United States 

Department of 

Agriculture 

Forest Service 

Survival of Northern Red Oak 

Acorns After Fall Burning 

Northeastern Forest 

Experiment Station 

Research Paper NE-678 L.R. Auchm00dy H. Clay Smith 
Abstract 

Survival of recently fallen northern red oak acorns after exposure to a cool fall 

burn was determined on experimental plots in northwestern Pennsylvania. The 

fire consumed the leaf litter and fine woody material of the forest floor and was 

considered as a typical fall burn for this region. No acorns were consumed by the 

fire but some were charred. Between 40 and 49 percent of the acorns contained 

in the litter were killed. The fire was not hot enough to kill Curculio weevil larvae 

within the acorns. Burned acorns infested with Curculio that survived the fire had 

20 percent lower germination rates than unburned acorns. 

The Authors 

L.R. AUCHMOODY is a research forester and principal soil scientist at the 

Northeastern Forest Experiment Station's Forestry Sciences Laboratory at 

Warren, Pennsylvania. He holds B.S. and M.S. Degrees from the State University 

of New York College of Forestry, and a Ph.D. degree from North Carolina State 

University at Raleigh. He conducts research on site evaluation, forest nutrition, 

and regeneration of oaks and Allegheny hardwoods. 

H. CLAY SMITH is Project Leader and principal silviculturist at the Northeastern 

Forest Experiment Station's Timber and Watershed Laboratory at Parsons, West 

Virginia. He received B.S. and MS. degrees from West Virginia and Purdue 

Universities, and joined the Northeastern Forest Experiment Station in 1962. 

Manuscript received for publication 12 May 1993 

Northeastern Forest Experiment Station 

5 Radnor Corporate Center 

100 Matsonford Road, Suite 200 

Radnor, Pennsylvania 19087-4585 

September 1993 
Introduction Methods 

Perhaps more than any single factor, fire has been 

implicated with the establishment and perpetuation of 

today's oak forests. Numerous reviews point out that the 

exclusion of fire from mesic sites results in the replacement 

of oaks by other species following virtually any type of 

cutting (Little 1974; Lorimer 1985, 1989; Crow 1988; Van 

Lear 1991 ; Abrams 1992). The problem of regenerating oak 

is serious throughout Eastern North America on good 

growing sites, and in Europe as well (Crow and lsebrands 

1986). Because of the link between fires and existing oak 

forests, there has been increasing interest in the use of 

prescribed burning to regenerate oaks (Nyland et al. 1982; 

Merritt and Pope 1991 ; Walters 1990). 

Although there is considerable documentation on the effects 

of fire on survival of different overstory species in oak 

stands (Rouse 1986), there is surprisingly little information 

on the survival of acorns that may be present in the forest 

floor during a fire. Korstian (1927) found that most acorns 

had cooked embryos after spring fires with temperatures 

ranging from 500° to 1000°F in the litter layer. He 

concluded that acorns had little chance of survival unless 

they were protected by some nonflammable material. In his 

review of fire in temperate forests, Little (1974) mentioned 

that fires can have an adverse impact on oak regeneration 

by destroying acorns and killing small oak seedlings. 

Similarly, Olson and Boyce (1971) reported that acorns are 

destroyed by burning in wildfires, though no estimates of 

mortality were given. 

In a study to determine the biotic factors that affect northern 

red oak (Quercus rubra L.) reproduction in northwestern 

Pennsylvania, burning was a treatment applied to the forest 

floor on a series of research plots. These fall burns were 

conducted shortly after the current-year's acorn crop had 

matured and fallen to the forest floor. Thus, these 

conditions provided an opportunity to determine the effects 

of fall burning on the survival of acorns that were present. 

The burning plots were located in maturing northern red oak 

stands on the Moshannon State Forest and on the 

Allegheny National Forest in northwestern Pennsylvania. In 

the fall of 1989, acorn samples were collected from 23 

burned and 24 unburned plots on the Moshannon State 

Forest, and in the fall of 1990 from 11 burned and 11 

unburned plots on the Allegheny National Forest. The plot 

size was 14 by 14 feet. Burned and unburned plots were 

located close to each other and generally had a mix of 

acorns from some of the same trees. 

