Simulating Regeneration Dynamics in Upland Oak Stands Powered By Powered by: USDA Forest Service Southern Research Station Dr. David Loftis Powered By Powered by: 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 USDA Forest Service Southern Research Station Dr. David Loftis Powered By Powered by: USDA Forest Service Southern Research Station Dr. David Loftis 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 (< 2 ft tall) 600 300 Medium (2 to 4 ft tall) 600 300 Large (> 4ft tall) 300 0 Total White Oak 200 100 0 300 Red Oak A. Beech Total 300 200 1600 150 150 1300 20 130 450 470 480 3350 Red Maple Sugar Maple 1500 600 Midstory Present, No Yellow-Poplar Seed Source Species composition of dominant/codominant canopy trees twenty years following overwood removal red maple 8.5% sugar maple 10.7% beech 10.3% northern red oak 70.6% Midstory Present, Yellow-Poplar Seed Source Present Species composition of dominant/codominant canopy trees twenty years following overwood removal 7.1% red maple sugar maple beech yellow poplar northern red oak 11.3% 8.6% 7.6% 65.4% No Midstory Present, Yellow-Poplar Seed Source Present 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 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 Species composition of dominant/codominant canopy trees twenty years following overwood removal 0.8% 0.4% red maple 18.7% sugar maple 0.5% 35.1% beech yellow poplar white oak northern red oak 44.4% Shade tolerant understory and midstory trees removed, Yellow-Poplar Seed Source Present 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 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 Species composition of dominant/codominant canopy trees twenty years following overwood removal yellow poplar white oak 33.3% northern red oak 62.6% 4.1% Simulating Regeneration Dynamics in Upland Oak Stands Powered By Simulations underscore: Powered by: • 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 USDA Forest Service Southern Research Station Dr. David Loftis 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. Evaluating Advance Oak Reproduction • Two approaches are generally used to evaluate levels of advance reproduction – Fixed Radius Plot (i.e. plot count) Inventory – Stocked Plot Inventory Evaluating Advance Oak Reproduction • 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 Evaluating Advance Oak Reproduction • 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 SILVAH Oak: Regeneration Plot • 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 SILVAH Oak: Regeneration Plot • 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. SILVAH Oak: Regeneration Plot • 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 SILVAH Oak: Interference 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 Oak: Interference Plot • 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 SILVAH Oak: Key Decision Variables SILVAH Oak: Key Decision Variables • 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 SILVAH Oak: Key Decision Variables • Oak stump sprout probability SILVAH Oak: Key Decision Variables • Oak Stump Sprout Stocking – SILVAH estimates the number of stump sprouts from overstory data and sprout probabilities – Estimated stocking percentages associated with sprout density SILVAH Oak: Key Decision Variables • 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 SILVAH Oak: Decision Making 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 SILVAH Oak: Decision Making 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. 2. 3. 4. 5. No Competitive Oak (0% stocked plots) Few Established Oak (5% stocked plots) Few All Oak (15% stocked plots) High level of Tall Woody Interference Site Limitation: Thick Duff Layer No site limitations MDM = 23 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 Example Scenario 1: Recommended Prescription 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. 2. 3. 4. Few Competitive Oak (15% stocked plots) Moderate Established Oak (40% stocked plots) All Oak (85% stocked plots) High level of Tall Woody Interference No site limitations MDM = 23 Comp. oak = 15% All Est. Oak = 40% All oak = 85% Stocking = 85% Interference = 70% Deer Index = 2 Example Scenario 2: Recommended Prescription Example Scenario 2: Recommended Prescription
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