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Waldrop, T. A.; Mohr, H. H.; Brose, P. H. 2006. Early dynamics of table mountain pine stands following stand-replacement prescribed fires of varying intensity. In: K. F. Connor. Proceedings of the 13th Biennial Southern Silvicultural Research Conference; February 28-March 4, 2005, Memphis, TN. General Technical Report SRS-92. USDA Forest Service, Southern Research Station, Asheville, NC: 471-474 [5].
Waldrop, Thomas A.; Brose, Patrick H. 1999. A comparison of fire intensity levels for stand replacement of table mountain pine (Pinus pungens Lamb.). Forest Ecology and Management. 113: 155-166 [4].
SPECIES INCLUDED IN THE SUMMARY:Study sites occur in the following plant communities and probably historically experienced one of the fire regimes described below:
| Fire regime information on the vegetation community studied in this Research Project Summary. Fire regime characteristics are taken from the LANDFIRE Rapid Assessment Vegetation Model [3]. This vegetation model was developed by local experts using available literature, local data, and/or expert opinion as documented in the .pdf file linked from the Potential Natural Vegetation Group listed below. | |||
| Vegetation Community (Potential Natural Vegetation Group) | Fire severity* | Fire regime characteristics | |
| Percent of fires | Mean interval (years) |
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| Table Mountain-pitch pine | Replacement | 5% | 100 |
| Mixed | 3% | 160 | |
| Surface or low | 92% | 5 | |
| Appalachian oak forest (dry-mesic) | Replacement | 6% | 220 |
| Mixed | 15% | 90 | |
| Surface or low | 79% | 17 | |
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*Fire Severities: Replacement=Any fire that causes greater than 75% top removal of a vegetation-fuel type, resulting in general replacement of existing vegetation; may or may not cause a lethal effect on the plants. Mixed=Any fire burning more than 5% of an area that does not qualify as a replacement, surface, or low-severity fire; includes mosaic and other fires that are intermediate in effects. Surface or low=Any fire that causes less than 25% upper layer replacement and/or removal in a vegetation-fuel class but burns 5% or more of the area [1,2]. |
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FIRE DESCRIPTION:
Prescribed burning was conducted on April 4, 1997. The burn unit was fired by helicopter using
a plastic sphere dispenser beginning at 1030 hours. Relative humidity was 51% at the time the
fire started, dropped to a low of 27% at 1220 hours, and increased to 32% at 1600 hours.
Temperatures ranged from 15 °C at 0830 hours to 21 °C at 1345 hours. Eye-level wind speeds
ranged from 3 to 13 km/h from the south and southwest. Moisture content was 8% for the duff and
6% for the litter layer at the time the fire started. Fire intensity was generally high, with
crowning in portions of the upper ridges and torching occurring intermittently along the ridge.
Other areas burned with high-intensity flames, but crowning was not observed.
| Mean values of discriminating variables by fire intensity category | ||||
| Fire intensity | Mean bark char height (m) | Height of largest dead tree (m) | Bark char as a percent of tree height | Prefire percent cover of mountain-laurel |
| Low | 1.8 | 10.1 | 14.3 | 26.2 |
| Medium-low | 2.0 | 14.9 | 18.8 | 29.6 |
| Medium-high | 6.6 | 16.4 | 44.3 | 41.1 |
| High | 12.2 | 14.9 | 87.0 | 85.9 |
All areas burned at sufficient temperatures to open serotinous cones. Pine and hardwood basal area decreased after burning at all fire intensities, moreso on high- than low-intensity plots. Low-intensity fire had little effect on pine basal area but decreased hardwood basal area by nearly 25%.
| Basal area (m²/ha) of pines and hardwoods before and after the first postfire growing season | ||||
|
Fire intensity |
Pine basal area | Hardwood basal area | ||
| Before burning | After burning | Before burning | After burning | |
| Low | 6.2a* | 5.9b | 22.1a | 16.8b |
| Medium-low | 10.9a | 6.0b | 23.6a | 5.1a |
| Medium-high | 7.9a | 1.1a | 15.5a | 0.5a |
| High | 6.6a | 0.0a | 20.4a | 1.0a |
| *Means followed by the same letter within a column are not statistically different at the 0.05 level | ||||
Overstory mortality increased for several years after burning, even in areas burned at low intensities. By the end of the 6th growing season, basal area of all surviving trees ranged from 0 m²/ha in the high-intensity plots to 0.5 m²/ha in the low-intensity plots.
