SPECIES: Ledum palustre
© 2005 Susan Aiken, Canadian Museum of Nature
Plants database provides a distributional map of
northern Labrador tea.
STATES/PROVINCES: (key to state/province abbreviations)
Alaska: Northern Labrador tea occurs in arctic and subarctic vegetation in the interior and coastal regions of Alaska. In the foothills of the Brooks range, approximately equal proportions of northern Labrador tea, sheathed cottonsedge (Eriophorum vaginatum), dwarf birch, and mountain cranberry (Vaccinium vitis-idaea) dominate the tussock tundra vegetation of the landscape .
In many northwestern Alaska vegetation types, northern Labrador tea is considered important. The birch-willow vegetation type includes bog birch (B. glandulosa), dwarf birch, diamondleaf willow, Richardson willow, and Alaska bog willow (S. fuscescens). The dwarf birch-heath/lichen vegetation type occupying rocky slopes with well-drained soils is typical habitat for dwarf birch, bog blueberry (V. uliginosum), black crowberry (Empetrum nigrum), and northern Labrador tea. The blueberry (Vaccinium spp.)-heath/lichen vegetation is widespread on hills of the Seward Peninsula. Bog blueberry dominates this community type but northern Labrador tea and scattered low growing dwarf birch are common too. The white arctic mountain heather (Cassiope tetragona)-blueberry and alpine bearberry (Arctostaphylos alpina)-mountain cranberry vegetation types are also northern Labrador tea habitat. The alpine bearberry-mountain cranberry type occupies gravelly sites of the Cape Nome headland. In the dwarf shrub-marsh community type, northern Labrador tea occurs with several characteristic bog species including cloudberry (Rubus chamaemorus), bog cranberry (V. oxycoccos), and sedges (Carex spp.). The cloudberry-dwarf shrub marsh vegetation type includes mountain cranberry, dwarf birch, black crowberry, cloudberry, and northern Labrador tea .
In the Yukon-Tanana uplands of Alaska, northern Labrador tea has 40% cover in black spruce/cottongrass (Picea mariana/Eriophorum spp.) communities that occur next to streambank vegetation. There is often standing water between the tussocks . In sheathed cottonsedge-dominated communities near Fairbanks, northern Labrador tea, bog blueberry, mountain cranberry, willow, dwarf birch, bog birch, and cloudberry can all occur . Northern Labrador tea also occurs in the following young forest community types found in the interior of Alaska: quaking aspen/russet buffaloberry (Populus tremuloides/Shepherdia canadensis), paper birch (B. papyrifera)-quaking aspen/highbush cranberry (Viburnum edule), paper birch-quaking aspen/mountain alder (Alnus viridis ssp. crispa), and white spruce (Picea glauca)-paper birch/mountain-fern moss (Hylocomium splendens) .
On wet coastal plains of Alaska, Bliss  recognizes northern Labrador tea in cottongrass-dwarf shrub heath tundra vegetation. Northern Labrador tea has 50% constancy and 3% cover in the early to mid-successional beach strawberry (Fragaria chiloensis) community type that occurs on barrier islands and coastal dunes of Alaska's Copper River Delta. Here the soils are well-drained, silt sands with pH levels near 6.4 . On the Kenai Peninsula, northern Labrador tea occurs with 50% constancy in the white spruce-black spruce/black crowberry-mountain cranberry/felt lichen (Peltigera spp.)-big red stem moss (Pleurozium spp.) community type .
Northwest Territories: Northern Labrador tea occurs in white spruce forests of the Mackenzie Delta region of Canada's Northwest Territories. Here white spruce trees are small, under 13 feet (4 m) tall, and widely spaced. Hummocks are covered by reindeer and cup lichens (Cladina and Cladonia spp.), and the shrub layer is dominated by willow, bog birch, and northern Labrador tea. Most of these communities are even-aged postfire forests. Northern Labrador tea is typical vegetation in sedge tundra that occurs on the Yukon coastal plain and the unglaciated tip of the Tuktoyaktuk Peninsula. Shrub tundra vegetation of the Mackenzie Delta includes grayleaf willow, bog birch, alder, Lapland rosebay (Rhododendron lapponicum), and white arctic mountain heather .
Yukon: Northern Labrador tea is a dominant species in several community types of the Yukon region. In the sheathed cottonsedge-northern Labrador tea-dwarf birch vegetation type, northern Labrador tea has 22.5% cover. This type is very similar to the tussock-sedge tundra community. The alpine bearberry-sheathed cottonsedge-northern Labrador tea community closely resembles dwarf shrub tundra vegetation. Some scattered black spruce trees may occur in this type where northern Labrador tea coverage averages 21.5%. In the lichen/bog birch/northern Labrador tea community type that is similar to lichen/shrub or alpine tundra types, northern Labrador tea community coverage averages 22.3%. Occasional stunted black and/or white spruce occupy this habitat that is typical on open, steep north-facing slopes in the Ogilvie Mountains. The black spruce-bog birch/northern Labrador tea community type typically supports northern Labrador tea coverages of approximately 20%. This type is also known as a spruce-tall shrub taiga type and occurs on tundra peat soils on gentle northeast or northern facing slopes of the Eagle Plains and Richardson Mountains. Black spruce/lichen/northern Labrador tea communities occupy flat to gentle slopes with western and southwestern exposures. This type is also referred to as the lichen/spruce taiga type .
