Betula glandulosa



INTRODUCTORY


  © Pat Breen, Oregon State University
AUTHORSHIP AND CITATION:
Tollefson, Jennifer E. 2007. Betula glandulosa. In: Fire Effects Information System, [Online]. U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station, Fire Sciences Laboratory (Producer). Available: http://www.fs.fed.us/database/feis/ [].

FEIS ABBREVIATION:
BETGLA

SYNONYMS:
None

NRCS PLANT CODE [147]:
BEGL

COMMON NAMES:
bog birch
dwarf birch
glandular birch
resin birch
scrub birch
swamp birch

TAXONOMY:
The scientific name of bog birch is Betula glandulosa Michx. (Betulaceae) [31,54,60,61,75,76,77,137,159,168].

Bog birch hybridizes with dwarf birch (Betula nana subsp. exilis and Betula nana subsp. nana) where their ranges overlap [54,77,159]. Bog birch also hybridizes with paper birch (Betula papyrifera) in interior Alaska [159]. Numerous other hybrids have been described including:

Betula × sargentii Dugle (B. nana × B. pumila)
Betula × eastwoodiae Sargent (B. nana × B. occidentalis) [31,51,54]
Betula × dugleana Lepage (B. nana × B. neoalaskana)
Betula × dutillyi Lepage (B. nana × B. minor, a putative hybrid) [54]

LIFE FORM:
Shrub

FEDERAL LEGAL STATUS:
No special status

OTHER STATUS:
Information on state-level protected status of plants in the United States is available at Plants Database.

DISTRIBUTION AND OCCURRENCE

SPECIES: Betula glandulosa
GENERAL DISTRIBUTION:
Bog birch is native to North America. It is widely distributed from interior Alaska to Greenland and south through Canada to New York, Michigan, and Minnesota in the East and Colorado, New Mexico, and California in the West [51,60,66,75,76,159,168]. Flora of North America provides a distributional map of bog birch.

ECOSYSTEMS [58]:
FRES10 White-red-jack pine
FRES11 Spruce-fir
FRES20 Douglas-fir
FRES23 Fir-spruce
FRES26 Lodgepole pine
FRES44 Alpine

STATES/PROVINCES: (key to state/province abbreviations)
UNITED STATES
AK CA CO ID ME MI MN MT NH NM
NY ND OR SD UT WA WI WY    

CANADA
AB BC MB NF NT NS NU ON PQ SK
YK    


BLM PHYSIOGRAPHIC REGIONS [21]:
2 Cascade Mountains
4 Sierra Mountains
8 Northern Rocky Mountains
9 Middle Rocky Mountains
10 Wyoming Basin
11 Southern Rocky Mountains
16 Upper Missouri Basin and Broken Lands

KUCHLER [90] PLANT ASSOCIATIONS:
K008 Lodgepole pine-subalpine forest
K012 Douglas-fir forest
K015 Western spruce-fir forest
K052 Alpine meadows and barren
K093 Great Lakes spruce-fir forest
K094 Conifer bog

SAF COVER TYPES [52]:
1 Jack pine
5 Balsam fir
12 Black spruce
13 Black spruce-tamarack
38 Tamarack
107 White spruce
201 White spruce
202 White spruce-paper birch
203 Balsam poplar
204 Black spruce
206 Engelmann spruce-subalpine fir
217 Aspen
218 Lodgepole pine
222 Black cottonwood-willow
251 White spruce-aspen
252 Paper birch
253 Black spruce-white spruce
254 Black spruce-paper birch

SRM (RANGELAND) COVER TYPES [131]:
216 Montane meadows
410 Alpine rangeland
901 Alder
904 Black spruce-lichen
911 Lichen tundra
912 Low scrub shrub birch-ericaceous
913 Low scrub swamp
916 Sedge-shrub tundra
917 Tall shrub swamp
918 Tussock tundra
919 Wet meadow tundra
920 White spruce-paper birch
921 Willow

HABITAT TYPES AND PLANT COMMUNITIES:
In the boreal forests of interior Alaska and Canada, bog birch is found in many black spruce (Picea mariana) and white spruce (P. glauca) communities and is especially common at the northern and altitudinal limit of trees [3,6,117,152,154,159]. In these northern environments, permafrost prevents the percolation of water, resulting in the development of muskegs, bogs, and ponds that often impede the growth of trees but support bog birch and other low-growing shrubs [55,159].

