Prescribed fire for fuel reduction in northern mixed grass prairie: influence on habitat and population dynamics of indigenous wildlife
Robert K. Murphy (PI), Todd A. Grant, and Elizabeth M. Madden
Executive Summary Introduction and Study Objectives
Study Area Results Acknowledgements
Montana. This management continues
despite sparse information on effects of fire on wildlife, introduced and native
plants, and wildlife-habitat relationships in the northern mixed-grass prairie
ecosystem. To address basic information gaps, we assessed direct and indirect,
short and long term impacts of fire or fire suppression on vegetation and
wildlife population dynamics at 4 NWRs in northwestern and north central North
Dakota during 1997-2003; most work was conducted at Des Lacs NWR and J. Clark
Salyer NWR. Funding from the Joint Fire Science Program during the final 2
years of our work helped us expand the inferential value of our studies while
giving land managers a novel chance to more clearly identify opportunities and
limitations with prescribed burning in relation to the mission and goals of
their respective NWRs. Our chief goals were to document effects of
prescribed burning of northern mixed-grass prairie on the abundance,
productivity, and nest site selection of migratory birds, especially grassland songbirds; measure
influences of major sources of woody
fuels and habitat edges (e.g.,
woodland, cropland, wetland) on occurrences and productivity of common bird species; and
assess relationships between fire history and vegetation composition and
structure on several spatial and temporal scales.
Our study area lies within a cool-season (C3)-dominated,
needlegrass-wheatgrass (Stipa-Agropyron) association. However, the
contemporary prairie we studied on the NWRs is invaded by introduced
,
cool-season grasses and native shrubs and trees, as are most other prairie
tracts managed by the U.S. Fish and Wildlife Service and other conservation
agencies in the northern Great Plains region. We used 2 basic approaches to
examine fire effects on vegetation and wildlife. First, we designed short-term
(<10 years) field experiments to test specific hypotheses regarding fire effects
on vegetation structure, plant community composition, and wildlife abundance and
productivity. Secondly, we assessed long-term (60-100 years) changes in plant
communities associated with changes in fire disturbance regimes during and after
settlement of the region by persons of European descent. To address study
objectives, we used standard methods to collect, analyze, and report data.
Fire is a fundamental ecological process in the evolution and maintenance of northern grasslands. In summarily addressing our objectives, our collective studies generally indicate the following for northern mixed-grass prairie.
(1) Avian occurrence/abundance and nest densities: Most species of breeding grassland birds are adapted to recurring fire (i.e., every 4-6 years) in northern mixed-grass prairie, returning to pre-burn levels of abundance and nest density following declines the first growing season after burning and by nesting in unburned patches.
(2) Fire effects on nest survival: Fire had almost no discernable impact on nest survival for all species of grassland birds examined, except Savannah sparrow (Passerculus sandwichensis) nest survival was reduced in the first post-burn growing season, a decrease that mainly was the result of increased nest parasitism by brown-headed cowbirds (Molothrus ater). In contrast, survival rates of mallard (Anas platyrhynchos) and gadwall (A. strepera) nests were highest during the first post-fire growing season.
(3) Fire effects on nest site selection: Fire consumed most residual vegetation. Despite reductions in plant litter, “skips” (i.e., unburned patches) remained after burning and these typically were sites where songbirds and ducks nested. For example, litter depth at nests of clay-colored sparrow (Spizella pallida) and Savannah sparrow were similar among study units the first, second, and third post-fire growing seasons after burning even though litter within these units nearly was absent, on average, during the first post-fire growing season.
(4) Fire effects on small mammals: Deer mice (Peromyscus maniculatus) were 5-6 times more abundant during the first post-fire growing season, when litter was mostly absent. Most other small mammal species were much less common during the first post-fire growing season than during 2-5 growing seasons after fire, over which time residual vegetation was incrementally more abundant.
(5) Fire effects on vegetation composition and structure – short term effects: The structure of contemporary northern mixed-grass prairie vegetation is markedly influenced by fire during the first, second, and third post-fire growing seasons after burning, or by the interaction between numbers of burns and time since the last fire, but the composition generally is unchanged over the short term (< 10 years). Among major introduced grass species, fire probably reduces the frequency of Kentucky bluegrass (Poa pratensis), but smooth brome (Bromus inermis) may be unaffected or slightly decrease with fire. However, frequencies of native herbaceous flora do not increase with prescribed burning in loamy soils dominated by smooth brome and Kentucky bluegrass, at least in the short term.
