Cover, frequency, and density of western snowberry on
unburned and burned sites following a single burn 
1st postfire growing season
This description provides characteristics that may be relevant to fire ecology, and is not meant for identification. Keys for identification are available (e.g., [23,56,60,71,78,79,100,144,147,159,167]).
Western snowberry is a stiffly erect and freely branching shrub [35,79,144] that grows from 1 to 5 feet (0.3-1.5 m) tall [23,35,60,71,78,79,100,144,167] and commonly forms dense, low thickets [79,144]. When young, the branches are minutely hairy [60,71,100,167]. As shrubs mature, bark forms on the branches that becomes shreddy with age [144,147,159]. Leaves are deciduous, 0.8 to 3 inches (2-8 cm) long, and 0.6 to 2.2 inches (1-5.5 cm) wide [23,60,71,79,144,147,159,166,167]. Juvenile shoots sometimes produce larger leaves that are 4 inches (10 cm) long and 3 inches (8 cm) wide . Flowers, born in racemes [35,79,167], occur in dense clusters of 2 to 10 at the end of branches and in the axils of leaves [60,71,100,117,144,165,166]. The fruits of western snowberry occur in crowded clusters and are berrylike drupes that each contain 2 nutlets [117,144]. Fruits are 6 to 9 millimeters in diameter, approximately 2.5 to 3.5 millimeters long, and 1.5 to 2.5 millimeters wide [35,60,71,79]
Colonies: Western snowberry forms dense colonies along ditches, streams, and floodplains; and in moist, open, grassy swales on mesas and plains [35,56,58,60,71,159,165,166,167]. Colonies range from 3 to 700 feet (1-200 m) or greater in diameter [25,83,117,122].
Rhizomes: Pelton  provides a detailed description of western snowberry rhizomes in 2 colonies in Minnesota. Western snowberry rhizomes tend to be very long and sparsely branched, and typically grow to a depth of 14 inches (35 cm). A rhizome from a 4-year-old plant at the periphery of a western snowberry colony measured 30 inches (80 cm) long, and roots from the rhizomes extended 5.09 feet (1.55 m) belowground. New sprouts from rhizomes develop in spring at approximately the same time shoots develop on older stems. In the first year of growth, new sprouts commonly attain the same height of mature stems and sometimes produce "abundant" fruit. Rhizome sprouts are generally reproductively mature for several years before the rhizome connection with the parent plant severs or decays. Rhizomes in the interior of one colony were approximately 20 years old .
Fire adaptations: Western snowberry is fire-tolerant [63,67,70] and sprouts after fire [6,27,53,57,63,140,141,142,145]. While the stems of western snowberry are sensitive to fire, the rhizomes and stem bases can survive fire due to their depth in the soil (0.8-14 inches (2-35 cm)) [7,117].
FIRE REGIMES: There is little information directly relating to western snowberry FIRE REGIMES. Western snowberry may occur where the fire-return interval is as short as 1 year and as long as 500 years.
Northern Great Plains/Mixed-grass prairie: Fire has played an important role in northern Great Plains mixed-grass prairies, where western snowberry occurs. The historically large tracts of continuous mixed-grass prairie, which occur in hot, dry areas, accumulated much fine fuel and were susceptible to frequent lightning fires. Early records kept by explorers, trappers, and settlers noted a high occurrence of fires, both natural and anthropogenic , with frequent low-severity fires occurring at intervals of 5 to 10 years [37,116,173]. In a review by Sieg , the fire-return interval for level to rolling topography in the northern Great Plains is 5 to 10 years. On more dissected topography, such as breaks and rivers, the fire-return interval ranges from 20 to 30 years. In mixed-grass prairies of Badlands National Park, South Dakota, frequent low-intensity surface fires occurred at frequencies of 1 to 25 years . Since the early 1900s, fire has been excluded and nonnative species, including Japanese brome (Bromus japonicus), smooth brome, Kentucky bluegrass, crested wheatgrass (Agropyron cristatum), and Canada thistle (Cirsium arvense), are widely established in the area . Fire exclusion has also allowed the encroachment of western snowberry into grasslands of the northern Great Plains [114,117].