The intensity of the burning treatment was relatively light 

and typical of cool fall fires that occasionally occur in this 

region, where fuel quantities are low and the humus and 

soil beneath the leaf litter are moist. In each of the 2 

burning years, the burns were conducted between 11 a.m. 

and 5 p.m. when the relative humidity was between 40 and 

60 percent, air temperatures near the ground were between 

56' and 71 OF, and winds were less than 6 miles per hour. 

The fires had a flame height of 1 to 3 feet, were relatively 

fast moving, and consumed only the surface litter, fine 

branches, and herbaceous vegetation. Larger branches with 

diameters exceeding 1 inch were not burned completely, 

partly because of their high moisture content. Experience 

suggests that the experimental burns were similar to 

uncontrolled fall fires that might be expected during an 

average season in northwestern Pennsylvania (Fred Noack, 

Allegheny National Forest, 1990, pers. commun.). At the 

time of the burning, we estimated that 95 percent of the 

current acorn crop had fallen and was present at different 

depths in the litter. 

Acorns were collected from two 2-foot-wide diagonal 

transects on each 14- by 14-foot plot within a week after the 

burning had been completed. On each plot, as many as 25 

acorns were collected if they were avaiiable. The actual 

number of acorns collected from individual plots ranged 

from 11 to 25, but there were 25 acorns on most plots. Only 
birned to the point where their high moisture content caused them to burst open. 

sound red oak acorns without Curculio weevil exit holes and 

without rodent damage were collected. In all, 1,610 acorns 

were collected and examined over the 2-year period. 

The collected acorns were placed in zip-lock bags with a 

few pin holes for oxygen exchange and stratified for 3 

months at 40° to 45OF in moist peat. After stratification, the 

acorns were kept moist at 76OF for 2 weeks to allow 

germination to proceed. After 2 weeks, each acorn was 

examined for germination, as indicated by a cracked shell 

and protruding radicle. Germinating acorns were cut open 

and inspected for soundness and for damage by the 

Curculio weevil. Nongerminating acorns also were cut open 

to determine if they had been destroyed by Curculio or from 

burning. Each acorn was classified into four categories: 

Sound and germinated; Curculio infested and germinated; 

Curculio destroyed; Fire destroyed. 

Results 

Acorn Damage By Fire 

One purpose of this study was to evaluate the effect of a 

typical fall burn on the survival of recently fallen acorns. 

Usually, the fire was not hot enough to cause the acorn 

seed coat to split, and no acorns on the sample plots were 

completely consumed by fire; however, many were charred 

(Fig. 1). Data indicated that a number of acorns were killed 

by fire, that is, the acorn embryos were "cooked" or dried 

out and the acorns did not germinate. For the study areas 

on the Moshannon State Forest, an average of 40 percent 

of the sample acorns was destroyed by fire. Similarly, 49 

percent of the acorns from the Allegheny National Forest 

plots were destroyed by fire (Table 1). 

Table 1 .-Number and percentage of northern red oak 

acorns destroyed by fire in northwestern Pennsylvania 

No. acorns Fire-destroyed acorns 

Location sampled Number Percent 

Moshannon 522 21 1 40.4 

Allegheny 270 132 48.9 

Acorn Damage By Insects 

Another purpose of the study was to evaluate the effect of 

the fire on viability and germination of Curculio-infested 

acorns. In general, the burns were not hot enough to kill the 

insects present in the acorns. For the study plots on the 

Moshannon State Forest, about 25 percent of the sample 

acorns were destroyed by insects on both the burned and 

unburned plots. For the Allegheny National Forest plots, an 

average of 8.5 percent of the acorns was damaged by 

insects for both treatments (Table 2). However, not all the 

insect-damaged acorns were destroyed. On the Moshannon 

plots, 43 percent of the acorns damaged by insects on the 
Table 2.-Insect-damaged northern red oak acorns that germinated and produced a 

seedling on burned and unburned plots 

Acorns on burned plots Acorns on unburned plots 

Germinating Germinating 

Number Damaged damaged Number Damaged damaged 

Location sampled Number Percent Number Percent sam~led Number Percent Number Percent 

Moshannon522 122 23.4 53 43.4 537 138 25.7 87 63.0 

Allegheny 270 23 8.5 2 8.7 281 24 8.5 5 20.8 

burned plots germinated and produced seedlings. For the 

unburned plots, 63 percent germinated and produced 

seedlings. On the Allegheny National Forest, 9 percent of 

the insect-damaged acorns on the burned plot germinated 

while 21 percent germinated on the unburned plots. For 

both areas, the unburned plots consistently had better 

germination of insect-damaged acorns and more acorns 

that produced seedlings, indicating that the influence of fire 

plus the insect damage to the seed cotyledon resulted in 

loss of germination. This means that the fire was not hot 

enough or of sufficient duration to kill the Curculio larvae 

inside the acorns without also directly killing the acorns. 