Fire effects on vegetation composition and structure – long term effects:
(a) influence of fire suppression on distribution of trees and tall shrub: Significant changes occurred in the extent of woodland cover across the 4 present-day NWRs during the 1800s and 1900s. Woodlands were rare when the region was settled by Europeans in the early 1900s, but expanded in river valleys mainly during the early- to mid-1900s, and in sandhills and a terminal moraine during mainly the mid- to late-1900s, changing much of the mixed-grass prairie to parkland and woodland edge.
(b) influence of long-term suppression of fire and grazing disturbances on prairie floristics:
We sampled the general floristic makeup of prairie on 2 NWRs (4300 ha total) that had been managed mainly by rest since the 1930s. The prairies were moderately to severely invaded by the introduced grasses, smooth brome and Kentucky bluegrass. Plant assemblages composed of native species were rare. We also sampled floristics on nearby, privately-owned prairies that had been grazed annually for decades. Native herbaceous flora was prevalent on grazed prairie near 1 of the 2 NWRs. The findings demonstrate pitfalls of managing disturbance-dependent grasslands as relatively static, late-succession systems for many decades, without basic inventory and monitoring to comprehend and address associated ecological changes.
(6) Influences of tall woody fuels and habitat edges on productivity: We detected no relationships between nest survival and prevalence of woody fuels at the nest site and nest patch scales. Survival of nests of 1 of 2 common sparrow species we studied increased as patches of tall shrub and trees decreased in the landscape, validating the importance of reducing these fuels for grassland bird management.
(7) Predictive models for land managers: Land managers typically apply prescribed fire to try to emulate the region’s natural fire regime. We provide models that forecast abundance, nesting density, and nest survival among breeding grassland bird species, and for the physiognomy (structure) and composition of grassland vegetation at several spatial and temporal scales, relative to successive, post-treatment seral stages and other potentially interacting factors (e.g., weather, landscape effects).
(8) Occurrence and productivity of uncommon grassland bird species: In addition to examining fire history relationships for species of birds that commonly nest in northern mixed-grass prairie, we amassed a database that includes roughly 5000 nests of 35 less common bird species that use grasslands as breeding habitat. The data will provide new insights on species breeding biology, including nest site selection and nest survival relative to various temporal and spatial scales of habitat and disturbance. Basic natural history data will be supplied for species for which such information is scarce, such as Le Conte’s sparrow (Ammodramus leconteii), Brewer’s blackbird (Euphagus cyanocephalus), and Sprague’s pipit (Anthus spragueii).
Our data support the notion that bird species native to northern mixed-grass prairie are well adapted to frequent defoliation by fire. In general, decreases in species abundance and nesting density during the first growing season after burning are offset by increases in following years, compared to pre-burn levels; nest survival appears unaffected. Short term unavailability of breeding habitat probably is outweighed by long term benefits from using fire to restore and maintain vegetation structure and manage fuel loads (i.e., reduce accumulating litter and woody vegetation) in northern mixed-grass prairie. Our data also indicate that occurrence and survival of nests of at least some bird species is negatively associated with the extent of trees and tall shrubs in the landscape; efforts to reduce these fuels via prescribed burning seem warranted for improving the productivity of grassland birds, as well as addressing other prairie restoration objectives.
To date, our work has resulted in 7 technical publications in peer-reviewed journals, another 7 manuscripts currently in review for publication or soon to be submitted for publication, 1 graduate (M.S.) thesis, 15 presentations at various professional conferences and symposia, and a web page available through 2 NWR web sites.
Introduction and Study Objectives
Northern mixed-grass prairie has declined 70–90% across states and provinces in the northern Great Plains, mainly due to conversion to cropland (Samson et al. 2004, Samson and Knopf 1994). The quality of remaining prairie tracts is increasingly diminished by fragmentation, the spread of woody and introduced plants, suppression or misapplication of fire, and certain livestock grazing practices (Samson and Knopf 1994, Grant and Murphy 2005, Murphy and Grant 2005). Concurrent with this decline is the reduction in breeding populations of most grassland-dependent bird species, especially those endemic to the northern Great Plains (Peterjohn and Sauer 1999).
