Ledum groenlandicum



INTRODUCTORY


Michael Simpson, University of Alberta, 2002

AUTHORSHIP AND CITATION:
Gucker, Corey L. 2006. Ledum groenlandicum. 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:
LEDGRO

SYNONYMS:
Ledum palustre spp. groenlandicum (Oeder) Hult. [74]
Ledum palustre var. latifolium (Jacq.) Michx. [79]
Rhododendron groenlandicum (Oeder) Kron and Judd [94]

NRCS PLANT CODE [185]:
LEGR

COMMON NAMES:
bog Labrador tea
Labrador tea
rusty Labrador tea
true Labrador tea

TAXONOMY:
The currently accepted scientific name of bog Labrador tea is Ledum groenlandicum Oeder (Ericaceae) [4,14,58,68,170,196]. In this review, any information cited that recognizes the Ledum genus alone, the common name, Labrador tea, will be used.

LIFE FORM:
Shrub

FEDERAL LEGAL STATUS:
No special status

OTHER STATUS:
Bog Labrador tea is considered threatened, endangered, or extremely rare in several states at the southern limit of its range, including Ohio, Connecticut, New Jersey, and Pennsylvania [26,121,126,132,169]. Bog Labrador tea is presumed extinct in South Dakota where the last known finding dates back to 1931 [72]. The Cholcotin Forest District of British Columbia considers the bog Labrador tea/sphagnum (Sphagnum spp.) community vulnerable as it has characteristics that make it "sensitive to human activities or natural events" [16].

DISTRIBUTION AND OCCURRENCE

SPECIES: Ledum groenlandicum
GENERAL DISTRIBUTION:
Bog Labrador tea is distributed throughout Canada, Alaska, and the northern fringe of the United States [170,196]. The southernmost Pacific and Atlantic coast extents of bog Labrador tea are Oregon and New Jersey, respectively [59]. As a result of land use, climatic, or other changes, bog Labrador tea is vulnerable or rare in several states at its southern limit including Ohio, Connecticut, New Jersey, and Pennsylvania [14,26,121,126,132,169]. Bog Labrador tea is presumed extinct from South Dakota [60,72]. Most bog Labrador tea distribution maps suggest that bog Labrador tea occurs in Idaho but not in Montana. However, there is no evidence of this species in Idaho [76], and Chadde and others [22] list bog Labrador tea as a typical shrub in poor and intermediate fens of west-central and southwestern Montana's Lolo and Beaverhead-Deerlodge National Forests.

Nature Serve Explorer provides a distributional map of bog Labrador tea.

ECOSYSTEMS [55]:
FRES10 White-red-jack pine
FRES11 Spruce-fir
FRES19 Aspen-birch
FRES23 Fir-spruce
FRES24 Hemlock-Sitka spruce
FRES26 Lodgepole pine

STATES/PROVINCES: (key to state/province abbreviations)
UNITED STATES

AK CT IL ME MA MI
MN MT NH NJ NY ND
OH OR PA VT WA WI

CANADA

AB BC MB NB NF NT
NS NU ON PE PQ SK
YK

BLM PHYSIOGRAPHIC REGIONS [12]:
1 Northern Pacific Border
8 Northern Rocky Mountains

KUCHLER [95] PLANT ASSOCIATIONS:
K001 Spruce-cedar-hemlock forest
K002 Cedar-hemlock-Douglas-fir forest
K003 Silver fir-Douglas-fir forest
K004 Fir-hemlock forest
K015 Western spruce-fir forest
K093 Great Lakes spruce-fir forest
K094 Conifer bog
K095 Great Lakes pine forest
K096 Northeastern spruce-fir forest

SAF COVER TYPES [46]:
1 Jack pine
5 Balsam fir
12 Black spruce
13 Black spruce-tamarack
15 Red pine
16 Aspen
18 Paper birch
21 Eastern white pine
22 White pine-hemlock
23 Eastern hemlock
32 Red spruce
33 Red spruce-balsam fir
35 Paper birch-red spruce-balsam fir
37 Northern white-cedar
38 Tamarack
107 White spruce
201 White spruce
202 White spruce-paper birch
203 Balsam poplar
204 Black spruce
205 Mountain hemlock
206 Engelmann spruce-subalpine fir
217 Aspen
218 Lodgepole pine
223 Sitka spruce
224 Western hemlock
225 Western hemlock-Sitka spruce
226 Coastal true fir-hemlock
227 Western redcedar-western hemlock
228 Western redcedar
251 White spruce-aspen
252 Paper birch
253 Black spruce-white spruce
254 Black spruce-paper birch

SRM (RANGELAND) COVER TYPES [164]:
ALASKAN RANGELANDS
904 Black spruce-lichen
907 Dryas
911 Lichen tundra
912 Low scrub shrub birch-ericaceous
913 Low scrub swamp
920 White spruce-paper birch

HABITAT TYPES AND PLANT COMMUNITIES:
Bog Labrador tea is recognized as a dominant species in the following vegetation classifications:

United States:
AK:
Interior taiga [49]
Oldest terraces of the Tanana River Floodplain [194]
Many Alaskan bog Labrador tea vegetation types identified by others are compiled in [189]

Canada:
AB:
Province[28]
West-central [29]
Northern Alberta plains [34]
Banff and Jasper National parks [97]
Southwestern Alberta [119]

BC:
Rocky Mountains [34]

ON:
Province[81,85]

PQ:
Saint Lawrence River Valley [32]

SK:
Central [147]

YK:
Rocky Mountains and lowlands [34]
Along Dempster Highway [172]
Along Alaskan highway [173]
Western Canada: [176]
Rocky Mountain National Parks [1]

Bog Labrador tea is typical of wet coniferous forests, bogs, alpine regions, and dwarf shrub barrens throughout its range. Feather mosses are common in the understory of bog Labrador tea habitats. In many cases feather moss is used to describe a group of mosses that may include 1 or more of the following mosses: Schreber's big red stem moss (Pleurozium schreberi), splendid feather moss (Hylocomium splendens), knights plume moss (Ptilium crista-castrensis).

While the above lists illustrate bog Labrador tea's overstory associations for the contiguous United States, they do not address some habitat associations for Alaska. Below are the Alaskan regions and vegetation types in which bog Labrador tea is common:

Interior and southeastern Alaska's coastal treeless bogs or muskegs with blueberry (Vaccinium spp.), willow (Salix spp.), and/or birch (Betula spp.) [196]

Tongass National Forest vegetation types including lodgepole pine/black crowberry (Pinus contorta/Empetrum nigrum), western hemlock-Sitka spruce (Tsuga heterophylla-Picea sitchensis)/blueberry/goose neck moss (Rhytidiadelphus spp.), Alaska-cedar-mountain hemlock (Chamaecyparis nootkatensis-Tsuga mertensiana)-western hemlock-Sitka spruce-lodgepole pine/blueberry, lodgepole pine/blueberry, and lodgepole pine/black crowberry [112,184]

Pike Lakes muskeg of Yakutat foreland with shore pine (Pinus contorta var. contorta) and occasionally mountain hemlock [133]

Southeastern Alaska muskegs with an overstory of western hemlock, lodgepole pine, western redcedar (Thuja plicata), and Alaska-cedar [179]


BOTANICAL AND ECOLOGICAL CHARACTERISTICS

SPECIES: Ledum groenlandicum

Michael Simpson, University of Alberta, 2002

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 [4,14,58,68,137,170,196].

Bog Labrador tea is an evergreen resinous shrub that grows to 4.9 feet (1.5 m) tall. The multiple branches are procumbent or upright and the growth form is rounded [23,58,137,170,196]. Young stems are coated with curly hairs, while older stems are hairless. Linear leaves are simple and arranged alternately. They measure up to 2 inches (5 cm) long by 2 cm wide and are firm and leathery. Leaf margins are revolute and undersides are woolly [4,68,137,170,196]. Numerous fragrant flowers are produced in clusters at branch ends [170,196]. Fruits are 5-parted capsules measuring 4 to 6 mm long and open at the base releasing a large number of seeds, typically in the fall. The empty capsule may persist for years [4,170,196].

The root system was studied on 25 bog Labrador tea plants growing in treed and treeless bogs in the Acadian forest of New Brunswick. Average depth of the deepest underground reproductive tissue was 18 inches (45 cm) below the surface of the moss layer [48]. Sixteen of 30 bog Labrador tea root specimens collected from a mature black spruce (Picea mariana) forest in northeastern Ontario showed ericoid mycorrhizal associations [108]. The excavation of bog Labrador tea plants in a black spruce/star reindeer lichen (Cladonia alpestris) woodland near Schefferville, Quebec, revealed that bog Labrador tea dry weight biomass distribution was 99.9 lb/acre (112 kg/ha) of leaf, 861 lb/acre (965 kg/ha) of stem, and 658 lb/acre (738 kg/ha) of root material [145].

