Stand Replacement Fires for Table Mountain Pine:Extreme or Necessary?

A COMPARISON OF FIRE INTENSITY LEVELS FOR STAND REPLACEMENT OF TABLE MOUNTAIN PINE (Pinus pungens Lamb.)

Thomas A. Waldrop and Patrick H. Brose

USDA Forest Service, Southern Research Station, 239 Lehotsky Hall, Clemson, SC 29634-1003, USA

Abstract. Stand-replacement prescribed fire has been recommended to regenerate stands of table mountain pine (Pinus pungens Lamb.) in the southern Appalachian mountains because the species has serotinous cones and is shade prescribed fire in northeast Georgia provided an intolerant. A 350-ha opportunity to observe overstory mortality and regeneration of table mountain pine at various levels of fire intensity. Fire intensity for each of 60 study plots was classified by discriminant function analysis. Fires of low and medium-low intensity gave rise to abundant regeneration but may not have killed enough of the overstory to prevent shading. High-intensity fires killed almost all overstory trees but may have destroyed some of the seed. Fires of medium-high intensity may have been the best choice; they killed overstory trees and allowed abundant regeneration. The forest floor remained thick after fires of all intensities, but roots of pine seedlings penetrated duff layers up to 7.5 cm thick to reach mineral soil. In this study area, fire intensity levels did not have to reach extreme levels in order to successfully regenerate table mountain pine.

Factors Suggesting the Need for Stand Replacement Fires Presence of serotinous cones. Seedlings are intolerant of shade. Seedlings may require mineral soil.

Problems with using Stand Replacement Fire Resources are limited. Forest Service standards and guideline were developed to prevent tree mortality.

Study Objectives To provide an inventory of southern Appalachian ridgetop pine communities. To develop fire prescription guidelines based on regeneration success. Conduct studies of regeneration ecology.

Tallulah Ranger District, Chattahoochee NF1. Tallulah Ridge – 375 ha, April 19972. Big Ridge – 450 ha, April 2003

Andrew Pickens Ranger District, Sumter NF3. Poor Mountain – 325 ha, March 19984. Toxaway Ridge – 375 ha, March 2001

Great Smoky Mountains National Park5. Gregory Ridge - 800+ ha, ??

Study Sites and Burn Dates

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Figure 4. Mortality by dbh class after fires of high intensity. BA changed from 118 to 4 sq. ft. per acre.Density changed from 370 to 4 stems per acre.

Figure 1. Mortality by dbh class after fires of low intensity. BA changed from 123 to 99 sq. ft. per acre.Density changed from 344 to 169 stems per acre.

Figure 2. Mortality by dbh class after fires of medium-low intensity.BA changed from 150 to 67 sq. ft. per acre. Density changed from 434to 67 stems per acre.

Figure 3. Mortality by dbh class after fires of medium-high intensity. BA changed from 105 to 7 sq. ft. per acre. Density changed from 362to 18 stems per acre..

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Possible Factors Contributing to Poor Regeneration withHigh-Intensity Fires

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Seedlings may require open conditionswith thin duff similar to the conditions provided by multiple low-intensity burning.

EARLY DYNAMICS OF TABLE MOUNTAIN PINE STANDS FOLLOWING STAND REPLACEMENT PRESCRIBED FIRES OF VARYING INTENSITY

Abstract--Interest in using stand replacement prescribed fires to regenerate stands of Table Mountain pine (Pinus pungens) has increased in the past decade but the type and intensity of fire needed to achieve success has been undefined. In an earlier paper, we concluded from first-year results that flames must reach into the crowns to kill most overstory trees and provide sunlight to the forest floor. In this paper, we show that lower-intensity flames will eventually achieve the same results.

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Hardwood and Shrub Regeneration afterPrescribed Burning by Intensity and Year.

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Height of Pines and CompetitorsEleven Years after Burning by Various Intensities

CONCLUSIONSFires of all intensities tested created successful stand replacement of TMP. Eventually, all overstory trees died and pine regeneration increased in density. In our earlier studies, we said that mortality only occurred when flames reached into the crowns of hardwoods and pines. Therefore, we recommended medium-high as flames a target for managers. Our new results suggest that lower-intensity fires, such as those with flame heights of 6 to 8 feet, can be just as successful and would be safer and easier to accomplish.

FAQs about TMP (based on a combination of experience and hard research data)

What are the target conditions for TMP regeneration? Open woodlands having TMP with healthy cones in the overstory, little or no midstory, sparse understory, 30 percent shade, duff less than 3 inches thick.

What type of fire will accomplish these targets? Multiple low-intensity fires on a 3- to 7-year cycle may eventually reach this goal. The key is to create a thin duff, partial shade, and maintain a seed source. Will a single stand-replacement fire accomplish the same objective? No. A single fire can be very successful at killing overstory trees and regenerating pines but it will not eliminate hardwood sprouting. Pine seedlings will compete well among hardwood sprouts but a pure stand of TMP will not result.

If I can only burn once, should I prescribe a crown fire? No. We found that the overstory was killed immediately if the flames were tall enough to reach into the lower portions of the crown. In other cases, overstory pines and hardwoods were killed over a 6-year period by fires with flame heights of 6 to 8 feet.

What is the impact to soils? As long as the duff remains intact, there is essentially no erosion or loss of soil fertility. Mycorrhizae are not as abundant after crown fires (50+ foot flames) but this effect is temporary.

Should I time the burn to match a good seed crop? No – but make sure you have seed. TMP has serotinous cones and can store seed for several years. However, cones can open without fire during hot droughty conditions so a quick check for closed cones is a good idea. Seed viability is about 30% for trees over 10 years old.

What is the history of fire in TMP stands? Every stand we measured was all-aged, with trees in every age class from 50 to 150+ years old. This suggests regeneration after frequent disturbances. Most were low-intensity fires but others were high-intensity stand-replacement fires. Regeneration was not evenly distributed possibly due in part to individual tree mortality or localized hot spots. Mountain laurel began regenerating about 50 years ago as fire exclusion became successful.

How old does the stand need to be reintroduce fire after regeneration? None of the stands that we have measured are tall enough to answer that question. With other pine species, a rule of thumb is to keep fire out until the trees are 20 feet tall. A few trees in stands burned in 1997 are reaching that height but most are smaller.

War Woman Table Mountain Pine Study through the Years

Height (ft) 2007 Age 11

Height (ft) 2012 Age 16

Height (ft) 2002 Age 6

Stand Characteristics in 2012Species DBH (in) Num/acOak 2.6 241Other Hwd 1.0 2,336Pine 2.4 1,024

3,702