An average of roughly 10,000 ha of grasslands, mostly native mixed-grass prairie, is prescribe-burned annually on National Wildlife Refuges (NWRs) in the Dakotas and eastern Montana, primarily to maintain or improve habitat for wildlife, attempt to restore native vegetation, and reduce accumulating fuels and the risk of catastrophic wildfire. Although prescribed fire has been used widely in the northern Great Plains for nearly 30 years, supportive published data on its effects specific to plant and wildlife communities in the region are scarce. Most available information on effects of fire on wildlife and wildlife-habitat relationships in northern mixed-grass prairie is anecdotal and unreliable, or is weakly inferred from different grassland ecosystems, especially tallgrass prairie. Consequently, managers can only vaguely predict impacts of prescribed fire as an ecological process that maintains prairies and populations of wildlife native to the northern Great Plains region. Depending on timing, frequency, and intensity, prescribed fire may not necessarily enhance the ecological integrity of native mixed-grass prairie communities and associated wildlife as surmised, and in some cases may be detrimental. Thus, our objectives were to:
(1) Document effects of fire history on occurrence/abundance of grassland passerines and upland-nesting ducks in examples of northern mixed-grass prairie characteristic of NWRs.
(2) Assess fire history effects on avian nest survival, including potential influences of fire history on rates of predation and nest parasitism.
(3) Quantify nest site habitat of nesting passerine birds, and compare to composition and structure of available habitat, accounting for fire history and its potential effects on nest site vegetation.
(4) Document effects of fire history on small mammal composition and abundance in northern mixed-grass prairie.
(5) Assess short- and long-term effects of fire and fire suppression on the structure and composition of vegetation in northern mixed-grass prairie, and establish an extensive basis for long-term monitoring.
(6) Assess influences of primary targets of prescribed fire – woodlands and woodland edges and other major sources of woody fuels – on passerine productivity and nest site selection.
(7) For land managers, provide basic models and other predictive tools supported by the findings, and synthesize relevant literature.
(8) Provide information on occurrence and productivity of less common grassland bird species (e.g., upland-nesting shorebirds, ground-nesting raptors) as encountered.
We conducted investigations at 4 NWRs (8000-24,000 ha) in north central and northwestern North Dakota (Figure 1): Lostwood NWR , Des Lacs NWR, Upper Souris NWR, and J. Clark Salyer NWR. These NWRs lie within the northern mixed-grass prairie physiographic region (Coupland 1950, 1992) of the northern Great Plains. Lostwood NWR is within the relatively narrow (20- to 30-km wide), rolling to hilly Missouri Coteau physiographic subregion. Des Lacs NWR, Upper Souris NWR, and J. Clark Salyer NWR are within the extensive Drift Plain physiographic subregion, which generally is characterized by flat to slightly rolling topography.
The landscape that includes each NWR was uniquely shaped by glaciation during the end of the Pleistocene Epoch. The Missouri Coteau, which encompasses Lostwood NWR, is dead ice moraine deposited by the Wisconsin glacier over a previously occurring escarpment (Bluemle 1991). Soils are thin, often gravely loams derived from glacial till. Des Lacs NWR, Upper Souris NWR, and J. Clark Salyer NWR are associated with the Souris River (Figure 1). Des Lacs NWR and, to a lesser degree, Upper Souris NWR, are characterized by steep, high-relief (50 m deep) valleys, while J. Clark Salyer NWR is low relief river valley. Upland soils of Des Lacs NWR, Upper Souris NWR, and the northern half of J. Clark Salyer NWR are mostly well-drained, moderately deep loams formed in glacial till. The southern one-half of J. Clark Salyer NWR is within a flat, deltaic outwash plain, characterized along the south and east sides by sandhills formed from wind and wave action of historic Glacial Lake Souris. Soils in this part of J. Clark Salyer NWR are mainly sand and gravel; water drainage is poor near the Souris River and the water table can be close to the surface in sandy soils, especially during years of above average precipitation.
