Morgan M. Robertson

 The practice of prescribed burning of upland habitats in the upper Midwest is a widespread restoration and management tool, and the ecological processes involved are becoming more fully understood as literature and practical experience develop on the subject. However, the equally-widespread practice of burning in wetlands has remained largely unresearched, its techniques borrowed from upland prescriptions, and its effects unmonitored. The USFWS Biological Report on Fire in North American Wetlands Ecosystems and Fire-Wildlife Relations makes this important summary statement:

 In general, fire has been treated as one of a number of management tools appropriate for wetlands, with its major use that of eradication of undesirable vegetation. Unlike the literature on fire in terrestrial upland communities, however, specific fire prescriptions, knowledge of fire behavior under different fuel loadings and environmental conditions, and the detailed consequences of differing fire frequencies, fire intensities, and fire severities in wetlands are largely unknown (Kirby et al.1988:10).

Furthermore, a complete literature review on the subject of fire in wetlands in 1988, found that only 20% of the literature in the United States dealt with the area of the Midwest and Great Plains, while only in the coastal marshes of Louisiana had enough data been collected to begin the process of constructing broad management prescriptions (Kirby et al.1988:15). Clearly, the effective use of fire in wetland restoration and managment is problematic. This review examines the accumulated knowledge and research associated with prescribed burning as a restoration and management tool in wetlands in the upper Midwest, at this nascent stage in its development as a systematic management technique, both through a review of literature and through information gathered from professional resource managers and scientists. The first section will cover the practical considerations of wetlands burning techniques, particularly as the technology and practical considerations differ from burning uplands. The second section will contain commentary on the use of fire to achieve several wetlands management goals articulated by professional managers, including brush removal, the creation of game bird habitat, and the promotion of natural vegetation

There is an informal literature on burn safety and procedure which dwells mostly on upland sites and does not reflect the concerns about wetlands burning which were mentioned in several interviews with professional managers. Pauly (1985) simply mentions the fact that wetlands will carry fire as well as uplands under moderately dry conditions, and cannot be counted on to serve as natural firebreaks. Conditions in a wetland leading to a more difficult burn procedure include fuel load, smoke density, and inaccessibility.

Due to higher productivity in wetlands and the density of the most common wetlands dominants (Phragmites, Spartina, Typha and Phalaris spp.), and to the fact that these frequently occur as monocultures, fuel loads are often considerably higher per unit area in wetlands than in uplands. This creates a much hotter burn, and under the right conditions, a faster one. The intensity of the updraft often carries embers farther than an upland burn might, and firebreaks may thus have to be wider. Steve Eggers, biologist with the US Army Corps of Engineers in St. Paul, MN notes that reed canary grass (Phalaris arundinacea), is particularly liable to produce windborne embers when stands are burned (pers. comm.). Ron Bowen of Prairie Restorations, Inc., explains that the density of vegetation also makes the creation of firebreaks much more difficult. Whereas burning small parcels of upland prairie is manageable with the creation of appropriate firebreaks, Bowen notes, burning a wetland in very difficult when a parcel boundary intersects the wetland because of the impossibility of creating adequate firebreaks.

Burning cattail marshes presents a problem of smoke management. While the smoke from upland fires can be thick and hazardous to a burn crew, cattails (Typha spp.) produce an extremely thick, black smoke that Patty Meyer, Project Leader at the Horicon Marsh NWR in Wisconsin, compares to the burning of tires (pers. comm.). This presents an even greater hazard to the burn crew, and Meyer notes that several cattail marshes near roads are virtually impossible to burn due to the smoke hazard presented to drivers.

The two considerations of smoke density and fire intensity create difficulties for burn crew members who, in wetlands, often must rely only on hand spraying from backpack-mounted water tanks. The large mobile water tanks that burn managers often use to saturate large areas as firebreaks, or to put out fires at the edges of the prescribed area, cannot maneuver through wetlands. Dan Rhode, Technical Officer at the Carlos Avery Wildlife Management Area in Minnesota, partially solves this problem with the use of a powerful truck-mounted spraying unit that carries thousands of gallons of water and can spray several hundred feet (pers. comm.). This unit must remain at the margin of the wetland, though, and clearly is not a substitute for mobility across the entire prescription area. Due to lack of accessibility, a burn crew in a wetlands area can use only the tools they can carry with them to the site, and the burn inevitably requires more personnel; this significantly alters the flexibility Meyer feels she has as a manager of wetlands burns in comparison to the upland burns she performs, and she feels that this explains why at Horicon Marsh wetlands are burned less frequently than uplands (pers. comm.).