RAUNKIAER [140] LIFE FORM:
Chamaephyte

REGENERATION PROCESSES:
Bog Labrador tea reproduces sexually through seed production [87] and asexually by vegetative sprouting [18,128]. The literature suggests that asexual regeneration predominates following disturbances, but sexual reproduction is important in maintaining viability in undisturbed communities. Research in central Alberta suggests that bog Labrador tea's longevity and asexual reproduction are important to the maintenance of bog Labrador tea populations [87].

Breeding system: Bog Labrador tea flowers are self-compatible, but cross pollination predominates. In peat bogs of southern Ontario, pollen transferred by the researcher to stamens of the same flower did produce seed. However, seed production was significantly reduced (p<0.01) when insects were excluded from flowers [142].

Pollination: Flower pollination is insect mediated. Bog Labrador tea has hidden nectaries, and in a southern Ontario peat bog, 20.7 insects per hour visited bog Labrador tea flowers [142]. Bog Labrador tea had the greatest diversity of insect visitors of the plant species studied, and bees were most common [141]. In a review, Limpert [102] suggests that butterflies may utilize bog Labrador tea nectar as well. Below is the summary of bee genera that visited bog Labrador tea flowers in the southern Ontario peat bog [142]:

Visitor Apis Bombus
(queens)
Bombus
(workers)
Andrena*

Average visitation rate (number of flowers/minute)

15.9 34.3 36 12.3 23.4
*12.3 flowers/min. for nectar and 23.4 flowers/min. for pollen collection

The average volume of nectar per bog Labrador tea flower was 0.22l, and the number of pollen tetrads per flower was .0037 [142]. In the Burns Bog area of the Fraser River Delta in British Columbia, bog Labrador tea flower and pollen production were measured in areas where bog Labrador tea coverage was 95% and flowering density was greatest. Pollen production was 330,000,000 tetrads/m/year, and 352 flowers were produced per 15.5 inches (100 cm). These values likely represent near maximum production [63].

Seed production: Bog Labrador tea is capable of producing a large number of seeds. Often greater than 50 seeds are produced per bog Labrador tea flower, and flowering is considered extensive most years suggesting that a substantial seed crop is produced annually [87].

Seed dispersal: Seeds are small and wind-dispersed [19]. Seeds are released as the capsule splits from the base along 5 sutures [197].

Seed banking: Because bog Labrador tea seeds are small, require light to germinate, and demonstrate decreased germination potential with seed age [87], the potential for seedling emergence from a seed bank is likely short-lived.

Germination: Bog Labrador tea seed requires light and warm temperatures to germinate. Peat and moss are the most typical germination substrates, and only seeds near the substrate surface receive enough light to germinate. Germination rates probably decrease in heavily shaded areas. Seeds shed in the fall normally germinate the following spring when daily maximum and minimum temperatures exceed 61 F (16 C) and 40 F (5 C), respectively [87].

Studies of bog Labrador tea seed collected in late August and early September of 1976 and 1977 revealed decreased germination with seed age and varied with pH. Germination levels were high without seed stratification, and most seeds germinated within 25 to 30 days. Fifty-eight percent of one-month-old seed germinated, but significantly less (p<0.001), 20%, of 13-month-old seed germinated. Germination levels were highest at 5.5 pH, less germination occurred at 3.5 pH, and even less at 7.5 pH. At 8.5 pH no seed survived to day 28 of the experiment [87].

Others report increased germination following cold exposure. Seed collected from open-grown plants near Fairbanks, Alaska, treated with a pregermination 30-day cold stratification, showed increased germination. Cold-stratified seed germination ranged from 98% to 78% at temperatures between 50 and 79 F (9-26 C). No germination occurred at 40 F (5C) [18]. Nichols [123] also found that more bog Labrador tea seed germinated and germination time decreased after seeds were exposed to low temperatures. Seeds were collected from the White Mountains of New Hampshire. Seeds were refrigerated for 83 days (temperature not reported) before planting. Decreased germination time following low temperature treatments may indicate an adaptation to short growing seasons.

Seedling establishment/growth: Bog Labrador tea seedlings are small, grow slowly, and establish best in moist areas with discontinuous moss cover. In disturbed central Alberta fens that experienced both fire and road construction in the previous 25 years, a large number of seedlings was recorded. From a greenhouse study, 1-month-old seedlings averaged 2 mm tall, and the mean 4-month-old seedling height measurement was 4 mm [87].

Asexual regeneration: Asexual regeneration is common following above-ground damage. If burned "lightly," such that some above-ground stem material survives, bog Labrador tea may sprout from stems. When completely top-killed, sprouting occurs from  root crown and rhizomes. Rhizome depth ranges from 5.9 to 20 inches (15-50 cm), so rhizomes are protected from shallow burning [128].

Bog Labrador tea clonal growth by layering is extensive, and sprout production is different on burned and unburned sites. Eleven complete clones were studied on burned and unburned sites near Fairbanks, Alaska. Six clones were on 4-year-old burned sites; the other 5 grew in a 70-year-old black spruce forest. Clones covered 50 to 100 feet (5-10 m), and there were 21 to 25 ramets per clone. Ratios of aboveground material to below-ground plant material were 1:5.0 and 1:2.5 on burned and unburned sites, respectively. Underground structures were typically limited to the organic layer (5.9 to 7.9 inches (15-20 cm)). Zero to 77 % of cuttings collected from underground portions of the clones produced shoots. The greatest percentage of cuttings producing shoots were collected in July and kept outdoors, and the number of cuttings producing shoots decreased with decreasing temperatures [18].

SITE CHARACTERISTICS:
Bog Labrador tea is typical of poorly drained habitats such as boreal forests, open conifer bogs, treeless bogs, wooded swamps, wet barrens, and peatlands throughout its range [89,92,152,196]. In the northeastern United States, bog Labrador tea is commonly found in subalpine and alpine regions [58,87]. Permafrost conditions are common in bog Labrador tea habitats [172].

Climate: As temperatures increase the likelihood of finding bog Labrador tea habitat decreases as this species is most well adapted to boreal, cool temperate, cool continental, and cool mesothermal climates [92,137]. However, within these cool climates a wide range of temperatures and precipitation patterns exist. Bog Labrador tea habitat on British Columbia's northern coast experiences mild, wet winters with an average January temperature of 30 F (0.8 C) and chilly, wet summers with an average August temperature of 55.9 F (13.3 C). Fog and rain typically occur all year, and the annual precipitation is 98 inches (2,500 mm) [8]. In the taiga of Alaska, bog Labrador tea is restricted to more easterly locations where at least summers are warm [192]. In the boreal white (Picea glauca) and black spruce zone of northwestern British Columbia, the climate is northern continental. Winters are long and cold, and growing seasons are brief. Mean temperatures are below 32 F (0 C) for 5 to 7 months of the year and exceed 50 F (10 C) for just 3 or 4 months of the year. Average annual precipitation is 10.2 to 18.3 inches (260-465 mm), 35% to 55% of which is snow [137]. Bog Labrador tea habitats in central Alberta are typically frost free for 80 to 100 days, receive on average 18 to 20 inches (460-510 mm) of precipitation per year, and average 20 to 22 inches (508-559 mm) of evapotranspiration [87]. A study in central Canada found that bog Labrador tea was positively correlated (r =0.51) with arctic air masses in white spruce forests [99].

Freezing patterns in a white spruce-black spruce/bog Labrador tea/feather moss forest near Fairbanks, were monitored for 14 years. The active soil layer began freezing in October and was fully frozen as early as 13 December. With greater snow accumulation, active layer freezing was slower, and snow cover was typically permanent by early October and fully melted by 6 May. Soils began thawing between mid-April and early May. During the course of the study, the maximum depth of thaw was 21 to 24 inches (54-61 cm) [195].

Under different moisture regimes bog Labrador tea root growth may vary. Mature plants taken from the field were subjected to controlled water levels. Plants maintained under wet (0 cm water level, constant) and wet-moist (0 cm water level for 3 days and 2.5 inches (5 cm) below soil surface water level for 4 days) conditions had roots in only the upper 0.8 inch (2 cm) of soil. Under moist (2.5 inches (5 cm) below) and dry (4 inches (10 cm) below) treatments extensive roots developed and extended down to water level [87].

