BIOCLIMATE MODELS AND CHANGE PROJECTIONS TO INFORM FOREST ADAPTATION IN SOUTHWESTERN COLORADO
Final Results And Application To Vegetation Management
Silvicultural Practices & Recommendations
Jeff Underhill Regional Silviculturist Rocky Mountain Region OUTLINE
Current Practices ✓ Density Reduction ✓ Other Practices
❖ Land Resource & Management Planning (Forest Plan & Project) ✓ Minimum Stocking Standards ✓ Prescriptive Flexibility
❖ Prescriptions ✓ Resiliency – Transition Adaptation Strategy ✓ Target densities ✓ Favor Drought Tolerant Species ✓ Aspect
❖ Reforestation ✓ Program Scales ✓ Seed Procurement Planning ✓ Seed Transfer
2 CURRENT PRACTICES Density Reduction ❖ Lower densities where possible: ✓ 40 sq. ft. residual live basal area in the Black Hills ponderosa pine forest. ✓ These treatments have been effective regarding resistance to mountain pine beetle attack. ✓ Past practices prescribed residual stand densities of 60-80 sq. ft. of basal area
3 CURRENT PRACTICES
❖ Variable Spacing - Thinning ✓ Clumps & Groups: Experimenting with different implementation methods
❖ Variable Residual Density ✓ COVER TYPE LIVE BASAL AREA (sq. ft.) Ponderosa pine / Douglas-fir 40 – 60 Dry Mixed Conifer 60 – 80 Mesic Mixed Conifer 80 – 100 Aspen (live conifer BA) 0 – 40
❖ Openings ✓ Patch cutting around aspen ✓ Persistent openings on south facing slopes
✓ Patch cuts on north slopes that regenerate aspen and pine / remove dense Douglas-fir & spruce
4 CURRENT PRACTICES Individual Trees & Clumps
RESIDUAL INDIVIDUAL TREE RESIDUAL CLUMPS SPACING
5 CURRENT PRACTICES
Density Reduction ❖ Variable density thinning, group selection, single tree selection, clear cuts, aspen enhancement in lodgepole pine, San Isabel NF. • 20-25% clearcut • 60% variable density thinning
• 10% group selection/1 acre • 10% untreated patch cuts
6 CURRENT PRACTICES
Density Reduction ❖ Species Composition
✓ Favor early seral species ✓ Aspen enhancement treatments, Pike National Forest
Treated
7 CURRENT PRACTICES
Density Reduction ❖ Species Composition ✓ Favor drought tolerant species
8 Land Resource & Management Planning (Forest Plan & Project)
❖ Minimum Stocking Standards ✓ Consider revision to minimum stocking standards during FP Revision, especially in dry cover types:
1984 Forest Plan - PSICC
Minimum Stocking Level Cover Type Distribution % (tpa) Inland Ponderosa Pine 190 70
Mixed Conifers 190 75
Lodgepole Pine 150 75
Engelmann Spruce – 150 75 Subalpine fir
Aspen 300 75
9 Land Resource & Management Planning (Forest Plan & Project)
❖ Include prescriptive flexibility for minimum stocking standards
✓ S-VEG-3: Conduct harvest to assure that the technology and knowledge exist to restock these areas adequately with trees within 5 years after final harvest. Minimum restocking levels for suitable timber lands are defined in Table 6. Exceptions to these levels are allowed if supported by a project-specific determination of adequate restocking.
✓ Restocking levels for nonsuitable timber lands must be specified with the silvicultural prescription. Project-specific determination of adequate stocking must be based on the plan’s desired conditions and objectives applicable to the area and project and be consistent with all other applicable plan components. (General Forest Geographic Area, Roadless Geographic Area, Specially Designated Geographic Area)
10 PRESCRIPTIONS ❖ Adaptation Strategies in Dry Mixed Conifer ✓ Consider Resilience – Transition Prescriptions
11 PRESCRIPTIONS ❖ Adaptation Strategies in Dry Mixed Conifer RESILIENCE
DFC/Goal Tactics •Increase drought-tolerant species •Reduce BA by 40-60% by •Relative densities: 45-75% PP, thinning 5-35% DF, 0-15% AS, 0-10% WF •Favor priority PP>DF>WF •Clumpy, multi-cohort structure •Create openings up to 1 ac •Basal area range: 57 to 78 ft2/ac •Leave legacy groups, clumps (range: 0 to 122)
TRANSITION DFC/Goal Tactics •Increase drought-tolerant species •Retain PP, AS (N slopes, swales) •Increase PP, allow Gambel Oak and •Remove all WF Juniper to increase •Canopy openness target of 30-40% • Open canopy ~ 40 ft2/ac (range 0 to •Enhance current openings 78) •Increase shrubs for big-game winter range
12 PRESCRIPTIONS
Target densities – Stand Density Index
❖ Silviculturists commonly use a relative density index to characterize stocking levels. A popular index in the western United States is stand density index (SDI), which is based on the relationship between tree size and the number of trees per acre (Daniel and others 1979b, Reineke 1933). ❖ Perhaps the greatest advantage of SDI and similar indexes is their independence from site quality and stand age.
✓ Limited moisture (near the lower limit for the species) can result in lower stocking capacity.
❖ Key thresholds for Stand Density Index: ❖ 25% of SDIMax = Onset of Competition/Crown Closure ❖ 35% of SDIMax = Lower Limit of Full Site Occupancy
13 PRESCRIPTIONS
Target densities – Stand Density Index
❖ SDI values and site carrying capacity may decrease in the future with warner, dryer weather patterns.
❖ Mangers may need to target lower SDImax values.
SPECIES CURRENT SDI PROPOSED SDI CHANGE VALUE VALUE
White fir 735 634 -101
Engelmann spruce 735 602 -133
Subalpine fir 735 620 -115
Lodgepole pine 675 679 +4
Ponderosa pine 529 446 -83
Douglas fir 560 570 +10
Gamble Oak 470 652 +182
14 PRESCRIPTIONS
❖ New residual density for a spruce stand could be
✓ 100 sq. ft. of basal area vs. 120 at 30% relative density
❖ Other Considerations
✓ Favor Drought Tolerant Species, where practical
✓ We need to balance short term goals with long term conditions • Current practices attempt to limit Gamble oak expansion.
✓ Other factors: • Aspect • Topography • Elevation • Windthrow • Soils REFORESTATION
❖ Program Scales ✓ Regional needs average 135,000 acres per year. ✓ 26,500 acres of reforestation annual but majority of this is natural regeneration. ✓ 3,000 – 4,000 acres are planted in R2 annually. ✓ Majority of these acres are in wildfire burn areas (Hayman – PSICC, Jasper – Black Hills, Missionary Ridge – San Juan)
❖ Seed Procurement Planning ✓ Forest seed banks are old, do not contain adequate seed for wildfire rehabilitation. ✓ Seed inventories do not contain seed collected for non- commercial, drought tolerant species for progeny tests.
16 REFORESTATION
❖ Assisted Migration / Seed Transfer ✓ Seed transfer beyond current protocol should be considered only with the input of regional geneticists. ✓ Empirical, long-term genetics data for our part of the Rocky Mountains do not indicate plant movement from lower elevations or lower latitudes is an appropriate Rx for climate change. ✓ There is no manual or handbook direction at this time to accommodate assisted migration for NFS.
Recommendations ✓ Consider lower stocking densities for reforestation and stand improvement prescriptions. ✓ Set up progeny tests. ✓ Experiment with other reforestation methods such as direct seeding.
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