The intelligent application of fire as a management tool will vary depending on the goal of the management, as well as the information-gathering strategies used in constructing that goal. Of four management professionals interviewed for this review, none reported the use of a system of monitoring the progress and change of burned sites, nor of long-term achievement of prescription goals. The USFWS has recently begun offering a course in pre-burn monitoring in order to improve both the ecological science of prescribed burning and the accountability of money disbursed from each regional office’s fire budget (Meyer pers. comm.). Meyer also reports that at the Horicon Marsh NWR, managers will begin the practice of taking pictures of burn sites before each burn, but that complicated monitoring systems will be extremely difficult to implement. This difficulty will be even greater in wetland sites, in which a prescribed burn may have to take place on very short notice because of the shortage of days suitable for burning; Meyer reports that in 1996, only two days of the year were appropriate for burning their wetland sites (pers. comm.). The lack of monitoring translates into a lack of ability to achieve management goals past the immediate prescription. Although managers have relied on a qualitative sense of progress or decline in the ecosystems under their care, efficient management and effective restoration will require the ability to know in quantitative terms the degree to which a goal has been achieved. Below, three of the primary management and restoration goals articulated by the professional managers contacted for this review are discussed, with reference to the literature where appropriate.

Brush removal was the most frequently mentioned benefit of wetlands burning mentioned by the four managers contacted. There is virtually no mention of brush removal in the literature on wetlands specifically, although it is a commonly-mentioned benefit of uplands burning, possibly because woody vegetation is not a management problem of open-water or shallow marshes, but of wet meadows and wet prairie; Salix species can quickly dominate and shade out desired vegetation in moist, but not inundated, soils. Brush removal is a primary goal of burning both mesic and hydric prairies (Thompson 1992, White 1986), and apparently interviewees were not making a distinction between emergent marshes and wet meadows in their responses. Brush removal is not a particularly controversial goal: it is easy to assess success or failure, and brush is not usually considered critical to the habitat wetlands-dependent species of wildlife in the upper Midwest.

Many wetlands across the upper midwest region of the United States are managed with the primary goal of providing nesting and breeding habitat for ducks (Eggers pers. comm.) and other game birds. Rhode reports that the primary use of fire in wetlands at Carlos Avery Wildlife Management Area is for the purpose of promoting dense stands of cattail and reed canary grass for nesting, while maintaining pockets of open water for foraging (Rhode pers. comm.). That a fall or spring burn will promote rejuvenation of reed canary grass is certainly borne out in the literature (Apfelbaum & Sams 1987), cattail (Mallik & Wein1986), Phragmites (Thompson & Shay 1985) and cordgrass (Johnson & Knapp 1995), although summer burns give more equivocal results. Furthermore, the coordination of burning with water-level manipulation in wetlands with controlled outlets can improve bird habitat: at both Carlos Avery WMA and Horicon Marsh it is common to draw down water levels and conduct a summer burn of a cattail marsh, and then to flood the unit, drowning the cattail stems for several weeks. The result of this is an open-water area which will be free of cattail for at least two years, and is attractive as duck foraging areas (Rhode pers. comm.; Meyer pers. comm.). Burns for bird habitat promotion in wetlands must take place before the nesting season to avoid bird mortality, an important seasonal constraint limiting spring burns to the earlier months (Weller 1981, Rhode pers. comm.). Burning wetlands, particularly peatlands, may combust a significant amount of organic matter on a site and produce a burned-out depression, creating an open-water marsh which will remain free of emergents for a significantly longer time than the simple flooding of cattails described above. Bowen (pers. comm.) echoes Weller (1981) in suggesting that this process is part of the natural recycling of wetlands in the North American midcontinental glacial landscape. However Weller warns that, as a restoration tool, such burns are difficult to direct as well as to extinguish. There is also data which suggests that periodic burning of the wetland-upland transition favors non-game bird habitat (Ryan et al. 1984) and small mammal habitat (Weller 1979), but this is very difficult to evaluate given the paucity of field data.

The use of fire in restoring upland prairie sites is well-established (Thompson 1992, White 1986). Among other functions, a correctly-timed fire provides a disturbance which can disrupt the life-cycle of exotic C3 (cool-season) grasses while promoting the growth of native C4 (warm-season) grasses. The restoration of natural communities using fire is a frequent goal of wetlands managers, though usually at a limited scale due to large areas, few windows of opportunity to burn, and the difficult task of reestablishing natural communities amid monocultures of pernicious species like Typha.