Soils: The soils typical of bog Labrador tea habitats are commonly described as moist to wet, acidic, nutrient-poor organics [87,92,96,137]. However, there are several exceptions to this generic description. In Itasca State Park, Minnesota, bog Labrador tea is restricted to organic peat soils, but 100 miles (160 km) north in the boreal forest zone, bog Labrador tea is common on well-drained mineral soils [80]. At Candle Lake in Saskatchewan, researchers sampled 113 stands along a gradient from rich fens to precipitation-fed bogs. Bog Labrador tea abundance was greatest on sites with pH levels between 2.9 and 4 but was also present on sites with a pH range of 4 to 6.9. Bog Labrador tea was not found on sites with pH levels of 7 to 7.9. On very moist forest sites where the depth to water was 24 to 31 inches (60-79 cm), bog Labrador tea was much more common than on sites with a 0 to 7.5 inch (0-19 cm) depth to water [82].

The water holding capacity of bog Labrador tea habitats in west-central Alberta varies dramatically. Below are several bog Labrador tea vegetation types and their soil moisture relationships [29]:

Vegetation type Soil moisture regime
lodgepole pine-black spruce/bog Labrador tea/Schreber's big red stem moss well to imperfectly drained
lodgepole pine-black spruce/bog Labrador tea/lichen spp. well to rapidly draining
black spruce/bog Labrador tea-cloudberry (Rubus chamaemorus) soils with poor to very poor drainage

Summarized below are the soil characteristics of bog Labrador tea habitats in Yukon Territory and Saskatchewan:

Vegetation Soil pH Other information Region Reference
black spruce and ericaceous bogs 4.5 peat >2 m deep Saskatchewan River Delta [36]
black spruce- and tamarack-dominated fens 6.4 peat >2 m deep Saskatchewan River Delta
bog Labrador tea/black spruce/paper birch (Betula papyrifera) pH 3.2-4.8 permafrost depth 45-120 cm Eagle Plains and eastern foothills of Richardson Mountains, Yukon Territory [172]
black spruce/bog Labrador tea/splendid feather moss pH 4.9-6.4 permafrost depth 25-60 cm,
fine-grained silt clay
southern Yukon, along AK highway
black spruce/bog Labrador tea-bog blueberry (Vaccinium uliginosum) pH 5.7-7.7 permafrost 33-50 cm southern Yukon, along AK highway
bog Labrador tea-groundcedar (Lycopodium complanatum)-tree reindeer lichen (Cladonia arbuscula) pH 4.9-6.9 gravel, sand, silt southern Yukon, along AK highway [173]

Soil changes following fire: Many have studied fire-induced changes in the organic soils typical of boreal forests. The frozen peat soils of northwestern Canada and Alaska are unlike frozen mineral soils. The insulation of these soils likely prevents fire from affecting the depth of the active layer [154]. In boreal forests north of Uranium City in the Northwest Territories, Rouse [153] compared surface soil and below surface soil temperatures on unburned and 1-, 2-, and 24-year-old burned sites. Soil surface temperatures were nearly 25 F (14 C) warmer on recently burned sites and 18 F (10 C) warmer on sites burned 24 years prior. Below surface soil temperatures on burned sites were just 5 to 9 F (3-5 C) warmer than on unburned woodlands. More information on soil changes due to fire is provided in a later section, Fire effects on soil.

Elevation: Bog Labrador tea's climatic tolerances likely dictate its elevational tolerances. In the southeastern portion of its range, bog Labrador tea is restricted to subalpine or alpine habitats. However, in black spruce forests of the Yukon Tanana Uplands of interior Alaska, bog Labrador tea was present in all but the highest elevation classes sampled along a downslope gradient from 10,000 to 0 feet (3,100-0 m). Bog Labrador tea coverage was greatest in the 3,600 to 9,200 feet (1,100-2,800 m) range, approximately 50% less in the 0 to 3,440 feet (0-1,050 m) range, and absent from the 9,500 to 10,000 feet (2,900-3,100 m) elevations [40].

Areas that report elevational tolerances for bog Labrador tea are provided below:

Region Vegetation type Elevation Reference
Pacific Northwest coast ---- low to mid-elevation [137]
Bolton Mountain, VT alpine vegetation 991 m [203]
White Mountains, NH alpine vegetation, krummholz fir (Abies spp.) and black spruce >1,450 m [171]
west-central AB ---- <1,800 m [29]
Banff and Jasper National parks lodgepole pine/bog Labrador tea/grouse whortleberry (Vaccinium scoparium) mid-montane to upper subalpine (1,100-1,750 m) [97]

SUCCESSIONAL STATUS:
Bog Labrador tea is typically present in late seral communities that result from primary succession. However, following disturbances in areas where bog Labrador tea is established, it often recolonizes the site rapidly.

Shade relationships: While some report that bog Labrador tea is shade intolerant [92], the following studies suggest some shade is tolerated by bog Labrador tea. Aboveground bog Labrador tea biomass was greater in open-canopy than dense closed-canopy coniferous forests in southwestern Nova Scotia. Forests were dominated by a mixture of red spruce (P. rubens), black spruce, and balsam fir (P. balsamea). The basal area of conifers was 13.8 m/ha and the aboveground biomass of bog Labrador tea was 91 lb/acre (102 kg/ha) in open-canopy forests, and conifer basal area was 30.8 m/ha and bog Labrador tea biomass was 8.9 lb/acre (10 kg/ha) in closed-canopy forests [180]. Bog Labrador tea was a dominant in mature black spruce forests with >55% canopy closure in central Saskatchewan [147].

Primary Succession: Bog Labrador tea is often not present in the early stages of primary bog and floodplain succession.

Floodplains: In the primary succession of floodplains, bog Labrador tea is often found in late-successional communities and on older substrates. In a study of floodplain succession on the Tanana River of interior Alaska, bog Labrador tea occurred on only older, 300- to 1,000-year-old surfaces [194]. 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 (Populus balsamifera ssp. balsamifera) stands, 120-year-old white spruce stands, 120-year-old white spruce-black spruce stands, and 120-year-old black spruce-dominated stands. Bog Labrador tea occurred only in 120-year-old black spruce stands that represented the climax community for the area. The author noted that soils "froze quicker and deeper" and reached lower temperatures in earlier than later seral stands [190].

Bogs: A general 3-staged successional development is described for eastern North American peat bogs. Initially areas of open water become dominated by aquatic species and emergent vegetation. The next stage of development is termed the "consolidation" or "settlement" phase when a nearly continuous sphagnum sod is formed. Bog Labrador tea is typically present at this stage and may dominate less moist sites or areas without great water table fluctuation. Bog Labrador tea persists into the final stage described as the "subclimax" or forest invasion stage [33].

Bog succession in central Minnesota is similarly divided into 3 phases, pioneer sedge (Carex spp.)-dominated vegetation, moss-heath (Ericaceae) shrublands, and bog forests. Bog Labrador tea was absent on pioneer vegetation mats, rare in moss-heath shrublands, but very common in bog forests. Bog Labrador tea occurred in early, mature, and late bog forests with black spruce, northern white-cedar (Thuja occidentalis), and/or tamarack (Larix laricina), but bog Labrador tea presence decreased with increased tree density characteristic of late bog forests [27].

In the Grasse River Bog of New York's Adirondacks, bog Labrador tea is considered especially important in later successional stages when conifers increase in importance. Bog Labrador tea persists and is typically taller in closed black spruce-tamarack forests [15].

Secondary Succession: A number of disturbances including but not limited to fire, logging, construction, and mining, are common in bog Labrador tea habitats. Typically bog Labrador tea appears early in the secondary succession of disturbed sites. However, coverage, frequency, and/or abundance of bog Labrador tea is often less on recently disturbed than undisturbed sites.

Fire: Within the black spruce-sphagnum forest type, there is little floristic change following fire. Typically only the structure of vegetation changes postfire. The majority of species present before fires are also present postfire [127]. Bog Labrador tea was considered an "early" postfire colonizer in the jack pine (Pinus banksiana) woodlands of northeastern Alberta and northwestern Saskatchewan [21]. In both mature and recently burned bogs of southeastern Manitoba's taiga, bog Labrador tea was present. Mature forests were >90 years old, and recently burned sites were 5 years old [157].

In well-drained lichen forests dominated by black spruce or jack pine in northern Quebec's James Bay, bog Labrador tea was present on all 11 sites sampled that burned between 3 and 110 years prior [50].

