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Salix alaxensis


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Salix alaxensis


INTRODUCTORY


 
Figure 1. Feltleaf willow on Victoria Island, Northwest Territories. Photo courtesy of Jeffrey M. Saarela, Canadian Museum of Nature.  

CITATION:
Innes, Robin. 2014. Salix alaxensis. In: Fire Effects Information System, [Online]. U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station, Missoula Fire Sciences Laboratory (Producer). Available: https://www.fs.fed.us /database/feis/plants/shrub/salala/all.html [].

Updates: On 31 January 2018, the common name of this species was changed in FEIS from Alaska willow to feltleaf willow.

SUMMARY:

This review summarizes the fire effects information and relevant ecology of feltleaf willow in North America that was available in the scientific literature as of 2014. Details and documentation of source materials follow this summary.

Feltleaf willow typically occurs in slightly acidic to mildly alkaline mineral soils that are aerated, relatively nutrient-rich, and well to moderately well drained. Soils in feltleaf willow communities may be underlain by permafrost that thaws deeply in summer. It dominates and is typically dense in early-seral riparian communities on newly exposed alluvial deposits that are periodically flooded. It is also a dominant plant on active sand dunes. It is sparse in riparian upland terraces with balsam poplar, white spruce, and black cottonwood. It occurs occasionally in black spruce and Sitka spruce forest openings. Community structure ranges from open to dense.

Feltleaf willow is a deciduous tree or shrub that sprouts from the root crown, roots from stem fragments, and layers. It has small, lightweight, wind- or water-dispersed seeds. Its seeds readily germinate in high light and in moist mineral soils. It has a transient soil seed bank.

Feltleaf willow is an early-seral species that quickly colonizes moist, disturbed sites. It is shade intolerant. Its density and cover typically peak within 10 to 20 years after disturbance. Flooding and sediment deposition are the most important factors setting back plant succession in feltleaf willow communities.

Low- to moderate-severity fire generally top-kills feltleaf willow plants. Severe fire may kill plants. Feltleaf willows typically sprout if they survive fire. Surviving plants may produce abundant seeds. Seeds are unlikely to survive burning.

Fire severity affects the mode of feltleaf willow postfire recovery. Following low-severity fires, most willows recover quickly, sending up new shoots from root crowns. Few, if any, feltleaf willow seedlings are likely to establish following low-severity fire because organic soils are only partially consumed and prevent establishment. Following severe fires, however, the primary mode of feltleaf willow recovery is likely seedling establishment. Severe fires that burn deeply into organic soils may kill feltleaf willows but expose mineral soils, which provide excellent seed beds for feltleaf willow. Early summer fires that occur prior to seed dispersal are most likely to benefit feltleaf willow because seeds would be available to germinate on the newly burned areas soon after fire.

Fire is not considered an important disturbance in feltleaf willow communities, where the main disturbances are frequent flooding and sediment deposition. Feltleaf willow may occasionally occur after fire in communities, such as black spruce forests, where fire plays a major role in ecosystem dynamics.

Prescribed fire is only occasionally used in feltleaf willow communities. Fire prescriptions and management recommendations for using prescribed fire in feltleaf willow communities are uncommon in the literature. Burning feltleaf willow stands under prescription may be difficult due to wet soils. A variety of wildlife species use feltleaf willow communities as habitat, including moose, snowshoe hares, and willow ptarmigan. Management recommendations include mechanically crushing feltleaf willows to induce sprouting and produce browse for wildlife.


FEIS ABBREVIATION:
SALALA

COMMON NAMES:
feltleaf willow [141]
Alaska willow [17]

TAXONOMY:
The scientific name of feltleaf willow is Salix alaxensis Anderss. Cov. (Salicaceae) [17,52,70,72]. Two varieties, overlapping in geographic range but differing in physical characteristics [17,97], are recognized:

Salix alaxensis var. alaxensis [17,76,113,128]
Salix alaxensis var. longistylus (Rydb.) Schneid. [17,76,113,128,141]

Potential hybrids between feltleaf willow and grayleaf willow (Hultén 1943 cited in [113]), woolly willow [29], and Richardson willow (Argus 1973 cited in [17]) were reported.

See the Appendix for scientific names of lichens and plants named in this review and for links to available FEIS reviews.

SYNONYMS:
Salix alaxensis subsp. alaxensis [70]
Salix alaxensis subsp. longistylis (Rydb.) Hult. [70,73]
Salix longistylis Rydb.[113,141]
Salix speciosa Hoo

LIFE FORM:
Tree-shrub

DISTRIBUTION AND OCCURRENCE

SPECIES: Salix alaxensis
GENERAL DISTRIBUTION:
Figure 2. Distribution of feltleaf willow by state and province. Green indicates that feltleaf willow is present. Map courtesy of the PLANTS Database [128].

Feltleaf willow is native to northern North America and eastern Siberia. In North America, it occurs from Alaska south to British Columbia to about 53 °N latitude, east to Québec, and north to Nunavut [17,70,72,97].

