USE OF F O R E S T ECOSYSTEM CLASSIFICATION SYSTEMS IN FIRE MANAGEMENT D O U G L A S J. M c R A E Natural Resources Canada, Canadian Forest Service, Ontario Region, P.O. Box 490, Sault Ste. Marie, Ontario, P6A 5M7, Canada
Abstract. Forest Ecosystem Classification (FEC) systems have been used in the past mainly for forest management decision-making. FEC systems can also serve an important role for decision-making in other disciplines, such as fire management for both wildfire suppression and prescribed burning operations. FEC systems can provide an important means of identifying potential fuels that may be present on a forest site. This fuel information, in combination with current fire weather conditions, as determined by the Canadian Forest Fire Weather Index (FWI) system, can assist fire managers in determining potential fire behaviour if ignition should occur. FEC systems provide a means of identifying the possible presence of a live understory vegetation component, a fuel layer that has been largely ignored in the past due to a lack of information. Dense understory vegetation can produce a very moist microclimate that can effectively hinder fire spread. The use of FEC systems can help in setting priorities on which wildfires need to be attacked aggressively. For prescribed burning, FEC systems can assist in achieving burn objectives better and more safely.
1. Introduction
Forest Ecosystem Classification (FEC) systems have assisted resource managers in their understanding of the heterogeneous nature of forests and have provided useful means of characterizing this variability. The primary use of FEC systems in Ontario has been in describing the forest and making important silvicultural management decisions (e.g., Racey et al., 1989). However, it is important to realize that FEC systems can also play important roles for decision-making in other disciplines, for example, fire management in both wildfire suppression and prescribed burning operations. One major problem in fire management is that we name different fuel types based upon the makeup of the forest (e.g., jack pine (Pinus banksiana Lamb.) fuel type, black spruce (Picea mariana (Mill.) B.S.E) fuel type, aspen (Populus tremuloides Michx.) fuel type, etc.). Because of this, we do not recognize that each of these forests or fuel types can have several major variations. For fire management, a FEC system can better reveal this condition by helping fire personnel in understanding the actual forest fuels and fire danger potentially present on any forest site. This may help fire managers to appreciate why, sometimes on a fire front, a portion exhibits an intense crowning fire while an adjacent portion is spreading as just a moderate-intensity surface fire. Only a few fire-related articles actually refer to FEC systems. Stocks et al. (1990) produced a photo-series with a detailed quantitative inventory of fuels for important Environmental Monitoring and Assessment 39: 559-570, 1996. (~) 1996 Kluwer Academic Publishers. Printed in the Netherlands.
560
DOUGLASJ, McRAE
FUEL (FEC TYPE)
Fig. 1. A "fire triangle" diagram showing the parameters needed for combustion.
FEC types as outlined in Sims et al. (1989). They hoped that by producing the photoseries, the fuel data would be useful to fire managers in calibrating fire behaviour and fire growth models of the Canadian Forest Fire Behaviour Prediction (FBP) system (Forestry Canada Fire Danger Group, 1992) better. Luke and Archibald (1994) modified the guidelines for forest operation response to fire danger levels for northeastern Ontario by incorporating FEC typing into the decision-making process. This prevented unnecessary shutdown on sites assessed as having low ignition potential, although the overall local fire danger rating was high. Springer et al. (1983) use the FEC system of Jones et al. (1983) to help in planning a prescribed burn. An ordination diagram is consulted to determine which sites may require chemical pretreatment to assist in fire spread based on the probable postharvest abundance of live vegetation. An ordination diagram is also used to describe optimal burning prescriptions for the different forest sites. Racey et al. (1989) interpreted some silvicultural opportunities for prescribed burning based on FEC typing. Use of FEC systems is yet to be fully incorporated into daily, fire suppression activities. This is unfortunate as FEC systems can help immensely in planning and coordinating fire activities. Some use is being made of FEC systems in the planning of prescribed burns. The purpose of this paper is to explain the important role that FEC systems may play in future fire management operations.
2. Fire Behaviour and Fuel Background The fire triangle (Brown and Davis, 1973) is used extensively for fire behaviour training (Figure 1). This simple concept assists students in remembering that fire (combustion) depends on three things to sustain itself: oxygen, heat and fuel. Fire is extinguished when any one of these parameters is taken away. The chemical equation for combustion requires oxygen to convert the fuel into carbon dioxide
561
ECOSYSTEM CLASSIFICATION IN FIRE MANAGEMENT
AERIAL FUELS
~
I MINERAL SOIL
Fig. 2. Profile of a forest showing location and classification of fuels.
