simulating regeneration dynamics in upland oak standsjmlhot2/courses/for350/regeneration evaluation...

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Simulating Regeneration Dynamics in Upland Oak Stands

USDA Forest Service Southern Research Station Dr. David Loftis



Regen for Excel is a simulation model that using rankings of expected postharvest performance to predict species composition of dominant and codominant trees twenty years following complete overstory removal

Midstory Present, No Yellow-Poplar Seed Source

Density of Advance Seedling Reproduction by Species and Height Class (ft) prior to complete overstory removal

Species Small Medium Large Total (< 2 ft tall) (2 to 4 ft tall) (> 4ft tall)

Red Maple 600 600 300 1500 Sugar Maple 300 300 0 600 White Oak 200 100 0 300 Red Oak 300 150 20 470 A. Beech 200 150 130 480 Total 1600 1300 450 3350

Midstory Present, No Yellow-Poplar Seed Source

Species composition of dominant/codominant canopy trees twenty years following overwood removal

70.6%

10.3%

10.7%

8.5% red maple

sugar maple

beech

northern red oak

Midstory Present, Yellow-Poplar Seed Source Present


65.4% 7.6%

8.6%

11.3%

7.1%

red maple sugar maple beech yellow poplar northern red oak

No Midstory Present, Yellow-Poplar Seed Source Present


Species Small Medium Large Total (< 2 ft tall) (2 to 4 ft tall) (> 4ft tall) Red Maple 600 0 0 600 Sugar Maple 300 0 0 300 White Oak 200 100 0 300 Red Oak 300 150 20 470 A. Beech 200 0 0 200 Total 1600 250 20 1870

No Midstory Present, Yellow-Poplar Seed Source Present


0.8% 0.4%

35.1%

44.4%

0.5% 18.7%

red maple

sugar maple

beech

yellow poplar

white oak

northern red oak

Shade tolerant understory and midstory trees removed, Yellow-Poplar Seed Source Present


Species Small Medium Large Total (< 2 ft tall) (2 to 4 ft tall) (> 4ft tall) Red Maple 0 0 0 0 Sugar Maple 0 0 0 0 White Oak 200 100 0 300 Red Oak 300 150 20 470 A. Beech 0 0 0 0 Total 500 250 20 770

Shade tolerant understory and midstory trees removed, Yellow-Poplar Seed Source Present


62.6%

4.1%

33.3%

yellow poplar

white oak

northern red oak


Simulating Regeneration Dynamics in Upland Oak Stands


Simulations underscore:

• Importance of having competitive advance oak reproduction present prior to final overstory removal

• Role of silvicultural treatments in controlling competing vegetation and enhancing the competitive position of oak reproduction

Evaluating Advance Oak Reproduction

• Evaluating the density, size, and species composition of advance reproduction is a critical step in planning regeneration systems like the shelterwood

• Successful regeneration of oak species typically requires a sufficient number of large, well-distributed advance reproduction prior to overstory removal

• Shelterwood overstory should not be removed until sufficient oak reproduction has developed.


• Two approaches are generally used to evaluate levels of advance reproduction – Fixed Radius Plot (i.e. plot count) Inventory – Stocked Plot Inventory


• Fixed Radius Plot (i.e. plot count) Inventory – Typically completed in conjunction with large tree inventory

• Density of potential stump sprouting oaks determined from large tree inventory.

– Plot size usually 1/1000 acre (3.72 ft radius) to 1/200 acre (8.33 ft radius)

– Advance reproduction density summarized by species and height class


• Stocked Plot Inventory – Inventory determines the percentage of plots stocked with an

advance reproduction stem of a specified species and size

– Density of potential stump sprouting oaks determined from large tree inventory

– Stocked plot percentage is then compared to a predetermined stocking percent benchmark

• Benchmark indicates the number of stocked plots typically necessary to result in successful regeneration of the target species or species group