Other northern Labrador tea community types include the following (listed in order of decreasing northern Labrador tea coverage): mountain alder-alpine bearberry-bog blueberry, netleaf willow (Salix reticulata)-dwarf birch-cloudberry, cloudberry/bog birch/bog blueberry, black spruce/sheathed cottonsedge-sedge, black spruce/bog blueberry/tamarack (Larix laricina), white spruce-paper birch/mountain cranberry on steep south slopes, and lichen/white arctic mountain heather/arrowleaf sweet coltsfoot (Petasites sagittatus) .
Northern Labrador tea is recognized as a dominant species in the following vegetation
Yukon, Canada: 
|© 2005 Susan Aiken, Canadian Museum of Nature|
Northern Labrador tea is a long-lived, resinous, evergreen shrub [8,37]. This multi-branched, prostrate shrub grows 4 to 24 inches (10-60 cm) tall and is capable of clonal growth through layering [1,2,8,71,81]. Northern Labrador tea has alternate linear leaves. The small, thick, linear leaves have a leathery appearance and are often 5 to 8 times long as they are wide. The upper leaf surface is shiny and glabrous, while the lower surface is densely hairy [1,2,37,71,81]. The margins of the leaves bend underneath to give a rounded appearance . Northern Labrador tea flowers are fragrant umbels [37,81]. The fruit is a 5-parted capsule measuring 2 to 3.5 mm long by 1 to 3.5 mm wide and opening at the base . Numerous small (1.7×0.3 mm) seeds are produced [1,38].
Growth dynamics: Northern Labrador tea grows in harsh arctic and subarctic environments and has prompted many to investigate its above- and below-ground growth dynamics. In the Atkasook study area southwest of Barrow, Alaska, researchers found that northern Labrador tea had less than 50% of its biomass underground and that leaves constituted almost 50% of its aboveground biomass. Northern Labrador tea maintains low nutrient levels, and soil nutrients are slowly transferred into the leaves throughout the growing season where they are stored through the winter .
In Eagle Creek, northeast of Fairbanks, Alaska, the underground structures of 100 northern Labrador tea plants revealed that northern Labrador tea's fine roots averaged 0.12 mm in diameter but ranged from 0.03 to 0.57 mm. From a sample size of 5, researchers estimated that northern Labrador tea root extension averaged 67 m/g. From aboveground and belowground measurements of 8 northern Labrador tea plants, researchers found that the mean fine root to leaf dry weight and fine root surface to leaf area ratios were 0.3 and 2.03, respectively .
Northern Labrador tea woody stem production and turnover investigations were made in Eagle Creek (1978) and Toolik Lake (1982-83), Alaska. In tussock tundra of Eagle Creek, the growth rate of 1- to 15- year-old northern Labrador tea plants was 15.4% per year. The relative secondary growth rate of 15-year-old ramets was 8% annually in moist tussock tundra of arctic Alaska . In Toolik Lake, production and turnover of woody materials was compared in tussock tundra and evergreen heath communities. In the tussock tundra, the growth rate for 1- to 20-year-old northern Labrador tea plants was 14.4% per year. In low-productivity, low-biomass evergreen heath vegetation, the 1- to 20- year-old growth rate was 8.9% annually. The turnover rate of nutrients and woody stem biomass was longer in evergreen heath communities as was the life expectancy of stems. The turnover rates and life expectancies of northern Labrador tea stems are summarized below for 2 vegetation types of Toolik Lake .
|Vegetation type||Biomass turnover (yr)||Nitrogen turnover (yr)||Phosphorus turnover (yr)||Stem life expectancy (yr)|
Breeding system: No information is available on this topic.
Pollination: The pollination of northern Labrador tea flowers was not addressed specifically in the literature. However, northern Labrador tea reportedly has nectaries and is likely visited by insects .
Seed production: A "large" number of seeds (>50) are produced per northern Labrador tea flower . In tussock tundra vegetation of Eagle Creek, Alaska, researchers reported that northern Labrador tea produced numerous very light seeds. However, just 33% were viable. Northern Labrador tea typically aborted seeds sometime between the time of fruit formation and seed dispersal. The table below summarizes the average flower, fruit, and seed production by northern Labrador tea in Eagle Creek. Observations coincided with what was considered a year of high flower production in the area .
|Number of growing points*/m²||221|
|Number of flowers/m²||38|
|Number of flowers/100 growing points||11|
|Number of fruits/m²||34|
|Mortality (proportion of flowers that did not produce fruit)||0.25|
|Number of full seeds/fruit||58|
|Proportion of viable seeds||0.33|
|Number of viable seeds/m²||650|
|Number of viable seeds/100 growing points||295|
From the values presented above, researchers calculated the percentage of total annual production that northern Labrador tea allocated to vegetative growth and reproductive effort. Sexual reproductive effort was 3.4% of northern Labrador tea's annual production, while vegetative growth was 95.6% .
|Total sexual reproductive effort¹||3.4%|
|Viable seed reproductive effort²||0.14%|
Seed dispersal: Northern Labrador tea seed is wind dispersed [15,18].