Much evidence supporting burning as a natural community restoration tool in wetlands is anecdotal. Eggers, Bowen and Meyer can all point to instances in which native grass or forb diversity has increased following burns (pers. comm.), but there has been no monitoring of diversity. Several authors have described an increasing forb diversity with increasing time since a burn (Johnson & Knapp, 1995; Mallik & Wein, 1986), as the monoculture of grass breaks up. Eggers (pers. comm.) notes that burning wetlands can be very effective in degraded communities in which a diversity of native species are still present. In exotic monocultures common in wetlands of the upper midwest, however, burning (as noted above) will only encourage the existing cover unless applied in coordination with disking, herbicides and/or water-level manipulation. An important difference between uplands burning and wetlands burning as restoration tools lies in the fact that wetland sedges, as well as several dominant native wetlands grasses (such as Calamagrostis and Spartina), are C3 cool-season plants, and will be disadvantaged as much as their exotic competitors by a mid- to late-spring burn. The practical importance of this has yet to be evaluated; Eggers, in particular, discounts the importance of this distinction, noting that if an April burns set both native and exotic grasses back while providing other benefits such as forb promotion, the burn is still beneficial on balance (pers. comm.). However Susan Galatowitsch, a wetland scientist at the University of Minnesota, is concerned that the light-triggered germination of Phalaris gives it a considerable competitive edge over more desirable plant species following a wetland burn.

The use of prescribed burning in wetlands as a restoration tool clearly suffers from a paucity of field data with which managers could evaluate its effectiveness in achieving various goals. Programs such as the USFWS’ which offers a budget for prescribed burning have promoted the spread of prescribed burning techniques into ecosystems beyond the upland prairie in which the techniques and knowledge was developed. The movement of restoration techniques and goals from upland to wetland sites may have taken place somewhat uncritically. The practical problems involved in maintaining a disctinction are clear; as both Bowen and Eggers point out, wetlands and uplands have been managed together as single burn units in many instances, and it is not always practical to keep an upland fire burn from spreading into an adjacent wetland. However, restoration goals and techniques are very different in wetlands ecosystems, and there should be an emphasis on the determination of appropriate prescriptions for these goals. Waterfowl habitat appears to be well served by regular prescribed burning, although managers must realize that this goal will be in conflict with a goal of natural vegetation restoration due to differences in the seasonal time of burn appropriate for each purpose. The maintenance of waterfowl habitat may also conflict with management for non-game wildlife, as Opler (1981) and Weller (1981) warn. In moderately degraded communities with patches of exotic grass or stands of brush, anecdotal evidence indicates that management with prescribed burns will be appropriate. However, severely degraded communities will require more intensive manipulation, and the simple application of fire may only make conditions worse.

Apfelbaum, SI and CE Sams. 1987. Ecology and Control of Reed Canary Grass. Natural Areas Journal 7(2): 69-72.

Clark, BK. And DW Kaufman. 1990. Short-term responses of small mammals to experimental fire in tallgrass prairie. Canadian Journal of Zoology. 68:2450-2454.

Eggers, S. Telephone interview, 4/25/1997. St. Paul, MN.

Galatowitsch, S. Discussion, 4/25/97. St. Paul, MN.

Johnson, SR and AK Knapp. 1995. The influence of fire on Spartina pectinata wetland communities in a northeastern Kansas tallgrass prairie. Canadian Journal of Botany 73: 84-90.

Kirby, RE, SJ Lewis and TN Sexton. 1988. Fire in North American Wetland Ecosystems and Fire-Wildlife Relations: An Annotated Bibliography. USFWS Biological Report 88(1).

Mallik, AU and RW Wein. 1986. Response of a Typha marsh community to draining, flooding, and seasonal burning. Canadian Journal of Botany 64: 2136-2143.

Meyer, P. Telephone interview, 4/29/1997. Horicon Marsh, WI.

Opler, PA. 1981. Management of prairie habitats for insect conservation. Journal of the Natural Areas Association 1(4): 3-6.

Pauly, WR. 1988. How to Manage Small Prairie Fires, 2^nd ed.. Madison: Dane County Parks Commission. Rhode, D. Telephone interview, 4/22/1997. Carlos Avery Wildlife Area, MN.

Ryan, MR, RB Renkin and JJ Dinsmore. 1984. Marbled godwit habitat selection in the northern prairie region Journal of Wildlife Management. 48(4): 1206-1218.

Thompson, DR, and JM Shay. 1985. The effects of fire on Phragmites australis in the Delta Marsh, Manitoba. Canadian Journal of Botany 63: 1864-1869.

Thompson, JR. 1992. Prairies, Forests & Wetlands: The Restoration of Natural Landscape Communities in Iowa. Iowa City: University of Iowa Press.

Weller, MW. 1979. Small-mammal populations and experimental burning of Dewey’s Pasture, northwest Iowa, 1970-74. Iowa State Journal of Research 53(4): 325-332.

Weller, MW. 1994. Freshwater Marshes: Ecology and Wildlife Management, 3^rd ed. Minneapolis: University of Minnesota Press.

White, AS. 1986. Prescribed Burning for Oak Savanna Restoration in Central Minnesota. USDA Forest Service Research Paper NC-266.

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