1. Intermediate Silvicultural Treatments

2. Summary of Intermediate Stand Treatments Thinning Release Improvement cutting (TSI) Sanitation and Salvage Fertilization Pruning Prescribed Fire

3. How intermediate treatments fit into a silvicultural system Components of even-aged silvicultural systems Stand Initiation

4. How intermediate treatments fit into a silvicultural system

5. Textbook Chapters by Topic Thinning: Ch 17, 18, 19 Release Treatments: Ch 16 Improvement, Sanitation and Salvage: Ch 22 Pruning: Ch 20

6. Thinning

7. What is Thinning? Defined by Nyland as: “A treatment to increase the diameter increment of residual trees, improve stand quality and health, and increase stand level production by cutting excess and potential mortality trees without permanently breaking the crown canopy”

8. When we thin a stand… We are reallocating growing space to the residual trees Which residual trees you choose depends on your objectives

9. Why do we thin? Residual trees increase DBH faster, maintain larger crowns and higher vigor Reduces rotation length (age) required to produce trees of a given diameter Typically improves average quality of trees (more valuable) Provide intermediate income May avoid stagnation in densely crowded stands Reduce wood losses to mortality Reduce a stand's susceptibility to insect infestation Increase potential seed production Improve wildlife food production and availability Improve aesthetics, by creating a more open, park-like appearance

10. Effects of Thinning on Individual Growth Thinning increases diameter growth –By allocating more growing space to residual trees, they are able to capture more above and belowground resources 19691979 1959

11. Effects of Thinning on Individual Growth Species and canopy position influence magnitude of diameter growth response

12. Effect of Thinning on Stand Growth Thinning recovers the yield in potential mortality trees and excess growing stock Increases total realized sawtimber yield over an even-aged rotation –Net Volume Yield = Final Harvest Volume + Volume Removed in Previous Thinnings Improved growth on residual trees compensates for the increment lost from cut trees –Ensuring full net production in stands with adequate residual stocking

13. Effect of Thinning on Stand Growth Production function for an even-aged stand thinned three times Net Standing Volume

14. Effect of Thinning on Stand Growth

18. Effects of Thinning Four major factors influencing long-term growth following thinning: 1.Timing of each thinning 2.Crown condition and position of residual trees 3.Post-thinning spacing and its influence over crown vigor and development 4.Interval between successive thinnings

19. Timing of thinning effect diameter growth responses Early thinning can yield increased diameter growth when compared to later or no thinning

20. Timing of thinning and site quality impact cumulative stand yield

21. Period of post-thinning growth increase vary due to spacing and a tree’s competitive position.

22. Effects of Thinning Some potential negative impacts from thinning –Tends to reduce total biomass production –Damage residual stems and site –May increase insect attack and disease losses –Temporarily increase wildfire hazard due to increased fuel load –Reduce tree quality due to increase limb retention and epicormic branching –Increased danger of wind and ice damage due to sudden exposure

23. What is epicormic branching?

24. Methods of Thinning Primary thinning methods 1.Low thinning 2.Crown thinning 3.Selection thinning 4.Geometric thinning 5.Free thinning

25. Methods of Thinning: Low Thinning Low thinning –Trees are removed from the lower crown classes –Must be very heavy or done early and frequently to appreciably increase growth of upper crown class trees –Most applicable in stands which nearly all trees are merchantable

26. Methods of Thinning: Low Thinning Low thinning intensities –Grade A (very light): remove overtopped –Grade B (light): remove overtopped and intermediate –Grade C (moderate): remove overtopped, intermediate, and some co-dominant –Grade D (Heavy): remove overtopped, intermediate, and most codominant Other names for low thinning: Thinning from below German

28. Methods of Thinning: Crown Thinning Crown thinning –Removes trees from upper crown classes to favor the best trees in those classes Removes mostly co-dominant trees, but intermediate or dominant trees interfering with desired residuals also removed –Unlike low thinning, no matter how lightly applied, principle cutting is made in the upper crown classes –Can provides greater income than low thinning –Other names for crown thinning Thinning from above French

