Salix arbusculoides, littletree willow
Esser, Lora L. 1992. Salix arbusculoides, littletree willow. In: Fire Effects Information System, [Online]. U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station, Fire Sciences Laboratory (Producer). Available: https://research.fs.usda.gov/feis/species-reviews/salarb
| Abbreviation | Common Name | Scientific Name | Classification | Status |
|---|---|---|---|---|
| Plants | ||||
| SALARB | littletree willow | Salix arbusculoides | Life Form: Plants/Shrub, Plants/Tree Kingdom: Plantae Class: Dicot Order: Salicales Family: Salicaceae Genus: Salix | Fed. Protected: No Nativity: Native Invasiveness: Noninvasive |
Taxonomy
The currently accepted scientific name for littletree willow is Salix arbusculoides Anderss. Recognized varieties are as follows [3,5]:
- Salix arbusculoides var. arbusculoides
- Salix arbusculoides var. puberula Anderss.
- Salix arbusculoides var. glabra Anderss.
Synonyms
- None
Other Common Names
peachleaf willow
General Distribution
Littletree willow occurs in central Alaska, the Yukon Territory and adjacent Northwest Territories eastward throughout the boreal forest to Hudson Bay. It extends southward in the eastern Rocky Mountains to northeastern British Columbia, northern Alberta, Saskatchewan, and Manitoba. Littletree willow does not occur in the contiguous United States [2,3,25].
States and Provinces
- United States: AK
- Canada: AB BC MB NT SK YT
Site Characteristics
Littletree willow along the South Nahanni River, Nahanni National Park Reserve, Northwest Territories, Canada. (CC BY-NC 4.0)
In Alaska and northern Canada, littletree willow is found in both upland and lowland forests. It grows in the open tundra above timberline, along riverbanks and streambanks, and on floodplains. In interior Alaska, it forms dense thickets in riparian habitats, and grows as small shrubs in white spruce (Picea glauca) and black spruce (P. mariana) woodlands and in black spruce muskegs [3,5].
Soils: Littletree willow grows best in deep, moist alluvial bottomlands but is found in a wide variety of substrates. The general pH range of the soil for willows is 5.5 to 7.5 [15]. Growth of littletree willow is reduced when water levels are maintained at or above the root collar for extended periods [15].
Plant Communities
Littletree willow is one of the most common early seral willows that dominate or codominate communities along streams and rivers in interior Alaska. Published classifications describing littletree willow as a dominant or codominant in community types are listed below:
- Subarctic community types of the Northwest Territories [20]
- Upland boreal community types of the Northwest Territories [9]
Plant associates: Littletree willow is commonly associated with the following species: black spruce, white spruce, paper birch, aspen, resin birch (Betula glandulosa), Cladonia lichens, alder (Alnum crispa and A. tenuifolia), willows (Salix scouleriana and S. bebbiana), grasses (Calamagrostis canadensis and Carex species), mosses (Polytrichum spp.), and herbs (Epilobium spp.) [4,26,37].
Botanical Description
Littletree willow, Yukon Territory, Canada. (CC0 1.0)
Littletree willow is an erect shrub 10 to 15 feet (3.3-4.5 m) tall or a small tree 25 to 30 feet (7.5-9 m) tall [2,5,17,37]. Twigs are slender and many branched, and are thinly hairy to hairless depending on age [5,36]. The bark is gray to reddish brown and smooth [5,37]. The leaves are green and hairless above and white and finely hairy beneath [37]. The mature leaves are 1 to 3 inches (2.5-7.5 cm) long. Roots of littletree willow are shallow. Catkins are small and slender on short stalks [5,37].
Raunkiaer Life Form (Raunkiaer 1934)
- Phanerophyte
Seasonal Development
Littletree willow flowers from April to early August [44]. The fruit ripens shortly after flowering; seed dispersal occurs form early to midsummer [16].
Regeneration Processes
Sexual reproduction: Male and female flowers are borne in catkins on separate plants. The fruit is contained in a capsule that splits in half to release many seeds that are then dispersed by wind or water [15]. Optimum seed production is reached when trees are between 2 and 10 years of age [15]. The flowers are mostly insect pollinated, with bees playing the most important role [11,15]. The seeds of littletree willow are short-lived and nondormant, and germinate immediately on moist surfaces [10,44]. The broad temperature range of germination for these seeds, 41 to 77 degrees Fahrenheit (5-25 deg C), appears to be a compensatory mechanism for the short seed life [10,44]. Germination occurs best in moist, exposed mineral substrates that receive substantial sunlight [15].
Vegetative reproduction: Littletree willow will sprout from the root crown or basal stems [8,16,]. It is also capable of vegetative reproduction by underground rhizomes or roots [38].
Successional Status
Littletree willow is a common early seral species that will invade fresh alluvium deposits, glacial outwash, and silty-sandy alluvial deposits [1,39]. It is a common species after fire in open stands of black spruce in wet sites, and is one of the most successful colonizers in other types of disturbed areas such as roads, borrow pits, bladed slopes, and mine sites [9,19,36]. Littletree willow can become established during periods of low water on floodplains but are usually swept away by high water later. Once they are well established they can withstand both flooding and silting and can slow down river flow [39]. Littletree willow has low shade tolerance and cannot persist on sites that are heavily forested [39].
Immediate Fire Effects
Fire will kill aboveground parts of littletree willow. High-severity fires that remove the soil organic layers can destroy the basal sprouting ability of this species [24].
