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Intermediate Silvicultural Treatments

Intermediate Silvicultural Treatments. Summary of Intermediate Stand Treatments. Thinning Release Improvement cutting (TSI) Sanitation and Salvage Fertilization Pruning Prescribed Fire. How intermediate treatments fit into a silvicultural system. Components of even-aged

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Intermediate Silvicultural Treatments

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  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 1969 1979 1959

  11. Effects of Thinning on Individual Growth

  12. Effect of Thinning on Stand Growth Production function for an even-aged stand thinned three times

  13. Effect of Thinning on Stand Growth

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

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

  16. 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

  17. What is epicormic branching?

  18. Methods of Thinning • Primary thinning methods • Low thinning • Crown thinning • Selection thinning • Geometric thinning • Free thinning

  19. 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

  20. 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:

  21. Methods of Thinning: Crown Thinning • Crown thinning • Removes trees from upper crown classes to favor the best trees in those classes • 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

  22. Methods of Thinning: Selection Thinning • Selection thinning • Removes dominant crown class trees in order to favor the growth of trees in lower crown classes • 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

  23. 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

  24. Methods of Thinning: Geometric Thinning • Row thinning removes strictly by rows in a plantation

  25. 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.org

  26. 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.

  27. Methods of Thinning: Geometric Thinning • Strip thinning (or corridor thinning) cuts trees in a strip of set width

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

  29. 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)

  30. 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.

  31. 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 index and initial density) • Upland hardwoods: in general commercial operations come much later than for conifers (slower diameter growth in dense stands and higher minimum size requirements) • 20-25 years if a pulpwood or fuelwood market is present • 30-50 years for small sawtimber

  32. 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.

  33. Timing of Thinning - When do we thin? Site Quality • May chose to thin only on better sites Live Crown Ratio • The best simple indicator of tree vigor and ability to respond to release • 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)

  34. 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 • Wildlife or grazing: low density to encourage understory vegetation

  35. 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

  36. 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 • 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

  37. Simple Measures of Stand Density • Trees per acre • Basal area per acre • Basal area is a combined measure of both, number of trees and their size • Widely used because it is:

  38. 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

  39. 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

  40. 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

  41. 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

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

  43. Thinning in the Central Hardwood Forest Region • Silvicultural approaches: • Area-wide thinning to a target residual stocking 2. Crop tree release

  44. Area-wide Thinning in theCentral 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 • Age of first commercial thinning could be between 40 to 50 if no market for small diameter (< 12 in) wood exists

  45. Area-wide Thinning in theCentral Hardwood Forest Region • How much to thin • Regardless of the site, the first thinning in young stands should be as heavy as possible. • 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

  46. 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

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