Fire and other disturbances: Bog Labrador tea coverage and frequency were lower on 14- and 21-year-old burned sites than on undisturbed and clearcut sites. Burned, logged, and undisturbed black spruce-Schreber's big red stem moss forests were compared in western and central Quebec. In the Dieppe area, regeneration of bog Labrador tea was evaluated on sites burned in a crown fire 21 years earlier, clearcut between 16 and 23 years prior, and on undisturbed sites. In the Mathieu area, bog Labrador tea coverage and frequency were compared on sites burned in a crown fire 14 years earlier, clearcut from 11 to 16 years prior, and on undisturbed sites. Recovery of bog Labrador tea was quicker on clearcut sites. Bog Labrador tea coverage and frequency are summarized below [122]:

Site Dieppe
(17 to 22 years old)
Mathieu
(11 to 16 years old)
Status Undisturbed Burned Clearcut Undisturbed Burned Clearcut
Frequency (%) 75 59 91 61 19 51
Cover (%) 6 5 14 7 2 5

Bog Labrador tea plants were smaller on burned sites following a high-severity fire in the Northwest Territories, but the frequency of small-sized shrubs had nearly reached prefire and unburned levels by the 3rd postfire year. The fire burned over a research site in the Northwest Territories, and allowed researchers to compare recovery of disturbed and undisturbed burned sites. The research area was previously disturbed when seismic lines and right of ways (ROW) were created. The ROW required the removal of all trees and shrubs in 1985. The seismic line created in 1972 and 1973 was used as a winter road from 1983 to 1985 and was still used for snowmobile and ATV travel at the time of the study. Before these disturbances the area was primarily open black spruce-lichen forest, and the oldest trees were approximately 300 years old. A "high intensity crown fire" burned on 6 June 1995 with temperatures hot enough to melt aluminum boat engine blocks and deform small aluminum and sheet metal animal traps that were in its path. Below is the percent frequency of bog Labrador tea on the ROW, forest, seismic line, and unburned areas. Prefire data was collected in 1987 (after ROW creation), and postfire data was collected in the 3rd postfire year (1997) [124].

Bog Labrador tea size class ROW Burned forest Seismic Line Unburned forest
  prefire 1997 prefire 1997 1997 1997
0.3-1 m 73.3 0 50.0 0 0 33.3
0-0.3 m 97.4 60.5 100 84.2 86.8 93.3

Comparisons of 80 burned or logged stands in northeastern Minnesota revealed a greater presence of bog Labrador tea in logged stands. Bog Labrador tea was present in 54% of logged stands and 40% of burned stands located in 3 forest types (quaking aspen (Populus tremuloides), jack pine, and black spruce) and 2 age classes (25-40 and 70-100 years). Bog Labrador tea presence was averaged across forest types and stand age [143].

Bog Labrador tea coverage on 8-year-old burned sites logged in 1946 ranged from 10% to 20% and on sites logged in 1954 ranged from 1% to 40% in the Charlevoix Highlands of southern Quebec. Some sites within the black spruce-dominated forests were clear cut in 1946, others in 1954. Spruce budworm infected stands from the late 1970s to the mid-1980s, and all sites burned in a June 1991 fire. At the time of the fire, greater than 90% of trees were less than 4 inches (10 cm) in diameter [129].

Logging: Bog Labrador tea coverage was 50% less on clearcuts than in unharvested black spruce forests in the Lake Abitibi Model Forest in northeastern Ontario. Bog Labrador tea coverage was also positively correlated (p=0.0006) with forest basal area [35]. In other black spruce-dominated sites of northeastern Ontario, bog Labrador tea coverage was greatest on "older" logged and unlogged sites. Time since disturbance on "older" logged sites was not provided, but sites were described as having a sparse black spruce overstory and a species poor understory. Mean coverage of bog Labrador tea was 2.6% or greater on all logged sites, indicating that it did occur on newly logged sites [17].

Peat mining: Based on information collected on mined peatlands in Quebec, bog Labrador tea is considered to have high immigration potential. Its presence in edge habitats, high fecundity, and production of easily wind dispersed seed suggests that the likelihood of colonizing disturbed sites is high [19].

Sites in southern Ontario's Wainfleet Bog were allowed to regenerate naturally for 1, 6, 10, and 24 years following vacuum mine operations. The peat extraction process required complete vegetation removal, peat drying, and extraction of the top 7 feet (2 m). Bog Labrador tea was present only on 24-year-old and unmined sites [86]. Bog Labrador tea recovery was faster on the Cacouna peatland in southeastern Quebec that was block cut mined (1942-1975) in the past and was more recently bulldozed, leveled, drained and vacuum mined from 1983 to 1989. Natural revegetation was assessed in 1994 and 1998. Bog Labrador tea cover increased significantly (p<0.01) from 6% in 1994 to 15.3% in 1998 [13].

Construction: In northern Manitoba, a portion of a black spruce-dominated peat plateau was cleared of surface vegetation for power line construction. Seven years following the disturbance bog Labrador tea frequency and biomass were greater on undisturbed than cleared sites; however, analysis of above ground growth revealed increased reproductive effort by bog Labrador tea on disturbed sites. The data are summarized below [166]:

Site condition Disturbed Undisturbed
Frequency (%) 68 86
Above ground biomass (kg/ha) 562 1889
Above ground biomass type Leaf Stem Reproductive Leaf Stem Reproductive
Distribution of biomass (%) 39.1 47 13.9 26.7 72 1.3

Colonization of a seismic line disturbance in the white spruce-mountain alder (Alnus viridis spp. crispa)-willow vegetation type in the Tuktoyaktuk Peninsula region of Northwest Territories was monitored for 3 growing seasons following its construction. Bog Labrador tea colonized the line in the 2nd postdisturbance year, and coverage increased on the line in the 3rd postdisturbance year. Colonization was thought to be chiefly vegetative. Bog Labrador tea coverage in successive postdisturbance years is provided below [67].

Postdisturbance growing season 1 2 3
Undisturbed sites 4.5 2.5 2.6
Seismic line 0 0.6 1.6

SEASONAL DEVELOPMENT:
Bog Labrador tea is thought to flower in late May or early June throughout the majority of its range [87].

Below are more specific bog Labrador tea flowering and fruiting times by area:

Flowering

Region Flowering period
Alaska mid-June to mid-July [196]
Connecticut May to June [26]
Michigan flowering typically peaks early June to mid-June
early July in late seasons [197]
New England May 20 to July 5 [162]
northeastern U.S. June to July [58]
Nova Scotia June 10th through 30th [152]
Ontario late May to early July [170], Wellington County: early June to early July [141]
Fruiting
Alaska fruits open in fall [196]
Ontario late July to August [170]

FIRE ECOLOGY

SPECIES: Ledum groenlandicum
FIRE ECOLOGY OR ADAPTATIONS:
Fire adaptations: Bog Labrador tea underground structures survive and sprout following fire. Bog Labrador tea regeneration following fire is typically rapid [160]. When burned only "lightly," such that some above ground stem material survives, bog Labrador tea may sprout from stems. When completely top-killed, sprouting occurs from the root crown or rhizomes. Rhizomes are typically 5.9 to 20 inches (15-50 cm) deep and survive shallow burning [128]. Provided a seed source is present, bog Labrador tea's high seed production and easily wind-dispersed seed suggests a high likelihood of burned site colonization [19].

Fire regimes:
Fuels, climate, and fire behavior: Fire is common in bog Labrador tea habitats. Climatic conditions together with vegetation structure and composition favor periodic fire in taiga, boreal, and subarctic regions. Fires in northern North America's taiga are often large (>50,000 ha). Surface fuels including lichens, mosses, and shrubs occupy large surface areas in bog Labrador tea habitats. These fuels are easily dried out by the dry, warm summers and long periods of sunlight. The flammable ericaceous shrub layer easily maintains a 2- to 3-foot (0.5-1 m)-tall flame that easily ladders into the canopy of black spruce trees via the lichen-covered low-growing branches. Lightning is common from June through August, and fire ignition by humans is important as well. Ground or crown fires typically kill overstory trees but leave some portion of the organic layer. Low-severity surface fires that reduce ground fuels but do not kill large trees are small in size and occur infrequently in boreal forests. Researchers suggest that fire is important to ecosystem function, stability, and viability by periodically converting energy in boreal and subarctic forests and shrublands [83,154,160,188].

Fires in black spruce forests of interior Alaska are described as intense. Above ground vegetation is normally killed completely. High densities of low-stature black spruce support a high likelihood of crown fires, and flammability is increased when dry lichens coat these trees [105]. In black spruce forests, muskegs, and bogs of Alaska's taiga the permafrost layer prevents heat from penetrating deep into the soil; although trees are killed, revegetation is rapid (within 3-5 years) from surviving underground tissue of willow, blueberry, and Labrador tea [191]. Fires in the black spruce/bog blueberry-bog Labrador tea/Schreber's big red stem moss habitat rarely consume root systems or seeds in cones, and recovery is quick [49].

A study of fire behavior in the Caribou Range of the Northwest Territories indicates that wind is often necessary to produce stand-replacing fires in black spruce-lichen forests. The lichen layer, while extremely flammable, supports a slow spread rate and small flame size. Lichen bulk density is too low to fully ignite the layer as the flaming front passes but is too high to sustain rapid spread. Wind is important in igniting black spruce trees with commonly 80% summer moisture content, increasing spotting potential by transporting burning needles, and preheating the lichen layer in front of the flame front so that both spread rate and flame size increase [3].

