More info for the terms: bog, fire regime, fuel, lichens, organic soils, peat, severity, shrubs, succession, tussock
Fire adaptations: Bog rosemary is adapted to fire by sprouting quickly and prolifically from rhizomes after the aboveground parts are killed [33,35,53]. Bog rosemary could potentially reestablish from banked seeds [55] following a fire, but no reports of this occurring have been found in the literature.
FIRE REGIMES: Fires in peat bog lands where bog rosemary commonly occurs tend to burn in irregular patterns with varying degrees of severity [1], affected by the spatial variability in species composition and site hydrology [5]. Bogs burn only in extremely dry years and typically originate in adjacent upland forest sites [33]. Fires can be severe enough to kill aboveground plant parts, and yet the high surface temperatures in organic soils are not transmitted deeply into the soil profile because of the insulating effects of the peat. Early revegetation in burned bogs can be rapid because plants that existed prior to the fire sprout from roots and rhizomes [35,72]. On rare occasions, in extremely dry conditions, peat fires can burn for weeks or months with a high degree of smoldering [5]. The depth of the burn may vary from an inch to several feet, and a large volume of peat can be consumed [39].
Peat plateaus form in continental northern climates of severe winters and low snowfall when the peat body lifts as a result of freeze and thaw cycles within the waterlogged core. These plateaus are subject to recurrent burning because their surfaces are high and well-drained relative to surrounding wetlands. They also carry an abundance of flammable fuel: black spruce with branches close to the ground, resinous ericaceous shrubs, and feathermosses (Hylocomium spp.) and lichens that dry quickly after rain. Peat plateaus situated on the lowest parts of the alluvial flats burn rarely compared to those at higher elevations. On a peat plateau in the Mackenzie Valley, Northwest Territories, the fire return interval was estimated at 35 to 170 years [85].
Bog rosemary persists in the early stages of tamarack, black spruce, and jack pine forest succession in wet, open areas that usually have many of the same site characteristics as conifer bogs. Conifer bogs are generally not as prone to fire as other forest stand types because they tend to occupy depressions and lowlands and are wetter. The high water table, green understory, and thick, wet organic layer render conifer bogs unsusceptible to fire except in severe drought years. Conifer bogs are often spared from large, high severity forest fires that occur in adjacent uplands, leaving unburned pockets of trees that become important seed sources for the regeneration of burned forest [28,73]. Conifer bog fires occur during prolonged droughts conditions when the water Table drops and the forest floor becomes thoroughly desiccated. Ignition typically occurs on adjacent uplands in late July to September during rainless thunderstorms. Under these conditions, with sufficient winds, the trees in conifer bogs can sustain major crown fires [28]. Heinselman [48] estimated the fire return interval for large forested spruce bogs in Minnesota was 100 to 150 years. Fuel loadings in conifer bogs are highly variable because of the multiple combinations of species found in this forest type [28].
The arctic sheathed cottonsedge tussock communities in which bog rosemary occurs have relatively small quantities of flammable vegetation, and the peaty substrate is wet even in years of low precipitation. Burns can be severe enough to kill all aboveground plant parts, but belowground parts are well protected by tussock bases, moss mats, and peat. Following these low-severity fires, new growth primarily comes from plant stocks protected by the organic surface, and new species rarely invade the burned area [72,103]. Arctic sheathed cottonsedge tussock communities occur on permafrost-influenced terrain, and fires on these sites can cause changes in soil properties. Surface fires rarely affect the depth of the active layer; however, removal of the vegetation and some or all of the organic layer can cause the depth of the active layer to increase. Soils tend to become drier and warmer due to the removal of the insulative moss mat, the removal of shading by vegetation, and reduced albedo of the burned surface. When the organic horizons survive the fire, the amount of postfire thaw is minimized [9,93,103].
The following table provides fire-return intervals for plant communities and ecosystems where bog rosemary is important. For further information, see the FEIS review of the dominant species listed below. This list may not be inclusive for all plant communities in which bog rosemary occurs. If you are interested in plant communities or ecosystems that are not listed below, see the complete FEIS Fire Regime Table.
Fire-return intervals for plant communities with bog rosemary
Community or Ecosystem Dominant Species Fire Return Interval Range (years) tamarack Larix laricina 35-200 [74] Great Lakes spruce-fir Picea-Abies spp. 35 to >200 black spruce Picea mariana 35-200 conifer bog* Picea mariana-Larix laricina 35-200 [28] jack pine Pinus banksiana <35 to 200 [18,28] *fire return interval varies widely; trends in variation are noted in the species review