FW 404: Uneven-aged Systems, 9/4-9/9

Uneven-aged Systems

• Create multi-age (greater than 2 ages) stand

• Generally, depends on natural regeneration

• Low impact on aesthetics since some trees are left and doesn’t look bad to the public

• Used to regenerate:

  • shade-tolerant (like sugar maple)

  • intermediate shade tolerant

    • many oaks

    • longleaf pine

Implementation

• Promote small and large trees

• Frequent harvest (15-30 years)

  • cutting cycle is the period between harvests

  • EX: if our rotation age is 100 years (reach maturity), and we want 4 age classes, what is our cutting cycle? → 25 years

• Remove low volume in each harvest

• Q-factor

  • multiplier between age classes that we use to find the ideal distribution of age classes on the landscape

  • remove trees from each age classto maintain Q-factor

Q-Factor

Why is this not a practical way to manage the forest?

• Little trees have a higher chance of dying, so higher risk

Target Q-factor is 1.5

Tree Size Distribution

• increasing number of small trees that will hopefully make it to next age class

• inverse J-shape on side is the ideal = 1.5

• make sure to remove trees from each age class to allow room to grow

Single-tree selection

• Individual trees removed

• Regeneration in light gaps

• Promotes shade-tolerant trees

• Not the commercial species of the SE

• Promotes vertical structure

• Small openings throughout promote vertical structure

Single-tree Selection Structure regarding harvest

Group Selection

• Create multi-tree openings (<0.5 ha)

• Can favor less shade-tolerant species

• Larger for specific objectives

• Promotes vertical and horizontal structure

• 

• Group opening= ~2x height of adjacent trees, but not an exact answer. Typically less than an acre

Group-selection Opening After

After:

• 

• edge of canopy is drip line, limits regeneration

• pre-harvest: single tree selection, consider light tolerance (shade tolerant)

• establishment cut: Group selection, remove groups of trees, trees favor a little more light

• post-removal cut: shelterwood, leave overstory or keep it (2h or single h stand)

Patch Cuts Are Even-aged

• Small clearcuts or large group selection?

• Patch clearcutting is an even-aged regeneration methods, patch cutting is small clearcuts

• Area regulation rather than by tree size

• Defined best by intent of the manager

• 

• could be considered group selection, depending on intention

Uneven-aged OR patch cut

• harvest different portions at different times

Group selection effects on vegetation

• promotes vertical structure

• promotoes horizontal patchiness

• promotes plant species richness

• retains canopy

• interspersion of forage and cover

  • hard mast production

  • patches of browse and low cover

Group selection effects on wildlife

• High within-stand wildlife richness

• Canopy and understory species

• Forest and some shrubland birds

  • not species of large disturbances

• Turkeys nest in openings

• Grouse broods in openings

• Deer bed and forage in openings

  • eat acorns adjacent to openings

Challenges with uneven-aged silviculture

• cost of frequent harvest

• large trees outcompete small trees

• mixed species vary in biology

  • light, water, nutrient requirements

• Allowing light for shade-intolerants

• Cutting small trees before commercial harvest

• < habitat for shrubland species

• Damage to residuals and skid trails

Bettering Uneven-aged stands

• Retain snags and downed logs

• Avoid high-grading

• Avoid residual tree damage

• Take care with skid trails

• Make openings 0.5 to 1 acre

  • used by shrubland species

  • Promote more shade-intolerant trees

Single-tree selection harvests:

A

are used in an uneven-aged silvicultural system

B

promote vertical vegetation structure

C

favor shade-tolerant tree species

D

all of the above

E

none of the above

…

Which of the following is a true statement?

A

preservation allows the wise use of natural resources

B

a proximate factor triggers the release of an innate habitat selection behavior

C

"selection" implies that animals are exploiting resources proportionate to their availability

D

all of the above

E

none of the above