More info for the terms:
basal area,
cover,
density,
fire management,
fire regime,
forb,
forest,
fuel,
herbaceous,
litter,
low-severity fire,
natural,
phenology,
potential natural vegetation,
potential natural vegetation group,
prescribed fire,
presence,
restoration,
series,
severity,
tree,
woodlandIn areas where fire has been excluded, a heavy density of American hazelnut
has developed, suppressing desirable tree species and contributing to
fuel buildup [10,21].
Repeated summer fires inhibit the ability of American hazelnut to sprout by
exposing and damaging underground stems and roots and exhausting stored
food reserves. Single fires may eliminate American hazelnut if humus is
sufficiently dry to be completely consumed [6].
FIRE CASE STUDY:
Effects of repeated prescribed fires at Cedar Creek Natural History Area, Minnesota
FIRE CASE STUDY CITATION: Fryer, Janet L., compiler. 2007.
Effects of repeated prescribed fires at Cedar Creek Natural History Area, Minnesota.
In: Corylus americana.
In: Fire Effects Information System, [Online].
U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station,
Fire Sciences Laboratory (Producer). Available:
https://www.fs.fed.us/database/feis/plants/shrub/corame/all.html#FireCaseStudies [
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SPECIES INCLUDED IN THE STUDY: This Fire Case Study contains information on the following species:
Common name Scientific name
American hazelnut Corylus americana
FIRE CASE STUDY REFERENCE: Unless otherwise indicated, the information in this Fire Case Study comes from the following
paper:
Axelrod, A. N.; Irving, F. D. 1978. Some effects of prescribed fire at Cedar
Creek Natural History Area. Journal of the Minnesota Academy of Science. 44(2):
9-11. [3].
STUDY LOCATION:
Prescribed burning was conducted on the Cedar Creek Natural History Area in Anoka and Isanti counties, Minnesota.
SITE DESCRIPTION:
The study sites are on Anoka sand plain upland soils, with fine sands in the
Sartell and Zimmerman series. Topography is generally level [3].
PREFIRE PLANT COMMUNITY:
Cedar Creek Natural History Area contains bur oak-northern pin oak-quaking aspen (Quercus macrocarpa-Q.
ellipsoidalis-Populus tremuloides) woodlands [35],
marshlands, and old fields. The study sites were on the oak woodlands.
American hazelnut clones dominated the understory, and there was an herbaceous ground layer.
Based on the unburned control plots, prefire American hazelnut density was approximately
11 stems/milacre [3].
Study sites are classified in
the following plant community and likely experienced the historic fire regime
described below:
Fire regime information on the vegetation community in which American
hazelnut occurs in this study. Fire regime characteristics are taken from the
LANDFIRE Rapid Assessment Vegetation Model [
38]. This vegetation model was developed
by local experts using available literature, local data,
and 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)
Minimum interval
(years)
Maximum interval
(years)
Northern oak savanna Replacement 4% 110 50 500
Mixed 9% 50 15 150
Surface or low 87% 5 1 20
*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.
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.
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
[
36,
37].
SPECIES PHENOLOGY: American hazelnut phenology was not described. American hazelnut was probably
rapidly elongating its stems
during the spring fires and flowering during the summer fires.
FIRE SEASON/SEVERITY CLASSIFICATION: Spring/low and moderate severity
Summer/moderate severity
FIRE DESCRIPTION: Fire Management Objective: Various repeat prescribed fire treatments were conducted to open stand structure in Cedar Creek's
oak woodland. Prescribed burning was conducted over
an 8-year period. The specific management objective was to reduce American hazelnut presence
in the understory.
Fire prescription and behavior: Four fire treatment sites and an unburned control were selected for this study.
Prescribed burning was conducted annually or on fire-and-rest cycles. A total of
19 prescribed fires were conducted on the 4 burn units. Seventeen of the fires
were conducted in spring, with the earliest fire on 11 April 1969 and the latest
on 16 May 1972. Surface fuels were oak litter and grasses (Poaceae). Fires on
spring-burned sites were conducted before green-up, when surface fuels were mostly or completely
cured. The majority of the prescribed fires were of moderate severity and fairly continuous; however,
Site 3 experienced 2 low-severity, patchy summer fires before the moderate-severity
April 1969 fire gave satisfactory fire continuity. April and May fires were ignited
in the late afternoon, usually after 5:00 p.m., 3 to 10 days after measurable precipitation.
Strip
head fires were used.
Stocking and treatment dates of prescribed-burn
sites on Cedar Creek, MN
Site Treatment Area (acres) 1972 basal area (ft?) Rx fire dates
Site 1 7 burns in 8 years 27 70 4 May 1965,
25 April 1966,
11 April 1967,
26 April 1968,
12 May 1969,
12 April 1971,
16 May 1972
Site 2 8 burns in 8 years 25 42 4 May 1965,
13 April 1966,
5 May 1967,
26 April 1968,
12 May 1969,
4 May 1970,
3 May 1971,
25 April 1972
Site 3 3 burns in 7 years 10 64 30 August 1966,
6 September 1967,
23 April 1969
Site 4 1 burn in 5 years 27 61 14 May 1969
Site 5 unburned control not provided 60 no recent fires
Weather conditions on days of burning ranged as follows:
Weather conditions and fire behavior for the
Cedar Creek burns
Air temperature Relative humidity Windspeed Rate of spread Fuel consumption Flame height* Depth of flame front*
56-91 ?F 26%-72% 1-20 mph 8-15 ft/min 917-6,500 lbs/acre ~2 in-3 ft <1ft in grass fuels
~3 feet in thick oak litter
*Flame height and flame front measures are for
spring fires only. These measures were not provided for the summer fire on
Site 3.
