-aged

22. Common characteristics of even-aged stands
Crown canopy is generally limited to a single layer elevated above the ground
Diameters vary widely only if shade-tolerant species are present
Only old stands have sawtimber sized trees
Small trees have short live crown length when compared to total height
Largest trees often have percent live crown, depending on stand density

23. Common characteristics of uneven-aged stands
Crown canopy is generally comprised of multiple layers and commonly extends close to the ground
Diameters range from seedling-sapling to sawtimber sizes, regardless of species present
Trees of all diameters have a large live-crown ratio, often as high as 40 to 60 percent in managed stands
Tree heights vary with tree diameter, with short ones having small diameters and tall trees having larger diameters

24. Even-aged vs. Uneven-aged Diameter Distributions
Bell-shaped (normal distribution)
Reverse J-shaped

25. Reverse J-shaped does not always indicate a true uneven-aged stand (3+ age classes)
Example from the Central Hardwood Region: Two-storied stand with oak-dominated overstory and midstory/understory canopy dominated by shade tolerants like beech and maple.

26. Silvicultural Systems
Even-aged and Uneven-aged systems
One age class vs. at least three age classes in a stand (an age class is defined at 20% of the rotation length)
Mature trees are removed:
Short window of time in even-aged
Periodically in uneven-aged
Maintains continuous canopy cover

27. Timeline of practices in an even-aged silvicultural system
During the rotation age r, treatments are applied across the entire stand to meet silvicultural objectives that are related to tree age

28. Concurrent application of individual practices of an uneven-aged silvicultural system during a cutting cycle harvest in a balanced uneven-aged stand
Treatments are applied to subunits of the stand depending on conditions within each subunit
Each cutting cycle harvest will support similar treatments

29. Silvicultural Systems
Two-aged systems
Hybrid of even- and uneven-aged
Uses even-aged methodology while maintaining some continual canopy cover
Regeneration is accomplished two times over a standard rotation
Referred to as: irregular shelterwoods, reserve shelterwoods, two-aged, or leave tree systems

30. Regeneration Methods Regeneration methods are classified as follows:
Even-aged
Clearcut
Seed-tree
Shelterwood
Uneven-aged
Selection
Two-aged (Hybrid)

31. Common Even-Aged Systems
Clearcut
Seed Tree
Shelterwood

32. Clearcutting
Clearcutting: A method of regenerating an even aged stand in which a new age class develops in a fully exposed microclimate after removal, in a single cutting, of all trees in the previous stand.
Regeneration is from natural seeding, direct seeding, planted seedlings, and/or advance reproduction.
Silvicultural clearcuts differ from ‘commercial clearcuts’
The first removes all trees, the second only merchantable trees

33. How Clearcutting Changes the Microenvironment
Full sunlight conditions
Air and soil temperature near the surface increases
Humidity decreases and surface evaporation increases
Soil moisture increases because transpiration decreases
Precipitation interception decreases, more water reaches the surface
Water infiltration and percolation increases; subsurface flow increases
Decomposition increases (warmer and wetter), releasing more nutrients
Nutrients not taken up or bound to soil leach out of system

34. Clearcutting Edge effect
Moisture increases on a gradient for feet into a clearing and then levels off
Shade (in the northern hemisphere) is more pronounced on the south edge of the clearing. East to west shade depends on time of day.

35. Clearcutting Alternate clearcutting arrangements Strip clearcut
Block clearcut
Patch clearcut
Use of alternative methods:
Ensure good seed rain
Manage shade patterns
Protect against wind or ice/snow
Improve aesthetics or meet policy-based constraints

36. Alternative Clearcutting Approaches
Block clearcutting
All trees are removed in a single operation
Size limitations are based on policy and site conditions, not on regeneration constraints

37. Alternative Clearcutting Approaches
Progressive strip clearcut
Alternate strip clearcut
Strip clearcuts, alternate or otherwise, are best oriented at right angles to prevailing winds. The width of the strips will depend on seedfall distances for the preferred species, wind hazard, and other factors

38. Alternative Clearcutting Approaches
Patch clearcutting
Stand is regenerated in a series of clearcuttings made in patches
Patch size influences light availability within the patch and should be chosen to match species silvics

