Underburning Prescriptions for Red and White Pine in Dry and Dry

Underburning Prescriptions for Red and White Pine in Dry and Dry

Underburning Prescriptions for Red and White Pine
in Dry and Dry-Mesic Northern Forests of the Lake States
The compilation of this document was prompted by a Lake States Fire Science Consortium
webinar on January 19, 2012 presented by Christel Kern (USDA FS Northern Research Station),
Greg Peterson (USDI Bureau Indian Affairs), Joe Harris (Red Lake Reservations, Department of
Natural Resources), and Scott Weyenberg (USDI National Park Service). Their presentation
highlighted long-term research on red pine understory burning at the Cutfoot Experimental
Forest (Buckman 1964; Alban 1977) as well as ongoing prescribed fire programs in pine
ecosystems at Red Lake Reservation and at Voyageurs National Park in northern Minnesota.
These prescription notes are intended to document underburning options for dry and dry-mesic
northern pine forests as published and applied by fire managers in the region.
Intended as context for the information that follows, these resource objectives, burn
requirements and potential site preparations are common examples for lake states pine.
Resource Objectives
1. Return sites to Fire Regime Condition Class 1 and maintain appropriate fire frequencies to
restore natural ecosystem structure, composition and function.
o Include frequent fire periods to reduce fuels and prepare seedbeds for pine
regeneration
o Include fire-free periods to allow for sapling recruitment to the overstory
2. Expose favorable seedbeds by removing Organic L & F layers, retaining some H layer
o (L)itter - organic horizon characterized by accumulation of organic matter derived
mainly from litter residues (leaves, twigs, and woody material). Original structures are
easily recognizable.
o (F)ermentation - organic horizon characterized by accumulation of partly decomposed
(e.g., occupation by filamentous fungi) organic matter derived mainly leaves, twigs, and
woody material. Some of the original structures are difficult to recognize.
o (H)umus - organic horizon characterized by accumulation of decomposed organic
matter in which the organic structures are indiscernible.
o Summer burns are more successful at reducing organic layers than spring burns. In
spring, the soil is cool and moist and do not carry fires as hot as summer burning.
3. Reduce understory competition for pine seedling recruitment
o Dense understory vegetation reduces available above- and below-ground plant
resources and increases the soil organic layer and relative humidity, conditions
unsuitable for pine seedling recruitment
o Single burns will likely reduce balsam fir and non-sprouting, fire-sensitive vegetation
o Multiple burns will likely be required to exhaust the seed bank and/or reduce abundant
sprouting hardwood
4. Reduce overstory tree competition for pine sapling recruitment
o Open canopy conditions increase light availability for seedling growth and survival and
decrease disease incidence by lowering relative humidity and overstory sources.
Overstory trees can be removed over multiple harvest entries; At the least, an initial
partial harvest creates suitable conditions for seedling establishment and another
complete or partial harvest releases sapling to ascend into the overstory
5. Favor Red Pine regeneration to maintain or increase its relative importance.
Burn Requirements
1. Produce sufficient heat on stems of undesirable species to girdle and top kill 80% of stems.
2. Reduce the organic soil layers and expose mineral soil on 40-60% of the burn area
3. Minimize crown scorch and basal char damages to limit overstory mortality to 10% or less.
4. Schedule regeneration burns, the expected last burn of a series of preparatory burns, in
good seed crop years to facilitate acceptable germination and recruitment and meet
seedling establishment objectives.
Potential Site Preparations
1. Use preparatory burns to reduce slash loads and competing vegetation
2. To extend growing season burn windows (for preparatory or regeneration burns), reduce
dense understory brush with spring burning or summer mowing one year prior to the
summer burn .
3. To promote seedling establishment, reduce % canopy cover to desired levels (<50% for Red
Pine and <80% for White Pine) before or just after the regeneration burn
Seasonal Suitability for understory burns: The Ponemah Pines Experience in Minnesota
Season of burn greatly affects the success of underburning. Growing season burns generate
more heat and consumption of fuels and the forest floor; thereby, severely damaging cambium
and roots and reducing vigor of shrubs and hardwoods. Dormant or spring burns are cooler,
top-kill hardwoods and shrubs, and consume little of the forest floor; as such, hardwood
rootstocks are protected under soil organic matter and capable of resprouting. Although
repeated summer burning is effective at reducing thick understories (Buckman 1964; Alban
1977), opportunities to burn in summer are limited by weather and fuel conditions.