Postfire pine seedling density ranged from 1,396 to 9,130 stems/acre. Unexpectedly, the lowest pine seedling densities were in plots burned at the highest intensity levels, possibly because high-intensity fire consumed cones or killed the seeds. The table below provides regeneration data for Table Mountain pine and pitch pine.
| Regeneration (seedlings/acre) of pines by fire intensity level, after the 1st and 6th growing seasons | |||
| Year | Fire intensity | Table Mountain pine | Pitch pine |
| 1997 | Low | 5,608 | 0 |
| 1997 | Medium-low | 9,130 | 0 |
| 1997 | Medium-high | 3,650 | 0 |
| 1997 | High | 1,396 | 0 |
| 2002 | Low | 2,640 | 3,116 |
| 2002 | Medium-low | 4,533 | 2,258 |
| 2002 | Medium-high | 2,578 | 2,702 |
| 2002 | High | 2,486 | 2,194 |
Competition from hardwoods and shrubs that sprouted after fire may inhibit the development
of a pine-dominated stand. There were no significant differences in the number of hardwood
sprouts/acre by fire intensity category for any species after the first growing season. By 2002,
mountain-laurel sprouts were exceptionally dense in plots burned at medium-high and high
intensities. Sprouts of all other species were dense but not significantly different in number
among fire intensity levels. Competition did not seem to greatly impact pine survival, even
though sprout densities were high. Regeneration of hardwoods and shrubs is described in the table
below.
| Regeneration (sprouts/acre) of predominant hardwood and shrub species by fire intensity level, after the 1st and 6th growing seasons | ||||||
| Year | Fire intensity | Blackgum | Oaks* | Sassafras | Other hardwoods | Shrubs |
| 1997 | Low | 6,473 | 1,894 | 192 | 1,076 | 378 |
| 1997 | Medium-low | 6,631 | 3,477 | 3,835 | 1,187 | 800 |
| 1997 | Medium-high | 6,155 | 2,477 | 759 | 1,375 | 3,030 |
| 1997 | High | 4,617 | 3,164 | 1,968 | 3,019 | 5,417 |
| 2002 | Low | 6,951 | 3,375 | 3,803 | 7,260 | 14,229 |
| 2002 | Medium-low | 6,626 | 4,619 | 1,671 | 7,058 | 12,724 |
| 2002 | Medium-high | 10,775 | 7,241 | 3,976 | 8,989 | 69,008 |
| 2002 | High | 9,063 | 11,853 | 6,902 | 8,569 | 81,033 |
| *Includes chestnut oak and scarlet oak | ||||||
Table Mountain pine survival can be hindered if the seedling roots cannot penetrate the duff left after fire. Duff depths varied significantly (P=0.05) among plots burned at different intensity levels, and there was no distinct relationship between duff depth and fire intensity. Height and rooting characteristics for Table Mountain pine seedlings are provided in the table below.