Native vegetation of the study area is a cool-season (C3)-dominated,
needlegrass-wheatgrass (Stipa-Agropyron) association (Coupland 1992,
Bragg 1995). Other native plant species characteristic of this association
include cool-season graminoids such as Junegrass (Koeleria pyramidata;
nomenclature follows Great Plains Flora Association 1986)
and several bluegrass
(Poa spp.) and sedge (Carex spp.) species; several warm-season (C4)
grass species, mainly blue grama (Bouteloua gracilis), sideoats grama
(B. curtipendula), plains muhly (Muhlenbergia cuspidata), prairie
dropseeed (Sporobolus heterolepis), and big bluestem (Andropogon
gerardii); the low shrubs (to 1.5 m tall), western snowberry (Symphoricarpos
occidentalis) and silverberry (Elaeagnus commutata); and many forb
species, mainly Asteraceae and Fabaceae. However, contemporary native prairie
on the NWRs, especially the “drift prairie” (i.e., native prairie on the Drift
Plain), is extensively invaded by Eurasian grasses, primarily smooth brome (Bromus
inermis) and Kentucky bluegrass (Poa pratensis). Native prairie on
the NWRs also is invaded to varying degrees by trees and tall shrubs, especially
quaking aspen (Populus tremuloides), green ash (Fraxinus pennsylvanica),
chokecherry (Prunus virginiana), hawthorn (Crateagus spp.), and
willow (Salix spp.), all of which are native to the region.
Climate of the study area is continental, with short summers and long, cold winters. Annual precipitation, although highly variable, averages roughly 42 cm (1936-1990 data, from NWR records).
NWRs where we conducted our studies have attributes and management issues similar to those on most other NWRs and on the somewhat similar, but smaller “Waterfowl Production Areas” that are managed by the U. S. Fish and Wildlife Service in the northern Great Plains. Attributes and issues among grasslands managed by other conservation agencies and organizations in the region also tend to be similar. Specifically, these grassland tracts are: 1) chiefly native prairie invaded by cool-season, introduced grasses and forbs, and often by native woody vegetation ; 2) managed mainly by rest, with periodic defoliation by fire, livestock grazing, or hay harvest; 3) usually large enough to contain area-sensitive species of grassland birds (e.g., northern harrier [Circus cyaneus], marbled godwit [Limosa fedoa]); 4) characterized by scattered or nearby, large seasonal and semi-permanent wetlands; and 5) bordered by annually tilled cropland and, to a lesser extent, by native rangeland, seeded grassland, and seeded hayland.
Fire effects on abundance of grassland birds
We determined short term effects of defoliation by
prescribed fire on species richness and abundance of breeding grassland birds at
J. Clark Salyer NWR during 1998-2003, and relationships between prescribed fire
history and abundance of birds at Des Lacs NWR during 2003. At J. Clark Salyer
NWR, fire altered the structure of vegetation within study units, especially
litter, maximum vegetation height, and the ratio of dead:live vegetation (see
following sections), which, in turn, influenced bird species richness and
abundance. Species richness and total pairs of all bird species combined
declined during the first post-fire growing season; abundance for some species
may also have declined 4+ post-fire growing seasons
(Figure 3). Of 8 species
for
which we had sufficient samples, abundances of 6 were affected by the
temporal proximity of the most recent fire. Abundances of sedge wren (Cistothorus
platenis),
clay-colored sparrow, Le Conte’s sparrow (Ammodramus leconteii),
Savannah sparrow, bobolink (Dolichonyx oryzivorus), and western
meadowlark (Sturnella neglecta) decreased during the first post-fire
growing season but generally recovered to pre-burn levels within 2–3 post-fire
growing seasons
(Figure 4).
At Des Lacs NWR, 6 passerine species were sufficiently common to support our analysis of relationships between bird abundance and a fire index that reflected interaction between numbers of prescribed fires conducted in the previous 10 years and time since the most recent fire. Three endemic, historically common passerine species – Baird’s sparrow (Ammodramus bairdii), chestnut-collared longspur (Calcarius ornatus) and Sprague’s pipit (Anthus spragueii) – were rare or absent regardless of fire history of study units. Abundances of common bird species were not strongly influenced by the index (Figure 5), which contrasts published findings from the nearby Missouri Coteau physiographic subregion (Madden et al. 1999). (Note: this work currently is in press in the Prairie Naturalist: Ludwick and Murphy 2006 in Deliverables)
Fire effects on nest densities of grassland birds
Fire-associated changes in vegetation structure at J. Clark Salyer NWR (1998-2003) influenced nest densities of grassland birds. For most species, nest density declined during the first post-fire growing season, especially for clay-colored sparrow, Savannah sparrow, mallard (Anas platyrhynchos), and gadwall (Anas strepera; Figure 6). Bobolink nest densities were highest during the first 2 post-fire growing seasons. Nest densities of blue-winged teal, northern pintail (Anas acuta) and northern shoveler (Anas clypeata) were unaffected by fire, although their patterns of post-fire response were similar to that of gadwall and mallard. Like bird relative abundance (previous section), nest densities recovered to preburn levels within 2-3 post-fire growing seasons (Figure 6).