The Red Lake Reservation Department of Natural Resources and the USDI Bureau of Indian
Affairs have an ongoing program of fire use in the management of the Ponemah Pines, a ~90year-old red pine site with a dense hazel understory in northern Minnesota. The program
objective is to naturally-regenerate the forest at the end of the rotation with prescribed fire
and timber harvest. Developing the fire program for the site has involved both spring and
summer burning. A key to their successful execution of numerous summer burns has been to
create suitable summer burning conditions prior to the actual summer burn. To do this, hazel is
mowed or spring-burned one year prior to the summer burn. This preparatory step changes
the understory microclimate and extends the summer burn window. The various underburns at
Ponemah Pines provide an example of suitable weather and fuel conditions for summer and
spring burning over the last 10-15 years (Table 1).
Table 1. Weather and fuel conditions related to season of burn
at the Ponemah Pines site. Days since rain (DSR) was collected
from nearby NOAA weather stations in Keliher and Bemidji,
MN. Litter and duff flammability are characterized by Days
Since Rain, Duff Moisture Code (DMC) and Buildup Index
(BUI). The Fire Weather Index (FWI) indicates overall fire
potential. The table’s cells are colored according to the
concurrence of actual weather and fuel conditions to ideal
prescription conditions.
Below Prescription
Within Prescription
Top of Prescription
Above Prescription
Date
Season
Days Since 0.1" Rain Days Since 0.5" Rain Duff Moisture Code Buildup Index
Fire Weather Index
Averages
Bemidji Kelliher
Bemidji Kelliher
Bemidji Kelliher
Bemidji kelliher Bemidji Kelliher DSR_.1" DSR_.5" DMC
5/1/1986 Spring
5/28/1997 Spring
5/1/1999 Spring
5/7/2001 Spring
5/12/2001 Spring
5/22/2002 Spring
5/18/2004 Spring
5/31/2006 Spring
5/23/2009 Spring
5
12
5
12
19
20
25
21
17
2
0
5
10
1
17
10
5
2
13
1
1
7
0
5
13
1
17
10
25
30
13
6
18
9
13
27
30
13
53
35
35
33
30
13
38
25
15
28
34
21
20
14
34
35
30
16
40
26
0.3
16
17
5
21
14
8
12
16
4
7
4
Average
7
6
7
16
27
28
22
29
13
8
7/22/2005 Summer
7/27/2005 Summer
8/5/2005 Summer
8/17/2007 Summer
8/18/2007 Summer
8/24/2007 Summer
7/13/2009 Summer
8/25/2011 Summer
7
1
2
22
23
2
1
2
4
9
18
6
7
13
16
12
21
26
36
22
23
29
16
6
10
15
24
36
37
43
16
17
62
47
40
87
88
60
49
20
33
44
70
70
73
83
54
47
79
68
70
107
109
85
68
30
43
56
85
95
98
111
74
70
31
18
32
34
33
27
21
13
14
13
28
24
26
19
22
19
Average
8
11
22
25
57
59
77
79
26
21
BUI
FWI
8.5
0
2.5
3.5
11.5
1
9
8.5
6
8.5
0
12.5
17.5
13
3.5
17.5
9.5
10
19.5
0
24
30
30
13
45.5
30
24
23
0
24.5
31.5
32
18.5
30
20
22
9.5
0
4.15
14
16.5
4.5
14
9
9
5.5
5
10
14
15
7.5
8.5
7
9
15.5
20.5
30
29
30
36
16
11.5
24
47.5
45.5
55
78.5
80.5
71.5
51.5
33.5
58
61
62
77.5
101
103.5
98
71
50
78
22.5
15.5
30
29
29.5
23
21.5
16
23
Burn Prescription Windows
Factor
Disturbance Regime
and
Burn Sequence
Seasonality
Overstory Damage
and Mortality
Parameters, Thresholds and Justifications
Disturbance Regime – Coordinate with Regeneration Plans:
 Though there is evidence that understory burning reduces
understory competition during stand development, the primary
objective of producing favorable seedbeds (along with reducing
understory competition) suggests that burns should be coordinated
with other regeneration efforts.
Burn Frequency – Multiple Burns over several years:
 Multiple growing season burns may be required to reduce
competition, especially with hardwood (hazel, maple) understory.
Buckman (1964) demonstrated that multiple annual summer burns
significantly reduce hazel competition.
Growing Season (June, July, August):
 Growing season burns are favored for both control of understory
competition and coordination with late summer/fall seed dispersal
and spring germination in Red and White Pine.
 Increase growing season burn windows by mowing or other brush
reduction practice the summer prior to a summer burn.
Dormant Season: April, May, (October?)
 Early spring understory burning may produce reduction of thickets,
but must be followed by growing season burn as soon as sufficient
surface fuels are available, generally the summer of the following
year.
 Slash Reduction may be accomplished under cool surface
temperatures (< 60F) and moderated Fine Fuel Moisture Code
(FFMC) of 85 or less in spring.