SILVAH Oak

Brose, Patrick H.; Gottschalk, Kurt W.; Horsley, Stephen B.; Knopp, Peter D.; Kochenderfer, James N.; McGuinness, Barbara J.; Miller, Gary W.; Ristau, Todd E.; Stoleson, Scott H.; Stout, Susan L. 2008. Prescribing regeneration treatments for mixed-oak forests in the Mid-Atlantic region. Gen. Tech. Rep. NRS-33. Newtown Square, PA: U.S. Department of Agriculture, Forest Service, Northern Research Station. 100 p

SILVAH Oak Regeneration Evaluation

• SILVAH Oak method uses data collected on: – Desirable seedling regeneration – Interfering plants – Site quality – Overstory shading – Deer impact

SILVAH Oak Regeneration Evaluation

• SILVAH summarizes set of key decision variables – Variables evaluated against thresholds according to the “stocked

plot” concept • For any key decision variable, a minimum, per-plot, threshold

has been established and any plot exceeding that minimum threshold is considered stocked

• Established from research and forestry practice

SILVAH Oak Inventory Method

• Evaluating regenerative potential of mixed-oak stands must simultaneously consider species present, abundance, size, and spatial distribution of reproduction, and factors limiting successful regeneration

• SILVAH uses three nested plots – Tree regeneration: 6 ft radius plot – Obstacles to successful regeneration: 26 ft radius interference

plot – Overstory conditions: 10 BAF prism

SILVAH Oak: Regeneration Plot

• SILVAH simultaneously evaluates regeneration abundance and size by the “stocked plot” approach

• Regeneration rooted in 6 ft plot is tallied using weighted counts into ten categories

• Stem counts for the different species groups are adjusted for size and are recorded as weighted counts


• Competitive Oak: Stump sprouts or stems >3 feet tall OR with a root collar diameter (RCD) >0.75 inches.

• Established Oak: Count all stems 0.5−3 feet tall OR with RCD 0.25−0.75 inches.

• New Oak: Count all stems <0.5 foot tall and a RCD <0.25 inches


• Black cherry: Count all seedlings ≥2 inches tall with 2 normal-sized leaves. Stems > 1 foot tall are counted twice.

• Yellow-poplar: Same as black cherry. Ignore if oak site index <65.

• Conifers: Count any hemlock, pine, or spruce seedling with 2 whorls OR 0.5-1 foot tall. Stems w/ ≥3 whorls or >1 foot tall are counted twice.

• Other desirables: Same as black cherry. Maples must pass the tug test. For hickory and walnut, count all stems meeting established oak criteria; stems meeting competitive oak criteria are counted twice.


• Saplings: If a past disturbance has allowed regeneration to grow into saplings (1 to 6-inch d.b.h.), tally them if they are a desirable species, have good form and vigor, and meet one of these density thresholds: two stems less than 2.0 inches d.b.h. or one stem 2 to 6 inches d.b.h. Record the code of the dominant species.

• Residuals: Good quality stems 6-10 inches dbh that are the same age as main canopy and will be retained after final harvest. Record species code.

• Tall woody interference: Undesirable species more than 6’ tall rooted in or near the plot. Record species code of the dominant stem.

SILVAH Oak: Interference Plot

• Interference plot assesses competing vegetation, deer impact, and site limitations

• Interference plot has 26-foot radius

• One interference plot with each regeneration plot


Interference plot tally categories: • Low Woody Interference: Visually group foliage of shrubs and undesirable

trees less than 6’ tall together. Estimate cover by 5% increments. Record percent cover and code of the dominant species.

• Fern (bracken, hay-scented, New York): Estimate percent cover by 5% increments. For other fern species, report half the cover. If >50% coverage, record in 10% increments.

• Grass and Sedge: Estimate percent cover by 5% increments. Record 1% even if only a trace of grass or sedge is present.

• Grapevine: Record the number of grapevines rooted in the plot.

• Site limitations: Record if present anywhere on the plot. 1= poor drainage, 2= rocky/thin soil, 3= thick duff.