States and provinces [128]:
United States: AK
Canada: AB, BC, MB, NT, NU, QC, YT

SITE CHARACTERISTICS AND PLANT COMMUNITIES:
Site characteristics: Feltleaf willow occurs on flat to steep slopes from coastal to alpine zones. It typically occurs in slightly acid to slightly alkaline mineral soils that are aerated, relatively nutrient-rich, and well to moderately well drained. Soils in feltleaf willow communities may be underlain by permafrost that thaws deeply in summer. Feltleaf willow occurs in northern climates with large seasonal variations in light and temperature and short growing seasons. Topography: Feltleaf willow occurs on all aspects [45,119] and on flat to steep slopes (0%-78%) [12,13,30,45,76,89,95,119]. It is very common on floodplains [30,45,76,113], outwash fans [76], glacial moraines [76,95,97], and active sand dunes [13,89,147] in the Low and High Arctic and Taiga [10,88].

Elevation: Feltleaf willow occurs from coastal up to montane and alpine zones [17,45,70,88,103], but it is less common at high elevations [11].

Soils: Feltleaf willow typically occurs in mineral soils. It is most common in gravel but is also common in sand and silt [11,17,61,71,76,112,113,137,143]. Organic soils in feltleaf willow communities tend to be absent or thin [13,137,143], while litter cover is variable [13,51]. In a 10- to 20-year-old feltleaf willow floodplain community along the Tanana River in interior Alaska, organic soil layers were thin and thoroughly mixed with recent flood deposits of silt and sand [143]. Feltleaf willow occurred on linear sand dunes of the Copper River Delta in southeastern Alaska. The dunes had no soil horizon development and thin litter cover [13]. On western Victoria Island in the Northwest Territories, litter was 2 to 4 inches (4-10 cm) deep in dense feltleaf willow stands. Soils were primarily coarse gravel with variable amounts of sand [51].

Feltleaf willow is most common in slightly acidic to mildly alkaline soils (6.2-7.6 pH) (e.g., [112,119]).

Feltleaf willow occurs in wet to dry soils [76,89] that are well drained to moderately well drained [13,51,61,89,95,112]. feltleaf willows typically establish in soils that are moist and periodically flooded, but individuals may persist in dry, unflooded soils [102] (see Seedling establishment and plant growth). Soils are typically aerated [51,78]. Feltleaf willow is considered a facultative species in Alaska, meaning that it is equally likely to occur in wetlands and nonwetlands [105,128].

Permafrost commonly underlies feltleaf willow communities [61]. Where permafrost occurs in feltleaf willow communities, soils are typically deeply thawed (3-5 feet (1-1.5 m)) in summer [10,11,61,112,119], which provides large rooting space and favorable soil temperatures for feltleaf willow [112]. Along main river channels in Alaska and Canada where water runs nearly year-round, feltleaf willow may grow near the river channels where ground does not completely freeze or freezes only for a short period during winter [51,137]. Viereck [137] examined soil temperature changes during plant succession at 4 sites along the Chena River in interior Alaska that represented a successional sequence from early successional stages dominated by feltleaf willow (along the floodplain and low terraces), through intermediate stages dominated by balsam poplar and white spruce, to late successional stages dominated by white spruce and black spruce (on upper terraces). In feltleaf willow stands, soils 1) thawed earlier in spring, 2) were warmer during summer, and 3) froze earlier and deeper in fall than in the other communities. Soils froze latest in the white spruce and white spruce-black spruce stands due to a thick, insulating moss layer. He concluded that floodplain feltleaf willow stands without permafrost would eventually succeed to upper terraces of white spruce and black spruce and then to black spruce wetlands with permafrost [137]. Reduced active layer depth, lower soil temperatures, and higher soil moisture apparently reduce the competitiveness of feltleaf willow on upper terraces [112].

Soils in lowland riparian feltleaf willow communities often contain higher nutrient levels than adjacent uplands [10,51]. Nonetheless, soils in feltleaf willow communities often have low nitrogen availability and very low organic matter content [112].

Climate: Feltleaf willow occurs in northern climates with large seasonal variations in light and temperature and short growing seasons [10]. It occurs throughout Alaska, where the climate varies from maritime with abundant precipitation along coastal areas in the south-central and southeastern regions to dry continental with temperature extremes in the interior. The record low and high temperatures are -80 and 100 °F (-62 and 38 °C), respectively. Abrupt spring and fall temperature changes are common. Southern coastal areas average 145 freeze-free days, while interior lowland basins average <100 freeze-free days [88].

Plant communities: Feltleaf willow dominates and is typically dense in early-seral riparian communities on newly exposed alluvial deposits that are periodically flooded (e.g., [47,70,76,88,95,129,139,141,142,143]). It is also dominant on active sand dunes [13,89,102,142,147]. Sand dune communities typically have only sparse plant cover (<1%), and the bases of feltleaf willows are often buried by wind-deposited sand [89].

Feltleaf willow frequently occurs along shores of lakes and ponds [30,76,88,89,97,113], on mesic talus slopes [36,76,95], and in tall shrub tundra [10]. It is sparse in upland riparian terraces dominated by balsam poplar, white spruce [89,134], and/or black cottonwood [63,89]. It occurs occasionally in black spruce [76,137,140,141] and Sitka spruce [37] forest openings.

BOTANICAL AND ECOLOGICAL CHARACTERISTICS

SPECIES: Salix alaxensis
This review includes information for many of the life history aspects of the species, but focuses on those life history aspects most relevant to fire. GENERAL BOTANICAL CHARACTERISTICS:
Botanical description: This description covers characteristics that may be relevant to fire ecology and is not meant for identification. Keys for identification are available (e.g., [17,52,70,97,113,141]).