Fire history and return intervals: Fire is generally less frequent in eastern than western portions of bog Labrador tea's range. The fire return interval in Alaska's black spruce forests is 50 to 100 years but may be greater than 500 years in wet regions of eastern Canada [188].

In the interior taiga of Alaska, black spruce-paper birch/bog blueberry-bog Labrador tea and black spruce/bog blueberry-bog Labrador tea/Schreber's big red stem moss vegetation types characteristically have fire return intervals of less than 100 years [49]. Hungerford and others [75], in a review, report that open black spruce forests of Alaska's Tetlin National Wildlife Refuge depend on fire to maintain black spruce populations. The fire return interval is an estimated 50 to 100 years. At least until the time of their review (1995), Hungerford and others [75] report that successful fire suppression efforts decreased the amount of area burned per year although the number of annual fires has increased.

From fire scar data, a mean fire return interval of 40.4 years was calculated for the jack pine-black spruce/bog Labrador tea/reindeer lichen (Cladina spp.) vegetation type that occupies north-facing slopes and depressions of the Athabasca Plains of northeastern Alberta and northwestern Saskatchewan [21]. A fire interval of 69 years was estimated for boreal white spruce forests in Wood Buffalo National Park, Alberta. From fossil pollen and charcoal sediment records taken from Rainbow Lake, researchers estimate that 12 large fires burned in the 840 year time period (1160-2000). Data was collected from a single site in this study, and reconstruction potential was limited [98].

Researchers conducted a fire history study of northwestern Ontario's Sachigo Hills area with even-aged jack pine, black spruce in low-lying areas, and balsam poplar and paper birch patches. From 89 fire-scar disks collected from 41 sites over a 2-year period, researchers estimated there were 10 "major" fires in last 136 years, average fire frequency was 14 years, and the shortest and longest periods between fires were 5 and 30 years, respectively [106].

A fire history study in southeastern Labrador used aerial photos, fire-scarred trees, and historical fire maps to estimate that 21% of the area had burned in the last 110 years suggesting a fire return interval of approximately 500 years for the area. However, the open lichen woodland stands between 39 and 91 years old are considered highly flammable. Vegetation in the area includes scattered conifers, abundant bog Labrador tea and sheep-laurel (Kalmia angustifolia) shrub growth, and an almost continuous reindeer lichen layer. This open vegetation is prone to drying in times of brief drought. Solar radiation easily decreases fuel moistures in dry conditions. Fires easily burn this vegetation but fire would fail to spread in closed-canopy black spruce-fir-feather moss forests in cool humid environments that require extreme drought conditions to burn. The widespread distribution of essentially "fire proof" vegetation, lakes, and peatlands is likely the reason for restricted fire spread and size in southeastern Labrador [51].

The following table provides fire return intervals for plant communities and ecosystems where bog 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)
silver fir-Douglas-fir Abies amabilis-Pseudotsuga menziesii var. menziesii >200 [5]
tamarack Larix laricina 35-200 [130]
Great Lakes spruce-fir Picea-Abies spp. 35 to >200
northeastern spruce-fir Picea-Abies spp. 35-200 [39]
Engelmann spruce-subalpine fir Picea engelmannii-Abies lasiocarpa 35 to >200 [5]
black spruce Picea mariana 35-200
conifer bog* Picea mariana-Larix laricina 35-200
red spruce* Picea rubens 35-200 [39]
jack pine Pinus banksiana <35 to 200 [25,39]
Rocky Mountain lodgepole pine* Pinus contorta var. latifolia 25-340 [9,10,178]
red pine (Great Lakes region) Pinus resinosa 3-18 (=3-10) [24,54]
red-white pine* (Great Lakes region) Pinus resinosa-P. strobus 3-200 [25,66,104]
eastern white pine Pinus strobus 35-200 [177,198]
eastern white pine-eastern hemlock Pinus strobus-Tsuga canadensis 35-200 [198]
quaking aspen-paper birch Populus tremuloides-Betula papyrifera 35-200 [39,198]
quaking aspen (west of the Great Plains) Populus tremuloides 7-120 [5,62,114]
Rocky Mountain Douglas-fir* Pseudotsuga menziesii var. glauca 25-100 [5,6,7]
coastal Douglas-fir* Pseudotsuga menziesii var. menziesii 40-240 [5,118,148]
western redcedar-western hemlock Thuja plicata-Tsuga heterophylla >200 [5]
eastern hemlock-white pine Tsuga canadensis-Pinus strobus =47 [25]
western hemlock-Sitka spruce Tsuga heterophylla-Picea sitchensis >200
mountain hemlock* Tsuga mertensiana 35 to >200 [5]
*fire return interval varies widely; trends in variation are noted in the species review

POSTFIRE REGENERATION STRATEGY [174]:
Small shrub, adventitious bud/root crown
Secondary colonizer (on-site or off-site seed sources)

FIRE EFFECTS

SPECIES: Ledum groenlandicum
IMMEDIATE FIRE EFFECT ON PLANT:
Most fires top-kill bog Labrador tea, but above ground portions may survive "light" burning [128].

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

PLANT RESPONSE TO FIRE:
When burned only "lightly," bog Labrador tea may sprout from surviving stems. When completely top-killed, sprouting occurs from the root crown or rhizomes. Rhizomes are typically 5.9 to 20 inches (15-50 cm) deep and survive shallow burning [128]. The deepest underground reproductive tissue, tissue that is capable of regenerating if the upper plant is destroyed, averaged 18 inches (45 cm) in 25 bog Labrador tea plants excavated from treed and treeless bogs in New Brunswick's Acadian forest. Bog Labrador tea survival of even severe fires is likely given this deep underground vegetative reproduction potential [47,48].

Following fire in black spruce/feather moss forests, bog Labrador tea sprouts may appear within just a few weeks of burning [186]. In white and black spruce forests of Alaska, bog Labrador tea is considered one of the most important postfire shrubs [196]. Bog Labrador tea is an early postfire colonizer in jack pine woodlands of northeastern Alberta and northwestern Saskatchewan [21].

DISCUSSION AND QUALIFICATION OF PLANT RESPONSE:
Bog Labrador tea is commonly present in even early postfire communities regardless of fire severity or season. Typically bog Labrador tea coverage, occurrence, frequency, and density are lower on burned than unburned sites for the 1st postfire years. However, comparisons of 5-year-old burned and adjacent unburned sites revealed greater bog Labrador tea frequency, 100%, on burned than on unburned, 94.4%, sites in southeastern Labrador. Fire severity or conditions at the time of burning were not described [53]. Bog Labrador tea was present on all 11 sites burned between 3 and 110 years prior in well-drained black spruce- or jack pine-dominated lichen forests in northern Quebec's James Bay area. Bog Labrador tea was reportedly "expanding." No information as to fire severity or season was given [50].

In the Agassiz Provincial Forest of Manitoba, a mid-May forest fire burned white spruce-dominated stands. The fire was considered severe and top-killed all above ground vegetation. By 16 months postfire, bog Labrador tea was widespread on burned sites, but abundance estimates were not provided [70]. Bog Labrador tea was also considered abundant on "lightly" burned sites following a summer fire in interior Alaska's mature, open black spruce-lichen forests. The "light" fire removed an average of 2 inches (5 cm) of the forest floor [41]. In the taiga of north-central Canada, Labrador tea growth was sparse on sites burned 1 year prior, but common on 2 to 3-year-old burned sites, and dense on sites burned 3 to 17 years ago. This study comprised a large area and many past fires. Fire season or severity were not described. Sparse, common, and dense were also undefined [116].

The frequency of bog Labrador tea was lower on burned than unburned 2nd growth mixed conifer-hardwood stands in Lake County, Minnesota. The Heart Lake area burned on 28 April 1952 when the ground was cold and moist and winds were strong. The Keeley Creek area burned 11 July 1955 in a fire described only as "hot." Bog Labrador tea frequency on burned sites was lower than on unburned sites even 14 years postfire. The frequency of bog Labrador tea on thirty plots, each 100-foot(10-m), is summarized below [93].

Burned area Unburned Heart Lake
(spring fire)
Keeley Lake
(summer fire)
Canopy vegetation 46% black spruce, 23% jack pine, 23% paper birch 60% black spruce-balsam fir, 16% jack pine, 14% swamp 45% black spruce, 35% jack pine, 5% balsam fir
Time since fire (sample year) 1956 1965 3 years (1954) 5 years (1956) 14 years (1965) 2 years (1956) 5 years (1959) 11 years (1965)
Frequency (%) 33 30 23 23 23 13 17 13

By the 10th postfire year, bog Labrador tea coverage was greater on burned than unburned sites in Alaska's interior black spruce/feather moss-reindeer lichen forests. The Wickersham fire burned with moderate severity in June 1971. Measurements on burned sites were made 2, 5, and 10 years postfire. The maximum thaw depth was 16 to 20 inches (40-50 cm) during the course of the study on unburned sites. Thaw depth increased each year on burned sites, reaching a maximum of 73.6 inches (187 cm) in the 10th postfire year. Bog Labrador tea coverage on burned sites was double that on unburned sites in the 10th postfire year. The recovery of bog Labrador tea on burned and fireline sites is summarized below. Bog Labrador tea recovery was also monitored on the fireline in this study; for that information see the earlier Fire and other disturbances section [193].