Seed banking: McGraw  suggests that northern Labrador tea seed has little dormancy, and while it may last in the soil for more than a single growing season, it is not viable once buried below the 1st substrate layer. In tussock tundra of Eagle Creek, Alaska, 40 soil samples taken from cores with 2 inch (5 cm) diameters at a maximum depth of 14 inches (35 cm) were collected on August 12, 1978. Vertical structure was maintained, and samples were stored at 1°F (-17 °C) for 4 months. On January 19, 1979, germination of the soil seed bank was encouraged under greenhouse conditions. Greenhouses received 20 hours of daylight, 4 hours of darkness, and an average daily temperature of 68 °F (20 °C). A total of 1,295±301 (s x) northern Labrador tea seeds/m² germinated. Most (90%) came from the top 2 inches (5 cm) of soil .
From soil samples (15×15×10 cm) collected in 4 undisturbed tundra communities of northern Alaska, no northern Labrador tea seedlings emerged under greenhouse conditions regardless of stratification. Sample collections occurred on July 23, 1981 and July 15, 1983, which is likely prior to northern Labrador tea seed dispersal .
Germination: Northern Labrador tea seed must be near the soil surface to germinate and germinates better given long day conditions. Cotyledons turn green prior to radicle extension inside the transparent seed coat. Ninety-four percent of northern Labrador tea seed collected in August of 1977 from the Mackenzie Delta of the Northwest Territories germinated. Seed did not require stratification .
Experiments conducted under controlled and natural conditions suggest that day length and soil temperature are also important factors in controlling northern Labrador tea germination. Seed was collected at the time of seed shed from the upper Dietrich River Valley in the Brooks Range. Unstratified seed germination was low at 50 °F (10 °C), 59 °F (15 °C), and 68 °F (20 °C) when subjected to short day lengths (13 hours of light). Cold stratification and long day treatments increased the percent germination and encouraged seed to germinate in even 41 °F (5 °C) temperatures. Seeds sown in natural settings on September 4 had not germinated by June 4, but seedlings did appear by June 16 when soils temperatures were greater than 41 °F (5 °C). This study suggests that day length may be important in maintaining northern Labrador tea seed dormancy after seeds are shed .
Seedling establishment/growth: Seedling growth is "exceedingly slow" for northern Labrador tea. Establishment of seedlings was studied in undisturbed tussock tundra near Eagle Creek, Alaska. From 40 sampled plots, 181±36 (s x) seedlings/m² emerged. Mortality was 77% per year during the first 3 years of seedling growth. After this period mortality decreased to between 5% and 15% annually. Even with these high rates of mortality, researchers maintained that "enough seedlings pass through the 1st high mortality establishment phase to contribute to the undisturbed vegetation community." Most northern Labrador tea seedlings germinated on dead leaves and dicranum moss (Dicranum spp.). Seedling growth is slow, and seedlings over 20 years old may still have juvenile leaves .
Asexual reproduction likely predominates following disturbances that top-kill northern
Labrador tea. The 1944 to 1953 oil exploration in northern Alaska left debris abandoned
on the tundra surface that was cleaned up in the late 1970s and early 1980s. Recovery of
the debris resulted in bare sites that were monitored 2 and 4 years following removal.
Northern Labrador tea vegetatively colonized some of the driest sites sampled. Frequency
after debris removal was 1% and coverage was 3%. There were no northern Labrador tea
Northern Labrador tea's slow growth rate and slow rate of nutrient, stem, and leaf turnover make it successful in low nutrient environments . It occupies wet and dry habitats in subarctic and arctic areas. Northern Labrador tea occurs with other heaths in dry, rocky areas that span the entire state of Alaska . It occupies sedge tussocks and wet depressions of arctic tundra and sphagnum bogs and wet black spruce vegetation types of boreal forests . Northern Labrador tea is also described in muskegs and alpine areas from Newfoundland to the Aleutian Islands . Dry areas and upper levels of stream banks in the Canadian Arctic Archipelago also provide northern Labrador tea habitat .
Soils: Northern Labrador tea habitats occur on dry to imperfectly drained soils that are acidic and underlain with a permafrost layer. In arctic environments, just the upper 8 to 24 inches (20-60 cm) of soil thaws in the summer; along rivers and lakes, soils may thaw to a depth of 79 inches (200 cm) . On the barrier islands and coastal dunes of Alaska's Copper River Delta, soils are well-drained, silt sands and the pH of the mineral soils averages 6.4 . The tussock tundra of the Imnavait Creek Watershed at the foothills of the central Brooks Range has poorly drained soils. A poorly developed mineral horizon with a pH of 5.5 overlays organic and permafrost layers ( cites others). In the black spruce/sheathed cottonsedge vegetation of the Yukon-Tanana Uplands of Alaska, northern Labrador tea has 40% cover on sites where there is standing water between the tussocks .
Substantial information was gathered on the soils of Yukon habitats in which northern Labrador tea dominates. This information is summarized below :
|Community type||Depth to permafrost (cm)||pH|
|sheathed cottonsedge/northern Labrador tea/dwarf birch||30-60||3.3-4.9|
|Alpine bearberry/sheathed cottonsedge/northern Labrador tea||39-55||3.4-3.9|
|Lichen/bog birch/northern Labrador tea||30-55||3.5-5.9|
|Black spruce/bog birch/northern Labrador tea||45-65||----|
|Black spruce/lichen/northern Labrador tea||100-150||2.8-3.8|
Elevation: Very little was reported on northern Labrador tea's elevation range. Hulten  suggests that northern Labrador tea occurs at elevations up to 5,905 feet (1,800 m) throughout Alaska.
