Eastern Oak Silviculture The role of prescribed fire. Dan Dey U.S. Forest Service, Northern Research Station Columbia, MO

Size: px
Start display at page:

Download "Eastern Oak Silviculture The role of prescribed fire. Dan Dey U.S. Forest Service, Northern Research Station Columbia, MO"

Transcription

1 Eastern Oak Silviculture The role of prescribed fire Dan Dey U.S. Forest Service, Northern Research Station Columbia, MO

2 6-20 yrs New Jerse Fire Frequency Guyette et al. 2012

3 Tallgrass Prairie Distribution Transeau 1935

4 Historic Distribution of Savannas and Woodlands? Modern Oak Forests Oak Savannas McPherson 1997 Million Acres Oak-Hickory 130 Oak-Pine 34 Oak-Gum-Cypress 30 Savannas in the Midwest 30 million acres Nuzzo % of forests are oaks Smith et al. 2001

5 Historic fire frequency MFI MFI MFI 6-20 MFI 6-20 Interactions between fire and topography, soils, climate effects vegetation composition & structure

6 Oak Adaptations to Fire 183 to to Brose et al ºF for 1 minute 1. Oaks are masting species 2. Acorns are buried in soil by animals Seed moisture Soil poor conductor of heat Location of root collar buds 3. Oaks preferentially store carbohydrates in roots

7 Oak seedlings & saplings have increasing capacity to sprout after fire topkill Low intensity fires can reliably topkill trees up to 4 dbh Oaks are favored by frequent burning

8 Bark protects trees from heat Time to reach 140 o F (a lethal temperature at one minute of exposure) Hare 1965

9 Overstory trees & Low intensity fires Mortality Topkill Slash Concentration 20 dbh Red Oak 5% loss of basal area 18 dbh Red Oak

10 Compartmentalization a boundary setting process a response to wounding Oaks are better than many species 1. Resists loss of normal function -- conductance of water, minerals and carbohydrates 2. Resists spread of fungal infection

11 Decay Resistance of the Heartwood FPL 1967 Resistant or very resistant Moderately resistant Slightly or nonresistant Bur oak Swamp chestnut oak Hickories Chestnut oak Baldcypress (young growth) Maples Post oak Honey locust Red & black oak White oak Longleaf pine Other pines Osage-orange Slash pine Yellow-poplar Black locust Sassafras Sweetgum Cottonwood

12 The Era of Fire Suppression Increasing Forest Density Fire Suppression * States from Minnesota to Louisiana eastward.

13 Fire Regime Condition Class Class I = Low departure from historic pre-euro veg. Class II = Moderate Class III = High Based on Changes in: Species composition Structural stage Canopy closure

14 Changes in Land use history & the forests of today

15 Oak Regeneration Success & Browsing Deer Density (per mi 2 ) Dk Brn = > 45 Tan = Yellow = Green = < 15 Low deer food: uncut mature forests Medium deer food: range of forest seral stages High deer food: forest interspersed with farmland

16 Mean Annual Change Importance Value Fei et al. 2011

17 Common Status of Oak Forests Overstory oaks mature 80 to 120+ yrs No oak in the midstory Oak advance reproduction is absent or small Abundant shade tolerant species Less than 5% of full sunlight on dry-mesic / mesic / hydric sites

18 Initial Floristics Determines Future Forest Composition In Eastern Hardwood Forests Overstory Composition and Size Structure: Seed production Seed bank reserves Stump sprouting capacity Midstory Composition and Size Structure: Sprouting Capacity Continued recruitment into the overstory Understory Composition and Size Structure: Sprouting capacity Continued recruitment into the overstory

19 Sound acorns per tree Red Oak Seed Production Oak seedlings establish in years of mast production Dominant and Codominant oaks are the seed producers Without Oak seed producers regeneration is by artificial methods seedling planting direct seeding Or succession toward non-oaks Sound acorns per tree DBH (cm) Diameter breast height (cm) Downs 1944

20 Survival Probability Survival of Red Oak Seedlings in the forest understory Years since germination fully stocked Mesic Forests: S. Appalachians NE Wisconsin Beck 1970 Loftis 1988 Crow 1992 Less than 5 % of full sunlight common

21 Sources of Oak Regeneration Seedlings Slow juvenile shoot growth 1 yr Preferential allocation of biomass to roots Seedling Sprouts 3 yr Exponential increase in sprouting ability with increasing diameter

22 Key to Oak Regeneration Success Abundant and Large Advance Reproduction Dominance probability Initial basal diameter (cm) (in) Probability of an oak being free-to-grow at age 8 yrs. S. Appalachian Clearcuts Site Index mft Site Index m ft Site Index mft (Loftis 1990)

23 Stump Sprouts Sprouts arising from cut stems > 2 in dbh Fastest growing source of reproduction Stocking insufficient to maintain composition 45 to 75% of dominant oak reproduction from stump sprouts Morrissey et al Gould et al Swaim et al. 2012

24 Not All Oaks Produce Stump Sprouts Probability of live sprout year Age 50 y Northern Red Oak SI = 75 ft SI = 60 ft Age 110 y Parent tree DBH (cm) (in) Southern Indiana clearcut Weigel and Johnson 1998

25 The Key to Sustaining Oak Stocking is Adequate Large Advance Reproduction Oak seedings have good growth 30 to 50% of full sunlight Maximum growth occurs between 50 to 100% full sunlight White oak Intermediate Scarlet oak Intolerant