Fire had no effect on the number of acorns destroyed by 

insects as infestation occurred before and was independent 

of the burn. 

Effects on Acorn Production 

The percentages shown in Tables 1 and 2 were applied to 

actual estimates of acorn production in the stands where 

the plots were located (Table 3). Seed-crop estimates were 

made using the cap count method (Shaw 1974), and were 

available for each study area. Using actual 1989 and 1990 

per-acre estimates of acorn-crop production emphasizes the 

impact of fire and insects on the availability of seed for 

establishing new oak seedlings. Table 3 shows the number 

of acorns per acre that would be directly killed by fire and 

the additional number of burned acorns that would be lost 

from insect infestation for a wide range of acorn crop sites. 

About 40 percent of the average acorn crop would be 

destroyed by a typical fall fire on the Moshannon State 

Forest, and an additional 13 percent would be destroyed by 

insects for a total of 53 percent. Based on data from the 

Allegheny National Forest, the percentage of acorns 

destroyed by fire was similar to that for the Moshannon 

plots, but the percentage of the acorns detroyed by insects 

was slightly less (8 percent). Thus, the Allegheny had 48 

percent of the acorn crop destroyed by fire and insects 

combined. 

Discussion and Summary 

The primary purpose of this study was to evaluate the 

effects of fire during the fall season on the survival and 

germination of red oak acorns. Included with this fire 

evaluation is the influence of insect-damaged acorns on 

acorn survival and germination. During the analyses, the 

Table 3.-Estimated numbers per acre of northern red oak acorns destroyed by lire 

and insects 

- -- 

Total 

Acorns Acorns destroyed Acorns destroyed acorns 

Location per acre by fire by insects destroyed - aMoshannon State Forest 

Smith Road 133,584 53,968 17,658 71,626 

Gordon Road 143,458 57,957 18,963 76,920 

Snotrail 38,188 15,428 5,048 20,476 

Average 105,077 42,451 13,889 56,340 

bAllegheny National 

Forest 

Route 337 136,972 55,337 10,653 65,990 

Keller Road 16,456 6,648 1,220 7,928 

Buehler Corners 22,264 8,995 1,732 10,727 

Whistletown 6,776 2,738 527 3.265 

-- 

Average 45,617 18,429 3,548 21,977 

a1989 acorn seed-crop estimates. 

b1990 acorn seed-crop estimates. 
effects of fire and insects were evaluated individually. The 

burns were monitored and classed as light-cool. This is 

typical of the wildfires occasionally occurring in the oak 

stands on the Allegheny Plateau of northwestern 

Pennsylvania during the fall season. 

On the basis of the results of this study, forest managers 

generally can expect about 40 percent of a given northern 

red oak acorn crop on the ground to be destroyed following 

a typical fall burn. Similarly, we would expect about 11 

percent of the burned acorn crop to be destroyed by 

insects-Curculio weevils and Valentinia moths. Thus, 

typical insect damage and a fire combined could destroy 

about 50 percent of the acorn crop. And this does not 

include acorn losses due to deer, other mammals and birds, 

or losses due to ground insects when the acorns germinate 

the following spring. Also, a fall burn will decrease the 

germination of insect-infested acorns. In our study, burning 

reduced the germination of acorns damaged by insects by 

20 percent at Moshannon State Forest and by 12 percent 

on the Allegheny National Forest. 