  Unburned

 Burned

Postfire year 2 5 10
bog Labrador tea coverage (%) 11 2 3 21

Bog Labrador tea frequency increased with each successive postfire sampling in black spruce/lichen and jack pine/lichen forests of northern Quebec's Ecomiak Lake area that burned in the summer of 1989. The postfire frequency of bog Labrador tea was higher in the black spruce than in jack pine forests. The sampling of multiple seasons in the 3rd postfire year suggests that the timing of postfire sampling may affect results. The percent frequency of bog Labrador tea in both forest types at increasing time since fire is provided below [167].

Sampling period July 1990 June 1991 July 1991 August 1991 July 1992 July 1993
Black spruce/lichen 1.2 1.2 2.2 3.1 8.0 9.1
Jack pine/lichen <0.5 <0.5 <0.5 0.5 1.1 1.2

Sites with longer recovery time had greater bog Labrador tea coverage and frequency in black spruce/Schreber's big red stem moss habitat types of western and central Quebec. For the Dieppe study area, comparisons were made on sites burned in a June crown fire 21 years earlier and on unburned sites. In the Mathieu study area, the regeneration of bog Labrador tea was evaluated on sites burned in a June crown fire 14 years prior and on unburned sites. No other fire severity or behavior characteristics were provided. On neither of the burned sites did coverage or frequency of bog Labrador tea reach that of unburned sites. The coverage and frequency of bog Labrador tea on burned and similar unburned sites are summarized below [122]:

Site Dieppe Mathieu
Time since fire 21 years 14 years
Status unburned burned unburned burned
Frequency (%) 75 59 61 19
Cover (%) 6 5 7 2

Bog Labrador tea was an early invader of a 1-acre (0.4-ha) plot of black spruce/bog Labrador tea/reindeer lichen vegetation burned on 18 July 1972 in north-central Alberta. The prescription fire burned in a 50-year-old stand where tree density was 597/ha. There was no precipitation for 6 days prior to the fire. Average air temperature was 73 F (22.8 C), relative humidity was 38%, and winds averaged 12 mi/h (19.3 km/h). The Canadian fire weather indices suggested moderate to extreme fire potential. The maximum headfire spread rate was 22 feet/min (6.6 m/min), while the backfire spread rate was just 1.8 feet/min (0.5 m/min). The prefire fuel loadings of bog Labrador tea foliage and woody material were 0.11 kg/m and 0.22 kg/m and moisture contents were 92% and 54% of oven-dried weight, respectively. The fire consumed all bog Labrador tea above ground biomass. The researcher estimated that bog Labrador tea height would be 1 foot (0.3 m) by 10 to 15 years postfire. Fuels in this area would likely recover and be able to support another fire in approximately 25 years  given moderate burning conditions [90].

Fire and other disturbances: Several studies provide information on bog Labrador tea recovery following fire on previously disturbed sites. Typically bog Labrador tea quickly appears on burned sites however, prefire or unburned coverage and frequency are not typically reached until 5 or more years following fire.

Bog Labrador tea plants were smaller on burned sites following a high-severity fire in the Northwest Territories, but the frequency of small-sized shrubs had nearly reached prefire and unburned levels by the 3rd postfire year. The fire burned over a research site in the Northwest Territories, and allowed researchers to compare recovery of disturbed and undisturbed burned sites. The research area was previously disturbed when seismic lines and right of ways (ROW) were created. The ROW required the removal of all trees and shrubs in 1985. The seismic line created in 1972 and 1973 was used as a winter road from 1983 to 1985 and was still used for snowmobile and ATV travel at the time of the study. Before these disturbances the area was primarily open black spruce-lichen forest, and the oldest trees were approximately 300 years old. A "high intensity crown fire" burned on 6 June 1995 with temperatures hot enough to melt aluminum boat engine blocks and deform small aluminum and sheet metal animal traps that were in its path. Below is the percent frequency of bog Labrador tea on the ROW, forest, seismic line, and unburned areas. Prefire data was collected in 1987 (after ROW creation), and postfire data was collected in the 3rd postfire year (1997) [124].

Bog Labrador tea size class ROW Burned forest Seismic Line Unburned forest
Postfire year prefire 3 prefire 3 3 3/NA
0.3-1 m 73.3 0 50.0 0 0 33.3
0-0.3 m 97.4 60.5 100 84.2 86.8 93.3

Using a propane torch, recently clearcut bogs of the Acadian forest were burned in the spring, summer, and fall. Twenty-five 77 feet (22 m) sites were burned, and all green material was blackened. A temperature of 130 F (55 C) was maintained for 5 minutes at a 0.8 inch (2 cm) depth in the consolidated duff layer. After burning, hot spots and smoldering were discouraged with water treatments. Clearcuts were dominated by leatherleaf (Chamaedaphne calyculata), rhodora (Rhododendron canadense), and bog Labrador tea before burning. By 5 months postfire, there were no significant (p=0.05) relative abundance differences in bog Labrador tea regrowth on spring, summer, or fall burning treatments, and no burned plot densities had recovered to preburn densities by the 5th postfire month. Regrowth was initially slowest on the spring-burned sites; however, by the 5th postfire month, regrowth on spring-burned sites exceeded that of both summer- and fall-burned sites [48].

Bog Labrador tea was removed from a white spruce/bog Labrador tea-mountain cranberry (Vaccinium vitis-idaea)/splendid feather moss community for at least the first 2 years following slash fires in a clearcut area. Bog Labrador tea coverage and frequency in undisturbed forests were 31.8% and 65%, respectively. The fire was described as severe enough to kill above and below ground portions of most species, and immediately following the fire 6% of mineral soil was exposed; this amount increased to 30% in the 1st postfire year [42].

Researchers assessed the recovery of Charlevoix Highlands vegetation in southern Quebec following several disturbances. Some sites within the black spruce-dominated forests were clear cut in 1946, others in 1954. Spruce budworm infected stands from the late 1970s to the mid-1980s, and all sites burned in a June 1991 fire. At the time of the fire, greater than 90% of trees were less than 4 inches (10 cm) in diameter. Bog Labrador tea coverage on burned sites that were logged in 1946 ranged from 10% to 20% and on sites logged in 1954 ranged from 1% to 40% in the 8th postfire year [129].

Fire chronosequences: Bog Labrador tea frequency and coverage are typically low immediately after fire but normally increase as time since fire increases. However, as time since fire increases beyond 20 or more years, trends are no longer consistent.

In burned areas of the Newfoundland's barren range, bog Labrador tea coverage and frequency were compared on sites burned at different times. All fires were natural and assumed to burn during dry conditions, but no other information of fire severity, season, or behavior was given. Bog Labrador tea coverage was greatest on sites burned 10 to 19 years prior but frequency was greatest on sites burned 20 to 36 years ago. Bog Labrador tea coverage and frequency on past-burned areas are summarized below [134]:

Time since fire (years) 0.5-1 2-5 6-9 10-19 20-36 37
Coverage (%) trace 1 3 5 4 3
Frequency (%) 11 24 39 38 59 45

On peat and lichen plateaus of Chick Lake Basin, Northwest Territories, bog Labrador tea coverage was compared on different aged burned sites. Fire characteristics were not reported. The coverage of bog Labrador tea on peat plateaus burned 4 years earlier was 18%, on sites burned 53 years prior was 7%, and on sites burned 92 years ago was 8%. On lichen plateaus, coverage of bog Labrador tea was 2% on sites burned 44 years earlier, 3% on sites burned 47 years prior, and 0% on sites burned 100 years prior to the study [154].

Bog Labrador tea coverage was greatest on black spruce/sphagnum sites burned 8 years prior in northeastern British Columbia when past burned areas were evaluated. The study included several forest types in areas burned between 8 and 24 years prior. Bog Labrador tea coverage was typically greater in forests burned more recently. However the inclusion of different forest types with different time since fire introduced confounding factors. It is likely that site conditions associated with the different forest types affected bog Labrador tea recovery. Below are the forest types, time since fire, and postfire bog Labrador tea coverage from single plots evaluated in this study [127]:

Forest type Time since fire in years (seasonality) Bog Labrador tea coverage (%) Additional information
Black spruce/sphagnum 8 (May fire) 80% bog Labrador tea coverage in similar unburned stands (old trees 117-160 yrs.) was 50%
Black spruce/feather moss 10 (June fire) 50% ----
Lodgepole pine-black spruce 19 (August fire) 40% plot located in Muncho Lake Provincial Park
Hardwood (quaking aspen, balsam poplar)-lodgepole pine-white spruce 24 (season not given) 25% plot above Moose Lake

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 [49] summarized changes in bog Labrador tea coverage and frequency. In white spruce stands, bog Labrador tea coverage and frequency were greatest on sites burned an average of 15 and 36 years earlier, respectively. In past-burned black spruce stands the frequency and coverage of bog Labrador tea did not follow any trend. Fire severity was not reported, and it is likely that unknown differences in sampled communities may have been as important as time since fire in resulting bog Labrador tea coverage. A summary of the data is presented below [49].