Western snowberry-dominant communities: Fire has played an active role in shaping the interior ponderosa pine/western snowberry and Rocky Mountain Douglas-fir/western snowberry communities of the Little Rocky Mountains  and the Rocky Mountain Douglas-fir/western snowberry communities of the Bear's Paw Mountains . In a review by Fischer and Clayton , it is suggested that the fire frequency of interior ponderosa pine communities with a shrub understory is "considerably" less than 50 years, and that of Rocky Mountain Douglas-fir ranges from 5 to 20 or more years. Long-term exclusion of surface fires has altered Rocky Mountain Douglas-fir sites, creating more flammable conditions. On Bureau of Land Management lands in southern and eastern Idaho, narrowleaf cottonwood/western snowberry and black cottonwood/western snowberry communities typically burn during the late summer and fall .
The following table provides fire regime information on vegetation communities in which western snowberry may occur. Find further fire regime information for the plant communities in which this species may occur by entering the species name in the FEIS home page under "Find FIRE REGIMES".Fire regime information on vegetation communities in which western snowberry may occur. For each community, fire regime characteristics are taken from the LANDFIRE Rapid Assessment Vegetation Models . These vegetation models were developed by local experts using available literature, local data, and/or expert opinion as documented in the .pdf file linked from the name of each Potential Natural Vegetation Group listed below. Cells are blank where information is not available in the Rapid Assessment Vegetation Model. Pacific Northwest Great Basin Northern Rockies Northern Great Plains Pacific Northwest
Fire behavior and fuel characteristics: To assess the maximum fire temperatures reached in western snowberry communities above and below ground, prescribed fires were conducted in late April and early May near Saskatoon, Saskatchewan. At the time of the fires, air temperature ranged from 59 to 64 °F (15-18 °C), relative humidity from 30% to 40%, and wind speeds less than 3 meters/second. The fuel load was 1,029 ± 228 g/m² dry weight (± SD) and fuel moisture content was 25 ± 8% (± SD) prior to the fires. At 3 measurement points above ground (4 inches (10 cm), 9.8 inches (25 cm), and 20 inches (50 cm)), fire temperatures exceeded 1,000 °F (800 °C). At all measurement points, maximum fire temperatures occurred within 2 to 3 minutes following ignition .Average maximum fire temperatures and average duration of fire temperatures above 100 °F (60 °C) (±SD) at selected heights in the western snowberry community  Measurement height (cm) -5 0 10 25 50 100 150 Avg. maximum fire temperature (°C) 40 ± 21 692 ± 118 843 ± 36 824 ± 43 835 ± 54 735 ± 11 697 ± 22 Avg. duration of fire temperatures above 60 °C (minutes) 0.1 ± 0 8.1 ± 6.0 4.7 ± 1.1 3.5 ± 0.5 3.1 ± 0.5 2.3 ± 0.5 2.2 ± 0.6
Bailey and Anderson  collected fuel and fire temperature data during April in a western snowberry community located within an aspen parkland in central Alberta. Fuels and temperatures at ground level during the fire at 3 locations within the western snowberry stand are presented in the table below. The inner third of the western snowberry community had significantly (P<0.05) greater western snowberry fuels and standing woody fuel and thereby a significantly higher surface temperature .Fuel loading and fire temperature data in a western snowberry community in central Alberta 
Type of vegetation/fuelPosition in stand Inner third Middle third Outer third Western snowberry shrubland (kg/ha) 25,173* 16,857 14,732 Standing woody fuel (kg/ha) 14,906* 9,349 8,798 Ground surface fuel (kg/ha) 8,270 7,508 6,270 Fire temperature (°C) 445* 368 381 *Significantly (P<0.05) greater than middle and outer third of stand
The researchers also took aboveground temperature readings during the western snowberry fire. Recorded headfire temperatures were higher than backfire temperatures. Fire temperatures for both head- and backfires were greatest at approximately 4 to 8 inches (10-20 cm) above ground. The mean and range of temperatures of the fires are presented in the table below. Both head- and backfires burned 100% of the area .
Temperature mean and range of head- and backfires in a western snowberry community 
Mean temperature (°C ± SE)
Temperature range (°C)Backfire 325 ± 19 204-427 Headfire 435 ± 17 232-704
Prescribed burning: Prescribed burning of western snowberry may be implemented to increase production, rehabilitate disturbed sites, and/or improve wildlife habitat.
