Use of prescribed fire to manage hawthorn and speckled alder in a Pennsylvania floodplain
Smith, Jane Kapler, comp. 2011. Use of prescribed fire to manage hawthorn and speckled alder in a Pennsylvania floodplain. 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/burgason-2011
Common names are used throughout this summary. For a list of the common and scientific names of species discussed in this summary and for links to FEIS Species Reviews, see the Appendix.
Source
The information in this Research Project Summary comes from the following paper:
- Burgason, Barry N. 1976. Prescribed burning for management of hawthorn and alder. New York Fish and Game Journal. 23(2): 160-169 [1].
The study area is in McKean County, northwestern Pennsylvania.
Site Description
The study was conducted in the Allegheny River floodplain, in an area with nearly level topography and sandy loam soil, "well below average" in nutrients. Cattle grazed the site until approximately 10 years before the study.
The study area was dominated by speckled alder and hawthorn, both of which were probably present when cattle grazing ended. It is likely that cattle grazing constrained speckled alder to the channels of intermittent streams; with cessation of grazing, speckled alder established in areas away from the streams. Browsing probably maintained hawthorns at heights less than 3 feet (1 m), with abundant ground cover. With cessation of browsing, hawthorns grew to heights of 7 to 8 feet (2 m), reducing light and ground cover.
Four vegetative types were recognized at the time of the study:
- Open (59% of area): Individual speckled alders and hawthorns <4 ft (1 m) tall, with grass and goldenrod species dominating the understory
- Speckled alder (26% of area): Dense stands mostly more than 8 feet (2 m) tall, with sparse understory
- Hawthorn (2% of area): Dense stands of hawthorn 5 to 8 feet (2 m) tall, with sparse understory
- Swale (13% of area): Intermittent stream channels filled with water during spring and periods of high water but generally dry during summer, dominated by bulrush
The study area occurs in a riparian zone in the northeastern United States. Very little is known about historical fire regimes in this plant community type.
Plant Phenology
Burning took place in spring, when understory species were emerging and thus most likely before shrubs had fully leafed out.
This study examined the use of prescribed fire to control hawthorn and speckled alder populations.
Burning was conducted in the early afternoon of 13 April 973. Fuels were "quite dry", but emerging forbs in the understory were moist enough to have "a dampening effect" on fire behavior. The air temperature was 70 F (20 °C), and wind was approximately 5 to10 miles/hour (8-16 km/hr) from the northwest. A drip torch was used to ignite the upwind corner of the study area. Drip-torch ignition continued completely around the perimeter and then crisscrossed the interior of the area. The fire burned readily through the open vegetation type (type 1), but the dense vegetation types (2 and 3) burned mainly along the edges.
Fire Season and Severity Classification
Spring, low
Fire effects were measured on 20 speckled alder and 20 hawthorn stems; measurements were completed within 9 months of the fire.
Fire top-killed 55% of sampled speckled alder stems and 60% of hawthorn stems. The 2 species responded similarly to fire: All stems less than 0.4 inch (1.0 cm) basal diameter were top-killed. Top-kill was greater than 60% for stems up to 1.2 inch (3.0 cm) basal diameter. Less than half of stems larger than 1.2 inch (3.0 cm) basal diameter were top-killed. Stems in dense stands seemed less likely to suffer top-kill than stems in open areas:
| Site condition | Speckled alder | Hawthorn |
|---|---|---|
| Open | 71.4% | 69.2% |
| Dense | 33.3% | 42.8% |
Within 9 months of the prescribed fire, most burned stems of both speckled alder and hawthorn had sprouted near the base of the stem, at or within 2 inches (5 cm) of the soil surface.
All top-killed hawthorn stems sprouted, and no unburned stems sprouted. Top-killed stems produced an average of 4.6 sprouts, with an average basal diameter of 0.1 inch (3 mm) and an average height of 13 inches (32 cm). Cottontails browsed 83.6% of hawthorn sprouts within 9 months of the burn.
Sprouting in speckled alder was not related to fire, occurring on burned and unburned stems at approximately the same rate (90%). Sampled stems produced an average of 8 to 10 sprouts, with basal diameters ranging from 0.1 to 0.5 inch (3-12 mm) and heights ranging from 9 to 47 inches (22-120 cm). Twelve percent of speckled alders were browsed within 9 months of the fire by either white-tailed deer or cottontails.
Speckled alder and hawthorn both sprout after fire, so burning will not eradicate them. However, frequent burning may maintain them as small plants, generally less than 1.2 inch (3 cm) basal diameter, which are susceptible to top-kill by fire. Based on an empirical relationship between stem basal diameter and age, the author recommends burning speckled alder every 9 years and hawthorn every 7 years. These recommendations should be applied with caution, however. The species may respond differently to repeated burning than to a single burn, and the ability to conduct repeated fires depends largely on the abundance of surface vegetation, which is influenced by many factors, including soil characteristics.
| Biophysical Setting | Mean Fire Interval (years) | Fire Severity Percent (%) | ||||||
|---|---|---|---|---|---|---|---|---|
| Code | Fire Regime Group | Low | Mixed | Replacement | All | Low | Mixed | Replacement |
| Series 13170 - Allegheny-Cumberland Dry Oak Forest and Woodland | ||||||||
| 13170_57_61 | I-B | 15 | 59 | 123 | 11 | 73 | 18 | 9 |
| Summary | ||||||||
| Minimum | 15 | 59 | 123 | 11 | 73 | 18 | 9 | |
| Maximum | 15 | 59 | 123 | 11 | 73 | 18 | 9 | |
| Mean | 15 | 59 | 123 | 11 | 73 | 18 | 9 | |
| Median | 15 | 59 | 123 | 11 | 73 | 18 | 9 | |
| 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] | ||||||||
Table A1: Common and scientific names of species mentioned in this summary.
| Common name | Scientific name |
|---|---|
| Forbs | |
| goldenrod species | Solidago species |
| Graminoids | |
| bulrush | Schoenoplectus (Scirpus*) species |
| Shrubs | |
| hawthorn species | Crataegus species |
| speckled alder | Alnus incana subsp. rugosa |
| *This genus has undergone a taxonomic split. The name in parentheses is that used in the source paper. | |
1. Burgason, Barry N. 1976. Prescribed burning for management of hawthorn and alder. New York Fish and Game Journal. 23(2): 160-169. [14317]