Fireline Intensity/Flame Length: Less than 3.3 ft (1 m)
 McRae, Lynham, and Frech (1994) suggest that backing flames of 57 inches may be sufficient for understory reduction.
 Using Canadian Forest Fire Behavior Prediction (CFFBP) Fuel Type C5 for Dry-Mesic Northern Forests, Initial Spread Index (ISI) of 6-8
with FFMC of 85-89 should produce adequate flames under typical
summer drought conditions.
 Using CFFBP Fuel Type C-3 for Dry Northern Forests, ISI of less than
4 with FFMC of 84-87 may be necessary to keep projected flames
low. It may be necessary to restrict fires to backing spread to obtain
acceptable windspeeds and smoke/heat ventilation under typical
summer drought conditions.
Maximum Ambient Surface Temperature : less than 75°F (opt.)
 Thresholds have been identified in some prescriptions in
combination with flame length limits to further protect overstory
trees from crown scorch.
Factor
Parameters, Thresholds and Justifications
Litter and Duff Reduction in growing season burns:
 Several parameters may be used as thresholds for this
consideration. Days since rain (both 0.1” and 0.5” thresholds), Duff
Moisture Code (DMC) and Buildup Index (BUI). They are highly
correlated and produce generally similar accuracy in characterizing
burn windows.
Burn Severity and
 The following thresholds are not hard boundaries. They are used as
Duff Reduction
guides. Values outside these ranges may be mitigated through
ignition patterns and rates.
o Days Since 0.10” Rain of at least 7 days since wetting rain and
Days Since 0.50” Rain of 2-4 weeks since last ½ “rain event.
o Duff Moisture Code (DMC): 30-63 for summer burns
o Buildup Index (BUI): 45-77 for summer burns
These parameters are frequently generated by agency policy and
surrounding values at risk.
 Growing season burns will produce more smoke and may dictate
more mitigating measures.
Smoke Management
 Fuel Consumption and Burn Duration: See Smoke Management
Plans
 Smoke Dispersal Indicators: See Smoke Management Plans
These parameters are frequently dictated by agency policy and
surrounding values at risk.
 Spotting Potential and Spread Rates: generally based on indicators
of ignition and spotting distances. FFMC, Windspeed, and/or ISI
are generally used as thresholds.
Holding and Control
 Fireline Intensity/Flame Length and Crown Fire Potential are usually
not holding & control problems when considering these understory
burns, especially during growing season conditions.
 Holdover fire problems may be identified by Drought Code (DC).
Ignition and Extinguishment
1. Growing Season: use strip headfire, keeping strips narrow and limiting the number of strips
ignited concurrently to control fire intensity and protect overstory trees. Extended duration may
accomplish needed duff reduction, however mopup to limit root collar damage may be needed.
2. Dormant Season: strip headfire and strip flanking fire may both be possible, allowing greater
intensity prior to bud flush. Little holdover fire should reduce need for mopup.
3. Slash Reduction: Because surface spread should be discontinuous, ignition of individual slash
jackpots will be necessary. Mopup may be necessary to limit reburn potential.
Monitoring Considerations
1. Seed production and dispersal should be evaluated once summer burns have commenced, with
seed traps placed in the units after each burn is completed to quantify production.
2. Bole Char damage should be evaluated after each burn to determine extent of damage.
References
Alban, D.H., 1977, Influence on soil properties of prescribed burning under mature red pine. USDA
Forest Service, St. Paul, Minnesota, Research Paper, NC-139.
Buckman, R., 1964. Effects of prescribed burning on hazel in Minnesota. Ecology 45, 626-629.
Burns, Russell M., and Barbara H. Honkala, tech. coords. 1990. Silvics of North America: 1. Conifers; 2.
Hardwoods. Agriculture Handbook 654, U.S. Department of Agriculture, Forest Service, Washington,
DC. vol.2, 877 p.
McRae, D. J., T. J. Lynham, and R. J. Frech. 1994. Understory prescribed burning in red pine and white
pine. The Forestry Chronicle, v. 70, no. 4, p. 395-401.
Any questions or comments regarding this document can be directed to any of the following
contributors:
Christel Kern, Research Forester, Northern Research Station – USDA Forest Service; [email protected]
Greg Peterson, Fire Management Officer, Minnesota Agency/Red Lake Forestry – USDI Bureau of
Indian Affairs; [email protected]
Joe Harris, Forestry Fuels Specialist, Department of Natural Resources – Red Lake Reservation;
[email protected]
Scott Weyenberg, Great Lakes Ecoregion Fire Ecologist, USDI National Park Service;
[email protected]
Robert Ziel, Program Manager, Lake States Fire Science Consortium – Joint Fire Sciences Program;
[email protected].