and water. Usually, no problems occur in supplying oxygen to a fire, and typically, oxygen supply cannot be considered a major controlling factor on how a fire behaves. Combustion also requires heat to occur. However, once a fire has been ignited there is generally a heat source to continue the combustion process. What does exert a major influence on fire behaviour is the fuel component. The type of fuel, the fuel moisture, and the amount of fuel are but a few of the variables that can drastically affect fire behaviour. A FEC system can be an important tool in understanding what potential fuels are present in any forest ecosystem. Although it does not quantify them, the FEC system does allow a better understanding of what categories of fuels may be present. In the forest, fuels are classified into three categories based on vertical distribution and their general properties: (1) aerial fuels, (2) surface fuels, and (3) ground fuels (Figure 2). A good fire manager understands how these different fuel layers affect fire behaviour. For example, an aerial fuel consisting of conifer species can support crowning fire behaviour, whereas a forest with predominately deciduous species does not support crowning fire behaviour. Deciduous forests are fire proof except for a short period during spring after snow melt and before leaves emerge, when fire will spread in the forest floor fuels but not in the crowns of the trees. Fire managers have generally looked at the surface layer as only containing woody fuels such as downed branches and logs. They have often overlooked the presence and significance of the live vegetation in this layer, as it is not generally considered a fuel able to support combustion. This vegetation, often consisting of herbaceous plants, shrubs, and hardwoods, is important as a deterrent to fire spread and can in fact stop a fire. The reason for this is that as leaves emerge and shield the ground from the direct sunlight, a moist microclimate develops at this level, increasing the fuel moisture of the downed woody materials and ground fuels preventing support
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DOUGLASJ.McRAE
of the combustion process. These sites will support fire spread only in the early spring before the leaves in this layer emerge. Abundance of live understory vegetation varies by FEC type. Ground fuels are important as they represent the fuels present in the organic forest floor. These can be fuels that are generally dry such as lichens (Cladonia spp.), compared with those that are often wet such as Sphagnum (Sphagnum spp.). It must also be emphasized that given the right weather (i.e., prolonged drought), any type of fuel will dry out and burn. FEC systems can help identify what vegetation (fuel) should be present, without having to do an on-site inspection. Fire managers can quickly identify the probable fuels present on any FEC Vegetation Type by viewing the supporting schematics showing the presence of different vegetation in any FEC handbook. By understanding the possible forest composition, a clear understanding of the fuel and fire potential can be developed. Vegetation Types V17, V28, and V29 are three jack pine forest types found in the FEC system for Northwestern Ontario (Sims et al., 1989). They are distinct enough that different fire behaviour among the three would be expected. For example, fire growth in the FEC V29 forest type (jack pine/ericaceous shrub/feathermoss sites) will be unhindered due to the lack of live understory vegetation. In contrast, under the same weather conditions, the V28 forest type (jack pine/low shrub) has a much better developed understory vegetation layer that can hinder a fire's progress due to a more moist understory microclimate. The extreme case for preventing fire spread would be the V17 condition (jack pine/mixedwood/shrub rich), where live understory vegetation is very abundant.
3. Wildfire Management The use of FEC systems can assist fire managers in making important decisions on how to act on wildfires by providing better fuel information to predict fire behaviour. This will lead to better suppression strategies and decisions. This section will review possible uses of FEC systems in wildfire management. The FBP system, using fuel moisture codes and fire behaviour indices of the Canadian Forest Fire Weather Index (FWI) system (Canadian Forestry Service, 1987), predicts several fire behaviour parameters (e.g., fuel consumption, rate of spread, etc.). It can be used to understand the fire danger or to predict the behaviour of actual fires in order to support suppression activities. The FBP system contains ten "benchmark" fuel types for natural standing forests (of which two, the mixedwood types, are split into two seasonal differences) for all of Canada (Table I). In addition, the FBP system has three slash and one grass fuel types. While the system is primarily used in predicting the average fire spread of major fuel types, the system's weakness is that it cannot identify differences in fire spread within variations of a common fuel type. The jack pine example of V-Types V17,
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563
TABLE I Fuel types of the FBP system (Forestry Canada Fire Danger Group, 1992). Group/Identifier Descriptivename
Conifelous C-I C-2 C-3 C-4 C-5 C-6 C-7
Spruce-lichen woodland Boreal spruce Maturejack or lodgepolepine Immaturejack or Iodgepolepine Red and whitepine Conifer plantation Ponderosa pine-Douglas-fir
Deciduous
D-1
Leaflessaspen
Mixedwood
M-I/M-2 M-3/M-4
Boreal mixedwood Dead balsam fir mixedwood
Slash
S-I S-2 S-3
Jack or lodgepolepine slash White spruce-balsam slash Coastal cedar-hemlock-Douglas-firslash
Open O- 1
Grass
V28, and V29, shows where variations in fire spread would be observed but could not be predicted by the present FBP system. If we continue to use jack pine as an example, the FBP system classifies this fuel type into three categories: immature, mature, and slash. The two former categories represent the standing forest and are used since initiation of a crown fire is generally easier in an immature forest. If a specific FEC system is chosen, such as Sims et al. (1989), a total of seven Vegetation Types having a major jack pine component are listed (Table II). Each Vegetation Type can, for fire management purposes, be regarded as a different fuel type. If we use the three categories of the FBP system of immature, mature and slash on these seven FEC V-Types, then we can obtain a potential of twenty-one different fuel types for jack pine. The use of an immature category must be done carefully as FEC systems are based on inventory of the mature forest only. This is due to stand dynamics that can change drastically with
564
DOUGLASJ.McRAE TABLE 1I FEC Vegetation Types in Northwestern Ontario which may contain a major jack pine component, as described by Sims et al. (1989). FEC Vegetation Type Descriptivename V17 V18 V28 V29 V30 V31 V32
Jack pine mixedwood/shrubrich Jack pine mixedwood/feathermoss Jack pine/low shrub Jack pine/ericaceous shrub/feathermoss Jack pine - black spruce/blueberry/lichen Black spruce -jack pine/tall shrub/feathermoss Jack pine - black spruce/ericaceousshrub/feathermoss
time, especially for mixedwood sites. Slash sites can be better allocated because FEC typing of the original mature forest is often available, and is used more for determining potential problems with emerging understory vegetation and forest floor type rather than forest structure. The increase in fuel types should help fire managers in better accounting for fuel differences and for better predicting fire behaviour based on these fuel differences. Fire researchers now need to study, understand and report fire behaviour differences between these vegetation or fuel types. In the meantime, fire managers must recognize the differences between Vegetation Types and plan accordingly. For example, the jack pine fuel type represented in the FBP system is V29. This forest has the least amount of understory vegetation and probably represents the worst situation for fire control. Other jack pine Vegetation Types will experience less severe fire spread. Until actual prediction systems based on Vegetation Types come out, fire managers will have to use their experience to judge these differences. A FEC system approach can assist fire managers in priorizing which fires should be attacked first. This is necessary on days when multiple ignitions are reported and firefighting resources are limited. Using the jack pine example again, a fire burning in a V29 should be attacked first since a fire in a V17 normally will not grow appreciably in size and could be dealt with later. It could also mean sending just minimum resources (i.e., one fire crew) to a V17 fire and several crews to a V29 fire, rather than diverting excessive resources to a benign fire. While this paper has emphasized fuels, it must be remembered that FEC must be used in conjunction with the FWI system calculated from fire weather data. The fuel moisture codes of the FWI system assist in determining fuel conditions, which will affect wildfire behaviour. Over a large region, this task can be simplified and easily presented to fire personnel by combining this information using a computerized Geographical Information System (GIS) approach. The addition of different
ECOSYSTEM CLASSIFICATION IN FIRE MANAGEMENT
565
resource values to this GIS base could assist in determining which wildfires to fight first, based on the expected fire-spread potential and economic loss, when multiple wildfires start on the same day. Such decision-aids are necessary to dispatch limited provincial firefighting resources in the most efficient manner in order to obtain the greatest benefits. The only problem in using FEC systems on wildfire suppression is that many remote areas have yet to be FEC mapped so that the information can be used in fire management decisions. On large, long-term fires, this information could be quickly assessed by surveying the forest area outside the fire perimeter using either on-ground surveys or aerial photographic interpretations. It would be advantageous for fire managers to find out what areas have been FEC-typed in their region prior to a fire event.