Postfire Regeneration Strategy (Stickney 1989)
- Tree with adventitious-bud root crown/root sucker
- Rhizomatous shrub, rhizome in soil
- Secondary colonizer - off-site seed
Fire Adaptations
Littletree willow is a fire-adapted species that can sprout from the root crown and roots [33]. Its small, light seeds are easily dispersed by wind, and are important in colonizing burned areas [26,33].
Plant Response to Fire
Littletree willow is one of the most common willows on recent burns in interior Alaska [36]. Invasion by willows after fire depends on the season and severity of fire, weather, and presence of a mineral soil seedbed [38]. In young black spruce stands originating following fire, littletree willow regenerated at about 4,000 to 5,000 stems per acre (9,880-12,350 stems/ha) [27]. The chance of littletree willow establishing years after a fire lessens as the available mineral soil seedbed sites are occupied by the faster growing herbaceous species or mosses [38]. Littletree willow is the dominant species following fire in black spruce communities for 6 to 25 years [38].
Fire severity can affect willow postfire recovery. High-severity fires can damage the roots and rhizomes to the point of no recovery [38]. Following low-severity fires most willows will recover quickly due to the ability of the root crown to send up new roots. Severe fires that destroy the organic soil layer kill willows but can expose the mineral soil necessary for seed propagation [24,38].
Fire Regimes
For fire regime information, search FEIS for this species by entering the species name on the Advanced Search page and selecting “Fire Regime” as the publication type.
Fire Management Considerations
Prescribed fire is a common wildlife management tool used to rejuvenate decadent littletree willow communities. Fires increase food for herbivores dependent on browse plants. Browse plants such as littletree willow and other willows proliferate in early postfire seres [23,36].
Federal Status
No special status.
Other Status
No entry.
Importance to Wildlife and Livestock
Littletree willow is an important browse species for moose, deer, caribou, snowshoe hares, beavers, small mammals, and some birds [15,16,28,29,31,42]. In young, seral communities in Alaska, moose in the winter feed primarily on willow shoots, quaking aspen (Populus tremuloides), paper birch (Betula papyrifera), and balsam poplar (Populus balsamifera) [28]. Of these plants, willow is considered the most preferred by moose, and littletree willow the most preferred willow [28,29]. In one study willows accounted for 94 percent of the biomass consumed by radio-collared moose during observed foraging periods, with littletree willow comprising 14 percent of total biomass consumed [32]. Snowshoe hares also utilize Salix spp. a great deal in interior Alaska, occasionally showing a preference for littletree willow [31].
Palatability and Nutritional Value
Littletree willow is highly palatable to moose [29]. On fertile sites, littletree willow has a high nutrient content which can contribute to the palatability level [29]. Littletree willow is comparatively unpalatable to snowshoe hares when other species are available [6]. Willow palatability increases as the season progresses [29].
Littletree willow is rated as fair in energy value and fair in protein value [28]. Protein content for littletree willow at the Kenai Peninsula study areas during the winter was 4.2 percent [28].
Nutrient composition of littletree willow consumed by moose in the winter in Denali National Park, Alaska, was as follows [32]:
- gross energy: 5.03 kcal/g
- % in vitro digestible organic matter: 40.9
- % of dry matter crude protein: 6.8
- lignin: 15.4
- ash: 1.5
- ether extract: 8.4
Cover Value
Littletree willow characteristically produces dense thickets along streams and rivers, which provide cover and protection for many avifauna and mammals. These thickets also provide shade for fish in streams and ponds [1,36].
Value for Rehabilitation or Restoration of Disturbed Sites
Littletree willow is useful in stabilizing streambanks and providing erosion control on severely disturbed sites [15]. Littletree willow successfully colonized local seismic lines in the Northwest Territories and borrow pits in continental tundra regions of northwestern Canada [19,20]. Littletree willow was found to be a poor colonizer of crude oil spills; plant recovery and establishment was extremely slow on these spills [18].
Other Uses
Native Americans used the flexible willow stems for baskets, arrow shafts, scoops, and fish traps. Willows also provided medicine for a variety of ailments such as diarrhea, indigestion, cuts, and worms [21].
Littletree willow is one of many willows that produces the "diamond willow" pattern on their trunks. These willows are carved into canes, lamp posts, furniture, and candle holders [36]. However, the small size of littletree willow makes it unsuitable for timber harvest [36]. Carey and Gill rated Salix spp. value for firewood as fair [7].
Other Management Considerations
Littletree willow is an important browse source for moose in Alaska. When assessing moose range conditions only the amount of browsing sustained by the highly and moderately preferred willow species, such as littletree willow, should be considered. Where these species are overutilized, certain nonpreferred species will scarcely be touched by moose [29].
Table A1— Forest and range ecosystems, Bureau of Land Management (BLM) physiographic regions, Kuchler plant associations, Society for American Foresters (SAF) forest cover types, and Society for Rangeland Management (SRM) rangeland cover types in which this species occurs.
Forest and Range Ecosystems (Garrison et al. 1977)
- FRES11 Spruce - fir
- FRES19 Aspen - birch
- FRES20 Douglas-fir
- FRES26 Lodgepole pine
- FRES44 Alpine
BLM Physiographic Regions (Bernard and Brown 1977)
- No entry.
Kuchler Plant Associations (Kuchler 1964)
- K012 Douglas-fir forest
- K052 Alpine meadows and barren
SAF Cover Types (Eyre 1980)
- 201 White spruce
- 202 White spruce - paper birch
- 203 Balsam poplar
- 204 Black spruce
- 210 Interior Douglas-fir
- 217 Aspen
- 218 Lodgepole pine
- 251 White spruce - aspen
- 252 Paper birch
- 253 Black spruce - white spruce
SRM Rangeland Cover Types (Shiflet 1994)
- No entry.
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