Green-up had begun on some sites burned in late spring,, so herbaceous surface fuels were only
partially cured. These late spring fires burned at lower severities, had slower
rates of spread, and produced more smoke than the other spring fires.
FIRE EFFECTS ON TARGET SPECIES: All the spring fires top-killed American hazelnut clones. Duration of flame
contact with American hazelnut stems was usually less than 1 minute, which was
enough to kill the cambium of aboveground stems. American hazelnut stems on
sites with heavy concentrations of fallen branches and other downed woody debris
from wind-damaged oaks remained in direct contact with flames for as long as 10
minutes. Effects of this longer-burning woody debris on American hazelnut's
underground system were not noted. Effects of the fires on stand structure
and American hazelnut growth are shown below.
Overstory density and American hazelnut density,
height, and biomass on study plots in the 4th
postfire growing season. Data are means (SD).
Treatment Oak overstory basal area (ft/acre) American hazelnut basal area (stems/0.001 acre) Stem height* (inches) Stem biomass (g)
Site 1 (7 burns in 8 years) 70 (46) 19.2 (4.6) 16 (6.1) 16.3 (3.6)
Site 2 (8 burns in 8 years) 42 (68) 19.9 (8.4) 18 (6.1) 30.6 (16.4)
Site 3 (3 burns in 7 years) 64 (39) 8.0 (2.7) 34 (14) 117 (92.2)
Site 4 (1 burn in 5 years) 61 (51) 10.0 (6.2) 30 (9.4) 92.1 (49.4)
Site 5 (unburned control) 60 (44) 11.0 (4.6) 33 (14.2) 150.4 (85.3)
*For American hazelnut stem
height, data are the means of the longest stem on each of 218 plots.
Statistical analyses showed no significant differences (P=0.05 for all
study measures) between either American hazelnut density or stem height on Sites 1 and 2, the annual
burn treatments. Similarly, there were no significant differences in stem
density or stem height between Sites 3 and 4, the treatments with rest years between fire
treatments. Data for the 2 annual fire treatments were therefore pooled and
compared to pooled data for the 2 fire-and-rest treatments. American
hazelnut stocking was significantly denser on annually burned plots (Sites 1 and
2) compared to fire-and-rest plots (Sites 3 and 4), and American hazelnut stems
were significantly taller on fire-and-rest plots (Sites
3 and 4) compared to annually burned plots. The authors attribute
these differences to age variation in American hazelnut stems. Annually burned plots had
only even-aged, 1-year-old stems. As time since fire increased on fire-and-rest plots,
even-aged stems from the first postfire growing season were
augmented with younger, shorter stems.
Both annual fire and fire-and-rest treatments initially reduced American
hazelnut stem density and height compared to the control; however, by fourth
growing season following 1 to 3 fires, there were no significant differences
between American hazelnut density, stem height, or biomass on fire-and-rest
plots compared to unburned plots. However, the series of annual fires
approximately doubled American hazelnut density and reduced mean stem height to
about one-half that of American hazelnut stems on unburned plots. Stems on
unburned plots were older and larger than stems on burned plots, so biomass of
unburned stems was approximately
4 times more than biomass of stems on annually burned plots.
FIRE MANAGEMENT IMPLICATIONS: Fire management objective: The
series of annual fires successfully controlled American hazelnut.
Although density increased, the proportion of the understory occupied by
American hazelnut was less due to reductions in height and biomass. Fire-and-rest
treatments did not control
American hazelnut.
Statistical analyses of the effects of the various fire treatments on the oak
overstory were not provided. Based on overstory oak basal area, overstory stand structures
were similar on fire-and-rest plots and control plots. The Site 1 annual burn
plots had greater oak density than the fire-and-rest and control plots, while
overstory density on the Site 2 annual burn plots was less than fire-and-rest
and control plots. Further burning treatments on Cedar Creek and restoration
fires on similar oak woodland/American hazelnut sites may help explain discrepancies in these study results.
Fire control of American hazelnut: The authors recommend repeated burning on a
regular schedule to restore and maintain oak savannas. Field observations by the
authors suggested that grass and forb cover increased where American
hazelnut height and biomass were reduced by annual burning.
The effect of repeated fires on American hazelnut was temporary, however. In this study,
American hazelnut regained most of its prefire
biomass by the fourth postfire growing season on fire-and-rest sites. Axelrod and Irving [
3]
predict that if burning is conducted at less than 7-year intervals, American hazelnut will completely
regain its prefire height and biomass. The results of this study suggest that a
schedule of annual or nearly annual fires provides optimal American hazelnut control.