Unburned plots consistently had more insect-damaged 

acorns that germinated and produced seedlings. This 

suggests that the fire was hot enough to kill or cause 

desiccation of the embryo, and/or kill a portion of the seed 

cotyledon. Also, Curculio weevil exit holes in the acorns 

would increase the likelihood of drying out or desiccating 

and being destroyed when burned. Although the burns were 

of light intensity, the fall burns resulted in about 50 percent 

mortality. Hotter fires would likely increase mortality, and 

cooler fires would decrease it. Thus, seed mortality in this 

study was related to desiccation of the acorn cotyledon and 

direct killing of the seed embryos by fire, and killing by 

insects. 

Buried acorns would have a much higher chance of survival 

when a typical fall burn occurs on the Allegheny Plateau. 

Also, for test purposes, the sample acorns in the study were 

stratified in moist peat, and the germination rate may be 

higher than obtainable in nature. In the normal environment, 

acorns would have a tendency to dry ou't as a result of the 

Gurculio weevil exit holes, but this did not occur in the moist 

peat. 

Seed crops are variable even within the same location. 

Also, more seed was collected in the Moshannon State 

Forest than in the Allegheny National Forest. In 1989, there 

was a good acorn seed crop at the Moshannon, so more 

plots were available to sample. In 1990, only one study site 

had a good acorn crop on the Allegheny, so fewer acorns 

were available to collect. Additional information on the 

variation in acorn seed crop produced on the study areas is 

discussed in Auchmoody et al.1 

There are additional effects of fire as related to vegetation 

establishment. For example, fall burns as used in this study, 

might stimulate dormant fire cherry (Prunus pennsylvania L.) 

seeds to germinate as well as other dormant seeds of 

herbaceous species stored in the soil and humus layers. Other 

light-seeded tree speciessuch as birch, maple, and ash would 

be destroyed unless some of the seed was buried in the soil. 

The significance of fire in combination with insects present in 

forest stands cannot be overlooked when acorn seed crops are 

evaluated. Although fire occurs in oakstands of the Allegheny 

Plateau only occasionally, 40 percent of the estimated acorn 

crop could be destroyed by a fall burn of light intensity. Thus, 

to some forest managers who may be trying to regenerate 

northern red oak, it may become even more important to keep 

fire out of the forest stands. 

Acknowledgments 

The authors recognize Jimmy Galford, Research Entomologist 

(U.S. Forest Service, retired) and Perry Fox, Forestry Technician 

(US Forest Service) for their efforts in coordinating and 

installing the treatment plots and collecting the data for this 

paper. Additional help was provided by the Pennsylvania 

Bureau of Forestry staff on the Moshannon State Forest at 

Clearfield, Pennsylvania, including Ed Richards, Lee Warren, 

and Paul Augustine. Fred Noack and staff from the Sheffield 

Ranger District of the Allegheny National Forest assisted in 

conducting the burns in this study. 

1Auchmoody, L.R.; Smith, H. Clay; Walters, Russell S. 1993. 

Acorn production in northern red oak stands in Pennsylvania. 

Manuscript in preparation. 
Literature Cited 

Abrams, Mark D. 1992. Fire and development of oak 

forests. Bioscience. 42: 346-353. 

Crow, T.R. 1988. Reproductive mode and mechanisms 

for self-replacement of northern red oak (Quercus 

rubra): a review. Forest Science. 34: 19-40. 

Crow, T.R.; Isebrands, J.G. 1986. Oak regeneration-an 

update. In: Proceedings, integrated pest management 

symposium for northern forests. Madison, WI: University 

of Wisconsin, Cooperative Extension Service: 73-86. 

Korstian, Clarence F. 1927. Factors controlling 

germination and early survival in oaks. Bull. No. 19. 

New Haven, CT: Yale University, School of Forestry. 

115 p. 

kit6, Silas. 1974. Effects of fire on temperate forests: 

northeastern United States. In: Kozlowski, T.T.; 

Ahlgren, C.E., eds. Fire and ecosystems. New York: 

Academic Press: 225-250. 

Lorimer, Craig G. 1985. The role of fire in the 

perpetuation of oak forests. In: Johnson, James E., ed. 

Proceedings, challenges in oak management and 

utilization. Madison, WI: University of Wisconsin: 8-25. 

Lorimer, Craig G. 1989. The oak regeneration problem: 

new evidence on causes and possible solutions. For. 

Res. Anal. No. 8. Madison, WI: University of Wisconsin, 

Department of Forestry. 31 p. 