Climate: Northern Labrador tea grows in harsh subarctic and arctic climates . Near Barrow, Alaska, where northern Labrador tea grows in tussock tundra habitats, the growing season lasts an average of 75 days from mid-June to late August. The average July temperature in 1975 was 45 °F (7.2 °C), and mean precipitation for the summer season was 3.2 inches (80 mm) . Northern Labrador tea also grows in the foothills of the central Brooks Range of Alaska. This area experiences severely cold winters, cool summers, little precipitation, and continuous winds (rarely exceeding 17 m/s). During a 1986 study, annual precipitation measured 13.5 inches (344 mm) with almost equal proportions of rain and snow. The minimum temperature for the year was -45 °F (-43 °C), and the maximum was 66 °F (19 °C) . Tundra vegetation on the northwestern shore of Hudson Bay has just a 6-week growing season, experiences frost at any time, and reaches a mean temperature of 50°F (10 °F) during the warmest month .
A study done in central northern Canada found that northern Labrador tea was strongly correlated (r =0.56-0.68) with arctic air masses in white spruce communities and Pacific air masses in rock field tundra communities. The author suggested that northern Labrador tea's conflicted correlations may be due to a wide tolerance of a variety of harsh conditions or may be due to some ideal adaptation to each site .
Starr and Oberbauer  found that northern Labrador tea was able to photosynthesize
at low rates when covered with less than 12 inches (30 cm) of snow. This finding suggests
a keen adaptation to growth in arctic conditions. Researchers reported that photosynthetic
rates increased with decreasing snow depth.
Northern Labrador tea is a shade intolerant species  that occurs predominantly in late-seral communities undergoing primary succession. However, following disturbances in areas where northern Labrador tea is established, this species rapidly recolonizes the site.
Shade relationships: The findings following a fire in black spruce forests near Fairbanks, Alaska, indicated that northern Labrador tea preferred open canopies to densely shaded conditions. Northern Labrador tea coverage on burned sites immediately following the fire was 0.6%, and 3 years after the fire was 9.3%. On similar unburned sites, the coverage of northern Labrador tea was 13.8% on open-canopy sites with low black spruce cover but was 2.5% on sites with very dense black spruce coverage .
General successional change: Assigning northern Labrador tea to a single successional stage is difficult since this species is associated with a wide variety of vegetation types that experience different successional changes. In the taiga, northern Labrador tea occurs in all seral stages but is highly prominent in mature vegetation types . In the beach strawberry community type that occupies the barrier islands and coastal dunes of Alaska's Copper River Delta, northern Labrador tea occurs with 50% constancy. This community is considered an early- or mid-seral type . In the Mackenzie Delta of the Northwest Territories, northern Labrador tea occurs in white spruce forests with trees aged 400 years or older. Here tree cover is sparse (10%) and white spruce tree seedlings are absent .
Northern Labrador tea appears in intermediate stages of primary bog succession. This process begins with open water that is colonized by immersed sedges and mosses which reproduce and multiply forming dense mats of vegetation. These mats are later colonized by shrubs species such as northern Labrador tea. Finally, black spruce trees colonize the area. A time table for this process was not provided .
In a study of forest succession along the Chena River north of Fairbanks, Alaska, researchers compared vegetation at different developmental stages. Sampling occurred in 15-year-old willow stands on an open gravel bar, 50-year-old balsam poplar stands, 120-year-old white spruce stands, 120-year-old white spruce/black spruce stands, and 120-year-old black spruce-dominated stands. The 120-year-old black spruce stands represented climax vegetation for the area. Northern Labrador tea occurred only in climax black spruce vegetation .
Response to disturbance: Bliss  describes arctic succession following disturbances as a shift in species' coverage rather than a change in species over time. In arctic tundra and boreal forests recovering from disturbances, northern Labrador tea often occurs in early-, mid-, and late-seral vegetation.
In tundra vegetation north of the treeline in the Yukon territory, researchers compared the average coverage of northern Labrador tea on undisturbed sites, in vehicle tracks, and in drainage ditch sites. The percent coverage on undisturbed sites was significantly greater (p>0.01) than on disturbed sites. However, the authors note that drainage ditches had standing water all growing season, and the vehicle tracks had pooled water in the early spring and summer months. Whether or not this affected northern Labrador tea growth is unknown. The largest factor contributing to northern Labrador tea's coverage, disturbance or standing water, is undeterminable .
When researchers removed all the vegetation and rhizomes in 6.6×6.6 foot (2×2 m) sections of tussock tundra near Eagle Creek, Alaska, northern Labrador tea did not recolonize cleared sites by the 2nd postdisturbance year. The predisturbance vegetation was a mix of sheathed cottonsedge, northern Labrador tea, bog blueberry, mountain cranberry, and Bigelow sedge (Carex bigelowii). The removal of northern Labrador tea's underground structures delayed colonization. Northern Labrador tea may take longer than 2 years to colonize bare sites through sexual reproduction .