Morphology: Feltleaf willow is a tree or shrub 2 to 33 feet (0.5-10 m) tall [17,52,89,97,141]. It typically grows in clumps of 5 to 20 stems [51]. Branches are typically erect, but in exposed High Arctic and alpine sites feltleaf willow may have a prostrate or semiprostrate form [17,76,141]. Trunks may be 4 to 7 inches (10-18 cm) in diameter [141]. Heavy browsing commonly hedges feltleaf willows [20,75,125].

Leaves are deciduous, alternate, and simple. They are 2.0 to 4.3 inches (5-11 cm) long and 0.4 to 1.6 inches (1-4 cm) wide [52,76,141].

The inflorescence is a catkin. Male catkins are 1.2 to 2.0 inches (3-5 cm) long, and female catkins are 2.0 to 5.9 (5-15 cm) long [97]. The fruit is a capsule, which splits open to release the seeds. A tuft of hairs plumes each seed [76].

Willow roots are typically shallow [69]. Feltleaf willow sometimes forms adventitious roots [78].

Stand structure: Feltleaf willow stands are open to closed [45,88,134]. Closed feltleaf willow stands (canopy closure >75%) are characteristic of floodplains and outwash deposits, while open feltleaf willow stands (canopy closure 25%-74%) occupy a variety of sites from sand dunes to riverbanks [134]. Along the Tanana River floodplain near Fairbanks, feltleaf willow density was approximately 8,300 stems/ha in 8-year-old stands and 30,000 stems/ha in 15-year-old stands [151]. On the Susitna River floodplain in south-central Alaska, there were approximately 8,600 feltleaf willow stems/ha [32].

Feltleaf willows may live >80 years [51,149]. On western Victoria Island, the oldest feltleaf willow was 81 years old; 3- to 7-foot (1-2 m) tall feltleaf willows ranged from 21 to 56 years old and 5- to 7-foot (1.5-2 m) tall feltleaf willows were ≥45 years old. The youngest willows occurred closest to the active river channel, while the oldest occurred farthest away [51]. On the Tanana River floodplain, the youngest feltleaf willows (mean: 6.7 years old) occurred on vegetated siltbars and the oldest (mean: 47 years old) occurred on upper balsam poplar terraces [144].

Raunkiaer [104] life form:
Phanerophyte

SEASONAL DEVELOPMENT:
Feltleaf willow catkins appear and pollination occurs in spring before leaves emerge [52,76]. In Alaska, flowering and seed dispersal occur from May to July [4,63,77,93,141,148,159,160,161]. In general, seeds are dispersed later as latitude and elevation increase [44]. Seed dispersal often coincides with receding spring floodwaters, when newly exposed mineral soil seedbeds are moist [63,96,144]. Feltleaf willow is often one of the first willows to disperse seeds in interior Alaska [158]. The rate of seed dispersal in willows depends on weather. Under warm, dry, windy conditions, all seeds may be dispersed within a few days. Under wet, cool conditions, dispersal may be spread out over a month [161]. Leaf senescence had begun by 6 August on the Sagavanirktok River floodplain in Arctic Alaska [93].

REGENERATION PROCESSES:
Feltleaf willow reproduces by seed, by sprouting from root crowns or stem bases, and by rooting of stems. It produces abundant, lightweight seeds that are dispersed by wind and water. It has a transient soil seed bank. Fresh feltleaf willow seeds germinate on moist seedbeds, often at rates exceeding 90%. Wet to moist mineral soils are the best germination substrates. Several years without extreme flooding may be needed for feltleaf willow seedlings to establish. Feltleaf willow grows best under high light in wet to moist soils. The fastest-growing feltleaf willows occur closest to active river channels. Rooting of feltleaf willow stem fragments is a potentially important means of floodplain colonization by feltleaf willow, although establishment by seed is apparently more common. Pollination and breeding system: Insects, such as bumblebees, pollinate feltleaf willows [148]. Feltleaf willow is dioecious [18,161].

Seed production: Feltleaf willows may produce abundant seeds [93]. In feltleaf willow communities along river floodplains in Alaska, feltleaf willow produced from 131 to 380 viable seeds/m² [93,144]. However, feltleaf willow may not produce catkins every year. At 3 sites on the Sagavanirktok River floodplain, 58% to 78% of individuals produced catkins in 1979, and 33% to 67% produced catkins the following year [93].

Feltleaf willow sprouts may flower at 3 years old [23], while plants established from seeds flower at approximately 6 to 10 years old [93]. Seed production peaked at approximately 15 to 20 years old on the Sagavanirktok River floodplain. The most fecund plants generally grew where herbs and low shrubs were not well developed and mineral soil was exposed. These areas were periodically flooded [93].

Heavy browsing may reduce catkin abundance and thus seed production [161]. For more information, see Importance to Wildlife and Livestock.

Figure 3. Close-up of female feltleaf willow catkins along the Meade River, Alaska. Photo courtesy of the Alaska Geobotany Center.

Seed dispersal: Wind and water disperse the small, lightweight, plumed seeds [44,93,100,161]. Feltleaf willow seeds can disperse long distances, but most seeds land near the parent plant [93]. Willow seeds are often concentrated on the downwind side of isolated pools of water or at the edges of receding pools [158].

Seed banking: Feltleaf willow has a transient soil seed bank [44,50,110,144,161]. Under field conditions, feltleaf willow seeds remain viable for up to about 4 weeks, depending on ambient temperature and humidity [44,163].