30. Methods of Thinning: Selection Thinning Selection thinning –Removes dominant crown class trees in order to favor the growth of trees in lower crown classes Trees favored in crown and low thinning are likely to be cut in selection thinning If incorrectly applied, leads to high-grading and reductions in residual stand growth and quality –Most commonly used to remove poorly formed dominant trees –Applied in some two-layered stands to remove taller layer –Repeated selection thinning is only appropriate for shade tolerant and negatively geotropic conifers

31. Methods of Thinning: Geometric Thinning Geometric thinning –Trees to be cut are chosen strictly on the basis of spacing or pattern with no regard to crown class –This results in removal from all crown classes and retention of trees in all crown classes –Most appropriate where there is little differentiation in crowns or in tree quality –Usually applied only as a first thinning in young stands

32. Methods of Thinning: Geometric Thinning –Row thinning removes strictly by rows in a plantation Every fifth row is common practice Provides easy access for large machinery Provides no improvement in stand quality

33. A geometric thin performed by removing every 5th row in a 14-year-old slash pine plantation in Georgia. Photo Credit: David Moorhead, UGA, Bugwood.orgBugwood.org

34. After 5th row thinning with thin from below in leave rows in a 14-year old stand. Initial Basal Area = 140 square feet per acre, Residual Basal Area = 70 square feet per acre.

35. Methods of Thinning: Geometric Thinning –Strip thinning (or corridor thinning) cuts trees in a strip of set width Applied most commonly for precommercial thinning in young overcrowded natural or direct seeded stands May use heavy mower or drum chopper in seedling stands

36. Aspen stand, 15 ft wide machine corridor, first summer post-harvest.

37. Methods of Thinning: Free Thinning Free thinning –Objective is to select the best trees, regardless of canopy position, and release them –Differs from crown thinning in that spacing across the site need not be uniform –Typically, a set number of crop trees are released (e.g. 50 or 100) Number of crop trees should be sufficient to fully stock the stand at the end of the rotation

38. Thinning Regimes Whether to thin? When to thin? How much to thin? What thinning method do we use? Often tough questions. Objectives, economics, growth rates, and current stand conditions will drive the decision.

39. Timing of Thinning - When do we thin? Merchantability To avoid capital investment, a commercial operation is desirable rather than pre-commercial –Southern pines: Commercial thinning tends to be possible at about age 12, depending on site quality and initial density –Upland hardwoods: Commercial thinning occurs later than for conifers due to slower diameter growth in dense stands and higher minimum merchantability requirements

40. Timing of Thinning - When do we thin? Objectives Pulpwood: thin late or preferably not at all Sawtimber: concentrate growth on best trees as soon as possible Density must be sufficient to encourage self pruning to at least 17 feet Wildlife: in general, thin early, frequently, and heavily from below to increase light levels in the understory and increase growth of shrubs, grasses, and forbs.

41. Timing of Thinning - When do we thin? Site Quality Thinning can occur earlier on more productive sites May chose to thin only on sites of medium to high productivity

42. Timing of Thinning - When do we thin? Live Crown Ratio Best simple indicator of tree vigor and ability to respond to thinning

43. What is Live Crown Ratio?

44. Timing of Thinning - When do we thin? Live Crown Ratio Critical threshold for crown ratio of overstory trees may dictate when thinning occurs Example for southern pines First thinning, attempt to keep most potential crop trees at least above 35% LCR; –40-45% is better for a high growth rate, but this slows self pruning For older stands, seek to keep LCR above 30% (higher for more diameter growth)

45. How much do we thin? Choosing a Residual Density Objectives Pulpwood: maintain high residual density (light or no cut) Sawtimber: lower residual density to keep diameter increment higher –Density should be high enough to maintain good self pruning Wildlife or grazing: low density to encourage understory vegetation

