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Research Project Summary: Effects of surface fires in a mixed red and eastern white pine stand in Michigan

Gucker, Corey L, comp. 2005. Research Project Summary: Effects of surface fires in a mixed red and eastern white pine stand in Michigan. In: Fire Effects Information System, [Online]. U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station, Fire Sciences Laboratory (Producer). Available: [].

Source: Unless otherwise indicated, the information in this Research Project Summary comes from the following paper:

Neumann, David D.; Dickmann, Donald I. 2001. Surface burning in a mature stand of Pinus resinosa and Pinus strobus in Michigan: effects on understory vegetation. International Journal of Wildland Fire. 10: 91-101.

Prescription fires were set in Compartment 7 of the W. K. Kellogg Experimental Forest (42 22' N, 85 20' W) of Kalamazoo County in Michigan's southwestern lower peninsula.

Burning occurred in a 4-ha red pine (Pinus resinosa) and eastern white pine (P. strobus) plantation established in 1932. The plantation was on a hillside sloping in an east to west direction; only 1 ha was level. Trees had been thinned periodically since 1950. Soils were well-drained, fine to coarse, sandy loams [4].

The study site is in the following vegetation classifications:

FRES10 White-red-jack pine [2]
K095 Great Lakes pine forest [3]
SAF 15 Red pine [1]
SAF 20 White pine-northern red oak-red maple

Prior to the fires, the average density of red pine was 131 trees/ha, dbh ranged from 16 to 40 cm, and average basal area was 29 m/ha. The average density of white pine trees was 93/ha, dbh measurements ranged from 20 to 60 cm, and basal area averaged 16 m/ha. Other prominent woody vegetation in the plantation included red maple (Acer rubrum), sugar maple (A. saccharum), hickory (Carya spp.), black cherry (Prunus serotina), white, red, and black oaks (Quercus alba, Q. rubra, Q. velutina), common buckthorn (Rhamnus cathartica), and northern bush honeysuckle (Diervilla lonicera). The most common understory species were violet (Viola spp.), spinulose woodfern (Dryopteris carthusiana), broadleaf enchanter's nightshade (Circaea quadrisulcata), and bedstraw (Galium spp.).

Phenology of the vegetation prior to the fires was not described.

Once-burned site:
10 May 1991/low severity

Twice-burned site:
10 May 1991/low severity
10 May 1993/low severity

Researchers burned plantation vegetation to assess the effects of fire on the associated species, since literature suggests that restoring natural ecosystem processes in pine forests is beneficial.

Prescription fires were strip headfires that burned on 2 sites, ignited with drip torches. Fire behavior was similar on the once-burned site and the site burned biennially. Strips were approximately 8 m apart on flat areas and a bit closer as slope steepness increased. Flame lengths ranged from 0.2 to 0.8 meter, and less than 10 pines had over 80% of their needles scorched. Almost all understory vegetation was top-killed, but no more than the top 1.5 cm of the needle-leaf litter layer was consumed. The humus layer was left intact, and no downed wood greater than 2.5 cm in diameter was consumed. The recorded Canadian forest fire weather indices indicate low-severity fires. Fire conditions are summarized below:

  Fireline weather conditions Canadian Forest Fire Weather Indices*
Fire date Temperature (C) Relative humidity (%) Wind (km/h) FFMC DMC DC ISI BUI FWI
10 May 1991 26-29 32-40 <3.2, gusts to 8 90.5 23 76 6.5 26 11.6
10 May 1993 28-32 20-22 <3.2, gusts to 8 92.7 33 84 8.1 34 15.6
*For a description of the fire weather indices, see the Research Project Summary Revegetation in a subalpine
forest after logging and fire in central British Columbia

The pine-dominated overstory remained relatively unchanged by fire; however, the proportion of hardwood species decreased on sites burned twice. Below are the proportions of overstory species in burned and unburned 0.4- to 0.5-ha plots as of 1995:

Common name Unburned Burned once Burned twice
eastern white pine 35% 32% 37%
red pine 61% 64% 61%
Hardwood species 4% 4% 2%

While the overstory was unaffected by fire, the pine and hardwood sapling and large seedling** forest layers decreased significantly (p= 0.05) when burned. Unburned plots had almost double the number of saplings and 15 times the number of large seedlings of plots burned once. Two fires completely removed the sapling layer, but some large seedlings persisted. Below are the densities of woody vegetation by size class and burn treatment in 1995:

Burn treatment Unburned Burned once Burned twice
Total overstory basal area
s (m/ha)
48.87.9a* 46.78.4a 47.511.2a
Saplings (2-5.9 cm dbh)
s (number/ha)
16,1119,010c 9,2777,870b 00a
Large seedlings**
(>1 m, ≤1.9 cm dbh)
s (number/ha)
3,9441,860b 277960a 1661,130a
* Values followed by different letters are significantly different (p= 0.05).
**Seedlings represents a small stem size class. Term does not imply or dispute origin from seed.

