Rehabilitation and Regeneration of Degraded Forest Stands

Mary Ann Fajvan and Susan StoutUSFS Northern Research Station

Acknowledgements: Jeff Stringer, Wayne Clatterbuck, Andy Ezell

Silviculture: Manipulating Stand Structure and Growth

Landowner Intentions: Manage for sustained yield of wood

products and other services.

Prescribed FireHerbicidesThinnings

ShelterwoodTwo-age Management

Group Selection

Landowner Goals vs. Land use history

• Grazing• Fire• Disease/Insects• Logging damage• Harvesting• Deer browsing• Invasive plants• Sprouting-rot, quality• Disturbance Interactions

Previous cutting, combined with other disturbances, can diminish the potential to

sustain quality yields of timber

Single or repeated harvests where the majority or all of the desirable trees have been cut leaving a stand of undesirable species and low quality.

“High-grading” “Diameter-limit cutting”

“Select Cut” “Exploitative Harvesting”

Effects of Partial Harvesting on Stand Structure: 1995 WV Assessment

Average diameter decreased10.2” 9.4”Total basal area decreased75.5 52.9 ft2/aPercent stocking decreased65% 45%

Classification of Harvested Stands

1. Silvicultural treatment (4)

2. Nonsilvicultural treatment(23) Both will produce sawtimber in 10-15 years

3. Stand should be regenerated (31)

4. Regeneration has/should occur (16)

5. NS treatment, quality timber potential lost, fiber possible (25)

Fajvan et al. May 1998. Journal of Forestry

FUTURE? Effects of Diameter-limit Cutting on Sustainability

Acknowledgements: Aaron Graves, Shawn Grushecky, Karl Knipling, Brian Tift, Travis Deluca

Stand Structure

Preharvest: 1993 Age: 60 Average BA: 120 ft2/a Average dbh: 11” Species Composition

Yellow-poplar 50% Red oak 30% Red maple 10% Black cherry 7% White oak 3%

Postharvest: 1995 BA 12-inch limit: 10-37,

AGS 16 ft2/a BA 16-inch limit: 34-76,

AGS 37 ft2/a Average dbh: 8.7-9.6 “ Species removed:

89-96% yellow-poplar and red oak

Stand damage 15-25 ft2/a

Effects of Residual Trees on Regeneration Development After Diameter-limit Cutting

Residual Clump Gap

Regeneration Species Importance Values: 9 Years After Harvest

BC RM OK BB YP SF AP SW BG DW WA BL HK CO SU SM AC WO FC EM0

0.05

0.1

0.15

0.2

0.25

0.3

0.35

0.4

Species

Imp

ort

ance

Val

ue

Rehabilitate and Regenerate

Future Sawlog?

Black Cherry

Retain AGS and seed trees

Reduce shade on saplings; liberation

Create/maintain gaps

Management Options* for Degraded Stands: Rehabilitate, Regenerate, or Combination?

Total Stand Rehabilitation Requirements:

A manageable stand of crop trees must exist

Owner must be willing to perform TSI and long-term management

*Ezell, A.W. 2004. Evaluating high-graded hardwood stands. Mississippi State University Extension Service. Publication 1834.

Adapting Stringer Guidelines to SILVAH System: Rehabilitate, Regenerate, or Combination?

• Dr. Jeff Stringer, U Ky, developed “Silvicultural Presriptions for Degraded Stands”

• Based on doing the best you can with what you have

• Adapted these guidelines to SILVAH variables and inventory processes

• Appropriate for stands with < 35% stocking of Acceptable

Growing Stock and low amounts of Seed Source UGS

Some new ideas and terminology• Normally, we call trees with no

potential to produce a sawlog “UGS” – Unacceptable Growing Stock– Caused by poor form– Caused by poor health– Caused by undesirable species