Effects of fire and distribution of tall woody fuels on the survival of grassland bird nests
Prescribed fire had little effect on nest survival for most grassland bird
species at J. Clark Salyer NWR. Among passerine birds, fire reduced Savannah
sparrow nest survival, a decrease that mainly was the result of increased nest
parasitism by brown-headed cowbirds during the first post-fire growing season
(Figure 7). In contrast, mallard and gadwall nest survival was highest during
the first post-fire growing season
(Figure 8). 
In 1997-98 and 2002, we examined nest survival of clay-colored sparrows and vesper sparrows (Pooecetes gramineus) relative to the distance nests were located from aspen woodland edges and relative to other habitat features near the nest. Contrary to what other studies have reported, we found that clay-colored and vesper sparrow nest survival was higher for nests located near woodland edges than for nests located far from edges. In addition, vesper sparrow nest survival increased as the percent cover of tall shrubs near the nest increased (Note: this work currently is in press in the Journal of Wildlife Management: Grant et al. 2006 in Deliverables)
At Des Lacs NWR, we had sufficient data to examine influences on nest survival for 2 species, clay-colored sparrow and Savannah sparrow. We detected no relationships between nest survival and prevalence of woody vegetation at nest site and nest patch scales. At the landscape scale, however, survival of clay-colored sparrow nests decreased as the number of tall woody patches within 100 m increased. Survival of Savannah sparrow nests was uninfluenced by numbers of tall woody patches in the landscape, however (Figure 9).
Influence of fire on avian nest site selection
At J. Clark Salyer NWR, we sought to determine how fire proximately affects the composition and structure of grassland vegetation and, ultimately, how fire shapes nest site selection by grassland birds. Fire altered the structure of grassland vegetation, and these changes affected selection of nest sites by grassland birds. Clay-colored sparrows nested in patches that were taller and denser than those generally available within nesting fields. Most grassland bird species require some dead plant material in which to construct nests. However, fire consumes most residual vegetation within study units, temporarily reducing the density of grassland bird nests, especially during the first post-fire growing season. Despite reductions in plant litter, “skips” (i.e., unburned patches) remained after a fire and these skips typically were sites where ducks and songbirds placed their nests. For example, litter depth at clay-colored sparrow and Savannah sparrow nests was similar among units with 1-, 2-, or 3-post-fire growing seasons, even though litter within these units nearly was eliminated, on average, during the first post-fire growing season (Figure 10). (Note: this work currently is in thesis format: Nenneman 2003 in Deliverables)
Fire effects on small mammals
Population levels of small mammal species were highly variable among years 1998-2000 and 2002 at J. Clark Salyer NWR, making it difficult to assess fire effects on relative abundances of these species. Dramatic fluctuations were most evident among voles (Microtus spp.), shrews (Sorex spp.), and jumping mice (Zapus spp.). In particular, the relative abundance of meadow voles (M. pennsylvanicus) fluctuated 12-fold over the 4 years. Regardless, we detected fire-associated changes in the relative abundance of several species. Deer mice (Peromyscus maniculatus) were 5-6 times more abundant during the first post-fire growing season, when plant litter was mostly absent (Figure 11). In contrast, voles, shrews, and ground squirrels (Spermophilus spp.) were less common during the first post-fire growing season than during 2-5 growing seasons after fire, when residual vegetation was more abundant.
Short-term fire effects on vegetation structure and composition
Annual precipitation and unit fire histories affected vegetation structure and, to a lesser extent, plant community composition at J. Clark Salyer NWR, 1998–2003. Fire had little overall effect on the composition of plant communities within study units during 1998–2003, except fire decreased Kentucky bluegrass cover during the first and second post-fire growing seasons (Figure 12). Conversely, cover of native grasses and forbs declined as units were rested (i.e., no disturbance) for 4+ post-fire growing seasons (Figure 12). Fire strongly influenced vegetation structure, especially the amount of residual vegetation within study units. Maximum vegetation height, litter depth, and the ratio of dead:live vegetation decreased for the first post-fire growing season (Figure 12). Significant fuels in the form of plant litter accumulated during each subsequent post-fire growing season. The ratio of dead:live vegetation and maximum vegetation height generally recovered to pre-burn levels by the second post-fire growing season (Figure 12).