Germination: Feltleaf willow seeds do not show dormancy. Viable feltleaf willow seeds germinate in high light within 1 day of dispersal on moist seedbeds [44]. Germination of new seeds is high, often exceeding 90%. Feltleaf willow seeds germinate at a range of temperatures [44,159,160]. In a laboratory, good germination (94%-97%) occurred at temperatures from 41 to 77 °F (5-25 °C) [160]. Stratification is not required [44,159,160]. Continual freezing in a laboratory can preserve viability of feltleaf willow seeds for at least 3 years, although germination rates of frozen seeds are less than that of fresh seeds (59%-74% for seeds frozen 36 months) [160].

High soil moisture is important to feltleaf willow germination [8,161]. In a laboratory, Feltleaf willow seeds collected from riverbars in interior Alaska germinated under water [77]. In the field, the highest feltleaf willow germination percentages of previously frozen seeds occurred in plots that were watered regularly (3.2% germination) and in plots in which stones had been added (1.2%). Stones apparently provided "safe sites" protected from the drying effects of wind and sun [8].

Moist mineral soil is typically the most suitable substrate for feltleaf willow germination, but other substrates, such as moss, are adequate when moist [8,161]. Feltleaf willow germinated on a variety of mineral soils on the Sagavanirktok River floodplain, provided they were moist [93]. Densmore and Zasada [44] observed rapid germination of feltleaf willow seeds on wet silt and in shallow water on the Tanana River floodplain; many seeds germinated within 24 hours after reaching the seedbed. On moist silt, seeds germinated only after 48 hours. Hypocotyl hairs (which anchor seedlings to substrates) were less developed on moist than wet silt [44]. Forest litter prevents feltleaf willow germination [144]. In thinleaf alder, balsam poplar, and white spruce communities on the Tanana River floodplain, germination of sown feltleaf willow seeds was 0% on forest litter. It ranged from 16% to 18% where forest litter was removed and mineral soil exposed [144].

Seed dispersal in feltleaf willow normally coincides with the retreat of spring floodwaters, when soil moisture is favorable for germination [77,144]. Bare gravel with shallow subsurface water movement provides some of the best germination substrate [41]. Silt is often moist enough for feltleaf willow establishment, while sand is rarely moist enough. Only during unusually wet years will soils on sandy sites be moist enough for germination to occur [77]. In a gravel mine on the North Slope, all moist gravels were rapidly colonized by feltleaf willow; moist silts were rapidly colonized by a mixture of feltleaf willow and low-statured willows; and dry soils were colonized by low-statured willows or no willows [41]. Along the Tanana River, feltleaf willow and sandbar willow were more common than balsam poplar on wet, frequently inundated sites. Only balsam poplar and sandbar willow were commonly found on xeric, sandy sites. All 3 species grew on mesic, silty sites [77].

Seedling establishment and plant growth: Feltleaf willow establishes in mineral substrates that are moist throughout the growing season [100], and recruitment may be infrequent. Studies in interior Alaska along Birch Creek [35] and the Tanana River [77] found few feltleaf willow seedlings established in dry mineral soils. Late ice breakup in spring delayed feltleaf willow seed production and thus dispersal on the Mackenzie River Delta in the Northwest Territories during 2 years, leaving a very short period for seedlings to grow large enough to survive ice breakup, flooding, and sedimentation the following spring. Unusually warm temperatures and low rainfall during the 2 growing seasons reduced feltleaf willow establishment. Feltleaf willow age structure indicated that recruitment occurred infrequently. The authors concluded that feltleaf willow recruitment may only occur in years when spring ice breakup is early and summer rainfall is sufficient to provide moist soils [100]. Moore [93] concluded that warm weather and lack of rain during seed dispersal probably accounted for low seedling recruitment on the Sagavanirktok River floodplain [93].

Several years without extreme flooding may be needed for feltleaf willow seedlings to establish [144]. Moore [93] reported high mortality of feltleaf willow seedlings on the Sagavanirktok River floodplain due to burial and erosion caused by spring flooding. Extreme flooding and silt deposition killed many 1- and 2-year-old feltleaf willows on siltbars of the Tanana River floodplain [144]. Mature feltleaf willows can apparently withstand flooding for >2 weeks [100].

Seedlings can be particularly dense on freshly deposited river alluvium [93]. Seedlings were dense along the Sagavanirktok River (up to 1,210 seedlings/m²). Seedling establishment was apparently the primary means of gravelbar colonization, although feltleaf willow stems occasionally washed up and rooted on gravelbars [93]. Establishment by seed appeared to be the most common means of feltleaf willow colonization on the Mackenzie River Delta (Gill 1971 cited in [93]) and on the Tanana River floodplain [144,155]. However, Bliss and Cantlon [11] noticed only a few feltleaf willow seedlings on gravelbars of the Colville River near Umiat in Arctic Alaska, but they observed numerous examples of vegetative propagation from clumps of feltleaf willows eroded from cut banks upstream and deposited on gravelbars. At the Oumalik Test Well site on the Arctic Coastal Plain in Alaska, feltleaf willow apparently originated from seeds dispersed to the site after disturbance rather than by vegetative means [50].