• SILVAH uses five levels of deer impact to estimate browsing pressure – Very low impact – Low impact – Moderate impact – High impact – Very high impact

SILVAH Oak: Overstory Plot

• Inventorying the overstory entails collecting basal area data by species, diameter, and stem quality.

• One overstory plot for every two regeneration plot

• The inventory can be inventoried using fixed-area or variable-radius sampling techniques

SILVAH Oak: Key Decision Variables

• Understory Regeneration Stocking – SILVAH determines regeneration stocking for the species and

species groups

– Number of qualifying stems recorded compared to “stocked” plot thresholds adjusted for site quality and deer impact


• Oak Stump Sprout Stocking – An important source of oak regeneration is sprouting of the

overstory oaks after they are harvested

– Sprouting probability of mature oaks varies considerably among the species and decreases as size class increases


• Oak stump sprout probability


• Oak Stump Sprout Stocking – SILVAH estimates the number of stump sprouts from overstory

data and sprout probabilities

– Estimated stocking percentages associated with sprout density


• Oak Stump Sprout Stocking

SILVAH Oak: Decision Making

SILVAH Oak uses a series of decision charts to determine the regeneration status of a stand. The decision chats use a number of summary variables.

Summary Variables

• Any Competitive Regeneration: A plot is stocked with Any Competitive Regeneration if it meets the stocking criteria

for any of the regeneration categories except New Oak, Established Oak, Established Desirables, and Total Oak


Summary Variables (continued)

• Any Established Regeneration: A plot is stocked with Any Established Regeneration if it meets the stocking

criteria for any of the regeneration categories except New Oak and Total Oak

• All Established Oak: A plot is stocked with All Established Oak if it meets the stocking criteria for

Established Oak or Competitive Oak

• All Oak: A plot is stocked with All Oak if it meets the stocking criteria for New Oak,

Established Oak, Competitive Oak, or Total Oak


Summary Variables (continued)

• Stocking of Regeneration Obstacles: Percentage of plots that are stocked with various kinds of interfering plants and site

limitations

• Any Interference: A plot stocked with any of the interfering vegetation types is considered to be stocked with Any Interference.

SILVAH Oak: Key Decision Points

1. Any Competitive Regeneration > 69% – Final removal cut for mixed hardwoods appropriate

2. Competitive Oak > 49% and Any Competitive Regeneration > 69% – Final removal cut for mixed-oak regeneration appropriate

3. All Established Oak > 49%:

– High site quality (SI > 70): First removal cut of shelterwood appropriate – Low to medium site quality (SI < 70): With Any Established

Regeneration > 69%, final removal cut

4. All Established Oak < 49%, but All Oak > 50%: Preparatory cut, herbicide, and reinventory

Example Oak Regeneration Scenario 1

Regeneration Inventory found: 1. No Competitive Oak (0% stocked plots) 2. Few Established Oak (5% stocked plots) 3. Few All Oak (15% stocked plots) 4. High level of Tall Woody Interference 5. Site Limitation: Thick Duff Layer

MDM = 23

No site limitations

Comp. oak = 0%

All Est. Oak = 5%

All oak = 15%

Oak sawlogs = 70 ft2ac-1

Thick Duff =30%

Any Int. = 70%

Deer Index = 2

Example Scenario 1: Recommended Prescription


Herbicide Herbicide is an effective, safe and economical technique for removing vegetation that interferes with establishment and growth of oak regeneration.

Five methods of herbicide application

1) Broadcast Spray 2) Cut and Spray 3) Stem Injection 4) Basal Application 5) Cut Stump

Example Oak Regeneration Scenario 2

Regeneration Inventory found: 1. Few Competitive Oak (15% stocked plots) 2. Moderate Established Oak (40% stocked plots) 3. All Oak (85% stocked plots) 4. High level of Tall Woody Interference

MDM = 23

No site limitations

Comp. oak = 15%

All Est. Oak = 40%

All oak = 85%

Stocking = 85%

Interference = 70%

Deer Index = 2

simulating regeneration dynamics in upland oak standsjmlhot2/courses/for350/regeneration evaluation...

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