Bog birch is characteristic of many mixed shrub and tussock tundra communities in Alaska and northern Canada [1,2,10,149]. In southwestern Canada and the contiguous United States, bog birch often occurs on wetland sites including bogs, fens and carrs, within lodgepole pine (Pinus contorta), Engelmann spruce (P. engelmannii), or subalpine fir (Abies lasiocarpa) forest types and is often associated with alders (Alnus spp.) and willows (Salix spp.) [15,22,84,86,110].

Bog birch is listed as a dominant species in the following vegetation classifications:

United States
Alaska: Colorado: Idaho: Montana: Canada
Alberta: British Columbia: Northwest Territories: Ontario: Yukon:


BOTANICAL AND ECOLOGICAL CHARACTERISTICS

SPECIES: Betula glandulosa
GENERAL BOTANICAL CHARACTERISTICS:
This description provides characteristics that may be relevant to fire ecology, and is not meant for identification. Keys for identification are available (e.g., [31,48,60,75,76,77,159,162,168]).

Bog birch is a deciduous, long-lived shrub. Plants are low and spreading to erect with 1 to several main stems. Bog birch ranges from 8 inches (20 cm) tall on upland sites and in arctic environments to 10 feet (3 m) in drainages and in more southern areas [31,44,60,76,77,77,102,137,159,168]. The bark is thin, smooth, and does not peel readily [51,75,159,168]. Leaves are thick and leathery and range from 0.2 to 1.2 inches (0.5-3 cm) long and 0.2 to 0.8 inch (0.5-2 cm) wide [75,76,77,159]. The inflorescences are catkins. Male catkins are 0.4 to 1 inch (10-25 mm) long, and female catkins are 0.3 to 0.8 inch (7-20 mm) long [31,159,168]. Fruits are narrow-winged, single-seeded samaras 1 to 1.5 mm long and wide [31,41,104]. Rhizomes are 0.8 to 2.4 inches (2-6 cm) thick and are found in the top 2.4 inches (6 cm) of soil [44]. Bog birch has an extensive root system [24,42,104]. Roots are ectomycorrhizal, an adaptation to arctic and alpine soils that are generally low in inorganic nitrogen and phosphorus [37,145].

RAUNKIAER [119] LIFE FORM:
Phanerophyte
Chamaephyte

REGENERATION PROCESSES:
Bog birch reproduces by seed and vegetatively by branch layering and sprouting [26,44]. Reproduction by seed is more common in southern populations, and vegetative reproduction is more common in northern populations [73,166,167].

Pollination: Bog birch is wind pollinated. In a bog birch population on Baffin Island, Northwest Territories, female catkins were smaller and contained 50% fewer flowers than were contained in female catkins from a more southern site in subarctic Quebec. There was an estimated 10-fold difference in pollen dispersed between the 2 sites. At the northern extent of its distribution, bog birch is clonal, and the distance between genetically distinct individuals is great. In these areas, female catkins are more likely to receive incompatible pollen, preventing fertilization from occurring [167].

Breeding system: Bog birch is monoecious [64,104]. Plants are not self fertile [167].

Seed production: Bog birch produces numerous catkins, each of which yields 30 to 50 samaras [166]. Seed production is generally high in more southern parts of its range [30,42,73]. In more northern areas, production of viable seed is limited by the shorter growing season, lower temperatures, and distance between genetically distinct individuals [166].

Seed dispersal: Bog birch seeds are dispersed in their samaras. Wind, water, and sometimes gravity disperse the samaras. Samaras may blow across crusted snow [11,44,104].

Seed banking: Bog birch produces numerous, tiny seeds and has a transient seed bank. In a review of the literature, Karrfalt [41] states that birch seeds may be abundant in the soil but the seeds are generally short lived. Rowe 1983 [124] states that viable bog birch seeds are "rare" in the soil seed bank. Bog birch seeds were present, however, in the first 1.2 inches (3 cm) of soil collected from alpine sites on the Gaspé Peninsula, Quebec [106]. Results of this study are provided in the table below.

Bog birch seed production and density on sites in Quebec [106]

Site Total seeds/m² Viable seeds/m² % cover in aboveground vegetation
1 3 0 0
2 275 0 18
3 1,263 13 10
4 1,003 6 10
5 6 0 0

Germination: Prechilling improves germination of bog birch seeds. Optimum germination temperature for many arctic species is 59 to 86 °F (15-30 °C) [26]. The germination rate of bog birch seeds collected from alpine sites in the White Mountains, New Hampshire, was 25% for refrigerated seeds and 4% for unrefrigerated seeds. Days required for germination ranged from 14 to 28 for refrigerated seeds and from 27 to 299 for unrefrigerated seeds [108].