Several studies noted the importance of moist, exposed mineral substrates and sparse vegetation for optimal establishment and growth of feltleaf willows [43]. Along a tributary of the upper Atigun River in the central Brooks Range, Alaska, feltleaf willow reached maximum height where exposed gravel was present and the total vascular plant cover was relatively low [43]. On the Sagavanirktok River floodplain, feltleaf willow established where mineral soils were moist most of the summer, where other vegetation was sparse, and when flooding and other physical disturbances were minimal [93]. Establishment of nonnative species may inhibit the establishment and growth of feltleaf willow. For more information, see Nonnative species.

Feltleaf willow grows best under full light [17,56,116,137,161].

Feltleaf willow plants are "fast-growing" [26]. Feltleaf willow may produce first-order branches during its first growing season [158]. On the Tanana River floodplain, 15- to 56-day-old feltleaf willow seedlings averaged 7 inches (18 cm) tall [78]. An 8-year-old feltleaf willow stem found on gravel deposits following deglaciation in Glacier Bay was 8 feet (2.4 m) tall and 2 inches (5 cm) in basal diameter [37]. On western Victoria Island, feltleaf willows grew most quickly in locations close to the river channel: >5-year-old feltleaf willows on stabilized bars 100 to 160 feet (30-50 m) from the active river channel had the largest annual growth (0.04-0.05 inch (0.9-1.2 mm) per year)) and greatest height (20-30 feet (6-9 m)) increments. The smallest annual growth increments (0.004-0.01 inch (0.1-0.3 mm) per year)) occurred farthest from the active channel [51]. Roots normally grow 2 inches (5 cm) deep in 1 growing season [43] and may grow 11 inches (29 cm) deep in 2 growing seasons [35].

Abundant winter precipitation may benefit feltleaf willow. Feltleaf willow ring widths of plants along the Kuujjua River on Victoria Island, Northwest Territories, were positively correlated with winter precipitation and thus the amount of spring flooding [157].

Sediment deposits may stimulate the formation of adventitious roots by feltleaf willow. Feltleaf willow occupies sites that may receive large amounts of sediment (2-4 inches (5-10 cm)) during spring ice breakup and flooding [100]. On the Tanana River floodplain, the number of adventitious roots per feltleaf willow seedling was positively correlated with the depth of silt deposited after flooding (r²=0.54, P<0.01) [78]. Bliss and Cantlon [11] noted that the best development of feltleaf willow along the Colville River occurred near or adjacent to the stream channel, where flooding occurs each spring.

Vegetative regeneration: Feltleaf willow sprouts from the root crown or stem base if aboveground stems are top-killed by herbivory, insects, flooding, or fire [54,57,64,77,125,155], or if the canopy permits light penetration to the base of clumps [51]. Young stems may sprout more readily than large or old stems [57]. Feltleaf willow also reproduces vegetatively by layering. Bent or broken stems quickly form adventitious roots along their length if buried and kept moist [42,64,68,77,158,161]. Thus, feltleaf willow stem fragments buried in sand and silt by floodwaters commonly develop new shoots and roots [42,93]. Feltleaf willow stem cuttings on severely burned areas in interior Alaska grew best where most of the organic layer was removed; even a shallow organic layer limited the growth of stem cuttings [162]. Large numbers of feltleaf willow stems may be shed each year. On the Tanana River floodplain, stems were shed from a range of age classes and branch orders [93]. Rooting of stem fragments that are washed downstream is a potentially important means of colonization by feltleaf willow [77], although seedling establishment appears more common [93,144]. Feltleaf willow does not regenerate from root fragments [68,158,161].

SUCCESSIONAL STATUS:
Feltleaf willow is an early-seral species [132]. It is shade intolerant [17,56,116,137]. Flooding and sediment deposition are the most important factors setting back plant succession in feltleaf willow communities [93,95,123]. Feltleaf willow communities are usually short-lived. Density and cover peak within approximately 10 to 20 years after disturbance [24,64,74,133,144,155]. Rapid sprouting, abundant wind-dispersed seed, and rapid germination allow feltleaf willow to quickly colonize moist, disturbed sites [10,77,100,139]. It is one of the first species to colonize newly formed gravel, sand, and silt riverbars [139]. It also pioneers on sand dunes [102]; recently deglaciated sites [95,106,136]; burns [38,99]; and sites disturbed by mining [39,41], road construction [8,9,74], and oil drilling [50]. Floodplains: The generalized pathway of floodplain primary succession in the Alaskan taiga starts with a bare alluvium stage and progresses through stands dominated by feltleaf willow, alder (thinleaf alder or mountain alder, depending on latitude and elevation), balsam poplar, white spruce, and finally black spruce (e.g., [1,20,47,65,129,132,135,137,139,143]). Alder often establishes within 5 years of initial feltleaf willow colonization [139]. The development of an alder overstory coincides with reduced feltleaf willow density [32,144]. Heavy browsing of feltleaf willow by snowshoe hare, moose, and possibly willow ptarmigan may accelerate the decline of feltleaf willows in these early-seral stands [20,26,64,125,144]. Balsam poplar often establishes with or shortly after alder and begins to dominate 20 to 30 years after feltleaf willow first colonizes the site. By this stage in succession, overstory shade has reduced feltleaf willow to a few scattered individuals [139]. On the Tanana River floodplain, the oldest feltleaf willow was 48 years old and was found in the balsam poplar stage of succession [144] (see Stand structure). Succession may be interrupted at any stage by frequent flooding, ice scouring, shifting channels, and sediment deposition [93,95].