In the northern Great Plains, spring burning (May-June) generally causes western snowberry to sprout, while frequent fires may reduce western snowberry cover. Prescribed burning guidelines for the northern Great Plains are available .
Successful spring burning of western snowberry shrub communities in the aspen parklands of Alberta requires the following: 1) A minimum temperature of 55 °F (13 °C), 2) winds of 2 to 12/mph, 3) 50% maximum relative humidity, and 4) at least 4 days following a precipitation event .
To increase production and caloric content of western snowberry, a prescribed burn was conducted on the Oakvile Prairie, near Grand Forks, North Dakota. On an unburned upland site, western snowberry production was 26.3 g/m² and caloric content was 4,822 kcal/g (ash-free) and 126,915 kcal/m². At postfire month 3 on burned sites, western snowberry production was 39.4 g/m² and caloric content was 4,855 kcal/g (ash-free) and 191,190 kcal/m² .
Site rehabilitation: The narrowleaf cottonwood/western snowberry streamside community type in eastern Idaho is "extremely" important in reducing sedimentation, stabilizing streambanks, and slowing flood waters. Overgrazing can lead to the complete removal of western snowberry and Wood's rose. Prescribed fire, if managed carefully, is a possible tool in maintaining or restoring this community type. If fire is used, livestock grazing should be excluded from the site for at least 5 postfire years and wildlife browsing should be closely monitored .
Wildlife: The effect of cool-season burns on wildlife was investigated in Wind Cave National Park, South Dakota. The fires, occurring on separate sites, were conducted on 17 October 1979 and 14 April 1980. Both fires were classified as low-severity. During the first postfire year, deer mice and songbird populations increased "dramatically". By the second postfire year, the effect disappeared or in some cases was reversed. Likely the deer mice and songbirds were attracted to the burn during postfire year 1 by an increase in food supply, which decreased by the second postfire year .
Following a prescribed fire in a rough fescue community at Kernen Prairie, Saskatchewan, the density of breeding pairs of birds was reduced for 3 postfire years. Western snowberry is a common shrub at the site. The fire was conducted in October 1986 and bird population counts were taken during the summers of 1987, 1988, and 1989. Averaging all 12 bird species counted on the burned and unburned sites, the density of breeding pairs on burned sites in the 3 years was 2.39, 2.47, and 2.95 breeding pairs/ha. On unburned sites, breeding pair density was 5.18, 5.22, and 4.24 breeding pairs/ha .
Western snowberry is commonly found in riparian areas such as alluvial floodplain terraces, upland ravines, swale-like depressions, and along streams and rivers [35,41,42,43,71,78,79,167]. It is also common in open deciduous woods, open prairies, rocky bluffs, pastures, and along roadsides and railway embankments [41,42,43,60,71,73,78,79,144,147,159].
Climate: Western snowberry occurs in continental-type climates characterized by extreme temperature ranges and light to moderate precipitation [32,117]. Western snowberry is adapted to survive moderate drought conditions [163,164].
Elevation: The elevational range of western snowberry by state or province is presented below.Elevation range of western snowberry State/province Elevation (feet) Colorado 3,500-8,500 [71,134] Montana 1,950-4,000  New Mexico 5,000-8,500  North Dakota 800-1,800  South Dakota 4,125-7,000 [21,115] Utah 1,525-7,000 [58,167] Wyoming 7,525-9,900  Alberta 2,000-4,685 [4,169]
Grasslands: Western snowberry is a common shrub component in mixed-grass prairies. In a mixed-grass prairie in The Gap Community Pasture near Regina, Saskatchewan, density of western snowberry was significantly (P<0.05) lower in plots with "low" water availability than in plots with "normal" to "high" water availability .
Invasive species: In Theodore Roosevelt National Park, the effect of leafy spurge on species richness was estimated in floodplain communities where western snowberry is an indicator species. Species richness was 19% lower in infested sites than in noninfested sites .
Soil: Western snowberry occurs on most soil textures except for loose sands . On floodplains where it occurs, alluvial soils are generally fine textured, composed primarily of silt with moderate quantities of clay and fine sand . It may also occur on infertile sand or rocky substrates, rich loams, or compact clays [117,126,164]. It can tolerate "imperfectly" drained soils and considerable flooding but is intolerant of prolonged flooding or permanent high water tables. Western snowberry is common on mildly alkaline to slightly acidic soils [22,67,164].
