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1.4 Ecosystem management: use of fire regimes as indicators

The understanding of fire effects is becoming increasingly important to land managers because wildland fire is a disturbance process closely associated with the concept of ecosystem management. Although governmental and private organizations differ on an exact definition of ecosystem management, the goal of sustainability is basic to most approaches (Christensen et al. 1996). This goal focuses on the delivery of goods and services. Christensen et al. (1996) defined ecosystem management as management driven by explicit goals, executed by policies, protocols, and practices, and made adaptable by monitoring and research based on our best understanding of the ecological interactions and processes necessary to sustain ecosystem structure and function. This definition places primary emphasis on the sustainability of ecosystem structures and processes necessary to deliver goods and services. Ecosystem management also includes other concepts such as the conservation of biodiversity, sustained yield of multiple resources, and ecosystem health (Salwasser 1994).

Managing fire to achieve beneficial effects and avoid unwanted results poses a complex challenge for natural resource managers (Brown and Smith 2000). Even attempts to eliminate harmful fire can cause long term undesirable consequences, such as increased risk of damaging fire and declining ecosystem health (Covington et al. 1994; Mutch et al. 1993). Fire regimes can be used as indicators to help determine appropriate strategies for wildfire protection and prescribed fire use.

A fire regime refers to the character of fire occurring over long time periods and the immediate effects of fire that generally characterize ecosystems. Descriptions of fire regimes are general and broad because of the enormous variability of fire in time and space. The fire regime concept brings a degree of order to a complicated body of fire behaviour and fire ecology knowledge; and provides a simplifying means of communicating about the role of fire among technical and non-technical audiences (Brown and Smith 2000).

There have been several different systems used in classifying fire regimes (Heinselman 1978; Agee 1993; Morgan et al. 1998; and Frost 1998). Brown and Smith (2000) classified fire regimes based on fire severity. Use of fire severity as the key component in describing fire regimes is appealing because it relates directly to the effects of disturbance, especially on survival and structure of the dominant vegetation. Brown and Smith (2000) described fire regimes as follows:

• Understorey fire (applies to forests and woodlands)--fires are generally non-lethal to the dominant vegetation and do not substantially change the structure of the dominant vegetation.

• Stand replacement fire (applies to forests, woodlands, shrublands, and grasslands)--fires kill aboveground parts of the dominant vegetation, changing the aboveground structure substantially. Approximately 80 percent or more of the aboveground dominant vegetation is either consumed or dies as a result of fires.

• Mixed severity fire (applies to forests and woodlands)--severity of fire either causes selective mortality in dominant vegetation, depending on different tree species' susceptibility to fire, or varies between understorey and stand replacement.

• Non-fire regime--little or no occurrence of natural fire.

Generally, the severity and intensity of fires are inversely related to fire frequency (Swetnam 1993). For example, stand replacement fires tend to occur in forests with low fire frequency, and understorey to mixed severity fires tend to occur in forests with high fire frequency (Brown and Smith 2000). Considerable variability exists within this generalization. The role of fire can be understood and communicated through the use of fire regimes. Significant changes in the role of fire due to management actions or possible shifts in climate can be described by shifts in fire regimes. Thus, fire regimes can be used to understand the past role of fire, current changes in fire regimes due to management actions, and as indicators to guide future management through more sustainable practices and policies.

References

Agee, J.K. 1993. Fire ecology of Pacific Northwest forests. Washington, D.C., Island Press. 493 pp.

Brown, J.K. & Smith, J.K., eds. 2000. Wildland fire in ecosystems: effects of fire on flora. Gen. Tech. Rep. RMRS-GTR-42, Vol.2. Ogden, Utah: U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station. 257 pp.

Christensen, N.L., Bartuska, A.M., Brown, J.H., Carpenter, S., D’Antonio, C., Francis, R., Franklin, J.F., MacMahon, J.A., Noss, R.F., Parsons, D.J., Peterson, C.H., Turner, M.G. & Woodmansee, R.G. 1996. The report of the Ecological Society of America committee on the scientific basis for ecosystem management. Ecological Applications. 6(3): 665-691.

Covington, W.W., Everett, R.L., Steele, R.T, Irwin, L.L., Daer, T.A. & Auclair, A.N.D. 1994. Historical and anticipated changes in forest ecosystems of the Inland West of the United States. In Sampson, N.R. & Adams, D.L., eds. Assessing forest health in the Inland West. p. 13-63. New York, Food Products Press.

Frost, C.C. 1998. Presettlement fire frequency regimes of the United States: a first
approximation. In Pruden, T.L. & Brennan, L.A., eds. Fire in ecosystem
management: shifting the paradigm from suppression to prescription
. Tall Timbers fire ecology conference proceedings, 20: 70-81. Tallahasee, FL., Tall Timbers Research Station.

Heinselman, M.L. 1978. Fire in wilderness ecosystems. In J.C.Hendee, G.H. Stankey & R.C. Lucas, eds. Wilderness Management. USDA Forest Service, Misc. Pub. 1365.

Morgan, P., Bunting, S.C., Black, A.E., Merrill, T. & Barrett, S. 1998. Past and present fire regimes in the Interior Columbia River Basin. In Close, K. & Bartlette, R.A., eds. Fire management under fire (adapting to change): Proceedings of the 1994 Interior West Fire Council meeting and program, 1994 November 1-4, Couer d’Alene, ID. Fairfield WA. p. 77-82. International Association of Wildland Fire.

Salwasser, H. 1994. Ecosystem management: can it sustain diversity and productivity?J. of Forestry . 92(8): 6-10.

Simard, A.J. 1997. National workshop on wildland fire activity in Canada: workshop report. Information report ST-X-13, Natural Resources Canada.

Swain, A. 1973. A history of fire and vegetation in northeastern Minnesota as recorded in lake sediment. Quaternary Research 3: 383-396.

Swetnam, T.W. 1993. Fire history and climate change in giant sequoia groves. Science. 262:885-889.


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