• In degraded stand situation, we separate these into– SSUGS – Poor form, good health,

desirable species – still Seed Source– UGS – Undesirable species, poor

health, unlikely to survive to produce seed

Some new ideas and terminology

• Normally, we look at stand level totals and averages– % stocked with desirable

regeneration– % stocked with interfering

plants

• In degraded stands, we’re interested in each patch as a potential lifeboat for the stand– % stocked with desirable regen

and no interference – “free to grow desirable regen”

SILVAH & Degraded Stands: Current Procedure

• If relative density (stocking) of AGS falls below 35%, SILVAH recommends regenerating

• If stand level seed source for desirable species is limiting, SILVAH recommends stand-wide artificial regeneration (planting)– When desirable seed source BA falls below 25 ft2/acre in

Allegheny/Northern Hardwoods– Below 40 ft2/acre in mixed oak stands

• These prescriptions are both costly and risky• They ignore any positives in degraded stands

Degraded Stand Inventory Procedure

Identify and evaluate AGS (age, vigor, form species)

Identify Seed Source Unacceptable Growing Stock (SSUGS) especially for at risk species.

Assess regeneration potential for desirables (sprouting too)

Assess site quality Determine spatial distribution of

AGS, SSUGS, regeneration

Rehabilitation requirements:

Minimum Basal Area:

20-30 ft2/acre saplings

40-50 ft2/acre poles/saw

Above C level, with at least 35% AGS/SSUGS

Spatial distribution of desirable trees

UniformScatteredClumped

Total Stand Regeneration:

There are insufficient/unsuitable crop trees; current rotation is over Owner must be willing to harvest low value, perform release operations and long-term management Spatial distribution of any advance regenerationAge of regeneration (development since harvest)Composition/shade tolerance of regenerationCompetitive status: Crown classLeave 5 seed trees/a; consider culls of desirablesMidstory canopy density; site prep on good sites for oakConsider Planting

Regeneration Requirements: AGS/SSUGS < 35% stocking, Regeneration Patches/Sources > 70%).

Combined Rehabilitation and Regeneration

Situation:

Sufficient AGS/SSUGS present but widely scattered or clumped. Regeneration potential spatially irregular.

Oak sapling

Combined Rehabilitation and Regeneration

Guidelines: Maintain clumps of AGS Keep/reduce BA <20 ft2/a in open areas Retain seed trees (scattered or within clumps) Maintain opening size 150’ diameter for oak;

1.25 ac for mixed species

Do the best with what you have:

• Use UGS of desirable spp. as seed source

• Capitalize on ANY desirable advance regeneration

• Practice a mix of releasing remaining AGS and regenerating where there are none (may include planting)

• Likely to take many entries

• As a forester, you need to feel good about each incremental improvement

• Speed and effectiveness of rehabilitation depend upon– landowner’s willingness to

invest (e.g. herbicide)– markets for small and/or

poor quality material

Chart O: Degraded Stand Analysis & RxAre there enough AGS plus SSUGS to manage?

SSUGS RD + AGSRD ≥ 35% and Seed Source BA ≥ 30 sq. ft./ac

SSUGSRD + AGSRD < 35% or Seed Source BA < 30 sq. ft./ac

YES NO

Use traditional SILVAH charts for regeneration, retaining SSUGS and AGS for seed source

Is desirable regeneration present?

NO

Any Des Regen and Any Des Regen No Deer = 0

Work with AGS and SSUGS to regenerate; supplement with art

regen; fence if needed

YES

Any Des Regen and Any Est Regen No Deer > 0

Is Des Regen free to grow?NO

YES

Release all Des Regen with 1 – 1.5 acre openings; work with AGS andSSUGS elsewhere; fence if needed

Treat interference to release Des Regen while creating 1 – 1.5 acre openings; work with AGS & SSUGS elsewhere; fence if needed

Degraded conditions cannot be corrected in one treatment

Requires time, money, management skill and patience

Best to PLAN BEFORE YOU CUT!