While northern Labrador tea is not a palatable shrub browsed by arctic mammals, the following study likely involved trampling effects and browsing on northern Labrador tea. On Rideout Island of the Northwest Territories, 500 to 1,000 caribou became stranded in the summer of 1987. The 15 square mile (40 km²) island could not sustain the caribou, and all died of malnutrition after severely grazing island vegetation. Researchers visited the island in late July, 1988, and compared the island vegetation to similar mainland communities. Coverage of northern Labrador tea was significantly lower in the low shrub tundra on the island due to trampling and/or browsing. Findings from the study are summarized below .
|Cover (%) in low shrub tundra||2±1||7±2*|
|Cover (%) in tussock tundra||6±2||4|
|Mean % of browsed shoots
The study of disturbed sites in the Tuktoyaktuk Peninsula of the Northwest Territories revealed that northern Labrador tea is sensitive to soil surface disturbances. A comparison of disturbed and undisturbed sites showed that northern Labrador tea coverage is reduced on disturbed sites regardless of when roads, trails, and seismic lines are used .
Northern Labrador tea does show some resistance to chemical disturbances, however. When sites in the western Canadian arctic were treated with oil (0-1.5 cm) in late June, northern Labrador tea regrowth was evident by August of the same year .
The fire effects section provides additional
information regarding northern Labrador tea and secondary succession.
Summer flowers and fall fruits are typical for northern Labrador tea. In Alaska, flowers appear in June and early July, fruits mature by July or August, seeds are released in the fall, but capsules may remain attached through the winter . More specific dates regarding northern Labrador tea's seasonal development in tussock tundra of central Alaska are provided by Murray and Miller . Between May 31 and June 13 flower buds swell, between June 27 and July 3 flowering is initiated, from July 9 through July 21 fruits are set, and after August 28 seeds are dispersed. In arctic and subarctic regions of Canada, flowers are possible anytime June through August, and seeds mature in the fall .
Fire regimes: Fires in northern Labrador tea habitats are common. Likely the fire return interval is shorter in shrub and tussock tundra vegetation than in boreal forests. Bliss and Wein  consider "tundra fires less damaging than forest fires because the amount of combustible materials is less, and cool wet soils usually prevent deep burning."
Arctic fire ecology: Fires in arctic lichen/heath/moss communities burn irregularly. The slowly accumulated litter beneath northern Labrador tea plants together with its resinous leaves and stems causes northern Labrador tea to "burn fiercely." Blackened circles around northern Labrador tea plants are common . Bliss  considers dwarf shrub heath and low shrub tundra the most common vegetation types burned in arctic fires. Fires in tundra vegetation serve several functions. The darkened soil surfaces can increase the depth of thaw by 30% to 50%, and nutrient release is important in these low-nutrient, slow-turnover systems . In tussock tundra vegetation of Alaska's Seward Peninsula, the evidence of fire is virtually undetectable after 7 years. Studies indicate that just the relative proportions of species change .
Boreal/taiga fire ecology: Canadian boreal forests burned "extensively and repeatedly" . Rowe and others  describe several factors contributing to the likelihood of fires. Lightning is common from June through August, summers are dry and warm, and long periods of daylight easily dry surface fuels. Mosses and lichens occupy large surface areas and dry out rapidly. In terms of boreal and subarctic regions, Rowe and others  assert that the question should not be whether these sites burned but when and how often. Fire is also considered important to energy cycling. Energy conversion together with selected fire regeneration traits is important to maintaining the "stability and viability" of boreal forests .
Studies of succession in upland taiga vegetation of Riley Creek in Denali National Park, Alaska, suggest a fire return interval of 40 to 60 years before the fire suppression era. Researchers suggest that "plants emerging from underground parts immediately after the last fire are typically the same individuals whose above ground biomass will support the next fire" .
In white spruce forests of the Mackenzie Delta region of Canada's Northwest territories, the fire return interval is likely longer than that of Denali's upland taiga. Most of these forests are even-aged postfire communities with widely-spaced, small white spruce trees under 13 feet (4 m) tall. Following fires in this vegetation type, shrubs return after 15 years, while trees take between 100 and 150 years to re-establish .
In peat plateaus, fire is common due to well-drained sites, an abundance of flammable fuels, black spruce trees with branches near ground, resinous shrubs such as Labrador tea, and quickly-dried surface fuels .
The following table provides fire return intervals for plant communities and ecosystems where northern Labrador tea is important. For further information, see the FEIS review of the dominant species listed below.
|Community or Ecosystem||Dominant Species||Fire Return Interval Range (years)|
|black spruce||Picea mariana||35-200|
|conifer bog*||Picea mariana-Larix laricina||35-200 |
|aspen-birch||Populus tremuloides-Betula papyrifera||35-200 [21,82]|
|quaking aspen (west of the Great Plains)||Populus tremuloides||7-120 [3,30,50]|
DISCUSSION AND QUALIFICATION OF FIRE EFFECT:
No additional information is available on this topic.