Seed viability varies with latitude. At the northern range limit of bog birch on Baffin Island, <0.5% of seeds were viable. Very few samaras contained seeds with fully developed embryos. At a southern site in subarctic Quebec, 70% of seeds were viable [166,167]. Seeds that overwinter on plants remain viable until they disperse the following spring [166].

Seed germination and samara weight may be correlated. In a germination study in Kuujjuaq, Quebec, no seeds from samaras weighing <0.09 mg germinated, few samaras weighing <0.12 mg had seed that germinated, and all samaras weighing >0.34 mg had seed that germinated [166]. Germination of wind-dispersed seeds may be highest on exposed mineral soils [104].

Seedling establishment/growth: Seedling recruitment rates in bog birch populations are usually very low. Site disturbance by fire increases the likelihood of seedling establishment [44]. Although recruitment from seed is almost nonexistent in northern bog birch populations, plants of all age classes were evident in a southern Quebec population [73,166]. Seedling growth is very slow, and seedling mortality is often high [41,44].

Vegetative regeneration: Bog birch reproduces vegetatively by branch layering and sprouting from dormant buds on the root crown and rhizomes [26,44]. Bog birch is clonal in the northern parts of its range [166].

SITE CHARACTERISTICS:
Bog birch occupies a wide variety of sites, ranging from rocky subarctic and alpine tundra to deep, organic, boreal soils [44]. It is typically a wetland species occurring most commonly on moist, acidic, and nutrient-poor organic sites including fens, swamps, bogs, muskegs, wet meadows, lake and stream margins, and seepage areas [22,31,48,60,75,76,77,159,168]. Bog birch is also found on upland sites including eskers, till ridges, rock outcrops covered with shallow soil, cliffs, sandy hillsides, and rocky ridges [5,31,51,82,137]. It dominates open valley bottoms in the Canadian Rocky Mountains [43] and is the most common shrub at treeline in interior Alaska, forming a nearly continuous zone between the treeline and alpine tundra in many areas [156].

Elevation: Bog birch occurs between 1,300 and 11,000 feet (400-3,400 m) across its range [66,75,79,80,123,125,168]. Elevational ranges are summarized below.

Elevational ranges for bog birch by state or province

State Elevation (feet)
California 6,500-7,500 [75,125]
   Sierra Nevada 6,500-8,500 [79]
Colorado 5,700-11,400 [46,66,80]
Montana 4,900-8,000 [46]
Utah 6,000-11,000 [46,168]
Wyoming 6,400-10,500 [46]
Nova Scotia 1,300 [123]

Temperature: Bog birch is tolerant of cold temperatures. It is common in black spruce forests in the Yukon where the mean annual temperature is 27 °F (-3 °C) [6]. Frost tolerance in bog birch is high, and bog birch grows abundantly over large areas of permafrost [87]. Bog birch tolerates severe winter temperatures by withdrawing water from the protoplast and freezing it in the cell walls [25].

Moisture: Although it is primarily a wetland plant, bog birch does not appear to tolerate continuous flooding. In bogs near Fairbanks, Alaska, bog birch abundance decreases as soil moisture increases. Bog birch is also more "vigorous" in communities that support taller tussocks [32]. In the Cariboo Forest Region of British Columbia, bog birch is common in wetlands that have no standing water late in the season [139]. In Montana, however, the water table is often within the rooting zone of bog birch throughout the summer, and bog birch grows in soils that remain flooded until midsummer or are saturated year-round [64]. In a willow (Salix spp.)-bog birch community near Churchill, Manitoba, the depth of the water table averaged 3 inches (6.5 cm) below the surface, and soil moisture in the organic layer was 63% [24]. Bog birch is an indicator of "substantial groundwater" in the North Thompson River valley, British Columbia [98].

Annual precipitation ranges from 4 to 9 inches (109-230 mm) on 2 northern Canadian study sites where bog birch is abundant [6,24]. While some authors describe bog birch as drought intolerant [141], in a review of the literature de Groot and others [41] state that bog birch appears tolerant of periodic drought.

Soils: Bog birch grows in a variety of soils, ranging from sandy and gravelly loam on river terraces to poorly drained, organic soils in bogs, muskegs, and other wetland habitats [43,64,114,121,141]. It is tolerant of moderate salinity [24] and pH ranging from 3.1 to 6.5 [105,141].