Mean time since fire s
(number of stands sampled)
Frequency (%) Coverage (%)
White spruce-dominated stands
6 7 months (n=4) 0 0
4 2 years (n=8) 2 2
15 8 years (n=9) 3 8
36 7 years (n=5) 22 3
87 38 years (n=11) 7 1
170 70 years (n=4) 0 0
Mesic black spruce-dominated stands
5 0 weeks (n=3) 37 7
2 2 years (n=19) 65 3
10 6 years (n=21) 39 6
48 9 years (n=12) 68 6
70 26 years (n=11) 35 2
121 56 years (n=4) 58 8


For information on prescribed fire and postfire responses of many plant species, including bog Labrador tea, see these Research Project Summaries: FIRE MANAGEMENT CONSIDERATIONS:
Bog Labrador tea habitats experience fire regularly. Several researchers have studied aspects of bog Labrador tea that relate to its fire management including smoke, fuel moisture, fire control, and postfire soils.

The smoke produced when bog Labrador tea burns is considered "mildly noxious." To control fires in treeless marshes dominated by bog Labrador tea in the Great Lake States, Johnson [84] recommends direct or parallel attack with immediate burnout.

Fuel moisture was measured for 21 understory forest species in the Boundary Waters Canoe Area of northeastern Michigan. Collections were made from 2 to 4 PM from 24 June to 26 August 1976. Drought conditions were described for the late summer. Bog Labrador tea had the lowest late summer moisture content of all species investigated. The early (24 June-24 July) bog Labrador tea mean fuel moisture was 160%, and for the late period (25 July-26 August) was 128%. Bog Labrador tea also had one of the largest fuel moisture changes between early and late collections [103].

Fire effects on soil: Soil temperatures, nutrients, and properties are often changed by fire in bog Labrador tea habitats. In boreal forests north of Uranium City in the Northwest Territories, Rouse [153] compared surface soil and below surface soil temperatures on unburned and 1-, 2-, and 24-year-old burned sites. Soil surface temperatures were nearly 25 F (14 C) warmer on recently burned sites than on unburned subarctic lichen woodlands and 18 F (10 C) warmer on sites burned 24 years prior. Below surface soil temperatures on burned sites were just 5 to 9 F (3-5 C) warmer. Soil temperatures measured at a depth of 4.3 inches (11 cm) on sites burned 3, 15, and 80 years earlier were 45 F (7.4 C), 44 F (6.7 C), and 36 F (2.1 C), respectively in upland boreal forests near Delta Junction, Alaska [183].

Changes in soil properties were evaluated in northern Quebec's open spruce/lichen woodlands in various stages of postfire regeneration. The 105- and 138-year-old sites were open black and white spruce-lichen forests. The 45-year-old site had black and white spruce, bog Labrador tea, and bog birch (Betula glandulosa) regrowth and a 2- to 4-inch (5-10 cm)-thick lichen layer. The youngest sites had scant bog birch cover. Soil pH did not change much following fire; pH of the L and H horizons ranged from a low of 3.9 on the 138-year-old site to a high of 4.5 on the 1- and 5-year-old sites. The Bm horizon ranged from a low of 2 inches (4 cm) on the 138-year-old site to a high of 4.6 cm on the 5-year-old site. Carbon and available nitrogen and phosphorus were greatest on the most recently burned sites, while cation exchange capacity was greatest on the 105- and 138-year-old sites. Results are summarized below [117]:

Time since fire Soil horizon* C Available N Available P Cation exchange capacity
years  kg/ha kg/ha kg/ha
1 L + H 6730 1.29 0.69 26.4
5 L + H 2830 0.77 0.23 28.5
45 L + H 5380 0.83 0.48 26.7
105 L 3535 0.34 0.21 41.7
H 3820 1.00 0.24 23.0
138 L 3595 0.60 0.23 40.9
H 3840 0.69 0.49 26.8
*On 105- and 138-year-old sites the L horizon was 1 to 2 inches (3-5 cm) thick and the H horizon was 2 inches (5 cm) thick.

MANAGEMENT CONSIDERATIONS

SPECIES: Ledum groenlandicum
IMPORTANCE TO LIVESTOCK AND WILDLIFE:
Bog Labrador tea is common in preferred ungulate grazing sites and important small mammal, game bird, and amphibian habitats. However, bog Labrador tea is not considered palatable and rarely comprises a majority of wildlife diets.

Caribou: Bog Labrador tea is typical in caribou habitats, but feeding on bog Labrador tea is likely just incidental or occasional. Labrador tea was 53% frequent in caribou craters (areas of snow excavated for feeding) dug in February and April of 1972 and 1973 in north-central Canada taiga [115]. Bog Labrador tea, although abundant on caribou ranges, is a minor diet component. Bog Labrador tea is likely avoided because of its low palatability and may only be consumed under "special circumstances" [168].

In northwestern Manitoba, bog Labrador tea was the most common plant at caribou feeding sites used in February. Bog Labrador tea stems showed trampling and browsing damage on grazing sites used in February. The researcher suggested that the presence of Labrador tea may indicate those feeding sites with easy snow excavation. From 12 to 16 caribou rumens, Labrador tea percent occurrence ranged from 67% to 100%, but the author notes that this high level of occurrence may reflect accidental ingestion from caribou feeding on nearby more palatable vegetation. Seasonal ingestion of Labrador tea is summarized below [115].

Collection period

January-February April November
1967 1966 1967 1968 1966 1967
Number of rumens 12 16 16 16 15 16
% occurrence of Labrador tea 67 75 94 94 100 81

In summer caribou habitats of northern Quebec and Labrador, coverage of bog Labrador tea in shrub tundra and dwarf birch dominated sites was lower on grazed than ungrazed sites sampled in late July and early August of 1992 and 1993. Decreased bog Labrador tea coverage on grazed sites may be a result of trampling and/or browsing damage. Study findings are presented below [109]:

Grazed (n=7) Ungrazed (n=4)
Shrub tundra vegetation 0 0.7 0.9 (s)
Dwarf birch vegetation* 0.7 1.1 0.8 1.2
*bog Labrador tea and northern Labrador tea (Ledum palustre)

In the Wallace-Aikens Lakes study area of southeastern Manitoba, bog Labrador tea was apparently avoided by caribou observed when feeding [158]. In 20 caribou rumens taken from northern Saskatchewan, northern Manitoba, and the Northwest Territories, bog Labrador tea and northern Labrador tea together made up just 2.9% occurrence by weight [159]. In south-central Alaska, the digestive tracts of 2 new-born caribou calves contained bog Labrador tea. The percent content of bog Labrador tea was not provided, but the majority of digestive tract contents was curdled milk [168]. Bog Labrador tea was frequently recovered from the rumina of 84 adult caribou in all seasons from 1957 to 1966. Bog Labrador tea made up the largest percentage of evergreen volume in summer diets. The frequency and volume (based on total evergreen volume) of bog Labrador tea by season are summarized below [11]:

Season Spring Summer Fall Winter
Frequency of occurrence (%) 93 100 100 88
Volume (% based on evergreen totals) 18 43 22 21

Deer and moose: Bog Labrador tea is considered poor quality deer browse; Verme [187] reports the bog Labrador tea is "almost worthless" as deer food following studies in northern Michigan. Observations of winter feeding by white-tailed deer in the Wilderness State Park of Emmet County, Michigan, revealed only "casual feeding" on bog Labrador tea although bog Labrador tea was common in the area [73]. Food habits of moose and white-tailed deer evaluated on sites burned 2 years prior in northeastern Minnesota's boreal forest revealed winter bog Labrador tea use by white-tailed deer but no utilization by moose. Bog Labrador tea received an average of 9% aggregate use by white-tailed deer in just December although the study was conducted from April to December of 1973 [78].

Mountain goats: Feeding on bog Labrador tea is low by mountain goats. The relative percent density of bog Labrador tea among plant fragments recovered by microhistological fecal analysis of mountain goats on Chopaka Mountain, Washington, was a high of 1.6% in the summer and a low of 0.4% in the fall [20].