PLANT RESPONSE TO FIRE:
Northern Labrador tea re-establishes on burned sites through root sprouts [5,57,67]. Chapin and Van Cleve  suggest that northern Labrador tea has "spotty" survival following fires in the taiga. Northern Labrador tea is rooted in the organic horizon and survives in patches of organic matter that are not totally consumed by fire. Researchers consider northern Labrador tea an important understory species throughout succession.
DISCUSSION AND QUALIFICATION OF PLANT RESPONSE:
Following fire, northern Labrador tea initially decreases in coverage and frequency. However, northern Labrador tea is often noted as an important or conspicuous species immediately following fires in tussock tundra, shrub tundra, and boreal forests. Likely fire severity and/or depth of burn dictate the time required for northern Labrador tea to regain prefire coverage and frequency.
Early postfire effects: The following studies highlight early northern Labrador tea postfire responses. In most cases, the re-emergence of northern Labrador tea is rapid. Following a June fire in stunted black spruce-dominated taiga of northwestern Manitoba, northern Labrador tea growth was common in the 1st postfire year. All upland vegetation was top-killed and mosses burned 4 inches (10 cm) deep in spots following this fire . Wein [83,84] considered northern Labrador tea's importance to be greater after tundra and forest tundra fires in northern Canada. In Alaska and Inuvik, northern Labrador tea and sheathed cottonsedge had the most growth in the 1st postfire year following fires that removed litter and charred tussocks . Of 4 sites burned in 1970 in north-central Saskatchewan, 2 supported dense Labrador tea growth by 1973. Fire severity was not described .
Following the Wickersham fire that burned black spruce forests near Fairbanks, Alaska, in late June, 1971, researchers measured vegetation and environmental changes. Sites burned "lightly" and "heavily" were compared to unburned sites. "Lightly" burned sites had less than 50% of the ground blackened with tree branches and crowns scorched but not consumed. "Heavily" burned sites had more than 90% of the ground surface blackened and tree crowns consumed. All burned sites had greater depths and rates of thaw in the 1st postfire year than did unburned sites. The snow-free period was 126 days on burned sites and 119 on unburned sites. Maximum soil temperatures at 4 inches (10 cm) were 51 °F (10.5 °C) reached by July 30 on burned sites and 43 °F (6 °C) reached by September 13 on unburned sites. Northern Labrador tea density and frequency were much lower on the heavily burned sites, and control levels were not reached by the 3rd postfire year on either burned site. Results from the study are given below .
In an additional study of sites burned by the Wickersham fire, Wolff  found that northern Labrador tea coverage on burned sites immediately following the fire was 0.6%, and 3 years later coverage was 9.3%. On similar unburned sites, the coverage of northern Labrador tea was 13.8% on open-canopy sites with low black spruce cover and 2.5% on sites densely covered by black spruce.
A lightning-caused fire burned 386 mi2 (1000 km²) from July 9 to September 12, 1977, in tussock tundra vegetation of Alaska's Seward Peninsula. The fire consumed most above ground vegetation. The frequency of northern Labrador tea in late May of the 1st postfire year was 0% on burned sites and 100% on unburned sites. By mid-June of the 1st postfire year, northern Labrador tea frequency on burned sites was 22% and 100% on unburned sites .
The recovery of northern Labrador tea on some burned tussock sites of Inuvik, Northwest Territories, took only 2 years. Researchers compared the annual production and nutrient content of northern Labrador tea on burned and unburned areas of 4 tussock communities. None of the fires were severe enough to kill entire tussocks, but did remove the evidence of shrubs and cryptogams. Site 1 burned in late June of 1969, and sites 2, 3, and 4 burned in August of 1968. The fire that burned site 4 was considered severe because of dry prefire conditions. The researchers noted that northern Labrador tea's recovery was the fastest of all shrub species investigated. The growth form of northern Labrador tea the 1st postfire year was abnormal; northern Labrador tea leaves were uncharacteristically thin and broad. This change in appearance was unnoticed by the 2nd postfire year. On sites 1 and 4, northern Labrador tea production was greater on burned than unburned sites by the 2nd postfire year. The production of northern Labrador tea on all sites is shown below :
|mean annual production
± (s x g/m²)
The nitrogen, phosphorus, potassium, and magnesium levels in northern Labrador tea plant tissues were significantly greater for burned plants. Below is the average nutrient content of northern Labrador tea plants from 4 burned sites and 1 unburned site .
|Measurement||% of dry weight||ppm|
Early and later postfire effects: The following studies describe both early and later postfire recovery of northern Labrador tea. Northern Labrador tea is typically present in early postfire communities; fire severity influences recovery time and postfire coverage of northern Labrador tea. Portions of Alaska's Seward Peninsula burned in July of 1977 when temperatures averaged 5 degrees above normal, and precipitation levels were 5% of normal. Fires burned in 3 vegetation types, and severity varied. The vegetation burned is listed in order of increasing fire severity: tussock shrub tundra, wet sedge-shrub tundra, and dry shrub tundra. Northern Labrador tea coverage was reduced on all burned plots initially. However, decreased coverage was longer lived on those sites burned with greater severity. On tussock shrub tundra sites that burned least severely, northern Labrador tea density (shoots/m²) was significantly (p=0.1) greater the 2nd postfire year than the 1st postfire year on 4 out of 5 sites sampled. The increase averaged 49 shoots/m². The prefire and postfire northern Labrador tea coverages are summarized below [55,56,58].