4. Prescribed Fire Management Prescribed fires, where the burn size can reach as much as 1 500 ha each, are routinely conducted in the Province of Ontario each year. Such large treatment areas clearly demonstrate the probable heterogeneous nature of the site which makes attaining a single objective, such as duff reduction, difficult because of varying conditions across the site. The use of a FEC system can assist in better achieving burning objectives by identifying these site differences when planning and conducting the prescribed fire. On many candidate prescribed burn sites, FEC typing is now available because of its use in planning the harvesting operation. The moisture regime ordination diagram (Figure 3) showing V-Type location, can prove very useful to the prescribed burn planner. This diagram indicates that sites which are assigned to Vegetation Types at the top of the diagram will be, on the whole, drier than those found at the bottom for any given condition as indicated by the FWI system. Higher fuel moisture codes to obtain similar fuel consumption and higher fire behaviour indices will be required for wetter sites so that the prescribed fire will spread well. During wet years, when the opportunities to burn have been reduced, prescribed burns scheduled on wetter FEC sites may have to be curtailed by mid-summer, as the remainder of the traditional burning period is probably too short to allow for any appreciable drying on these sites. Only on better-drained sites (i.e., those associated with Vegetation Types shown at the top of the ordination diagram), where the moisture regime is dry or fresh, would there be a potential to complete a prescribed burn under these wet conditions. This type of decision support, provided by FEC systems, can help managers determine whether candidate prescribed burn sites may realistically be burned. Managers using this information can also concentrate on those burns that have a high probability of being accomplished rather than wasting time on futile sites. A particularly useful ordination diagram is one showing forest-floor vegetation cover (Figure 4). On shallow, lichen sites (e.g., V30, Sims et al., 1989), prescribed burning should
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proceed only when removal of organic material from the forest floor will be minimized. Prescribed burning may in fact be one of the few treatments that can be effectively carried out on these shallow bedrock sites. Lichen and dead feathermoss sites, because of their unique hydraulic properties, dry out very quickly after any precipitation. In fact, after just a few hours of good drying weather, these sites burn well enough to allow fire to spread (McRae, 1986; Alexander et al., 1991). This is beneficial on shallow sites (e. g., V30) as the fire will spread well enough to consume the harvesting residue but only a minimal amount of organic forest floor. On the other hand, litter-dominated forest floors usually require several days of drying after precipitation has ended before they burn well. This is due to the compacted nature of the forest floor that prevents it from drying quickly. Sphagnum moss retains water well and is generally a poor fire carder. However, Sphagnum will dry out and be burnable if drought conditions prevail. Under normal prescribed burning conditions, Sphagnum-dominated sites will require extensive slash material to assist the spread of fire. Only Sphagnum-dominated sites that have been tree-length harvested should be considered as potential burning sites; fulltree harvested Sphagnum-dominated sites should not be considered for prescribed burning because they will not have the slash conditions required to allow fire to spread well, Prescribed burning should also be carefully evaluated on moist-wet and fresh-moist sites of V1, V2 and V21 (Figure 3) that have been full-tree harvested
567
ECOSYSTEM CLASSIFICATION IN FIRE MANAGEMENT
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Fig. 4. Ordinationdiagramfor the ForestEcosystemClassificationfor NorthwesternOntario(Simset al., 1989) characterizingthe relativesimilarityamong 38 VegetationTypesof forest-floorvegetation
cover characteristics. because these sites will similarly lack the slash required to support fire spread. Prescribed burning guidelines for estimating forest floor removal (depth of burn) could potentially be improved by combining forest floor type and moisture regime of the FEC system, with a fuel moisture code ranking from the FWI system. FEC systems can assist in determining the best ignition strategies for accomplishing a prescribed burn. The use of aerial ignition devices (AID) that use pingpong incendiaries should be avoided on wetter sites such as the moist-wet (e.g., V22, V23, and V34-V38) and fresh-moist (e.g., V1, V2, and V21) sites. The reason for this is that the ping-pong balls can be easily extinguished when they fall into water or onto moist areas. Use of an aerial helitorch can provide better ignition on these sites as it drops a greater number of incendiaries than the AID, compensating for some of them being extinguished by wetter fuel conditions. The use of AID is ideal (and less expensive) on drier sites, such as those with significant cover by lichen and feathermoss. Often when the ground is exposed to full sunlight after harvesting, understory vegetation (especially on shrub-rich sites) can drastically increase. The vegetation growing on such sites can quickly block sunlight from reaching the ground, changing the microclimate underneath the vegetation to one that is too moist to support prescribed fire spread. The area labelled "rich" in Figure 5 represents these shrubrich sites. Any prescribed burning on these sites needs to be scheduled within the
568
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al.,
first growing season after harvesting. After that time, understory vegetation growth may be a significant deterrent to fire spread and the accomplishment of burning objectives. Use of prescribed fire after the first growing season may require a prebum treatment of herbicide to kill the vegetation, thus allowing the site to dry out prior to burning. This type of treatment is referred to as a "brown and bum" technique. Burning on shrub-poor sites can often be delayed two to three years without causing serious problems to fire spread. The area labelled "poor" in Figure 5 represents these types of sites. The two areas of Figure 5 labelled "moderate" (connected with a hatched line) represent sites that have an intermediate understory vegetation development and should be carefully inspected to prescribe proper burning strategies. In years when, due to limited resources or weather, only a limited number of bums can be conducted, priority for burning should be given to the shrub-rich sites, in order to avoid the need for expensive herbicide spraying in following years. Vegetation-poor sites can remain untreated for a few years without any real loss in bumability.