SUCCESSIONAL STATUS:
Bog birch is shade intolerant [42,44,87]. It is characteristic of canopy openings in black spruce woodlands in boreal Canada [3]. It establishes from seed or, more commonly, by sprouting after fire and other disturbances [23,43,148,149] and in many communities persists through subsequent successional stages. In many black spruce communities in central Alaska and northern Canada, bog birch appears soon after low- to moderate-severity fires and is dominant in the vegetation 6 to 25 years after fire. Trees begin to dominate after 25 to 30 years, but the low shrub layer of bog birch and associated species continues to expand and increase in cover [149,150]. In black spruce woodlands in the Northwest Territories, bog birch is most common 15 to 20 years after fire but is also present in stands as old as 300 years [23].

The table below summarizes an analysis of 5 stands representing a vegetation chronosequence on gravel outwash of the Muldrow Glacier in Denali National Park, Alaska. Bog birch was not present in the earliest successional stage but was abundant in intermediate stages and persistent in the oldest stands [153].

Frequency (%) and cover (%) of bog birch at 5 successional stages [153]
Successional stage Frequency Cover
Pioneer stage (25-30 years) 0 0
Meadow stage (100 years) 80 <5
Early shrub stage (150-200 years) 100 50-75
Late shrub stage (200-300 years) 100 50-75
Climax tundra (5,000-9,000 years) 100 25-50

SEASONAL DEVELOPMENT:
In bog birch, leaf growth begins soon after snow melt, and growth continues throughout the growing season as shoots elongate [41]. Male catkins develop in late summer or fall and expand with or before leaf development the following spring. Female catkins appear with the leaves in the spring [78,104]. Flowering dates vary and are summarized below.

Flowering dates for bog birch by region
Alaska May-June [159]
Sierra Nevada, California April-June [79]
Gaspé Peninsula, Quebec June-August [106]

Fruits mature between July and October and can persist through the winter [104,106,159,166]. Samara dispersal occurs in the fall, just prior to snow fall, and in the following spring soon after snow melt [78,166]. Leaves begin to senesce in late summer, and leaf abscission is complete by late September [118].

Phenological stages for bog birch in a valley-bottom floodplain in west-central Alberta are summarized below.

Seasonal development of bog birch in west-central Alberta [44]
5 May most plants initiating leaf-break
10 June male catkins dropped; female catkins small and turning darker green
29 June female catkins at mature size
11 Aug. female catkins brown; terminal buds large
1 Sept. half of leaves on most plants yellow

FIRE ECOLOGY

SPECIES: Betula glandulosa
FIRE ECOLOGY OR ADAPTATIONS:
Fire adaptations: Bog birch can survive low- to moderate-severity fires. On many sites, bog birch has deep roots and rhizomes that are protected from all but high-severity fires [12,42]. Bog birch regenerates after fire by sprouting from the root crown and from dormant buds on the rhizomes [43,44,82,112,165]. In arctic and boreal ecosystems, bog birch increases sprout production, sprout height, and aboveground biomass production during the first 1 to 2 years after a fire. Bog birch responds to top-kill by sprouting from dormant buds on the root crown and rhizomes after top-kill release. Burned plants may produce large leaves that senesce later in the fall than leaves on undisturbed plants, thereby maximizing photosynthate production [43]. Bog birch samaras are dispersed by wind and can invade burned areas from off site [11]. Although bog birch can establish from seed after fire, seedlings are susceptible to both drought and shade [43,44].

Fire regimes: Bog birch is adapted to a wide range of fire regimes, from subarctic and alpine areas that seldom burn to boreal environments that burn frequently [42,44]. Wetland areas where bog birch grows burn infrequently due to the high moisture content of the vegetation and soil. These sites sometimes act as firebreaks. Fires do occur, however, during dry summers or in the spring and fall when the vegetation is dry [35,43,44,86,104,143].

In interior Alaska, bog birch is found on poorly drained and permafrost underlain sites occupied primarily by black spruce stands, muskegs, and bogs. These types are widespread in Alaska and burn frequently [154,158]. Black spruce-birch (Betula spp.) is the most widespread forest type in interior Alaska and also the type with the highest frequency of fire [158]. Native Americans were an important cause of fires in the black spruce-birch ecosystem [96]. Fire frequency increased with the increase in mining activity in the 1800s [154]. Today, most fires are lightning caused [70,95]. Between 1940 and 1969, lightning was responsible for 78% of the area burned in interior Alaska [154].

Fires occur in interior Alaska between 1 April and 30 September. Most fires occur in May, June, and July, corresponding with the highest annual temperatures, longest day length, lowest humidity and precipitation, and high winds [55,154]. Fires can occur, however, whenever fuels are not covered with snow and are exposed to sufficiently warm temperatures and drying winds [154].