| Height and rooting characteristics of Table Mountain pine seedlings by fire intensity category, after the 1st postfire growing season | |||||
| Fire intensity | Postfire forest floor depth (cm) | Seedling height (cm) | Total root length (cm) | Length of root in soil (cm) | Percentage of seedlings with roots in the soil |
| Low | 5.3ab* | 6.9a | 9.4a | 4.6a | 71.1a |
| Medium-low | 3.8a | 8.6b | 10.4a | 6.4b | 94.6b |
| Medium-high | 7.6b | 7.1a | 10.2a | 3.6a | 63.0 |
| High | 6.6b | 7.4a | 9.7a | 4.3a | 56.1a |
| *Means followed by the same letter within a column are not significantly different at the 0.05 level | |||||
Pine regeneration and hardwood and shrub sprouts were measured following the 6th growing season
after burning. Hardwood sprouts overtopped pines regardless of fire intensity level. Hardwoods
were approximately 2.4 m tall, Table Mountain pines were 1.2 to 1.5 m tall, and pitch pines were
0.9 to 1.2 m tall. Table Mountain pine overtopped shrubs. Even though hardwoods overtop the pines,
they are not expected to eliminate the pines completely, since pines are numerous and are continuing
to receive overhead sunlight.
FIRE MANAGEMENT IMPLICATIONS:
This study provided valuable information on the types of fire needed to create conditions for
successful regeneration of Table Mountain pine. In the first publication, overstory mortality
was thought to occur only on plots where flames reached into the crowns of both hardwoods and
pines. Fires of all intensities killed essentially all overstory trees, but mortality was not
immediate and occurred over a 3- to 6-year period. Regardless of fire intensity, pine regeneration
was abundant in all study plots after 6 years. Fires of all intensities resulted in heavy hardwood
competition. Shrub density was very high, especially in areas where shrub density was high before
burning. Pines remain overtopped by hardwoods, but are expected to survive and may eventually
outgrow the hardwoods.
Observations made the 6th growing season after fire suggest that lower intensity fires, such as those with flame heights of 1.8 to 2.4 m, can be just as successful as the previously recommended medium-high flames at regenerating Table Mountain pine stands. These fires would be safer, easier to accomplish, and can be achieved during an even larger burning window than medium-high or high-intensity fires.
| Common name | Scientific name |
| mountain-laurel | Kalmia latifolia |
| blackgum | Nyssa sylvatica |
| Table Mountain pine | Pinus pungens |
| chestnut oak | Quercus prinus |
| scarlet oak | Quercus coccinea |
| sassafras | Sassafras albidum |
1. Hann, Wendel; Havlina, Doug; Shlisky, Ayn; [and others]. 2005. Interagency fire regime condition class guidebook. Version 1.2, [Online]. In: Interagency fire regime condition class website. U.S. Department of Agriculture, Forest Service; U.S. Department of the Interior; The Nature Conservancy; Systems for Environmental Management (Producer). Variously paginated [+ appendices]. Available: http://www.frcc.gov/docs/1.2.2.2/Complete_Guidebook_V1.2.pdf [2007, May 23]. [66734]
2. LANDFIRE Rapid Assessment. 2005. Reference condition modeling manual (Version 2.1), [Online]. In: LANDFIRE. Cooperative Agreement 04-CA-11132543-189. Boulder, CO: The Nature Conservancy; U.S. Department of Agriculture, Forest Service; U.S. Department of the Interior (Producers). 72 p. Available: http://www.landfire.gov/downloadfile.php?file=RA_Modeling_Manual_v2_1.pdf [2007, May 24]. [66741]
3. LANDFIRE Rapid Assessment. 2007. Rapid assessment reference condition models. In: LANDFIRE. U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station, Fire Sciences Lab; U.S. Geological Survey; The Nature Conservancy (Producers). Available: http://www.landfire.gov/models_EW.php [66533]
4. Waldrop, Thomas A.; Brose, Patrick H. 1999. A comparison of fire intensity levels for stand replacement of Table Mountain pine (Pinus pungens Lamb.). Forest Ecology and Management. 113: 155-166. [29450]
5. Waldrop, Thomas A.; Mohr, Helen H.; Brose, Patrick H. 2006. Early dynamics of Table Mountain pine stands following stand-replacement prescribed fires of varying intensity. In: Conner, Kristina F., ed. Proceedings of the 13th biennial southern silvicultural research conference; 2005 February 28 - March 4; Memphis, TN. Gen. Tech. Rep. SRS-92. Asheville, NC: U.S. Department of Agriculture, Forest Service, Southern Research Station: 471-474. [66295]