ECOSYSTEMCLASSIFICATIONIN FIREMANAGEMENT
569
5. Summary The use o f FEC systems, in combination with current fire weather conditions as determined by the F W I system, can assist fire managers in determining fuel conditions that affect fire behaviour. Such a task could be greatly simplified and visually presented by combining the information using a GIS approach. The consideration o f different resource values within a GIS environment may help in the prioritization o f wildfires for first attack, based on information such as expected fire spread potential and e c o n o m i c values, when multiple wildfire ignitions occur on the same day. Such decision aids are necessary to dispatch limited firefighting resources in the most efficient manner to obtain the greatest benefits. Prescribed burning success can be improved by using a FEC system approach which can help the forest manager to better appreciate the different moisture regimes and Vegetation Types found on the site. Moisture content o f the ground layer vegetation and surface soil layers may hinder prescribed fire spread thus preventing the attainment o f the burning objectives. Prediction o f forest floor removal (i.e., depth o f a burn) can be better estimated, in combination with the F W I system, by using FEC systems to determine the proposed b u m area s forest floor type and moisture regimes. Decisions to use herbicide spray in a "brown and burn" operation for improving late-season burning conditions due to heavy surface vegetation growth may be better understood using a FEC system. In combination with harvesting information, FEC may also assist in understanding whether a site should even be considered for prescribed burning.
References Alexander, M.E., Stocks, B.J. and Lawson, B.D.: 1991, 'Fire behavior in black spruce-lichen woodland: the Porter Lake Project', Infor. Rep. No. NOR-X-310, For. Can., Edmonton, Alberta, 44 pp. Brown, A.A. and Davis, K.P.: 1973, Forest Fire Controland Use (2nd ed.), McGraw-Hill Book Co., New York, 686 pp. Canadian Forestry Service: 1987, 'Tables for the Canadian Forest Fire Weather Index System' (4th ed.), For. Tech. Rep. No. 25, Dep. Environ., Can. For. Serv., Ottawa, Ontario, 48 pp. Forestry Canada Fire Danger Group: 1992, 'Development and structure of the Canadian Forest Fire Behavior Prediction System', lnfor. Rep. No. ST-X-3, For. Can., Ottawa, Ontario, 63 pp. Jones, R.K., Pierpoint, G., Wickware, G.M., Jeglum, J.K., Arnup R.W. and Bowles, J.M.: 1983, 'Field guide to forest ecosystem classification for the Clay Belt, Site Region 3E', Ont. Min. Nat. Resour., Toronto, Ontario, 161 pp. Luke, A.B. and Archibald, D.J.: 1994, 'Forest operations and fire danger in northeastern Ontario', Tech. Note No. TN-004, Northeast Sci. and Tech. Unit, Ont. Min. Nat. Resour., Timmins, Ontario, 7 pp. McRae, D.J.: 1986, 'Potential use of prescribed fire on full-tree harvested jack pine sites', in: A.L. Koonce (ed.), Prescribed Burning in the Midwest: State of the Art, Proceedings of a Symposium, Mar. 3-6, 1986, Univ. Wisconsin, Steven s Point, Wisconsin, pp. 34-37. Racey, G.D., Whitfield, T.S. and Sims, R.A.: 1989, 'Northwestern Ontario forest ecosystem interpretations', NWOFTDU Tech. Rep. No. 46, Nothwestern Ont. For. Tech. Dev. Unit, Ont. Min. Nat. Resour., Thunder Bay, Ontario, unpaginated.
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Sims, R.A., Towill, W.D., Baldwin, K.A. and Wickware, G.M.: 1989, 'Field guide to the forest ecosystem classification for northwestern Ontario', Ont. Min. Nat. Resour., Toronto, Ontario, 191 pp. Springer, E.A., Wearn, V.H., Amup R.W. and Tarini, A.M.: 1983, 'Supplement #1 - 198Y, in: V.H. Weam, E.A. Springer and A~ Lesage (compilers), Forest Managers Photo Guide to Prescribed Burn Planning, Ont. Min. Nat. Resour., Kapuskasing, Ontario, pp. 49-72. Stocks, B.J., McRae, D.J., Lynham T.J. and Hartley, G.R.: 1990, 'A photo-series for assessing fuels in natural forest stands in northern Ontario', COFRDA Rep. No. 3304, For. Can. - Ont. Region, Sault Ste. Marie, Ontario, 161 pp.