|Vegetation type||Organic horizon removed||Prefire||Postfire year 1||Postfire year 2||Postfire year 3||Postfire year 24|
|Moist tussock-shrub tundra||≤5 cm||9%||1.2%||3.4%||4%||36%|
|Wet sedge-shrub tundra||5-15 cm||4%||tr||tr||tr||1%|
|Dry shrub tundra||~50%||6%||0||0||0||1%|
Fetcher and others  compared burned and unburned sites 1 and 13 years following a June 1969, fire that burned northwest of Fairbanks, Alaska, in sheathed cottonsedge communities. The fire did not burn severely enough to kill entire tussocks but removed all shrubs and cryptogams. Researchers found that the depth of thaw in the 13th postfire year was 20 inches (52 cm) on burned sites and 15 inches (39 cm) on unburned sites. These differences were significant (p<0.01). Northern Labrador tea production recovered by the 13th postfire year. The table below summarizes the findings of Fetcher and others .
|annual production ± s x (g/m²)||4.8±1||15±1.3||26.9±5.5||31.3±3.4|
Northern Labrador tea recovered from a severe fire in tundra and forest-tundra vegetation of Inuvik, Northwest Territories, by the 22nd postfire year. The fire burned from August 8 through 18, 1968. Researchers described the deep-penetrating fire as burning with "unusually great severity." Fire scarred black spruce trees suggest the area last burned 120 years ago. Burned and unburned sites were compared in August of 1973, and burned sites were resampled in August of 1990. Northern Labrador tea was present immediately following fire. Northern Labrador tea coverage on burned sites was significantly (p<0.01) greater than in previously unburned tundra vegetation by 1990. Northern Labrador tea recovery is summarized below :
Forest-tundra ecotone (n=9)
|% cover ± s x||18.5±2.1||4.4±1.2*||16.3>±4.7||15.1±2.2||6.4±1.2||26.8±2.7*|
On peat and lichen plateaus of Chick Lake Basin, Northwest Territories, the coverage of northern Labrador tea on different aged burned sites was compared. Fire characteristics were not provided. The coverage of northern Labrador tea on peat plateaus burned 4 years earlier was 2%, on sites burned 53 years prior was 48%, and on sites burned 92 years ago was 24%. On lichen plateaus, coverage of northern Labrador tea was 28% on sites burned 44 years earlier, 32% on sites burned 47 years prior, and 6% on sites burned 100 years ago .
After visiting 130 white spruce- and black spruce-dominated stands that burned between 1 month and 200 years earlier in the taiga of interior Alaska, Foote  summarized the changes in northern Labrador tea coverage and frequency in black spruce stands. Fire severity was not reported. The results are presented below. It is likely that unknown differences in sampled communities could have been as important as time since fire in resulting northern Labrador tea coverage.
|Mean time since fire
(number of stands sampled)
|Frequency (%)||Coverage (%)|
|5 weeks (n=3)||0||0|
|2 years (n=19)||16||8|
|10 years (n=21)||1||3|
|48 years (n=12)||18||1|
|70 years (n=11)||1||7|
|121 years (n=4)||16||2|
Swanson  studied northern Labrador tea coverage and constancy on different permafrost soils as they related to time since fire. Sites were in boreal forests of the Kobak Preserve in northwestern Alaska. Included postfire communities were open black spruce, black spruce with paper birch and quaking aspen, and white spruce with mountain alder. Postfire soils were described as frozen, thawed, and dry. Frozen soils remained frozen even after fire. Thawed soils were wet soils with permafrost before the fire, but drier and lacking permafrost within the top 3 feet (1 m) after fire. Dry soils had no evidence of past wetness or permafrost in the top 3 feet (1 m) prior to burning. Time since fire was not as important as soil type in predicting northern Labrador tea coverage which was lowest on dry soils. Study results are summarized below:
|Time since fire (years)||10-50||>100||10-50||10-50||>100|
The following study investigated northern Labrador tea's fuel characteristics which may be valuable to its fire management. In the forest-tundra vegetation of Inuvik, Northwest Territories, researchers collected plant leaves and stems in July and late August of 1974 and 1975. In 1975, the study area experienced drought conditions. All northern Labrador tea fuel was less than 0.25 inch (6.4 mm) in diameter. Of the live vascular plants investigated in the study area, northern Labrador tea's fuel potential rating was highest. Below are the measured fuel characteristics :
|Fuel characteristic||Mean height (cm)||Surface/volume ratio (mmˉ¹)||Moisture content (%)||Caloric content (cal/g)|
Caribou: Alaska and northern Canada's arctic and subarctic communities in which northern Labrador tea is common are important caribou habitat [32,47]. Rumen contents of 20 caribou collected in December and January from Manitoba, Saskatchewan, and the Northwest Territories contained 2.9% northern Labrador tea. The highest concentration (4.9%) was found in 4 rumen contents collected in the Northwest Territories . However, in feeding sites of northwestern Manitoba and north-central Saskatchewan, northern Labrador tea was not purposefully consumed .