39. Other considerations when using even-aged methods
Stream Side Management Zones (SMZ’s)
Typically leave an unharvested or partially harvest buffer
Legacy trees
Travel corridors for wildlife
Management of viewscapes
Orientation on landscape
Aesthetic buffers
Alter shapes, adjacencies
Avoid straight edges and square corners
Limit harvest size

40. Clearcutting and Site Preparation
Site preparation considerations for natural regeneration
Some important questions
Is it needed or would it be detrimental?
Do you need it for a desired species?
Does species need a mineral seedbed

41. Scarification → mineral seedbed Control slash residues
Site preparation and clearcutting: Considerations for natural regeneration
Scarification → mineral seedbed
Control slash residues
Partial shade or browse protection afforded by slash
Control slash cover to manage seed eating mammals
Mechanical or chemical vegetation control
Competing vegetation that may inhibit or delay regeneration and effect subsequent growth rates

42. Advantages Clearcutting with Natural Regeneration
Good method for most shade intolerant species
Commercially attractive
Ease of administration and implementation of regulated forest
Clean site eases site preparation
Easy machine access eases harvesting
Total overstory removal reduces some pests (e.g. dwarf mistletoe)
Facilitates regeneration of species with serrotinous cones
Precludes blow down
Increases herbaceous cover (browse and cover for many wildlife species)

43. Shortcomings of Clearcutting with Natural Regeneration
Problems with dependable seed sources and seedling establishment
Seed shortage limits regeneration to light seeded species
Poor seed years may lead to regeneration failure or irregular stocking
Overstory removal limits within stand seed production following harvest
Density and uniformity of a species is difficult to control
Issues associated with no high forest cover and high light environment
Lack of cover may adversely impact some tree species and may increase competition by herbaceous and shrubs
Dense competition may require costly site preparation
Cold air drainage may damage reproduction
Dry sites may not have sufficient surface moisture to support germination
Reduced chance for genetic improvement

44. Shortcomings of Clearcutting with Natural Regeneration
Impacts on soils and hydrology
Wet sites may become wetter
Wet soils may become unstable on steep slopes
Mineral soil exposure may increase soil erosion
Increased decomposition rates and potential nutrient leaching
Decreased visual aesthetics
Increased fuel loading and fire danger
Decreased wildlife habitat for some species

45. Coppice Silviculture

46. Coppice
The term "coppice" is commonly applied to any regeneration arising from sprouts or suckers—typically hardwoods of young to moderate age
As a method, it is where regeneration is solely from sprouts or root-suckers
Associated with short rotation production of pulpwood or fuelwood
Historically associated with charcoal iron production

48. Coppice Some coppice principles:
Low stumps produce better quality sprouts
Best sprouts originate from the root collar
Sprouting vigor tends to decline with age and size of stems
smaller stems, better sprouting
Sprouting is most vigorous from dormant season cutting
Least vigorous from late spring cutting

49. Coppice Coppice for energy, bioremediation, environmental cleanup
Repeated crops without replanting
Vegetative propagation maintains genetic integrity of plantation
Increased growth rates allow large volume production on limited land base
Short cycle provides quick return on investment
Second and third rotation often produces greater biomass in shorter time frame due to multiple stems from sprouts

52. Coppice
The cutting cycle is set by when the MAI intersects PAI

54. General shortcomings of coppice systems
Financial success depends on access to markets for small diameter wood
Serve limited set of management goals
Frequent entry requires extra caution to minimize soil disturbance and may increase loss of soil nutrients after repeated harvests
Coppices susceptible to freezing and browse
It takes time to convert from coppice to high forest methods
Coppice stands have limited non-market values
General shortcomings of short-rotation biomass plantations
Require guaranteed markets
Require fertile soils with abundant moisture as well as fertilization to maintain critical nutrients
May require protection from browse
Mechanized systems needed for efficient harvesting require fairly level sites with uniform surfaces and highly trafficable soils.