Abstract. Forest Ecosystem Classification (FEC) systems have been used in the past mainly for forest management decision-making. FEC systems can also serve an important role for decision-making in other disciplines, such as fire management for both wildfire suppression and prescribed burning operations. FEC systems can provide an important means of identifying potential fuels that may be present on a forest site. This fuel information, in combination with current fire weather conditions, as determined by the Canadian Forest Fire Weather Index (FWI) system, can assist fire managers in determining potential fire behaviour if ignition should occur. FEC systems provide a means of identifying the possible presence of a live understory vegetation component, a fuel layer that has been largely ignored in the past due to a lack of information. Dense understory vegetation can produce a very moist microclimate that can effectively hinder fire spread. The use of FEC systems can help in setting priorities on which wildfires need to be attacked aggressively. For prescribed burning, FEC systems can assist in achieving burn objectives better and more safely.
1. Introduction
Forest Ecosystem Classification (FEC) systems have assisted resource managers in their understanding of the heterogeneous nature of forests and have provided useful means of characterizing this variability. The primary use of FEC systems in Ontario has been in describing the forest and making important silvicultural management decisions (e.g., Racey et al., 1989). However, it is important to realize that FEC systems can also play important roles for decision-making in other disciplines, for example, fire management in both wildfire suppression and prescribed burning operations. One major problem in fire management is that we name different fuel types based upon the makeup of the forest (e.g., jack pine (Pinus banksiana Lamb.) fuel type, black spruce (Picea mariana (Mill.) B.S.E) fuel type, aspen (Populus tremuloides Michx.) fuel type, etc.). Because of this, we do not recognize that each of these forests or fuel types can have several major variations. For fire management, a FEC system can better reveal this condition by helping fire personnel in understanding the actual forest fuels and fire danger potentially present on any forest site. This may help fire managers to appreciate why, sometimes on a fire front, a portion exhibits an intense crowning fire while an adjacent portion is spreading as just a moderate-intensity surface fire. Only a few fire-related articles actually refer to FEC systems. Stocks et al. (1990) produced a photo-series with a detailed quantitative inventory of fuels for important Environmental Monitoring and Assessment 39: 559-570, 1996. (~) 1996 Kluwer Academic Publishers. Printed in the Netherlands.
560
DOUGLASJ, McRAE
FUEL (FEC TYPE)
Fig. 1. A "fire triangle" diagram showing the parameters needed for combustion.
FEC types as outlined in Sims et al. (1989). They hoped that by producing the photoseries, the fuel data would be useful to fire managers in calibrating fire behaviour and fire growth models of the Canadian Forest Fire Behaviour Prediction (FBP) system (Forestry Canada Fire Danger Group, 1992) better. Luke and Archibald (1994) modified the guidelines for forest operation response to fire danger levels for northeastern Ontario by incorporating FEC typing into the decision-making process. This prevented unnecessary shutdown on sites assessed as having low ignition potential, although the overall local fire danger rating was high. Springer et al. (1983) use the FEC system of Jones et al. (1983) to help in planning a prescribed burn. An ordination diagram is consulted to determine which sites may require chemical pretreatment to assist in fire spread based on the probable postharvest abundance of live vegetation. An ordination diagram is also used to describe optimal burning prescriptions for the different forest sites. Racey et al. (1989) interpreted some silvicultural opportunities for prescribed burning based on FEC typing. Use of FEC systems is yet to be fully incorporated into daily, fire suppression activities. This is unfortunate as FEC systems can help immensely in planning and coordinating fire activities. Some use is being made of FEC systems in the planning of prescribed burns. The purpose of this paper is to explain the important role that FEC systems may play in future fire management operations.
2. Fire Behaviour and Fuel Background The fire triangle (Brown and Davis, 1973) is used extensively for fire behaviour training (Figure 1). This simple concept assists students in remembering that fire (combustion) depends on three things to sustain itself: oxygen, heat and fuel. Fire is extinguished when any one of these parameters is taken away. The chemical equation for combustion requires oxygen to convert the fuel into carbon dioxide
561
ECOSYSTEM CLASSIFICATION IN FIRE MANAGEMENT
AERIAL FUELS
~
I MINERAL SOIL
Fig. 2. Profile of a forest showing location and classification of fuels.
