Early postfire response of Georgian Table Mountain pine stands burned under prescription at varying intensities
Reeves, Sonja L., comp. 2007. Research Project Summary: Early postfire response of Georgian Table Mountain pine stands burned under prescription at varying intensities. In: Fire Effects Information System, [Online]. U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station, Fire Sciences Laboratory (Producer). Available: https://research.fs.usda.gov/feis/fire-studies/waldrop-et-al-2007
| Abbreviation | Common Name | Scientific Name | Classification | Status |
|---|---|---|---|---|
| Plants | ||||
| KALLAT | mountain laurel | Kalmia latifolia | Life Form: Plants/Shrub Kingdom: Plantae Class: Dicot Order: Ericales Family: Ericaceae Genus: Kalmia | Fed. Protected: No Nativity: Native Invasiveness: Noninvasive |
| NYSSYL | blackgum | Nyssa sylvatica | Life Form: Plants/Tree Order: Cornales Family: Cornaceae Genus: Nyssa | Fed. Protected: No Nativity: Native Invasiveness: Noninvasive |
| PINPUN | Table Mountain pine | Pinus pungens | Life Form: Plants/Tree Kingdom: Plantae Class: Conifer Order: Pinales Family: Pinaceae Genus: Pinus | Fed. Protected: No Nativity: Native Invasiveness: Noninvasive |
| QUECOC | scarlet oak | Quercus coccinea | Life Form: Plants/Tree Kingdom: Plantae Class: Dicot Order: Fagales Family: Fagaceae Genus: Quercus | Fed. Protected: No Nativity: Native Invasiveness: Noninvasive |
| QUEMON | chestnut oak | Quercus montana | Life Form: Plants/Tree Kingdom: Plantae Class: Dicot Order: Fagales Family: Fagaceae Genus: Quercus | Fed. Protected: No Nativity: Native Invasiveness: Noninvasive |
| SASALB | sassafras | Sassafras albidum | Life Form: Plants/Shrub, Plants/Tree Kingdom: Plantae Class: Dicot Order: Laurales Family: Lauraceae Genus: Sassafras | Fed. Protected: No Nativity: Native Invasiveness: Noninvasive |
Unless otherwise indicated, the information in this Research Project Summary comes from the following papers:
- 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].
Study sites were located in the War Woman Wildlife Management Area of the Tallulah Ranger District of the Chattahoochee National Forest, Georgia.
Site Description
Study areas occur on sharp ridgetops and steep slopes with northeastern or southwestern aspects. Soils are moderately deep, somewhat excessively drained, and are very strongly acidic to strongly acidic. The elevations of the 3 study sites were 885 m, 915 m, and 1,100 m.
Common names are used throughout this summary. For a complete list of the common and scientific names of species discussed in this summary and for links to related FEIS species reviews, see the Species in this Study section, above.
Prefire Plant Community
Prior to burning, mean basal area of overstory trees in the study stands was 30.3 m²/ha. Hardwoods made up 21.3 m² of this total, and pines (almost all were Table Mountain pine) the remaining 8.9 m²/ha. Chestnut oak, with 9.2 m²/ha basal area, was the predominant hardwood. Few overstory trees were more than 41 cm DBH and only 2 were over 15 m tall. The shrub layer consisted almost entirely of mountain-laurel, ranging in density from "very thick" to completely absent.
Plant Phenology
Phenology of the vegetation before the spring burn was not described.
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.
Three months after burning, the entire burn unit was surveyed to study the range of fire intensities. Fire intensities were classified as low, medium-low, medium-high, and high and distinguished by mean bark char height, height of tallest tree killed, and bark char height as a percentage of total tree height. Higher percentage of prefire mountain-laurel (a ladder fuel) cover led to higher intensity fires (see table below).
| 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 |
Fire Season/Intensity Classification
Spring/low, medium, and high intensity.
Postfire effects reported were surveyed on 60 plots following the 1st (1997) and 6th (2002) growing seasons.
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%.
| 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.
| Year | Fire intensity | Table Mountain pine | Pitch pine |
|---|---|---|---|
| After 1st growing season | |||
| 1997 | Low | 5,608 | 0 |
| 1997 | Medium-low | 9,130 | 0 |
| 1997 | Medium-high | 3,650 | 0 |
| 1997 | High | 1,396 | 0 |
| After 6th growing season | |||
| 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.
| Year | Fire intensity | Blackgum | Oaks* | Sassafras | Other hardwoods | Shrubs |
|---|---|---|---|---|---|---|
| After 1st growing season | ||||||
| 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 |
| After 6th growing season | ||||||
| 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.
| 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.
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.
| Biophysical Setting | Mean Fire Interval (years) | Fire Severity Percent (%) | ||||||
|---|---|---|---|---|---|---|---|---|
| Code | Fire Regime Group | Low | Mixed | Replacement | All | Low | Mixed | Replacement |
| Series 13520 - Southern Appalachian Montane Pine Forest and Woodland | ||||||||
| 13520_53_54_57_59_60_61 | I-A | 5 | 101 | 88 | 5 | 89 | 5 | 6 |
| Series 13150 - Southern Appalachian Oak Forest | ||||||||
| 13150_48_53_57_59_61 | I-B | 16 | 138 | 604 | 14 | 88 | 10 | 2 |
| Summary | ||||||||
| Minimum | 5 | 101 | 88 | 5 | 88 | 5 | 2 | |
| Maximum | 16 | 138 | 604 | 14 | 89 | 10 | 6 | |
| Mean | 11 | 120 | 346 | 10 | 89 | 8 | 4 | |
| Median | 11 | 120 | 346 | 10 | 89 | 8 | 4 | |
| Percentage of fires in 3 fire severity classes, derived from LANDFIRE succession modeling. Replacement-severity fires cause >75% kill or top-kill of the upper canopy layer; mixed-severity fires cause 26%-75%; low-severity fires cause <26%. | ||||||||
| LANDFIRE. 2020. Biophysical settings models and descriptions, [Online]. Washington, DC: U.S. Department of Agriculture, Forest Service; U.S. Department of the Interior; U.S. Geological Survey; Arlington, VA: The Nature Conservancy, (Producers). Available: https://www.landfirereview.org/search.php [96496] | ||||||||
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