26 How do we develop larger oak advance reproduction? Net photosynthesis (mg CO 2 /gm dry wt/ hour) saturation point compensation point NET CARBON GAIN NET CARBON LOSS (dark respiration) Northern Red Oak Light Compensation 2 to 5% f.s. Light Saturation 20 to 40% f.s. Increasing height growth 50 to 70% f.s. Light intensity (ue m -2 s -1 )

27 Percent Structure and light Oak seedlings have good growth 30 to 50% of full sunlight PAR and canopy closure as a function of stocking Maximum growth occurs between 50 to 100% full sunlight canopy closure Stocking(%) photosynthetically active radiation Upland oak stands in Missouri Ozarks Blizzard et al. 2013

28 Stand Density & Oak Growth 60 ft 2 per acre or more: reduces survival of oak stumps reduces growth of oak stump sprouts Dey et al reduces oak advance reproduction growth and survival, and hence, density of large oak seedlings Larsen et al Green 2008 Kabrick et al discriminates against red oak species causing shifts to white oaks or other shade tolerant species Kabrick et al Arthur et al Oaks need 30 to 50% f.s. but competitors must be controlled

29 Fire in the Life Cycle of Oak Arthur et al. 2012

30 A leaf covering helps maintain acorn moisture content Leaf litter > 2 deep is a barrier to acorn germination Equilibrium in leaf litter accumulation in yrs Leaf litter recovers to 75% of equilibrium in 4 yrs after fire Fire before acorn drop Fire after acorn drop Fire kills 70% of acorns in Pennsylvania Auchmoody & Smith % mortality in 1-yr-old northern red oak Johnson 1974

31 Advance Repro Survival & Fire Oaks are favored by frequent burning Dey and Hartman 2005

32 Frequent Fire & Stand Structure in an Ozark Forest 79 ft 2 /ac basal area 69% stocking After 10 years -- <5% reduction in overstory basal area Midstory removal can increase light to 10 to 20 % of full sunlight Depending on forest cover type and ecosystem

33 Combining Fire with Group Openings Can Promote Oak Regeneration 3 or 5 fires begun 7 years before gap formation and ending 1 to 2 years after promoted the development of large white oak advance repro Hutchinson et al. 2012

34 Scenario #1: Mature forest no oak advance reproduction It may take 10 to 30 yrs to get a good acorn crop and develop large oak advance reproduction Site preparation burning to reduce leaf litter, reduce competing advance reproduction & midstory, destroy seed in forest floor, and xerify the seedbed to inhibit mesic species germination That is enough time for advanced decay to develop, but larger trees are more resistant to scarring in low intensity burns

35 Scenario #2: Mature forest with abundant small oak advance reproduction Shelterwood harvest removing 50% basal area or to B-level stocking Release burning with low intensity dormant season burn in ±3 years Remove shelterwood, burn in ±3 years If oak seedlings 0.75 basal diameter consider moderate to higher intensity fire in late spring early leaf out Risks advance decay in any overstory trees that will be retained for the long-term, especially with higher intensity burns

36 Scenario #3: After final shelterwood removal, or clearcutting Before crown closure and stem exclusion stage of stand development If competing stems are <4 to 5 dbh, especially with low intensity fires Release burning with low to high intensity fires every 3-5 years as needed to develop competitive oaks If oak reproduction is large enough (e.g., 0.75 basal diameter) go with higher intensity burns in early leaf out to summer season

37 Scenario #4: Crown closure, stem exclusion stage Release burning inhibits continued recruitment into the overstory and is a clumsy, indiscriminant way to control stand density and composition Risk of bole wounding and advanced decay in sapling & polewood crop trees is high Mechanical/chemical release is a better alternative

38 Scenario #5: Uneven-aged management Not appropriate for oaks on mesic & hydric sites Regeneration and overstory recruitment occur simultaneously Fire would set back to seedling stage stems meant for overstory recruitment Midstory stems are dominated by shade tolerant, fire sensitive species Risk of bole wounding and advanced decay in sapling, polewood and small sawtimber trees is high Hard to burn small group openings in a matrix of uncut or single-tree harvest

39 Scenario #6: Savanna & woodland management To reduce density in a mature forest requires moderate to high intensity fires that would cause large bole wounds to residual trees Similar to the fire regimes in the early 1900s that led to so much decay, and volume and value loss The longevity of wounded and decayed trees is reduced due to windthrow and stem breakage It would be better to harvest the overstory to desired stand stocking & use low intensity fires to achieve other ecological objectives and control small hardwood sprouts

40 Dbh age 10 (inches) Oak overstory recruitment: Requires a fire-free period Vigorous oak saplings grow 1.6 in in dbh in 10 years site index 65 ft in Missouri 3.5 Oak stump sprouts grow initially faster in the open Stump Sprout DBH 10 years after Harvest Clearcut Group Single-tree White oak Scarlet oak Black oak

41 Recruitment to Dominance needs to be managed Hilt 1985 Morrissey et al Zenner et al Ward and Stephens 1994 Ward 2009 Only dominant oaks remained at end of stem exclusion Those were largely stump sprouts Oaks were more competitive on xeric & lower quality sites Recommend oak release thinning at crown closure Only oaks that are dominant at end of crown closure are likely to remain dominant/codominant at maturity

42 Crop Tree Release Stand age 10 to 20 years Canopy closure 50 to 75 crop trees per acre 4-sided crown touching method

43 Homogenization of the forest landscape & the need for active forest management to promote oak ecosystems and diversify the landscape 60 to 70% of eastern forests are 40 to 100 years old Shifley et al With developing shade tolerant understories Dominated by woody species and shade tolerant forbs in the understory