46. How much do we thin? Choosing a Residual Density Live Crown Ratio If crowns are small, thin lightly and frequent Site Quality More flexibility in residual density is possible on good sites –Productive sites can carry higher density without losing vigor, yet openings close rapidly

47. Stand Density and Stocking Quantitative tools for determining how much we should thin Stand density is an absolute measurement based on basal area or number of trees per acre –Stand density reflects the degree of crowding of stems within a stand Stocking is a relative term that relates a given stand density to a management objective –Because size-density relationships influence the amount of available growing space in a stand Two stands with equal stand density may not have an equivalent stocking –Example: 100, 4 inch trees do not occupy an equal amount of growing space as 100, 18 inch trees

48. Simple Measures of Stand Density Trees per acre –Simple –Not helpful when describing uneven-aged stands but useful for plantations Basal area per acre –Basal area is a combined measure of both, number of trees and their size –Widely used because it is: Simple to measure via point sampling Highly correlated with volume and growth of even-aged forest stands Works well for single species plantations

49. Stocking Stocking Chart for Upland Hardwoods (Gingrich 1967) –A graphical tool to allocate growing space on a relative basis for upland hardwood stands in the Central Hardwood Forest Region

50. Properties of the Upland Hardwood Stocking Chart Average Maximum Density (A-Line) is set at 100% Stocking Shows the upper limit of a fully stocked stand

51. Properties of the Upland Hardwood Stocking Chart Area between the A-Line and B- Line indicates that a stand is fully stocked A similar level of merchantable volume produced within the range of full stocking

52. Properties of the Upland Hardwood Stocking Chart B-Line identifies the minimum density of full site occupancy Typically, residual stocking for thinning in upland oak stands would be at or just above B-Line Below B-Line risks increasing epicormic branching

53. Properties of the Upland Hardwood Stocking Chart C-line is the lowest stocking that will grow to the B-line within ten years

54. Thinning in the Central Hardwood Forest Region Silvicultural approaches: 1.Area-wide thinning to a target residual stocking Crown thinning preferred over low thinning 2. Crop tree release Free thinning that releases a predetermined number of crop trees Unlike area-wide thinning, a target residual stocking percentage is not defined –Crop tree release should not result in an understocked stand Preferred over area-wide thinning in cases where stand value is concentrated on a small percentage of trees

55. Area-wide Thinning in the Central Hardwood Forest Region When to thin –Commercial thinning may begin as early as 30 years in upland oak stands on site index 80 or better Site index 70 may have to delay the first cut until age 35 Site index 60 we should be able to start by age 40 Age of first commercial thinning could be between 40 to 50 if no market for small diameter (< 12 in) wood exists

56. Area-wide Thinning in the Central Hardwood Forest Region How much to thin –Regardless of the site, the first thinning in young stands should be as heavy as possible. Young stands respond most to thinning and the crowns close very quickly –Typically, residual stocking for area-wide thinning in upland oak stands would be at or just above B-Line –The stand should approach average maximum density (A-line stocking) before subsequent thinning –Aim for a well stocked stand with at least 50 high quality trees per acre for the final harvest cut

57. Area-wide Thinning in the Central Hardwood Forest Region How Often to Thin –Frequency of thinning depends on the intensity of the first and subsequent cuts, site index, and rotation age –Rotation age varies with site index if our goal is to produce high quality sawlogs 80 year rotation for site index 80 100 year rotation for site index 70 120 year rotation for site 60 Shorter rotations may not produce enough sawtimber size trees

58. Area-wide Thinning Mature Stands in the Central Hardwood Forest Region Foresters generally consider upland oak stands mature when they are 80 to 100 years old or have reached a specified rotation age However, by the time stands are 50 to 60 years old and in the large pole/small sawtimber size, they have generally slowed in height growth, their annual basal area growth has leveled off, and except for size, they have many of the characteristics of older stands