Above treeline in Alaska, floodplain succession generally progresses from a pioneer perennial herb community to an feltleaf willow community. This is followed by a low-statured mountain alder-willow-heath community, and finally to cottongrass tussock-heath tundra or wet sedge tundra as depth of thaw increases [10,11,12,41,118]. Vegetation succession is determined in part by substrate and moisture availability. Feltleaf willow stands are most likely to establish on gravelbars. As silt accumulates on these bars, low-statured willows establish to form a mixed stand. Occasionally the initial substrate is silty and a mixed stand may establish immediately [11,41,93].

Dunes: American dunegrass and feltleaf willow are important pioneer species on open sand dunes. Entireleaf mountain-avens and red fruit bearberry succeed the pioneer stage in areas with moderate rates of sand deposition. Feltleaf willow persists in this stage of dune succession by rooting of stems as sand accumulates around plants [102]. Mountain-avens persists and forms mats as dunes stabilize [10,102]. Mountain-avens mats eventually succeed to communities characterized by witch's hair lichen and dwarf evergreen shrubs [102].

Deglaciated sites: In southeastern Alaska, the primary successional sequence following glacial retreat starts with a mountain-avens-perennial herb stage, followed by Sitka alder-feltleaf willow-Sitka willow thickets, Sitka spruce-black cottonwood transition forest, Sitka spruce forest, western hemlock-mountain hemlock forest, and finally muskeg. Feltleaf willow is present in the first 3 stages of succession and is densest in the alder-willow thicket stage [2,37,106].

Burns: Feltleaf willow is common after fire. It was present in mesic willow-polargrass-tall cottongrass communities within 4 years of pile burning on the Oumalik Test Well site [49]. In the Lower Sheenjek River Valley in northeastern Alaska, feltleaf willow was one of the dominant plants on 2 "recent" wildfire burns [80]. It was common on an 11-year-old burn in bottomland black spruce forest in interior Alaska. At this site, feltleaf willow, grayleaf willow, and tea-leaf willow constituted 11,757 shrubs/ha [155]. A generalized pathway of postfire succession in mesic black spruce sites starts with a newly burned stage (~0-1 years after fire), followed by a moss-herb stage (~1-5 years after fire). These are followed by a tall shrub-sapling stage (~5-30 years after fire), a dense tree stage (~30-55 years after fire), a mixed hardwood-black spruce stage (~56-90 years after fire), and finally, a black spruce stage (~91+ years after fire). In various locations in interior Alaska, feltleaf willow was densest (25 stems/ha) in the tall shrub-sapling stage and the mixed hardwood-black spruce stage (16 stems/ha) and absent from the other stages [53]. See the Research Paper of Foote's [53] study for detailed information.

FIRE EFFECTS AND MANAGEMENT

SPECIES: Salix alaxensis
FIRE EFFECTS:
Immediate fire effects on plant: Low- to moderate-severity fire likely top-kills feltleaf willow. Severe fire may kill feltleaf willow plants, but as of this writing (2014), no studies reported feltleaf willow mortality due to fire.

Immediate fire effects on seeds: The thin, soft seed coat and little or no endosperm of feltleaf willow seeds seem to provide little protection to the embryo from the high temperatures of fire. Thus, feltleaf willow seeds are unlikely to survive burning [138].

Postfire regeneration strategy [122]:
Tree with adventitious buds and a sprouting root crown
Tall shrub with adventitious buds and a sprouting root crown
Small shrub with adventitious buds and a sprouting root crown
Initial off-site colonizer (off site, initial community)

Fire adaptations and plant response to fire:
Fire adaptations: Feltleaf willow sprouts from the root crown following fire [54,155]. Sprouts likely develop more rapidly than seedlings after fire [60,155]. Feltleaf willow's lightweight seeds may be dispersed by wind or water after fire [44,93,100,161]. Its seeds readily germinate in high light and in moist mineral soils [44]. It has a transient soil seed bank [44,50,110,144,161]. Out of 30 species examined in black spruce forests in interior Alaska, feltleaf willow ranked moderate in expected occurrence after fire. It occurred in plots after low-, moderate-, and high-severity fires in 14 black spruce communities that burned during wildfires in 2004, even though it was not observed in these plots before the fires [6,7].

Plant response to fire: Feltleaf willows typically sprout after fire [54,155]. Feltleaf willow has a transient soil seed bank [44,50,110,144,161], and seeds are unlikely to survive fire if burned [138] (see Immediate fire effects on seeds). However, wind and water may disperse seeds from nearby sources [44,93,100,161], and surviving on-site plants may produce abundant seeds [93] soon after fire.

Fire severity affects the mode of feltleaf willow postfire recovery. Following low-severity fires, most willows recover quickly, sending up new shoots from root crowns. Few, if any, willow seedlings establish following low-severity fire because organic soils are only partially consumed and prevent establishment. Following severe fires, however, the primary mode of willow recovery is seedling establishment. Severe fires that burn deeply into organic soils may kill willows but expose mineral soils, which provide excellent seedbeds for willows, including feltleaf willow [163]. A comparison of prefire and postfire vegetation at 14 burned black spruce forest sites burned in wildfires in interior Alaska during 2004 found that there was an increase in feltleaf willow occurrence in 900-m² plots, especially on high-severity and high-moisture sites [66]. Following experimental fires on black spruce/feather moss sites in interior Alaska, artificially sown feltleaf willow seeds germinated only on plots where fire removed all organic matter. On these plots, 181 seedlings out of 400 survived 3 growing seasons, but no seedlings survived on plots where burning only partially removed organic soil layers (Table 1) [163]. See the Research Project Summary of Zasada and others' [48,162,163] studies for detailed information.