At Des Lacs NWR, vegetation composed exclusively of native graminoids or of a mix of native graminoids and forbs occurred rarely, regardless of fire history. The frequency of smooth brome decreased with increasing applications of fire (Figure 13). Native-dominated, herbaceous vegetation may have increased as smooth brome-dominated vegetation declined with increasing fire experience, but the trend was not significant. Litter depth and vegetation height-density decreased with increasing fire experience (Figure 13). There was little variation in vegetation structure, however, especially in plant height-density, among units that experienced the most fire. We detected no relationships between bird species abundances and vegetation composition and structure, perhaps because smooth brome continued to be a pervasive structural influence on all study units regardless of fire history. ). (Note: this work currently is in press in the Prairie Naturalist: Ludwick and Murphy 2006 in Deliverables)
Long-term fire effects on vegetation communities
We found that significant changes occurred in the extent of woodland cover across our study area during the 1800s and 1900s. Woodlands were rare when the region was settled by Europeans in the early 1900s, except green ash-American elm (Ulmus americana) woodland occurred within the floodplain of the Souris River, and stunted copses of quaking aspen-bur oak (Quercus macrocarpa) occurred along fire-protected scarps of sandhills prairie in north central North Dakota. Ash-elm woodland expanded in valleys of the Des Lacs and Souris rivers especially along adjoining, intermittent tributaries (coulees), mainly during the early- to mid-1900s (Figure 14). Aspen woodland expanded in sandhills of the Souris Lake Plain and in the Missouri Coteau during mainly the mid- to late-1900s, changing much of the mixed-grass prairie to aspen parkland (Figure 14). With settlement by people of European descent, large herbivores were extirpated from the region and natural and anthropogenic fires were suppressed. These changes are implicated in expansion of woodland into native prairies. (Note: this work recently was published in Natural Areas Journal: Grant and Murphy 2005, in Deliverables)
We sampled general floristic makeup on 4300 ha of drift prairie at Des Lacs NWR and J. Clark Salyer NWR during 1998–2002. These prairies had been managed mainly by rest since the 1930s. We also sampled about 1200 ha of nearby, annually grazed drift prairie for comparative purposes. Vegetation dominated by low native shrub was common on both NWR prairies and on grazed prairies near Des Lacs NWR, occurring roughly in a 1:3 ratio with herbaceous-dominated vegetation, versus < 1:5 historically. Nearly all prairies were moderately to severely invaded by introduced plant species, mainly smooth brome and Kentucky bluegrass on NWRs, and Kentucky bluegrass, almost exclusively, on adjacent grazed prairies (Figure 15). Smooth brome-dominated types were twice as prevalent as Kentucky bluegrass-dominated types on NWRs, indicating that with little or no fire and grazing disturbance, smooth brome may be more competitive than Kentucky bluegrass, at least in northern mixed-grass prairies of the Drift Plain. Plant assemblages composed of native species were encountered rarely, except they occurred fairly often on grazed drift prairie next to J. Clark Salyer NWR. (Note: this work recently was published in Natural Areas Journal: Murphy and Grant 2005, in Deliverables)
Financial and/or logistic support were provided by the Joint Fire Science Program, U. S. Fish and Wildlife Service’s Divisions of Refuges and Wildlife and of Migratory Bird Management (Region 6), U. S. Geological Survey – Northern Prairie Wildlife Research Center, University of Missouri, University of Montana, University of Wisconsin-Stevens Point, and University of North Dakota. For assistance with study design, data collection and compilation, data analyses, and/or technical consultation, we especially thank C. Aucoin, A. Beckington, B. Bedard, G. Berkey, K. Berg, K. Baus-Christopherson, B. Cofell, J. Derrig, M. Friel, J. Gault, C. Golde, C. Guariglia, S. Finkbeiner, M. Graft, J. Hanlon, K. Hansen, E. Harrold, E. Howell-Wilde, N. Kadrmas, C. Kerschner, C. Kerns, Kuzyk, R. Laubhan, T. Ludwick, S. Marshall, J. Martin, R. McManus, M. Nenneman, A. Phillips, P. Pietz, C. Rubin, M. Ryan, T. Shaffer, M. Sondreal, R. Smith, P. Stanich, J. Thury, R. Van Berkom and personnel of the U.S. Fish and Wildlife Service’s J. Clark Salyer and Des Lacs NWR Complexes and Fire Management Programs.
Revised: January 31, 2006