59. Area-wide Thinning Mature Stands in the Central Hardwood Forest Region In older stands with 80 percent or more stocking, a very light thinning or improvement cut can be used to remove some cull trees, undesired species, or some short-lived species or old residuals from past logging –Do not reduce stocking below 75 percent and do not make large holes in the stand –Trees 60 years old and older in dense stands will have relatively small crowns and do not respond well to release –Epicormic branching may become a problem when trees this age are released too much

60. Area-wide Thinning Mature Stands in the Central Hardwood Forest Region If current stocking is 60 to 80 percent, it is usually best to hold off on thinning – Any cutting in such stands will probably not benefit the entire stand and may allow an unwanted understory to develop rapidly –By simply waiting for about 10 years, stocking will increase and you may be able to get an operable cut without depleting stocking

61. Crop Tree Release in the Central Hardwood Forest Region Miller, G.W., J.W. Stringer, and D.C. Mercker. 2007. Technical guide to crop tree release in hardwood forests. University of Kentucky, Cooperative Extension Service. Southern Regional Extension Forestry Publication, Professional Hardwood Notes, FOR-106. 23 p.

62. Crop Tree Release What is Crop Tree Release (CTR)? –CTR is an intermediate silvicultural treatment and type of free thinning –CTR is intended to provided increased growing space through the removal of crown competition from adjacent trees –CTR assures most site resources are focused on a small number of selected trees rather than being widely distributed among all residual trees ‘Low thinning’ and ‘crown thinning’ methods intend to reach area-wide residual density targeting specific size or crown class trees

63. Crop Tree Release Increasing growing space available to individual trees

64. Crop Tree Characteristics by Management Objective

65. How Crop Trees Respond to Release Increased growing space provides more light, water, and nutrients Released crop trees respond with faster root and crown growth, then faster dbh and volume growth Although CTR can produce a significant response in the first growing season, maximum growth usually occurs 2 to 3 years after release

66. Approach to Releasing Crop Trees “Crown-touching” release applied to deaden or fell adjacent competing trees whose crowns touch that of the crop tree

67. Approach to Releasing Crop Trees Lower crown class trees need not be removed –Minimal influence on crop tree growth –Help discourage epicormic branching

68. Intensity of Release and Crop Tree Growth

69. Crop Tree Release How many crop trees to manage? –Nearly all economic value in hardwood stands is found in a relatively small number of trees –Maximum of 60 to 70 crop trees per acre Release strategies: –Full crown-touching release for rapidly growing species and young trees in the sapling/pole stage –Less than a full crown-touching release (at least three sides released) for small sawtimber to limit the risk of epicormic branching –Sub-canopy trees retained to protect crop trees and add other benefits to the stand, unless they conflict with management objectives

70. Economic value in hardwood stands found in a relatively small number of trees

71. Declining number of crop trees with increasing stand age

72. Timing of Crop Tree Release Treatments Best time for application is when canopy begins to close or within 10 to 15 years following canopy closure –High quality sites, canopy closure 8 to10 years –Poorer sites, canopy closure 13 to 15 Can be successful used in large poletimber and sawtimber stands to promote vigor in selected crop trees –Number of crop trees greatly diminished in older stands

73. Application Techniques for Crop Tree Release Mechanical fell or fell and herbicide stump treatment –Difficult to fell trees in young stands Chainsaw girdle: double girdle 1” deep, 6 in apart –Diffuse porous trees are poor candidates for girdling without herbicide due to there resilience to girdling Cut surface herbicide application Basal bark spray (trees < 6 in) Cost: $40 to 60 per acre ($100 to $150 per acre contract cost) Focus on best available crop trees regardless of spacing –Arbitrary spacing rules may lead to inefficient investments in substandard trees

74. Benefits of Crop Tree Release Increase diameter growth and volume of crop trees Increases stand value by increasing the proportion of high- value crop trees Greatest economic gains are when large differences exist between values of crop trees and their competitors due to species or quality

75. Risks Associated with Crop Tree Release Epicormic branching –May reduce log grade and tree value Windthrow or damage from ice or snow