Detailed analyses of soils where western snowberry occurs in Minnesota , eastern North Dakota , wooded draws of the southern Great Plains , and southwestern North Dakota  are available.
Topography: In the more humid parts of its range, western snowberry occurs on drier topographic sites such as exposed bluffs, open hillsides, and south and west facing slopes. In drier areas, western snowberry is most commonly found on moister sites such as depressions, ravines, the shores of lakes and sloughs, along stream banks and floodplains, at the base of steep slopes susceptible to runoff, and on north or east facing slopes .
Livestock: In the eastern part of its range, western snowberry is rarely eaten by livestock, even when other forage is scarce . Yet in the western part of its range, western snowberry is considered an important livestock browse species [117,122,145,158,159], particularly during winter [117,145]. Western snowberry is often more heavily utilized by livestock and wildlife in the first few years following fire . Western snowberry may also be browsed by domestic goats . Stands of western snowberry can become so thick that they exclude livestock and wildlife .
Small mammals/birds/insects: The fruits of western snowberry are an important source of food for some small mammals and birds . Upland game birds heavily utilize western snowberry fruits since they persist on the plant through the winter [63,82,117,147]. In Minnesota, western snowberry fruits are eaten by waterfowl . Western snowberry flowers are also a valued bee food [145,159].
Ungulates: Western snowberry is an important forage species for elk, mule and white-tailed deer, pronghorn, bighorn sheep, and moose [22,36,38,39,44,47,89,99,108,113]. In the Bridger Mountains of Montana, antelope bitterbrush (Purshia tridentata) and western snowberry are the 2 most important fall browse species for mule deer . Western snowberry was the most important browse plant for white-tailed deer on the Charles M. Russell Wildlife Refuge, in north central Montana, during a yearlong study from June 1964 to June 1965. Western snowberry was found in 100% of summer, fall, and winter rumen samples and 85% of spring samples. Utilization of western snowberry is greatest in fall (55% total rumen sample volume), followed by winter (25%), summer (19%), and spring (10%) . Western snowberry is a principal food source for white-tailed and mule deer in the Black Hills of South Dakota and Wyoming. An analysis of stomach contents showed that the frequency of occurrence of western snowberry ranged from a high of 62% for the period May through September to a low of 45% for the period October to December [76,77,117].
Palatability/nutritional value: The palatability of western snowberry for cattle and domestic sheep is generally rated as "fair" [22,40,63,151] and "poor" for horses [22,40]. Western snowberry palatability for deer and elk is rated as "good" [40,63,76].
In northwestern Montana, western snowberry provides "fair" energy and protein value for livestock and wildlife . The nutritional value for ungulates, small mammals, and birds in 5 western states is rated as follows :Western snowberry nutritional value rating  Species Utah Colorado Wyoming Montana North Dakota Elk Good Poor Fair Fair N.D. Mule deer Good Poor Fair Good Fair White-tailed deer N.D. N.D. Good Good Fair Pronghorn N.D. N.D. Fair Fair Fair Upland game birds Good N.D. Good Fair Fair Waterfowl Poor N.D. Poor N.D. Poor Small nongame birds Fair N.D. Good Fair N.D. Small mammals Good N.D. Good Fair N.D. N.D. = No Data
At the Ministik Wildlife Research Station near Edmonton, Alberta, seasonal changes in percent digestibility and crude protein of western snowberry leaves were measured in an aspen-dominated boreal forest .Seasonal digestibility and crude protein of western snowberry leaves  Late spring Summer Autumn Digestibility (%) 57.4 61.3 59.5 Crude protein (%) 15.0 17.5 12.3
The cellulose and protein content of western snowberry at 3 stages of growth were evaluated in a rough fescue community in southwestern Alberta .Nutritional content of western snowberry during 3 stages of growth  Growth stage Cellulose (%) Digestible protein (%) Leafing 15.5 4.0 Flowering 19.2 1.8 Seed ripe 15.5 1.1
Western snowberry fruit is an important fall and early winter food for sharp-tailed grouse. As the fruits dry, however, their nutritional value decreases substantially. Western snowberry fruit taken from the plant in South Dakota during fall, at a time when it is fed upon by sharp-tailed grouse, provided 4.916 kcal/g and 5.5% crude protein .Composition of western snowberry on 4 dates in 1945 on the Black Hills, South Dakota  Date Moisture (%) Carotene (µg/g) Ash (%) Crude fat (%) Crude protein (%) Crude fiber (%) N-Free extract (%) Ca (%) P (%) Fe (ppm) Mn (ppm) 18 January 36.80 13.54 2.38 1.28 3.32 23.20 33.02 0.36 0.072 165.82 61.76 16 May 58.01 4.01 2.02 1.06 5.42 12.75 20.74 0.26 0.166 128.41 39.95 27 June 66.12 40.62 2.26 1.24 4.46 5.41 20.51 0.21 0.15 40.83 8.71 22 October 54.01 14.35 2.67 2.20 2.99 5.77 32.36 0.54 0.144 87.88 28.31
Cover value: Western snowberry communities provide cover for a variety of animal species, particularly small mammals and birds [10,22,73,117,122,132,147]. The narrowleaf cottonwood/western snowberry and black cottonwood/western snowberry grazing disclimax communities along streams provides cover for fish and other aquatic species . Given the shrub's height, western snowberry only provides "poor" to "fair" cover for large ungulates [22,40].