and water. Usually, no problems occur in supplying oxygen to a fire, and typically, oxygen supply cannot be considered a major controlling factor on how a fire behaves. Combustion also requires heat to occur. However, once a fire has been ignited there is generally a heat source to continue the combustion process. What does exert a major influence on fire behaviour is the fuel component. The type of fuel, the fuel moisture, and the amount of fuel are but a few of the variables that can drastically affect fire behaviour. A FEC system can be an important tool in understanding what potential fuels are present in any forest ecosystem. Although it does not quantify them, the FEC system does allow a better understanding of what categories of fuels may be present. In the forest, fuels are classified into three categories based on vertical distribution and their general properties: (1) aerial fuels, (2) surface fuels, and (3) ground fuels (Figure 2). A good fire manager understands how these different fuel layers affect fire behaviour. For example, an aerial fuel consisting of conifer species can support crowning fire behaviour, whereas a forest with predominately deciduous species does not support crowning fire behaviour. Deciduous forests are fire proof except for a short period during spring after snow melt and before leaves emerge, when fire will spread in the forest floor fuels but not in the crowns of the trees. Fire managers have generally looked at the surface layer as only containing woody fuels such as downed branches and logs. They have often overlooked the presence and significance of the live vegetation in this layer, as it is not generally considered a fuel able to support combustion. This vegetation, often consisting of herbaceous plants, shrubs, and hardwoods, is important as a deterrent to fire spread and can in fact stop a fire. The reason for this is that as leaves emerge and shield the ground from the direct sunlight, a moist microclimate develops at this level, increasing the fuel moisture of the downed woody materials and ground fuels preventing support
562
DOUGLASJ.McRAE
of the combustion process. These sites will support fire spread only in the early spring before the leaves in this layer emerge. Abundance of live understory vegetation varies by FEC type. Ground fuels are important as they represent the fuels present in the organic forest floor. These can be fuels that are generally dry such as lichens (Cladonia spp.), compared with those that are often wet such as Sphagnum (Sphagnum spp.). It must also be emphasized that given the right weather (i.e., prolonged drought), any type of fuel will dry out and burn. FEC systems can help identify what vegetation (fuel) should be present, without having to do an on-site inspection. Fire managers can quickly identify the probable fuels present on any FEC Vegetation Type by viewing the supporting schematics showing the presence of different vegetation in any FEC handbook. By understanding the possible forest composition, a clear understanding of the fuel and fire potential can be developed. Vegetation Types V17, V28, and V29 are three jack pine forest types found in the FEC system for Northwestern Ontario (Sims et al., 1989). They are distinct enough that different fire behaviour among the three would be expected. For example, fire growth in the FEC V29 forest type (jack pine/ericaceous shrub/feathermoss sites) will be unhindered due to the lack of live understory vegetation. In contrast, under the same weather conditions, the V28 forest type (jack pine/low shrub) has a much better developed understory vegetation layer that can hinder a fire's progress due to a more moist understory microclimate. The extreme case for preventing fire spread would be the V17 condition (jack pine/mixedwood/shrub rich), where live understory vegetation is very abundant.
3. Wildfire Management The use of FEC systems can assist fire managers in making important decisions on how to act on wildfires by providing better fuel information to predict fire behaviour. This will lead to better suppression strategies and decisions. This section will review possible uses of FEC systems in wildfire management. The FBP system, using fuel moisture codes and fire behaviour indices of the Canadian Forest Fire Weather Index (FWI) system (Canadian Forestry Service, 1987), predicts several fire behaviour parameters (e.g., fuel consumption, rate of spread, etc.). It can be used to understand the fire danger or to predict the behaviour of actual fires in order to support suppression activities. The FBP system contains ten "benchmark" fuel types for natural standing forests (of which two, the mixedwood types, are split into two seasonal differences) for all of Canada (Table I). In addition, the FBP system has three slash and one grass fuel types. While the system is primarily used in predicting the average fire spread of major fuel types, the system's weakness is that it cannot identify differences in fire spread within variations of a common fuel type. The jack pine example of V-Types V17,
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TABLE I Fuel types of the FBP system (Forestry Canada Fire Danger Group, 1992). Group/Identifier Descriptivename
Conifelous C-I C-2 C-3 C-4 C-5 C-6 C-7
Spruce-lichen woodland Boreal spruce Maturejack or lodgepolepine Immaturejack or Iodgepolepine Red and whitepine Conifer plantation Ponderosa pine-Douglas-fir
Deciduous
D-1
Leaflessaspen
Mixedwood
M-I/M-2 M-3/M-4
Boreal mixedwood Dead balsam fir mixedwood
Slash
S-I S-2 S-3
Jack or lodgepolepine slash White spruce-balsam slash Coastal cedar-hemlock-Douglas-firslash
Open O- 1
Grass
V28, and V29, shows where variations in fire spread would be observed but could not be predicted by the present FBP system. If we continue to use jack pine as an example, the FBP system classifies this fuel type into three categories: immature, mature, and slash. The two former categories represent the standing forest and are used since initiation of a crown fire is generally easier in an immature forest. If a specific FEC system is chosen, such as Sims et al. (1989), a total of seven Vegetation Types having a major jack pine component are listed (Table II). Each Vegetation Type can, for fire management purposes, be regarded as a different fuel type. If we use the three categories of the FBP system of immature, mature and slash on these seven FEC V-Types, then we can obtain a potential of twenty-one different fuel types for jack pine. The use of an immature category must be done carefully as FEC systems are based on inventory of the mature forest only. This is due to stand dynamics that can change drastically with
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DOUGLASJ.McRAE TABLE 1I FEC Vegetation Types in Northwestern Ontario which may contain a major jack pine component, as described by Sims et al. (1989). FEC Vegetation Type Descriptivename V17 V18 V28 V29 V30 V31 V32
Jack pine mixedwood/shrubrich Jack pine mixedwood/feathermoss Jack pine/low shrub Jack pine/ericaceous shrub/feathermoss Jack pine - black spruce/blueberry/lichen Black spruce -jack pine/tall shrub/feathermoss Jack pine - black spruce/ericaceousshrub/feathermoss
time, especially for mixedwood sites. Slash sites can be better allocated because FEC typing of the original mature forest is often available, and is used more for determining potential problems with emerging understory vegetation and forest floor type rather than forest structure. The increase in fuel types should help fire managers in better accounting for fuel differences and for better predicting fire behaviour based on these fuel differences. Fire researchers now need to study, understand and report fire behaviour differences between these vegetation or fuel types. In the meantime, fire managers must recognize the differences between Vegetation Types and plan accordingly. For example, the jack pine fuel type represented in the FBP system is V29. This forest has the least amount of understory vegetation and probably represents the worst situation for fire control. Other jack pine Vegetation Types will experience less severe fire spread. Until actual prediction systems based on Vegetation Types come out, fire managers will have to use their experience to judge these differences. A FEC system approach can assist fire managers in priorizing which fires should be attacked first. This is necessary on days when multiple ignitions are reported and firefighting resources are limited. Using the jack pine example again, a fire burning in a V29 should be attacked first since a fire in a V17 normally will not grow appreciably in size and could be dealt with later. It could also mean sending just minimum resources (i.e., one fire crew) to a V17 fire and several crews to a V29 fire, rather than diverting excessive resources to a benign fire. While this paper has emphasized fuels, it must be remembered that FEC must be used in conjunction with the FWI system calculated from fire weather data. The fuel moisture codes of the FWI system assist in determining fuel conditions, which will affect wildfire behaviour. Over a large region, this task can be simplified and easily presented to fire personnel by combining this information using a computerized Geographical Information System (GIS) approach. The addition of different
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resource values to this GIS base could assist in determining which wildfires to fight first, based on the expected fire-spread potential and economic loss, when multiple wildfires start on the same day. Such decision-aids are necessary to dispatch limited provincial firefighting resources in the most efficient manner in order to obtain the greatest benefits. The only problem in using FEC systems on wildfire suppression is that many remote areas have yet to be FEC mapped so that the information can be used in fire management decisions. On large, long-term fires, this information could be quickly assessed by surveying the forest area outside the fire perimeter using either on-ground surveys or aerial photographic interpretations. It would be advantageous for fire managers to find out what areas have been FEC-typed in their region prior to a fire event.