Game birds: Bog Labrador tea is common in game bird habitats and may provide cover, food, and/or nesting sites for grouse and waterfowl. In the barren vegetation of Newfoundland, bog Labrador tea is consumed by ptarmigans [134].

The analysis of spruce grouse habitat in north-central Washington revealed that bog Labrador tea presence was proportionally greater than expected (p<0.05) on plots where spruce grouse were found. Researchers suggested that spruce grouse may prefer the coverage provided by bog Labrador tea for hiding, insect feeding, and/or ease of flight take-off [139].

Alaskan habitats for ruffed grouse, spruce grouse, sharp-tailed grouse, and blue grouse typically include bog Labrador tea in the understory. Analysis of 11 blue grouse crop contents taken in August revealed that bog Labrador tea was 5% of the total volume. Of 57 blue grouse taken in September, bog Labrador tea was just 1% of the total volume of crops. No bog Labrador tea was recovered from crops taken in October. Whether or not bog Labrador tea is important to grouse directly or was merely associated with important vegetation is not evident from this study [199].

Waterfowl: In northern New England and especially Maine, poorly drained areas in which bog Labrador tea is typical are considered important waterfowl habitat [163].

By radio tracking 24 mallards through the breeding season in the Chippewa National Forest of Beltrami County, Minnesota, researchers located 12 nests. Four of the 12 nests were in clumps of leatherleaf or bog Labrador tea. The presence of woody vegetation appeared important in nest site selection [56].

Timber wolves: Research suggests that bog Labrador tea may be incidentally ingested by wolves when feeding at a kill site and is likely found in wolf habitats. The analysis of wolf scat collected for 3 years in the northern Highlands area of northern Wisconsin revealed a 1% to 2% frequency of bog Labrador tea in the scat [181].

Snowshoe hares: Bog Labrador tea is found in snowshoe hare habitats and is sometimes utilized as a food source. A study near the University of Alaska campus revealed heavy usage of muskeg vegetation by snowshoe hares. There were extensive well-traveled paths or "runways" in the muskeg understory of bog blueberry, bearberry (Arctostaphylos uva-ursi), and bog Labrador tea. Likely this vegetation provided cover during snowshoe hare travel [125]. Six of 16 radio-collared snowshoe hares preferred habitats in which bog Labrador tea was a dominant understory species. Four of the snowshoe hares strongly preferred black spruce bogs and 2 preferred tamarack bogs [135].

Usage of bog Labrador tea by snowshoe hares likely depends on the availability of more palatable browse. Bog Labrador tea availability was 3.4%, and its use by snowshoe hares was 2.4% in the Sheffield Lake area of Newfoundland where the relative density of snowshoe hares was considered low. On the approximately 0.33-mi (0.87 km)- Emberly Island in Placentia Bay, Newfoundland, snowshoe hare density was high, and authors noted that bog Labrador tea was nearly dead from heavy browsing [37]. Analysis of snowshoe hare stomachs taken from Goldstream Valley, Alaska, from October 1972 through September 1974 revealed some reliance on bog Labrador tea for food. Bog Labrador tea was present in stomachs more often and made up a greater proportion of the diet in the summer and fall. Below is a summary of the results [201]:

Season

Spring

Summer Fall Winter
Months April May July-Sept. Oct.-Nov. Dec.-Feb.
Number of stomachs 21 40 11 35 20
% composition > sx 1.90.7 0.90.3 7.63.3 3.30.9 0.40.4
% frequency 38 20 64 47 5

However, in a feeding trial, researchers established that bog Labrador tea is highly unpalatable to snowshoe hares. When provided only evergreen browse, snowshoe hares ate white and black spruce significantly (p<0.0001) more than bog Labrador tea [144].

Other small mammals: The heather vole was captured most frequently in a 20-year-old burn site near Labrador City, Newfoundland, where bog Labrador tea was most common [165].

Amphibians: Researchers found several frog species in tamarack and black spruce forests of Itasca State Park, Minnesota, where bog Labrador tea was common. A total of 855 frogs were found throughout the 5 years (1949-1953) of mid-August field studies. Of the 855 frogs, 316 occurred in the tamarack and black spruce vegetation. Microclimates, vegetation type, coverage, and/or potential escape areas likely affected habitat choice. The occurrence of frog species in the tamarack and black spruce vegetation types is shown below [110].

Species

Number found in tamarack and black spruce habitat types

Total number found

% of total found in tamarack and black spruce vegetation

mink frog 3 5 60
leopard frog 69 330 21
wood frog 179 372 48
spring peeper 32 61 52
swamp tree frog 31 75 41
tree frog 2 11 18

Insects: In a review, Limpert [102] suggests that bog Labrador tea provides an excellent source of nectar for butterflies. This nectar is also important to bees [142].

Palatability/nutritional value: Bog Labrador tea has low palatability. It contains alkaloids which are considered toxic to sheep and other livestock [137]. In a review, bog Labrador tea was reported as unpalatable and/or slightly poisonous [120].

Bog Labrador tea collected in the summer (21 June) from caribou feeding sites in northwestern Manitoba had 8.3% protein and 566 kcal/100g. The researcher indicated that fall bog Labrador tea protein and energy contents were high, but levels were not reported [115]. Dry matter nutrient content of bog Labrador tea's current year's growth and Labrador tea leaves in Wallace-Aiken lakes area of southeastern Manitoba is provided below. The current year's growth was collected from July and August of 1984 and 1985, and leaves were collected in April 1986 and February 1987 [158].

Species/genus Crude protein (%) Acid detergent fiber (%) Ca (%) P (%) Dry matter digestibility (%)
Bog Labrador tea current year's growth 9.4 48.1 0.34 0.08 49.3
Labrador tea leaves 8.7 46.3 0.68 0.14 37.6

Cover value: Bog Labrador tea may be important cover for many wildlife species as it is a typical species in many important wildlife habitats. This information has been integrated into the above Importance to livestock and wildlife section. See the species group of interest within this section for additional cover value information.

VALUE FOR REHABILITATION OF DISTURBED SITES:
Bog Labrador tea may be useful in revegetating disturbed sites. Bog Labrador tea seedlings established well on a right of way cleared in a 200-year-old black spruce forest north of Fort Norman in the Northwest Territories. A trench, 7 feet (2 m) wide and 20 inches (50 cm) deep, was dug and backfilled in July and August of 1986. Locally collected bog Labrador tea seed was sown at 0.5 g/m, and 375 seedlings/m established in the 1st growing season. Seedlings were clumped and had not advanced beyond the seedling stage by the end of the 1st growing season [111].

OTHER USES:
Native people of the pacific northwest coast, British Columbia, and Canada's maritime provinces utilized bog Labrador tea as a food and to treat a variety of ailments. The Nuxalk people of British Columbia seasonally harvested and preserved bog Labrador tea for food [101]. Aboriginal people and early European settlers of the Pacific northwest coast drank tea of bog Labrador tea. The tea relaxed some, caused drowsiness in others, and prevented sleepiness in yet others. It was also used to treat colds and sore throats [137]. Elias and Dykeman [45] caution that bog Labrador tea leaves should not be boiled with the water as this practice may release harmful alkaloids.

Robuck [151] reports that 2 or 3 bog Labrador tea leaves are "occasionally refreshing to chew," and that bog Labrador tea taken internally can soothe nerves and stomachs. Bog Labrador tea applied externally can treat some skin ailments. In a review, bog Labrador tea was reportedly used to treat asthma, common colds, indigestion, scurvy, fever, dysentery, leprosy, and lice. An external application was thought to provide relief from burns, ulcers, and stings [120]. A study of plants used by the Micmac and Malecite tribes of Canada's maritime provinces revealed that bog Labrador tea contains campesterol, β-sitosterol, β-amyrin, α-amyrin, and taraxasterol [71].

OTHER MANAGEMENT CONSIDERATIONS:
Allelopathy: The chemical analysis of soils with and without bog Labrador tea and growth rate differences in black spruce grown on sites with and without bog Labrador tea suggests that bog Labrador tea may produce allelopathic compounds [77].

Biomass predictions: Yarie and Mead [202] provide coefficients for predicting leaf, twig, and combined dry biomass of bog Labrador tea in a variety of Tanana River Basin communities in interior Alaska.

Indicator potential: Bog Labrador tea may be a valuable indicator of contaminated sites and easily reforested sites. Analysis of bog Labrador tea on Faro mine sites in the Yukon Territory revealed that it may be a useful bioindicator of lead and iron metal contamination [138]. In the Lake States, bog Labrador tea is an indicator of swamp sites that could easily be reforested to coniferous swamps. Of 45 plots, bog Labrador tea was present on more than 40% of the coniferous swamp forest types and less than 5% of other forest types visited [156].

Pollution: For information on the effects of sulfur dioxide pollution on bog Labrador tea, see [2].


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