Fire years are sporadic in occurrence but tend to occur at least once every decade [71]. “Exceptional fire years” are characteristic of the black spruce-birch ecosystem. In Alaska, 6 years (1941, 1950, 1957, 1969, and 1977) accounted for 63% of the total area burned between 1940 and 1978 [160]. The average acreage burned each year in interior Alaska is approximately 1 million acres [96]. Fires tend to be large and may spread over thousands to hundreds of thousands of acres or more [71,94,150].

Estimated fire-return intervals in the black spruce-birch ecosystem vary from 50 to 200 years [71,160]. Fires occur every 50 to 70 years in black spruce-white spruce/bog birch/reindeer lichen communities in interior Alaska [55]. Heinselman [71] estimates a fire-return interval of 130 years for open black spruce/reindeer lichen forest and 100 years for closed-canopy black spruce forest. Mean fire-return intervals in lowland black spruce forests on the Kenai Peninsula, Alaska, range from 89 to 195 years [4,97].

Black spruce-birch communities experience high-severity, stand-replacing fires. These communities are highly flammable due to the abundance of ericaceous shrubs, the prevalence of dead, low-hanging branches on the black spruce trees, which are often covered with highly flammable epiphytic lichens, and the thick moss and lichen mats that cover the forest floor and become highly flammable after periods of low rainfall [94,95,155]. There is often nearly continuous fuel from the forest floor to the tree crowns [160]. Most fires in black spruce-birch communities are either crown fires or ground fires severe enough to damage or kill aboveground vegetation, including overstory trees. Fires may be severe enough to completely expose the mineral soil layer [50,71,150,160].

The following table provides fire return intervals for plant communities and ecosystems where bog birch is important. For further information, see the FEIS review of the dominant species listed below.

Fire-return intervals for plant communities with bog birch
Community or Ecosystem Dominant Species Fire Return Interval Range (years)
birch Betula spp. 80-230 [142]
tamarack Larix laricina 35-200 [113]
Great Lakes spruce-fir Picea-Abies spp. 35 to >200
northeastern spruce-fir Picea-Abies spp. 35-200 [50]
Engelmann spruce-subalpine fir Picea engelmannii-Abies lasiocarpa 35 to >200 [7]
black spruce Picea mariana 35-200
conifer bog* Picea mariana-Larix laricina 35-200 [50]
jack pine Pinus banksiana <35 to 200 [34,50]
Rocky Mountain lodgepole pine* Pinus contorta var. latifolia 25-340 [16,17,144]
aspen-birch Populus tremuloides-Betula papyrifera 35-200 [50,161]
quaking aspen (west of the Great Plains) Populus tremuloides 7-120 [7,62,103]
Rocky Mountain Douglas-fir* Pseudotsuga menziesii var. glauca 25-100 [7,8,9]
*fire return interval varies widely; trends in variation are noted in the species review

POSTFIRE REGENERATION STRATEGY [140]:
Small shrub, adventitious buds and/or a sprouting root crown
Rhizomatous shrub, rhizome in soil
Initial off-site colonizer (off site, initial community)

FIRE EFFECTS

SPECIES: Betula glandulosa
IMMEDIATE FIRE EFFECT ON PLANT:
Bog birch is easily top-killed by fire due to its thin bark, small stem diameter, and resinous, flammable twigs [44,77,159]. Both young and old bog birch plants are susceptible to top-kill by fire [44]. High-severity fire can kill bog birch plants by heating or consuming organic soil layers and scorching root crowns, rhizomes, and roots [93,169]. Seeds are easily killed by fire [44].

DISCUSSION AND QUALIFICATION OF FIRE EFFECT:
No additional information is available on this topic.

PLANT RESPONSE TO FIRE:
Fire has a substantial influence on bog birch growth and population dynamics [43,44]. Bog birch survives most low- and moderate- severity fires by sprouting from the root crown and/or rhizomes after top-kill by fire [43,44,82,112,165]. It flowers "profusely" from young sprouts [11] and produces large leaves after burning. Bog birch leaves were up to 3 times larger 1 year after fire than leaves on unburned plants near Inuvik, Northwest Territories, a response that may be linked to the increase in available nutrients following the fire [164,165]. A large proportion of phosphorus released into the soil after fire is absorbed by the roots of bog birch and then incorporated into new stem and leaf tissue. Changes in bog birch root biomass, root phosphorus concentration, and root phosphorus mass with burning of a mature 140-year-old black spruce/star reindeer lichen woodland at Schefferville, Quebec, were as follows [11]:

Changes in root biomass and root phosphorus in bog birch before and after fire [11]
Root characteristics Mature (140-year-old) Burned (0-year-old) Change (%)
root biomass (kg/ha) 9,159 8,886 -4
concentration of P in roots (% dry weight) 0.047 0.133 +283
mass of P in roots (kg/ha) 4.30 11.80 +274

Bog birch increases after low- to moderate-severity fires [164]. Repeated fires near treeline and on some wet sites in Alaska and northern Canada result in thickets of bog birch, mountain alder, and willows (Salix spp.) [82,154]. On tundra sites near Inuvik, Northwest Territories, total vascular plant cover on a burned area was more than twice that on an adjacent unburned area. The increase was due in large part to bog birch, which increased 8.8% after the burn [92].

Because of its ability to sprout from the root crown and rhizomes, bog birch is among the first plants to regenerate after fire in many communities [26,43,44,69,105,149,150]. Bog birch also persists into middle and late successional stages [23,105,133,149,150]. It was present in all postfire successional stages observed in a black spruce/reindeer lichen woodland in northern Quebec, but was most abundant in the intermediate stages between approximately 20 and 50 years after fire [56]. Frequency of bog birch at each successional stage is summarized below.

Frequency (%) of bog birch at 4 postfire stages [56]
postfire year 5 postfire year 20 postfire year 50 postfire year 90
24 63 69 1

In subarctic black spruce forests of western Labrador, bog birch was most abundant 18 to 40 years after fire. Mean canopy volume of bog birch between 2 and 140 years after fire is summarized below [132].

Mean canopy volume (m³) of bog birch across 5 postfire successional stages [132]
postfire year 2 postfire year 18 postfire year 40 postfire year 80 postfire year 140
0.01 2.23 1.04 1.01 0.00

Low-severity fire and spring burning promote sprouting in bog birch. In a study conducted during the 1992 growing season in the Rocky Mountains of Alberta, bog birch plants were burned in low-, medium-, and high-severity treatments. Plants burned earlier in the growing season and in low-severity treatments produced more and taller sprouts by the end of the first year after burning than plants burned late in the growing season or in severe fire treatments. Bog birch in the high-severity treatments sprouted latest. Following high-severity fire, new sprouts originated from the bottoms of rhizomes, indicating mortality of buds closer to the soil surface. No sprouting occurred on plants burned after late June, which may be related to seasonal variation in plant hormones that release buds from dormancy and promote stem extension in bog birch. Fall burning resulted in greatest plant mortality than spring and summer burning. Some plants burned in the fall sprouted the following year [43,44].

Bog birch was more abundant in "lightly" burned areas than in "heavily" burned areas following a June 1971 wildfire in black spruce forest near Fairbanks, Alaska [151]. Density of bog birch for 4 years following the fire is provided below.

Bog birch density (stems/ha) after wildfire in heavily and lightly burned areas [151]
  postfire year 1 postfire year 2 postfire year 3 postfire year 4
heavy 125 1,625 750 1,625
light 1,125 4,500 1,750 3,375

The response of bog birch to fire in a valley-bottom floodplain in the Rocky Mountains of Alberta varied with fire severity. Bog birch stem density increased for 2 years after a spring prescribed, low-severity fire in 1984 due to abundant sprouting. Following high-severity burns in 1987 and 1993, however, both stem density and canopy cover sharply declined. Results of this study are given in the figure below [29].

Although survival of bog birch plants decreases when fire severity is high, seedlings establish more easily on the bare mineral soil that is exposed after a high-severity fire [23,42].

On some sites, including in Wisconsin fens, bog birch increases in the absence of fire [38]. In the Rocky Mountains of Alberta, bog birch forms extensive, closed-canopy stands where fire has been excluded [29].

DISCUSSION AND QUALIFICATION OF PLANT RESPONSE:
No additional information is available on this topic.

FIRE MANAGEMENT CONSIDERATIONS:
Prescribed burning can reduce bog birch cover. Naturally occurring fires controlled the spread of bog birch on Canadian Rocky Mountain rangelands prior to active fire exclusion. Today, prescribed fires are used to reduce the spread of bog birch and other shrubs and to restore and maintain native grasslands [45]. The effects of prescribed burning on bog birch vary depending on burning conditions, fire season, severity, and postfire growing conditions. Burning bog birch stands in spring, when carbohydrate reserves are lowest, apparently promotes postfire sprouting and growth. Increased fire severity and fall burning both increase mortality in bog birch [43].