Table 1. Total number of feltleaf willow germinants and willow seedlings on moderate- and high-severity plots [163]
Germinants
1st-year seedlings
3rd-year seedlings
Moderate
severity
High
severity
Moderate
severity
High
severity
Moderate
severity
High
severity
Artificial regeneration of feltleaf willow
1 400 0 278 0 181
Natural regeneration of willows
0 0 0 0 0 13

Because willow seeds are viable for only a few weeks, the time of fire may be important in determining which species of willow colonizes a burn the first postfire year [138]. Early-summer fires that occur prior to seed dispersal are most likely to favor feltleaf willow because newly dispersed seeds would be available to germinate on burned areas soon after fire. Late-summer fires are more likely to favor willows that disperse seeds in late summer and fall, such as grayleaf willow [138,158].

For further information on prescribed fire and postfire response of feltleaf willow and other plant species in Alaskan taiga, see these Fire Studies:

FUELS AND FIRE REGIMES:
Fuels: Feltleaf willow stands on floodplains are moist and commonly contain few fine fuels, such as grass, so they do not burn readily [98]. However, total fuel loadings in feltleaf willow communities can be abundant. Mean total biomass of feltleaf willow can exceed 5,500 kg/ha [83,84,121,133].

Fire regimes: Fire is not considered an important disturbance in feltleaf willow communities, where the main disturbance processes are frequent flooding and sediment deposition. Suarez and others [123] found no evidence of fire in a white spruce/feltleaf willow-grayleaf willow-bog blueberry community along the Agashashok River in northwestern Alaska. Parminter [99] stated that alluvial balsam poplar-white spruce floodplain forests of northern British Columbia owe their existence to fluvial processes and "have not been influenced by fire to a significant degree, if at all". Feltleaf willow may occasionally occur after fire in communities, such as black spruce forests, where fire plays a major role in ecosystem dynamics [38,99].

Find 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 MANAGEMENT CONSIDERATIONS:
Prescribed fire is only occasionally used in feltleaf willow communities (e.g., [48,49,162,163]). Therefore, fire prescriptions and management recommendations for using prescribed fire in feltleaf willow communities were uncommon in the literature. On the Yukon Flats National Wildlife Refuge, Alaska, fire managers noted the difficulty of burning feltleaf willow stands under prescription because the sites were "too wet to burn" in early July [55].

MANAGEMENT CONSIDERATIONS

SPECIES: Salix alaxensis
FEDERAL LEGAL STATUS:
None

OTHER STATUS:
Information on state- and province-level protection status of plants in the United States and Canada is available at NatureServe.

IMPORTANCE TO WILDLIFE AND LIVESTOCK:
Mammals: Feltleaf willow is a very important browse species for moose, particularly in winter [4,25,32,58,84,91,101,107,109,151]. When browsing, moose often break and pull down feltleaf willow branches and trunks up to 1.5 inches (4 cm) in diameter [141]. Milke [90] considered feltleaf willow one of the most important moose browse species in interior Alaska because of its high palatability, wide distribution, and relatively high abundance. In some areas of the North Slope, it provided >95% of winter moose browse (Neiland and others 1981 cited in [41]). Mean browsing intensity of feltleaf willow by moose in 14 stands in Denali National Park was 65% (range: 35%-86%); browsing was heavier in pure feltleaf willow stands than in mixed stands [154]. Moose forage preferentially on new growth of previously browsed plants [14,15,92]. Use of feltleaf willow by moose in winter may increase in years of deep snow and decrease in years of shallow snow. In the Tyone Creek and Oshetna River drainages in Alaska, winter use of feltleaf willow ranged from a high of 82% during a winter of record deep snow to a low of 12% during a winter of shallow snow (P<0.01) [31]. Feltleaf willow is also important browse for caribou, reindeer [79,115,147], and muskoxen [51,111,147].

Numerous small mammals eat feltleaf willow. Feltleaf willow is highly preferred food of snowshoe hares [25,56,152], Alaskan hares [3], and arctic ground squirrels [5].

Birds: During winter, willow ptarmigan feed preferentially on feltleaf willow, which may make up to 80% of their diet [22,145]. In April and May, willow ptarmigan consumed feltleaf willow catkins until the supply was "completely exhausted" [94]. Northeast of Toolik Lake, willow ptarmigan browsed 42% of feltleaf willow buds [125]. Snow depth affects willow ptarmigan browsing of feltleaf willow. In an area of tall riparian shrublands at Toolik Lake Field Station, 3% of feltleaf willow buds buried beneath the snow were browsed, 90% of buds <12 inches (30 cm) above the maximum snow depth were browsed, and 45% of buds above that height were browsed [125].

Insects: See these sources for information on insects common on feltleaf willow: [57,85,87].

Palatability and nutritional value: Feltleaf willow is highly palatable to moose [108]. A review stated that high moisture, protein, and caloric contents of feltleaf willow likely explain the high preference of feltleaf willow to moose [101]. Concentrations of phenolic compounds in feltleaf willow were the lowest of 8 tree and shrub species tested in Denali National Park and Preserve, but concentrations of condensed tannins were highest [109].