4. Prescribed Fire Management Prescribed fires, where the burn size can reach as much as 1 500 ha each, are routinely conducted in the Province of Ontario each year. Such large treatment areas clearly demonstrate the probable heterogeneous nature of the site which makes attaining a single objective, such as duff reduction, difficult because of varying conditions across the site. The use of a FEC system can assist in better achieving burning objectives by identifying these site differences when planning and conducting the prescribed fire. On many candidate prescribed burn sites, FEC typing is now available because of its use in planning the harvesting operation. The moisture regime ordination diagram (Figure 3) showing V-Type location, can prove very useful to the prescribed burn planner. This diagram indicates that sites which are assigned to Vegetation Types at the top of the diagram will be, on the whole, drier than those found at the bottom for any given condition as indicated by the FWI system. Higher fuel moisture codes to obtain similar fuel consumption and higher fire behaviour indices will be required for wetter sites so that the prescribed fire will spread well. During wet years, when the opportunities to burn have been reduced, prescribed burns scheduled on wetter FEC sites may have to be curtailed by mid-summer, as the remainder of the traditional burning period is probably too short to allow for any appreciable drying on these sites. Only on better-drained sites (i.e., those associated with Vegetation Types shown at the top of the ordination diagram), where the moisture regime is dry or fresh, would there be a potential to complete a prescribed burn under these wet conditions. This type of decision support, provided by FEC systems, can help managers determine whether candidate prescribed burn sites may realistically be burned. Managers using this information can also concentrate on those burns that have a high probability of being accomplished rather than wasting time on futile sites. A particularly useful ordination diagram is one showing forest-floor vegetation cover (Figure 4). On shallow, lichen sites (e.g., V30, Sims et al., 1989), prescribed burning should
566
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proceed only when removal of organic material from the forest floor will be minimized. Prescribed burning may in fact be one of the few treatments that can be effectively carried out on these shallow bedrock sites. Lichen and dead feathermoss sites, because of their unique hydraulic properties, dry out very quickly after any precipitation. In fact, after just a few hours of good drying weather, these sites burn well enough to allow fire to spread (McRae, 1986; Alexander et al., 1991). This is beneficial on shallow sites (e. g., V30) as the fire will spread well enough to consume the harvesting residue but only a minimal amount of organic forest floor. On the other hand, litter-dominated forest floors usually require several days of drying after precipitation has ended before they burn well. This is due to the compacted nature of the forest floor that prevents it from drying quickly. Sphagnum moss retains water well and is generally a poor fire carder. However, Sphagnum will dry out and be burnable if drought conditions prevail. Under normal prescribed burning conditions, Sphagnum-dominated sites will require extensive slash material to assist the spread of fire. Only Sphagnum-dominated sites that have been tree-length harvested should be considered as potential burning sites; fulltree harvested Sphagnum-dominated sites should not be considered for prescribed burning because they will not have the slash conditions required to allow fire to spread well, Prescribed burning should also be carefully evaluated on moist-wet and fresh-moist sites of V1, V2 and V21 (Figure 3) that have been full-tree harvested
567
ECOSYSTEM CLASSIFICATION IN FIRE MANAGEMENT
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cover characteristics. because these sites will similarly lack the slash required to support fire spread. Prescribed burning guidelines for estimating forest floor removal (depth of burn) could potentially be improved by combining forest floor type and moisture regime of the FEC system, with a fuel moisture code ranking from the FWI system. FEC systems can assist in determining the best ignition strategies for accomplishing a prescribed burn. The use of aerial ignition devices (AID) that use pingpong incendiaries should be avoided on wetter sites such as the moist-wet (e.g., V22, V23, and V34-V38) and fresh-moist (e.g., V1, V2, and V21) sites. The reason for this is that the ping-pong balls can be easily extinguished when they fall into water or onto moist areas. Use of an aerial helitorch can provide better ignition on these sites as it drops a greater number of incendiaries than the AID, compensating for some of them being extinguished by wetter fuel conditions. The use of AID is ideal (and less expensive) on drier sites, such as those with significant cover by lichen and feathermoss. Often when the ground is exposed to full sunlight after harvesting, understory vegetation (especially on shrub-rich sites) can drastically increase. The vegetation growing on such sites can quickly block sunlight from reaching the ground, changing the microclimate underneath the vegetation to one that is too moist to support prescribed fire spread. The area labelled "rich" in Figure 5 represents these shrubrich sites. Any prescribed burning on these sites needs to be scheduled within the
568
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first growing season after harvesting. After that time, understory vegetation growth may be a significant deterrent to fire spread and the accomplishment of burning objectives. Use of prescribed fire after the first growing season may require a prebum treatment of herbicide to kill the vegetation, thus allowing the site to dry out prior to burning. This type of treatment is referred to as a "brown and bum" technique. Burning on shrub-poor sites can often be delayed two to three years without causing serious problems to fire spread. The area labelled "poor" in Figure 5 represents these types of sites. The two areas of Figure 5 labelled "moderate" (connected with a hatched line) represent sites that have an intermediate understory vegetation development and should be carefully inspected to prescribe proper burning strategies. In years when, due to limited resources or weather, only a limited number of bums can be conducted, priority for burning should be given to the shrub-rich sites, in order to avoid the need for expensive herbicide spraying in following years. Vegetation-poor sites can remain untreated for a few years without any real loss in bumability.