Prescribed burning at 3- to 6-year intervals in the Rocky Mountain foothills of Alberta has decreased shrub cover and increased forage production [45]. Bog birch cover decreased by 35% following a moderate-severity, prescribed spring fire in wood bison habitat in Fort Providence, Northwest Territories. After 3 months, bog birch cover increased by 26% [59]. Due to bog birch's "vigorous" sprouting response, burning at regular intervals is necessary to minimize its regrowth [29].

Fuel potential of bog birch is low because leaf moisture content is high [143]. Moisture content of bog birch measured near Inuvik, Northwest Territories, is given in the table below [164].

Moisture content (%) of bog birch in dry and wet tundra [164]
  18 July 1 August 15 August
Dry tundra 44 47 47
Wet tundra 56 50 51

In very wet places bog birch stands act as natural fire breaks [64].

MANAGEMENT CONSIDERATIONS

SPECIES: Betula glandulosa
IMPORTANCE TO LIVESTOCK AND WILDLIFE:
Bog birch is only lightly to moderately browsed by most classes of livestock [19,107]. It accounted for 2.7% of summer cattle forage, for example, on the Red Rock Lakes National Wildlife Refuge in Montana [47]. Browse production may be moderate to high in some bog birch communities. However, cattle tend to avoid the boggy soils associated with this species unless the soil becomes dry enough to walk on, usually in late summer [40,64,86,104]. Cattle eat bog birch in riparian wet meadows in the southern Blue Mountains, Oregon [120].

Numerous wildlife species eat bog birch, including moose, mule deer, white-tailed deer, Rocky Mountain elk, mountain goats, caribou, grizzly bears, American black bears, small mammals, birds, and insects [14,68,74,81,91,109,126,146,159]. Bog birch is a "preferred" browse species for game animals in Teton County, Wyoming [18]. It is dominant in tamarack swamps in southwestern Manitoba. These swamps provide habitat for moose, jumping mice, northern river otters, shrews, Canada jays, black-capped chickadees, white-throated sparrows, and Connecticut warblers [22].

Moose: Bog birch accounted for 11.8% of summer and 0.7% of winter moose forage on the Red Rock Lakes National Wildlife Refuge [47]. It is preferred browse in Banff and Jasper National Parks, Alberta [53], but is not preferred by moose in Alaska [30].

Caribou: Buds, leaves, and sprouts of bog birch are preferred foods for caribou in Alaska in the spring and early summer. The rumens of 6 caribou examined in mid-June contained almost exclusively bog birch. Caribou eat the leaves extensively into June and July, but by mid-September the leaves are less palatable than willow (Salix spp.) leaves [135,159]. Caribou also eat bog birch in summer and winter in northern Canada [20,36,72,128]. Heavy browsing by the Rivière George caribou herd in northern Quebec depleted winter carbohydrate reserves in bog birch, leading to decreased bog birch growth in spring [36].

Birds: Several species of ptarmigan and grouse eat bog birch in Alaska, Canada, and the contiguous northern United States [107,159]. Sharp-tailed grouse and greater prairie-chickens eat bog birch buds in Wisconsin in the winter [127], and spruce grouse eat bog birch seeds in central Alaska [163]. Bog birch and dwarf birch buds and catkins comprised 11% of the food in rock ptarmigan crops in Alaska in spring, 12% in summer, 45% in fall, and 79% in winter. For willow ptarmigan the 2 birches comprised 0% of food in crops in spring, 3% in summer, 4% in fall, and 12% in winter [163].

Small mammals: American beavers eat bog birch [109]. Bog birch is a preferred winter food of snowshoe hares in the southwestern Yukon [39,88,122,136]. Eastern heather voles eat bog birch bark in the winter in Canada [57]. White spruce/bog birch communities in the Kluane Region, Yukon, provide habitat for a number of small mammals including deer mice, northern red-backed voles, meadow voles, and heather voles [89].

Fish: Bog birch provides overhanging shade and cover for fish along low-gradient streams in western Montana [28].

Insects: Insect herbivores can cause "moderate" damage to bog birch. During the 1976 to 1980 growing seasons, bog birch plants in northern Quebec lost 20% to 50% of leaf biomass to insects [118]. In Alaska, the total number of herbivorous insects decreased with increases in latitude and altitude and distance from the white spruce forest zone. More detailed information on insects found on bog birch foliage is available [85].

Bog birch importance rankings for 9 ungulate species in British Columbia are provided below.