55. Coppice with standards: scattered, individual stems allowed to grow on through several coppice cycles

56. Seed Tree Method
Definition: even-aged method retaining widely spaced, uniformly distributed seed bearing trees
Reproduction source: from seeds disseminated from trees left after harvest

57. Seed Tree Method
Remaining seed trees may be removed after suitable regeneration is established, but this is not necessary to the method's application
Produces an even-aged stand
Inherently works well for wind dispersed species, but not hard seeded trees such as oaks and hickories
The method removes size constraints on the regeneration area (also shape and orientation issues)

58. Seed Tree Regeneration Method
Regeneration must be established in a short period of years, or else the site will be occupied by other plants
Produces early successional conditions on the site (the same as a clearcut):
High light levels, high exposure to wind, and extremes in temperature at ground level.
Retained trees do not provide enough canopy cover to alter the stands microenvironment in comparison to open condition
Density of retained trees that would alter microenvironment is species-specific

59. Key considerations for the seed tree method
Number and spacing of seed trees depends on:
Size and species of seed trees
Amount of viable seed per tree
Percent of seed trees that may survive
Percent of seed that produces an established seedling

60. Considerations for number and spacing:
Distance to which seed from desired species can be dispersed to fully stock an area
Do not exceed maximum dispersal distances
Nature of the seedbed
If unfavorable (e.g., heavy duff or sandy topsoil), leave more seed trees (but, better to prepare it by fire or disking)
Anticipated competition level
Increase the number of seed trees if there will be a high competition level with no or inadequate competition control
Above all, know the silvics of species to be retained

61. Considerations for number and spacing:
Light seeded trees can disseminate 2 to 5 times their height
Amount of viable seed is usually limiting factor
Influence of spacing on pollination alter total seed production
Because of year-to-year variation in seed production, it is best to ensure enough reserve trees to restock area in one moderate seed year
Usually, 4 to 20 trees per acre retained

62. 8 seed trees per acre in a loblolly-shortleaf pine stand. Arkansas.

63. Recommended minimum number of seed trees for major southern pines, by DBH class. Number per acre. (Average distance between trees, in ft, shown in parentheses). Will provide value for commercial removal
Species
DBH (inches)
Loblolly
Shortleaf
Slash
Virginia 9 10 12 14
16+ NA
12 (60)
9 (69)
6 (85)
4 (104)
20 (47)
14 (56)
5 (93)

64. Characteristics of Quality Leave Trees
Windfirmness
Shallow rooted trees or species with weak wood are not desirable
Wide, deep crowns, with high live crown ratio
Indicators of vigorously growing trees
Dominant or better codominant crown class
Seed production is linked to crown area
Height
Height can influence distance of seed dispersion
Age
Must be old enough to produce seed

65. Cutting Strategies – Seed Tree System
Preparatory Cut: Optional initial treatment to increase tree vigor and seed production
Establishment Cut: Treatment to establish seedling reproduction within the stand
Removal Cut: Removal of final overwood to release established seedlings
Multiple cuttings can be used and are the same as for a shelterwood except for the density of the establishement cut (i.e. can have a preparatory cut and a removal cut)

66. Cutting Strategies – Seed Tree System
Additional Management Options:
Reserve Cutting: Retain seed trees to help make an early thinning of the next stand more economically feasible
Not competing removal cut and retaining seed tree through next rotation to meet multiple-use objectives

67. Seedtree Reserve Cutting Considerations
Do economic gains out-weight positives to retention?
Damage to established reproduction
Is area fully stock with reproduction?
Additional site preparation may be necessary if reproduction does not develop
If removal is chosen and growth of established reproduction is your primary objective…
Implement removal cut when site is fully stocked with seedlings of desired height
Level of stocking and seedling height required is species-specific

68. Site Preparation Considerations for Seed Tree Method
Site Conditions: An adequate seedbed and low level of competition are required
Some well-distributed exposed soil is desirable, since seeds are small
Best case: thin, discontinuous litter, with some mineral soil exposed
Dispersed skidding during logging may be sufficient, particularly if the stand has been burned regularly
Consider a prescribed burn (for pines) if a heavy litter layer exists
Best if before harvest, and not between seedfall and a winter/early spring harvest
Mechanical site preparation
provides some density/distribution control

69. Site Preparation Considerations for Seed Tree Method
Reduce anticipated competition, if needed
Logging operations can damage competition vegetation present at time of harvest
Pre- or post-harvest chemical control
A burning regime prior to harvest
Involves planning many years ahead
May be part of your silvicultural system for pines
May need to include one or more summer burns just before the anticipated harvest