ECOSYSTEMCLASSIFICATIONIN FIREMANAGEMENT
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5. Summary The use o f FEC systems, in combination with current fire weather conditions as determined by the F W I system, can assist fire managers in determining fuel conditions that affect fire behaviour. Such a task could be greatly simplified and visually presented by combining the information using a GIS approach. The consideration o f different resource values within a GIS environment may help in the prioritization o f wildfires for first attack, based on information such as expected fire spread potential and e c o n o m i c values, when multiple wildfire ignitions occur on the same day. Such decision aids are necessary to dispatch limited firefighting resources in the most efficient manner to obtain the greatest benefits. Prescribed burning success can be improved by using a FEC system approach which can help the forest manager to better appreciate the different moisture regimes and Vegetation Types found on the site. Moisture content o f the ground layer vegetation and surface soil layers may hinder prescribed fire spread thus preventing the attainment o f the burning objectives. Prediction o f forest floor removal (i.e., depth o f a burn) can be better estimated, in combination with the F W I system, by using FEC systems to determine the proposed b u m area s forest floor type and moisture regimes. Decisions to use herbicide spray in a "brown and burn" operation for improving late-season burning conditions due to heavy surface vegetation growth may be better understood using a FEC system. In combination with harvesting information, FEC may also assist in understanding whether a site should even be considered for prescribed burning.
References Alexander, M.E., Stocks, B.J. and Lawson, B.D.: 1991, 'Fire behavior in black spruce-lichen woodland: the Porter Lake Project', Infor. Rep. No. NOR-X-310, For. Can., Edmonton, Alberta, 44 pp. Brown, A.A. and Davis, K.P.: 1973, Forest Fire Controland Use (2nd ed.), McGraw-Hill Book Co., New York, 686 pp. Canadian Forestry Service: 1987, 'Tables for the Canadian Forest Fire Weather Index System' (4th ed.), For. Tech. Rep. No. 25, Dep. Environ., Can. For. Serv., Ottawa, Ontario, 48 pp. Forestry Canada Fire Danger Group: 1992, 'Development and structure of the Canadian Forest Fire Behavior Prediction System', lnfor. Rep. No. ST-X-3, For. Can., Ottawa, Ontario, 63 pp. Jones, R.K., Pierpoint, G., Wickware, G.M., Jeglum, J.K., Arnup R.W. and Bowles, J.M.: 1983, 'Field guide to forest ecosystem classification for the Clay Belt, Site Region 3E', Ont. Min. Nat. Resour., Toronto, Ontario, 161 pp. Luke, A.B. and Archibald, D.J.: 1994, 'Forest operations and fire danger in northeastern Ontario', Tech. Note No. TN-004, Northeast Sci. and Tech. Unit, Ont. Min. Nat. Resour., Timmins, Ontario, 7 pp. McRae, D.J.: 1986, 'Potential use of prescribed fire on full-tree harvested jack pine sites', in: A.L. Koonce (ed.), Prescribed Burning in the Midwest: State of the Art, Proceedings of a Symposium, Mar. 3-6, 1986, Univ. Wisconsin, Steven s Point, Wisconsin, pp. 34-37. Racey, G.D., Whitfield, T.S. and Sims, R.A.: 1989, 'Northwestern Ontario forest ecosystem interpretations', NWOFTDU Tech. Rep. No. 46, Nothwestern Ont. For. Tech. Dev. Unit, Ont. Min. Nat. Resour., Thunder Bay, Ontario, unpaginated.
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Sims, R.A., Towill, W.D., Baldwin, K.A. and Wickware, G.M.: 1989, 'Field guide to the forest ecosystem classification for northwestern Ontario', Ont. Min. Nat. Resour., Toronto, Ontario, 191 pp. Springer, E.A., Wearn, V.H., Amup R.W. and Tarini, A.M.: 1983, 'Supplement #1 - 198Y, in: V.H. Weam, E.A. Springer and A~ Lesage (compilers), Forest Managers Photo Guide to Prescribed Burn Planning, Ont. Min. Nat. Resour., Kapuskasing, Ontario, pp. 49-72. Stocks, B.J., McRae, D.J., Lynham T.J. and Hartley, G.R.: 1990, 'A photo-series for assessing fuels in natural forest stands in northern Ontario', COFRDA Rep. No. 3304, For. Can. - Ont. Region, Sault Ste. Marie, Ontario, 161 pp.