There were no saplings on sites burned twice, and most woody species decreased after single fires. Exceptions were common buckthorn and sassafras (Sassafras albidum), which increased on burned plots, and two species, viburnum (Viburnum spp.) and tuliptree (Liriodendron tulipifera), that occurred only on burned plots. The density of boxelder (A. negundo), red oak, and elderberry (Sambucus spp.) was unchanged by the single fire.

The number of dominant seedlings on burned plots was substantially fewer than on unburned plots. Dominant seedlings included red maple, black cherry, and sugar maple. Many large seedlings occurred only on unburned plots. These were American hornbeam (Carpinus caroliniana), northern bush honeysuckle, green ash (Fraxinus pennsylvanica), and common prickly ash (Zanthoxylum americanum). Below are the densities of large woody seedlings** (<1 m, ≤1.9 cm dbh) on burned and unburned plots as of 1995.

Common name Scientific name Unburned Burned once*
box elder Acer negundo 56 56
red maple Acer rubrum 3,611 833
sugar maple Acer saccharum 1,111 667
American hornbeam Carpinus caroliniana 56 0
hickory Carya spp. 722 167
hackberry Celtis occidentalis 111 0
flowering dogwood Cornus florida 56 0
beaked hazelnut Corylus cornuta 167 111
northern bush honeysuckle Diervilla lonicera 1,278 0
glossy buckthorn Frangula alnus 778 444
white ash Fraxinus americana 333 111
green ash Fraxinus pennsylvanica 333 0
tuliptree Liriodendron tulipifera 0 222
mulberry Morus spp. 111 56
sweet cherry Prunus avium 167 56
black cherry Prunus serotina 3,167 500
white oak Quercus alba 667 389
red oak Quercus rubra 667 667
black oak Quercus velutina 333 0
common buckthorn Rhamnus cathartica 944 1,722
elderberry Sambucus spp. 444 444
sassafras Sassafras albidum 556 2,389
viburnum Viburnum spp. 0 444
grape Vitis spp. 389 0
common pricklyash Zanthoxylum americanum 56 0
*There were no large seedlings on plots burned biennially.
**Seedlings represents a small stem size class. Term does not imply or dispute origin from seed.

Three years following fire, the coverage of small woody seedlings was significantly (p=0.05) greater on singly and biennially burned plots than unburned plots. Hickory, oak (Quercus spp.), common buckthorn, sumac (Rhus spp.), sassafras, poison-ivy (Toxicodendron radicans), Virginia creeper (Parthenocissus quinquefolia), and blackberry (Rubus spp.) all had greater coverage on both singly and biennially burned plots than on unburned plots. Coverage of Virginia creeper and blackberry was more than double on burned plots. Glossy buckthorn (Frangula alnus) was found only on plots burned biennially. Ash seedling coverage remained relatively unchanged by fire. Rose (Rosa spp.) and grape (Vitis spp.) coverage increased on plots burned once but was lower on plots burned twice. Bristly greenbrier (Smilax tamnoides) coverage was substantially lower on plots burned once, but on plots burned twice coverage was nearly the same as on unburned plots. Maple (Acer spp.), northern bush honeysuckle, pine (Pinus spp.), cherry (Prunus spp.), and basswood (Tilia americana) seedling coverage was greatest on unburned plots. The mean percent cover of small (<1 m) woody seedlings** on burned and unburned plots in 1994 is summarized below.

Common name Scientific name Unburned Burned once Burned twice
maple Acer spp. 2.11 1.57 0.44
hickory Carya spp. 0.28 0.51 0.38
northern bush honeysuckle Diervilla lonicera 0.64 0.4 0.4
glossy buckthorn Frangula alnus 0 0 0.28
ash Fraxinus spp. 0.23 0.28 0.24
Virginia creeper Parthenocissus quinquefolia 4.88 11.98 11.11
pine Pinus spp. 0.73 0.23 0.32
cherry Prunus spp. 1.1 0.36 0.27
oak Quercus spp. 0.5 1.89 0.87
common buckthorn Rhamnus cathartica 0.53 1.9 1.5
sumac Rhus spp. 0 0.26 0.21
rose Rosa spp. 0 0.11 0
blackberry Rubus spp. 2.73 12.66 16.73
elderberry Sambucus spp. 0.08 0.01 0.48
sassafras Sassafras albidum 2.68 4.78 4.78
bristly greenbrier Smilax tamnoides 0.87 0.24 0.89
basswood Tilia americana 0.5 0.13 0
eastern poison-ivy Toxicodendron radicans 0.74 1.44 1.34
grape Vitis spp. 1.35 1.82 0.43
Total* 2024.1b 40.633.5a 40.738 a
*Values followed by different letters are significantly (p= 0.05) different.
**Seedlings represents a small stem size class. Term does not imply or dispute origin from seed.