Importance of bog birch in the diets of ungulates in British Columbia [27]
Sitka black-tailed deer low
mule deer low
white-tailed deer low
mountain goat low
bighorn sheep low
Roosevelt elk low
Rocky Mountain elk moderate
moose high
caribou moderate

Palatability/nutritional value: The palatability of bog birch in several states is as follows

Palatability of bog birch for livestock and wildlife [28,38,46,67,125]:
  California Colorado Montana Wisconsin Wyoming
cattle poor fair poor ---* fair
domestic sheep fair-poor fair fair --- fair
horses poor poor poor --- fair
white-tailed deer --- --- poor --- ---
mule deer --- --- poor --- ---
moose --- --- -- --- high
elk --- --- poor --- ---
pronghorn --- --- poor --- ---
rabbits --- --- --- high ---
* No data available.

The energy and protein values of bog birch are low [28]. Sugar content in bog birch leaves declines in late summer. Nitrogen concentration in leaves peaks early in spring then declines throughout the growing season [118]. Nutritive values measured in bog birch plants near Inuvik, Northwest Territories, are given in the table below [129,130].

Nutritive values in bog birch twigs and leaves [129,130]
Plant part Month Cu Mo Fe Mn Zn K Mg Ca P crude fat crude fiber crude protein
    ppm %
twigs July 2.8 0.23 50 157 87 0.70 0.20 0.34 0.08 8.9 26.1 3.5
twigs Aug. 4.6 0.21 161 67 178 0.21 0.10 0.41 0.09 10.7 27.4 5.4
twigs Nov. 3.7 0.31 332 121 206 0.09 0.11 0.62 0.06 4.9 33.7 4.2
twigs Feb. 4.6 0.21 205 78 160 0.18 0.10 0.47 0.06 9.3 30.6 4.9
twigs May 4.7 0.23 102 92 152 0.23 0.10 0.47 0.09 9.8 28.5 6.0
leaves May 4.4 0.21 83 151 108 0.66 0.34 ---* --- --- --- ---
leaves July --- --- --- --- --- --- --- 0.44 0.13 7.3 12.7 10.4
leaves Aug. --- --- --- --- --- --- --- 0.63 0.15 7.9 15.8 12.1

* No data available.

Bog birch produces carbon and nitrogen-based antiherbivore compounds that deter browsing [41]. Sugar and nitrogen content is highest in the leaves in early spring. Bog birch allocates the greatest portion of its photosynthate to the production of antiherbivore phenolics at that time; otherwise, leaves would be susceptible to browsing insects [118].

Cover value: The table below summarizes thermal or feeding cover values of bog birch.

Cover values of bog birch for wildlife in 3 western states [28,46]
  Colorado Montana Wyoming
elk good poor poor
mule deer poor poor poor
white-tailed deer ---* poor poor
upland game birds good fair fair
waterfowl   good poor
small nongame birds good fair good
small mammals good fair good
* No data available.

Bog birch provides cover for willow, rock, and white-tailed ptarmigan in southwestern Yukon [115]. Grizzly bears in the central Canadian Arctic constructed their dens under bog birch cover more than any other plant species. Bog birch was present at 84% of 52 den sites, and it was the highest in percent cover around den entrances. Bog birch roots formed ceilings of several dens studied [102].

VALUE FOR REHABILITATION OF DISTURBED SITES:
The erosion control potential for bog birch is high. In Montana, the dense underground network formed by bog birch and rhizomatous sedges help stabilize streambanks [28]. Because bog birch grows slowly, its short-term (1-3 years) revegetation potential is low. Bog birch is, however, suitable for long-term (>3 years) revegetation of exposed mineral soil [28,101].

Black spruce seedling survival after fire in the boreal forest may be facilitated by shading from bog birch and other shrubs that reproduce vegetatively and grow quickly [134].

OTHER USES:
No information is available on this topic.

OTHER MANAGEMENT CONSIDERATIONS:
Bog birch decreases with grazing. Bog birch cover was significantly (P=0.01) greater on ungrazed sites (88%) than on grazed sites (47%) within the summer range of the Rivière George caribou herd in northern Quebec and Labrador, Canada. Browsing and trampling by caribou have opened the closed canopy of bog birch and reduced leaf biomass by 60% [99]. Bog birch plants heavily browsed by snowshoe hares near Kluane, Yukon, exhibited rapid growth of new twigs when hare numbers declined [136].

Expanding bog birch populations on Canadian Rocky Mountain rangelands reduce forage for elk, bison, and other grazing animals. Removal of bog birch increases the production of forage grasses [43].

Information on the effects of herbicides on bog birch is available in Chapin and others [14].

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