Western snowberry stands are common nesting sites for waterfowl, wild turkeys, and sharp-tailed grouse [97,120,133]. In south-central North Dakota, western snowberry was found to occur at 62.8% of all sharp-tailed grouse nesting sites . In northeastern South Dakota, western snowberry is an important cover species for nesting female Rio Grande and eastern wild turkeys. While shrub vegetation (primarily western snowberry) was the least available vegetation type (10%) at the study site, 54% of females chose this vegetation type for nesting cover .
Western snowberry is described as a dominant
species in the following vegetation classifications and locations.
Flowering dates for western snowberry are presented below.Western snowberry flowering periods in the United States and Canada Illinois June-August  Minnesota June-September  Nebraska June-July  New Mexico May-August [100,159] Oklahoma May-July  South Dakota June-July  Texas May-July  Great Plains June-August [60,151] Intermountain West June-August  North-central Plains June-August  Northeastern United States and adjacent Canada June-August  Pacific Northwest June-August  Uinta Basin, Utah May-July  Ontario July-August 
From 1979 to 1984 first-flowering dates and flowering periods for western snowberry were observed and reported in a mixed-grass prairie near Woodworth, Stutsman County, North Dakota. Flowering dates and periods for western snowberry are presented below .First-flowering dates and periods for western snowberry  Earliest first bloom Latest first bloom Median date of first 10 plants with flowers Median date of full flowering Median date when flowering 95% complete Length of flowering period 13 May 1980 10 July 1979 25 June 6 July 28 July 33 days
The phenological development of western snowberry in a prairie habitat northwest of Lincoln, Nebraska was observed by McMillan and Pagel  in 1956 and 1957.Phenological development of western snowberry during 1956 and 1957  Observation year Leaf bud opening Initial anthesis 1956 26 March-21 April 16 June-22 July 1957 13 April-21 April 23 June-22 July
Seed dispersal: Western snowberry seeds are dispersed primarily by small mammals and birds [103,117,149], though wind and water may play a small part in their dispersal. In a feeding trial, 10.7% of 150 western snowberry nutlets passed through the digestive tract of domestic chickens intact and viable. Western snowberry nutlets will float in water for approximately 48 hours before sinking .
Seed banking: Little information is available on western snowberry seed banking. Pelton  claims that western snowberry utilizes a seed bank "limitedly". The fruit of western snowberry can remain on the plant for a year or more .
Germination: Western snowberry has embryo dormancy, requiring an afterripening period for adequate germination . Warm stratification at room temperature for 3 to 4 months followed by cold stratification at 41 °F (5 °C) for 4 to 6 months increases germination [72,117]. Pelton  notes that western snowberry seeds likely require more than 1 summer and winter in the soil to break dormancy.
Western snowberry seeds appear to favor cool season germination. Western snowberry seed germination rates under constant and alternating temperatures are presented below. In the alternating temperature experiment, the western snowberry seeds were exposed to the high temperature for 8 out of each 24 hours.