Feltleaf willow is moderately to highly palatable to snowshoe hares [21,23,114]. Feltleaf willow palatability to snowshoe hares increases with increased shading and increased soil nutrients [19,20,21]. Rohleder (1985 cited in [20]) found that feltleaf willow growing under alder on the floodplain of the Chena River near Fairbanks, Alaska, was 4 times more palatable to snowshoe hares than feltleaf willow grown in full sun [20]. Feltleaf willow stump sprouts were less palatable to snowshoe hares than mature twigs from adult plants in laboratory feeding trials. Sprouts came from the confluence of the Tanana and Chena rivers near Fairbanks [23,114].

For information on nutrient concentrations in feltleaf willow, see these studies: [15,20,82,109,114,126,130,131,146].

Cover value: Feltleaf willow communities provide cover and habitat for wildlife, including moose [46,59,81,91,124,127], muskoxen [111], snowshoe hares [153], willow ptarmigan [94], and undoubtedly numerous other species. Feltleaf willow was one of the most common species used for nest sites by yellow warblers in Churchill, Manitoba [150]. In summer, brown bears in Denali National Park frequently foraged in feltleaf willow-alpine sweetvetch communities in alpine areas along the Toklat River [120].

VALUE FOR REHABILITATION OF DISTURBED SITES:
Within its range, feltleaf willow is recommended for wildlife habitat restoration, streambank protection, erosion control, and reclamation of sites disturbed by mining and construction (e.g., [8,28,35,41,74,97,156]). Feltleaf willow stem cuttings successfully established on sites disturbed by pipeline construction in Alaska [41] and in the Northwest Territories [86]. Cultivars for rehabilitation have been developed [27,156]. General methods of planting feltleaf willow on disturbed sites in Alaska are: 1) planting stem cuttings [41,42,68,86], 2) transplanting containerized, rooted stem cuttings or seedlings [8,40,156], 3) planting bundles of dormant stems cuttings [156], and 4) planting seeds [35]. For information on collecting, storing, and planting feltleaf willow seeds and stem cuttings, see these sources: [67,68,161].

OTHER USES:
Several authors reported that Alaskan Natives ate the inner bark of feltleaf willow [62,70,141]. The young, tender leaves were also eaten [62].

OTHER MANAGEMENT CONSIDERATIONS:
Nonnative Species: Nonnative, invasive yellow sweetclover appears to inhibit feltleaf willow recruitment and growth. A removal study along the Healy and Nenana rivers, Alaska, found that dense patches of yellow sweetclover reduced recruitment of feltleaf willow during the earliest seral stages of glacial floodplain succession, apparently due to shading. Feltleaf willow seedlings growing in plots with yellow sweetclover had lower survival rates than seedlings growing with native vegetation (P<0.05) [116,117]. Along the Stikine River, Alaska, feltleaf willow importance was highest in belt transects where yellow sweetclover importance was low, suggesting a negative competitive interaction [33,34].

Seeding with nonnative grasses may reduce feltleaf willow density and cover. Along the Atigun River in the central Brooks Range, feltleaf willow density, cover, and branch length were less on 11-year-old disturbed sites that were fertilized and seeded with nonnative red fescue than on adjacent disturbed sites that were naturally revegetated. Red fescue probably reduced soil moisture in the upper soil profile [43].

Browse Management: Feltleaf willow has been cut to produce browse for wildlife. Three years after mechanically crushing 660- to 2,620-foot (200-800 m) wide strips in interior Alaska, the number of feltleaf willow stems available to moose was greater on crushed sites than on an uncrushed site [16].

APPENDIX: Lichen and plant species mentioned in this review


This table includes a list of lichen and plant species mentioned in this review. For further information on fire effects, follow the highlighted links to the FEIS reviews on these taxa.

Common name Scientific name
Lichens
witch's hair lichen Alectoria spp.
Bryophytes
feather moss Hylocomiaceae
Fern allies
horsetail Equisetum spp.
Forbs
alpine sweetvetch Hedysarum alpinum
yellow sweetclover Melilotus officinalis
Graminoids
American dunegrass Leymus mollis
cottongrass Eriophorum spp.
red fescue Festuca rubra
sedge Carex spp.
tall cottongrass Eriophorum angustifolium
wideleaf polargrass Arctagrostis latifolia
Shrubs
alder Alnus spp.
arctic dwarf birch Betula nana
blueberry willow Salix myrtillifolia
bog blueberry Vaccinium uliginosum
dwarf birch Betula glandulosa
entireleaf mountain-avens Dryas integrifolia
grayleaf willow Salix glauca
heath Ericaceae
mountain alder Alnus viridis subsp. crispa
mountain-avens Dryas spp.
red fruit bearberry Arctostaphylos rubra
Richardson willow Salix richardsonii
sandbar willow Salix interior
Sitka alder Alnus viridis subsp. sinuata
Sitka willow Salix sitchensis
tea-leaf willow Salix planifolia
willow Salix spp.
woolly willow Salix calcicola
Trees
balsam poplar Populus balsamifera subsp. balsamifera
birch Betula spp.
black cottonwood Populus balsamifera subsp. trichocarpa
black spruce Picea mariana
feltleaf willow Salix alaxensis, this review
mountain hemlock Tsuga mertensiana
Scouler willow Salix scouleriana
Sitka spruce Picea sitchensis
thinleaf alder Alnus incana subsp. tenuifolia
western hemlock Tsuga heterophylla
white spruce Picea glauca

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