The following study of 500 to 1,000 caribou that became stranded on the 15 mi² (40 km²) Rideout Island of the Northwest Territories in the summer of 1987 suggests that northern Labrador tea may be consumed when other more palatable vegetation is unavailable. The stranded caribou died of malnutrition after severely grazing the island vegetation. The researcher visited the island in late July of the following year and compared it to similar mainland communities. No northern Labrador tea on the mainland was browsed, while browsing of northern Labrador tea on the island averaged 5%. Likely decreases in northern Labrador tea coverage on the island reflect both browsing and trampling damage .
|Cover (%) ± s x in low shrub tundra||2±1||7±2*|
|Cover (%) in tussock tundra||6±2||4±2|
|Mean % of browsed shoots (both communities)||5±3 (n=8)||0 (n=4)|
Deer: The single study that addressed northern Labrador tea in black-tailed deer feeding suggests that northern Labrador tea is not utilized as a food source. Feces collected in the summer on Admiralty Island of southeastern Alaska contained a trace (<0.5%) amount of northern Labrador tea. The composition that was northern Labrador tea in feces collected in all other seasons was 0% .
Moose: LeResche and Davis  report that moose on the Kenai Peninsula of Alaska occasionally feed on northern Labrador tea throughout the year.
Small mammals: Tundra vegetation in which northern Labrador tea is typical is important habitat for many small mammals such as arctic foxes, arctic ground squirrels, brown lemmings, collared lemmings, and common muskrats. Wolverines utilize tundra vegetation in the winter. Shrub, sedge, and black spruce tundra vegetation is important to American minks, northern red-backed voles, and/or tundra voles [47,87].
Birds: Northern Labrador tea tundra habitat is important to many breeding and nesting birds. Common loons, yellow-billed loons, arctic loons, gyrfalcons, snowy owls, black-bellied plovers, semipalmated plovers, and dunlins use tundra vegetation as breeding habitat . The tundra nesters include brants, white-fronted geese, northern shovelers, and whimbrels. Whistling swans nest in both moist sedge and low shrub tundra. Rock ptarmigans nest exclusively in tundra vegetation. Willow ptarmigans use dry shrub and tussock tundra habitats in the summer and nest in open forest tundra. Surf scoters aggregate in molting flocks on tundra sites . The Lapland longspurs utilize tussock tundra habitats where northern Labrador tea is very common .
Palatability/nutritional value: Northern Labrador tea's leaves and twigs are very unpalatable and have low digestibility [9,33]. Phenolic resins, terpenes, saponins, and tannins are present in high concentrations in northern Labrador tea . Northern Labrador tea is also thought to contain ledol, a poison that causes cramping or paralysis . Several researchers suggest that northern Labrador tea's chemical defenses are an evolutionary adaptation that allows northern Labrador tea to retain nutrients stored in above ground plant parts [9,11].
Below are the total nitrogen and calcium contained in above and below ground northern Labrador tea structures collected from Alaskan tundra. Presented is the average milligram per individual. Sample size was 4 .
|Sampling date||July 23||August 25||July 23||August 25|
|current leaves and stem||2.2||3.4||0.37||0.86|
|2-year (and older) leaves||1.3||1.3||0.79||0.84|
|2-year (and older) stem||1.0||1.0||0.38||0.35|
|above-ground main stem||1.8||1.9||0.46||0.45|
|below-ground main stem||2.3||2.2||0.48||0.51|
The seasonal changes in the chemical composition (%) of northern Labrador tea leaves collected from Reindeer Preserve near Inuvik, Northwest Territories, are presented below. Scotter  notes that northern Labrador tea crude fat was significantly (p<0.05) higher than most of the other 8 species investigated.
|Crude protein||Crude fat||Crude fiber||N-free extract||Ash||Ca||P||Carotene
(mg/lb of forage)
For information regarding changes in the nutrient content of northern Labrador tea plant tissue following fire, see the fire effects section of this review.
No information is available on this topic.
VALUE FOR REHABILITATION OF DISTURBED SITES:
No information is available on this topic.
Northern Labrador tea has several medicinal uses. A tea of northern Labrador leaves soothes stomach aches and sore throats. The tea may also provide strength to someone who has bled heavily. Northern Labrador tea leaves when chewed relieve toothaches and canker sores. When leaves are made into an ointment with seal fat, it can be used to treat eye disorders, moisten skin, and ease breathing when rubbed on the chest ( cited others). Native people of Fort Yukon, northeastern Alaska, suggest that northern Labrador tea leaves and stems boiled into a tea aid in the healing of colds and hangovers . Research suggests that northern Labrador tea has anti-inflammatory properties useful in treating rheumatism, degenerative joint disease, and insect bites .
OTHER MANAGEMENT CONSIDERATIONS:
Many have investigated northern Labrador tea's growth as it relates to its habitat. In Canada, northern Labrador tea typically grows on nutrient-poor soils with dry soil moisture regimes. Northern Labrador tea is considered an indicator species for these site characteristics . Other research includes experimental studies of climate change. Temperatures and carbon dioxide levels are often manipulated while northern Labrador tea and associated tundra species growth is monitored. The following references provide more information on how changes in climate may affect arctic species [13,35]. Further research into environmental conditions and northern Labrador tea growth was done by Yarie and Mead . They provide the coefficients for predicting leaf, twig, and combined dry biomass in different communities that can be used in biomass estimation equations.
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