Herbaceous coverage was significantly (p= 0.05) less on unburned than both singly and biennially burned plots. The mean coverage of herbaceous species was double that of unburned plots on both the singly and biennially burned plots. Biennially burned plots had a substantial understory that averaged less than 1 m in height. The understory of once-burned plots that had a longer recovery period averaged 1 to 1.5 m in height. Seventeen of the twenty-three forb species had greater or unchanged coverage on both burned plots than on unburned plots. The rest of the forb species had greatest coverage on either the singly or biennially burned plots. American pokeweed (Phytolacca americana) and groundnut (Apios americana) displayed the greatest coverage differences between burned and unburned plots. Both graminoid genera also had greater coverage on the burned plots. The average percent cover of herbaceous species on burned and unburned plots in 1994 is given below [4].

Common name Scientific name Unburned Burned once Burned twice
groundnut Apios americana 0.29 1.62 1.09
lesser burrdock Arctium minus 0 1 0.07
common milkweed Asclepias syriaca 0 0.83 0.11
aster Aster spp. 0.08 0.91 0.14
broadleaf enchanter's nightshade Circaea lutetiana ssp. canadensis 0.57 0.29 1.09
pointedleaf ticktrefoil Desmodium glutinosum 0 0.18 0.4
spinulose woodfern Dryopteris carthusiana 2.88 4.39 3.24
Virginia strawberry Fragaria virginiana 0.03 0.2 0.12
bedstraw Galium spp. 0.43 0.52 0.3
orange hawkweed Hieracium aurantiacum 0 0.33 0.07
prickly lettuce Lactuca serriola 0 0.07 0.14
partridgeberry Mitchella repens 0 0.33 0
Clayton's sweetroot Osmorhiza claytonii 0.18 0.33 0.06
mountain woodsorrel Oxalis montana 0 0.06 0.22
American lopseed Phryma leptostachya 0.23 0.32 0.16
American pokeweed Phytolacca americana 0.08 1.26 4.84
Canadian clearweed Pilea pumila 0.29 0.02 0.4
mayapple Podophyllum peltatum 0 0.2 0.01
smooth Solomon's-seal Polygonatum biflorum 0.29 0.63 0.26
common sheep sorrel Rumex acetosella 0 0.10 0.13
common dandelion Taraxacum officinale 0.04 0.11 0.13
trillium Trillium spp. 0 0.03 0.14
violet Viola spp. 1.74 0.67 2.69
sedge Carex spp. 0.03 0.28 0.08
bluegrass Poa spp. 0.03 0.37 0.17
Total* 7.312.4b 15.420a 16.422.4a
*Values followed by different letters are significantly different (p= 0.05).

The researchers provide frequency data in the original paper that are not presented here.

This study allowed researchers to assess the changes that may accompany the reintroduction of fire into mixed pine communities. Prescription fires in this mixed pine plantation caused considerable changes in the herbaceous layer, and woody seedling and sapling composition, and stand structure. However, the pine-dominated overstory was relatively unchanged by fire. Herbaceous and small woody seedling coverage increased on burned plots, while large woody seedling coverage decreased on plots burned once. The entire large woody seedling layer was removed from biennially burned plots. While the likelihood of fires every 2 years in this system is unlikely today or historically, the tolerance of this fire regime by many of the species is noteworthy. The researchers suggest a fire return interval of 5 to 10 years to produce an old-growth mixed pine community like those that existed prior to European settlement of the area.


1. Eyre, F. H., ed. 1980. Forest cover types of the United States and Canada. Washington, DC: Society of American Foresters. 148 p. [905]
2. Garrison, George A.; Bjugstad, Ardell J.; Duncan, Don A.; Lewis, Mont E.; Smith, Dixie R. 1977. Vegetation and environmental features of forest and range ecosystems. Agric. Handb. 475. Washington, DC: U.S. Department of Agriculture, Forest Service. 68 p. [998]
3. Kuchler, A. W. 1964. United States [Potential natural vegetation of the conterminous United States]. Special Publication No. 36. New York: American Geographical Society. 1:3,168,000; colored. [3455]
4. Neumann, David D.; Dickmann, Donald I. 2001. Surface burning in a mature stand of Pinus resinosa and Pinus strobus in Michigan: effects on understory vegetation. International Journal of Wildland Fire. 10: 91-101. [40201]

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