70. Advantages to Seed Tree Method:
Allows for the control of species and phenotypic characteristics of seed source
Seed source abundant and uniformly spaced
Provides full sun growth conditions
Disadvantages:
Exposes seed source to increased risk of premature destruction.
Does not provide protection to reproduction on harsh sites
Application of Seed Tree Method:
Southern Pines: slash, shortleaf, loblolly, sand
Hardwoods: yellow-poplar, cottonwood, willow, ash
Western Conifers

71. Ponderosa Pine
Shortleaf Pine
Slash Pine

72. Shelterwood System
Definition: an even-aged silvicultural system where the reproduction method removes mature community in two or more successive cuttings, temporary leaving some old trees to serve as seed source and to protect the regeneration.
Characteristics:
Relatively low density stand left of vigorous seed-bearing trees
Residual overstory provides sufficient canopy to mitigate sensitive environmental conditions.
Especially important on harsh or exposed sites.
Residual trees are removed once new reproduction reaches adequate size (i.e. height) and density

73. Uniform Shelterwood Components
Preparatory Cut
An optional initial treatment to:
Increase tree vigor and seed production in mature stand
Remove undesirable seed sources
Alter understory environment to promote development of advance reproduction

74. Uniform Shelterwood Components (continued)
2. Establishment Cut
Artificially moves stand into understory reinitiation phase of stand development
Promotes seed germination and establishment by creating permanent openings in main canopy
Opens the canopy for sufficient light availability to allow regeneration
Maintains some control (“shelter”) of understory vegetation
Generally, ft2/ac residual basal area
30-40 ft2/ac southern pines, ft2/ac for oak
Should retain dominant, vigorous trees of favorable phenotypes

75. Uniform Shelterwood Components (continued)
2. Establishment Cut
Considerations for success:
Appreciably modify the understory environment
Retain sufficient residual cover to create conditions that favor target species and seed supply
Understory environment must promote seedling development of desired species

76. Tradeoffs Between Overstory Retention, Light Environment, and Understory Competition
*Optimal level is dependant on species, site productivity, and stand history

77. Uniform Shelterwood Components (continued)
3. Removal Cut
A harvest to take away the overwood, so the reproduction can develop uninhibited
Conducted only after satisfactory establishment of reproduction based on density, height, and distribution of seedlings
Will impact (i.e. damage) established reproduction
Remove the overwood before suppression of regeneration

78. Applicability of the Shelterwood Method
Most flexible even-aged method
A good method for heavy-seeded species
A good method where the seed supply is irregular
Obtain rapid increment of high quality wood
Increase mast production
Maintain aesthetics

79. Uniform Shelterwood Methods
Three-cut Method: Preparatory, Establishment, and Removal cut are used
Two-cut Method: Establishment and Removal cut only

80. Other Types of Shelterwood Systems
Irregular or Reserve Shelterwood:
Leaves residual overstory for an extended period of time into new rotation – creates two-aged stand
Has ecological/aesthetic vs. economic/operational tradeoffs

81. Other Types of Shelterwood Systems
Group Shelterwood:
Takes advantage of existing patches of reproduction
Removal cuttings done in patches containing reproduction
Preparatory and establishment cuts done in areas lacking favorable reproduction

82. Group Shelterwood

84. Other Types of Shelterwood Systems
Strip Shelterwood:
Removal of mature age classes over a series of entries by cutting narrow strips not exceeding the height of adjacent standing trees
Residual strips provide seed and partial shade to openings
Strip Orientation:
Long axis of strips at right angles to prevailing winds to reduce blow-down
Alignment in relation to sun’s path influences proportion of direct and diffuse radiation

85. Strip Shelterwood

86. Application of the Shelterwood System
Upland and bottomland oak forests
Eastern pines: red pine, eastern white pine
Southern pines: longleaf pine
Rocky mountain conifers: western white pine, ponderosa pine, Douglas-fir (Rocky Mountain variety), western larch (on harsh sites).
Cascade and coastal range regions: western hemlock/Sitka spruce type and Douglas-fir

87. Upland Oak Shelterwood

88. Shelterwood in longleaf pine

89. Brief Comparison: Clearcut, Seed Tree, and Shelterwood
Entire canopy removed in one operation
Seedlings grow under open field conditions
Seed Tree:
Canopy removed in 2 to 3 stand entries
Residual trees retained to provide a seed source
Seedlings grow under essentially open field conditions
Shelterwood:
Residual trees retained to provide a seed source and modify understory microenvironment
Canopy removed in 2 to 3 stand entries