Merritt, Clair; Pope, Phillip E. 1991. The effect of 

environmental factors, including wildfire and 

prescribed burning, on the regeneration of oaks in 

Indiana. Bull. 612. West Lafayette, IN: Purdue 

University, Agricultural Experimental Station. 52 p. 

Nyland, R.D.; Abrahamson, L.P.; Adams, K.B. 1982. Use of 

prescribed fire for regenerating red and white oak in 

New York. In: America's hardwood forestsopportunities unlimited. Proceedings of the 1982 

convention of the Society of American Foresters; 1982 

September 19-22; Cincinnati, OH. SAF Publ. 83-04. 

Bethesda, MD: Society of American Foresters: 163-1 67. 

Olson, David F., Jr.; Boyce, Stephen G. 1971. Factors 

affecting acorn production and germination and early 

growth of seedlings and seedling sprouts. In: Oak 

symposium proceedings. Upper Darhy, PA: U.S. 

Department of Agriculture, Forest Service, Northeastern 

Forest Experiment Station: 44-48. 

Rouse, Cary. 1986. Fire effects in northeastern forests: 

oak. Gen. Tech. Rep. NC-105. St. Paul, MN: U.S. 

Department of Agriculture, Forest Service, North Central 

Forest Experiment Station. 7 p. 

Shaw, M.W. 1974. The reproductive characteristics of 

oak. In: Morris, M.G.; Perring, F.H., eds. The British oak: 

Its history and natural history. Hampton, England, UK: 

Botanical Society of the British Isles by E.W. Classey: 

162-1 81. 

Van Lear, D.H. 1991. Fire and oak regeneration in the 

southern Appalachians. In: Nodvin, Stephen C.; 

Waldrop, Thomas A., eds. Fire and the environment: 

ecological and cultural perspectives. Gen. Tech. Rep. 

SE-69. Asheville, NC: US. Department of Agriculture, 

Forest Service, Southeastern Forest Experiment Station: 

75-21. 

Walters, Russell S. 1990. Site quality, fire, and herbicide 

effects on establishment, growth, and development 

of regeneration three years after partial cutting of oak 

stands. Syracuse, NY: State University of New York. 196 p. 

Ph.D. dissertation. 
Auchmoody, L.R.; Smith, H. Clay. 1993. Survival of northern red oak 

acorns after fall burning. Res. Pap. NE-678. Radnor, PA: U.S. 

Department of Agriculture, Forest Service, Northeastern Forest 

Experiment Station. 5 p. 

Survival of recently fallen northern red oak acorns after exposure to a cool fall 

burn was evaluated in northwestern Pennsylvania. Although no acorns were 

consumed by the fire, some were charred. Between 40 and 49 percent of the 

acorns in the litter were destroyed. The fire was not hot enough to kill Curculio 

larvae within the acorns. Burned acorns infested with Curculio that survived 

the fire had 20 percent lower germination rates than unburned acorns. 

Keywords: Fire, northern red oak, acorn damage, Curculio 

a U. S. GOVERNMENT PRINTING OFFICE: 19931750-123160027 
Headquarters of the Northeastern Forest Experiment Station is in Radnor, Pennsylvania. Field laboratories are maintained at: 

Amherst, Massachusetts, in cooperatfon with the University of Massachusetts 

Burlingion, Vermont, in cooperation-with the University of Vermont 

Delaware, Ohio 

Durham, New Hampshire, in cooperation with the University of New Hampshire 

Hamden, Connecticut, In cooperation with Yale University I. 

Morgantown, West Virginia, in cooperation'with ~estvir~lnia University 

Orono, Maine, in cooperation with the University of Maine 

Parsons, West Virginia 

Princeton, West Virginia 

Syracuse, New York, in cooperation with the State University of New York, 

College of Environmental Sciences and Forestry at Syracuse University 

University Park, Pennsylvania, in cooperation with The Pennsylvania State University 

Warren, Pennsylvania 

Persons of any race, color, national origin, sex, age, religion, or with any handicapping condition are welcome to use and enjoy all facilities, programs, and services of 

the USDA. Discrimination in any form is strictly against agency policy, and should be 

reported to the Secretary of Agricukure, Washington, DC 20250. 

'Caring for the Land and Serving People Through Researcl;r'