Percent germination of western snowberry seeds under alternating and constant temperatures Alternating temperatures (°C) -5/5 -5/10 5/10 5/15 5/20 10/15 10/20 10/25 15/20 15/25 Germination (%) 0 0 45.2 45.7 35.3 45.8 37.0 29.4 22.3 20.1 Constant temperatures (°C) 5 10 15 20 25 Germination (%) 35.5 44.1 40.1 18.7 5.9
Seedling establishment/growth: Western snowberry rarely establishes by seedlings [24,117,122]. In Minnesota, western snowberry seedlings growing in "poor" soil reached a height of 4 inches (9 cm) by the end of the first growing season. During the same time period, seedlings grown in "rich" potting loam reached a height of 18 inches (45 cm). While the seedlings in the potting loam grew "vigorously", they did not produce rhizomes or flowers during the first growing season . In a review by Moles and Westoby , the cause of western snowberry seedling mortality during 1 growing season in a grazed pasture in Minnesota was discussed. Major mortality agents included fungal attack (18.9%), herbivory (32.8%), and drought (29.9%).
Vegetative regeneration: Western snowberry regenerates vegetatively by rhizomes [1,35,60,79,147,151,159]. It can be propagated by stem and root cuttings  and will sprout following mowing or cutting . Research on other sprouting species indicates that development of new shoots on shrubs is controlled by apical dominance. The death of apical buds removes the hormonal control of lateral buds on rhizomes .
Western snowberry occurs in climax communities [25,101] but is generally found in seral communities on immature soils and in the transition zones between grasslands and forests . Western snowberry is most commonly found where full or nearly full sunlight is available. However, it is also frequently found at forest borders where it can survive under partial to dense shade [67,117].
Disturbed sites: Western snowberry thrives following disturbances such as fire [57,109,119], logging , animal activity [18,150], and various other soil disturbances [144,161]. On alluvial floodplains in northwestern Montana, the western snowberry community type generally represents a disturbance-induced seral stage of the interior ponderosa pine/red-osier dogwood (Cornus sericea) and/or Rocky Mountain Douglas-fir/red-osier dogwood habitat types .
Grazing: Western snowberry sometimes occurs in communities characterized as a moderately disturbed secondary successional stage following grazing and/or browsing . On low-elevation riparian and wetland sites in central and eastern Montana, prolonged browsing of eastern cottonwood/red-osier dogwood communities leads to the disturbance-induced eastern cottonwood/western snowberry community-type . In eastern Idaho, continued grazing or browsing pressure in narrowleaf cottonwood/red-osier dogwood and black cottonwood/red-osier dogwood communities leads to a grazing disclimax narrowleaf cottonwood/western snowberry community and black cottonwood/red-osier dogwood community. If grazing or browsing is heavy enough, all shrubs will be eliminated, leaving an herbaceous understory dominated by Kentucky bluegrass (Poa pratensis), timothy (Phleum pratense), smooth brome (Bromus inermis), and variety of "weedy" forbs .
Grasslands: When western snowberry spreads onto grasslands, it reduces forage production . Pelton  states that western snowberry's most important successional role is that it can successfully invade grasslands to the point where it shades out grasses, thereby facilitating the invasion of trees. In Canada, the invading tree is quaking aspen (Populus tremuloides), while in Iowa and Nebraska it is primarily bur oak.
Western snowberry produces an extensive rhizome/root system, making it an excellent soil binder for the prevention of erosion [63,147,159,163,164]. It is also a good species for restoring disturbed sites [63,107,118,128,145]. If western snowberry is used to rehabilitate erosive sites, complete grazing exclusion may be necessary during establishment .
A western snowberry cultivar ('common') is available .
Symphoricarpos occidentalis, commonly called western snowberry or wolfberry, is a woody species of flowering plant in the honeysuckle family. Wolfberry is not to be confused with Lycium chinense and L. barbarum (goji), which are also known as wolfberry.
Symphoricarpos occidentalis is a creeping shrub, with pink, rounded to bell-shaped flowers and spherical or bulbous shaped, white or pink-tinted fruits.
Symphoricarpos occidentalis, commonly called western snowberry or wolfberry, is a woody species of flowering plant in the honeysuckle family. Wolfberry is not to be confused with Lycium chinense and L. barbarum (goji), which are also known as wolfberry.