SPECIES: Fraxinus nigra

Choose from the following categories of information.

• Introductory
• Distribution and occurrence
• Botanical and ecological characteristics
• Fire ecology
• Fire effects
• Management considerations
• References

INTRODUCTORY

DISTRIBUTION AND OCCURRENCE

• GENERAL DISTRIBUTION
• ECOSYSTEMS
• STATES/PROVINCES
• BLM PHYSIOGRAPHIC REGIONS
• KUCHLER PLANT ASSOCIATIONS
• SAF COVER TYPES
• SRM (RANGELAND) COVER TYPES
• HABITAT TYPES AND PLANT COMMUNITIES

American elm (Ulmus americana) is listed as a codominant in many black ash habitat and community type descriptions. It is important to note that many American elm populations declined considerably following the introduction of Dutch elm disease in the early 1930s. Some black ash habitat types and community descriptions are from dated literature, and the presence of American elm may be exaggerated in studies that predate population losses to Dutch elm disease.

Black ash-American elm-red maple forest cover type: The black ash-American elm-red maple (Acer rubrum) forest cover type occurs throughout the northeastern United States and eastern Canada. Of the 3 major species, black ash is most restricted to this vegetation type. In the Great Lake states and the western Canadian Range, balsam poplar (Populus balsamifera ssp. balsamifera), balsam fir (Abies balsamea), and yellow birch (Betula alleghaniensis) are common to this cover type. Silver maple (Acer saccharinum), swamp white oak (Quercus bicolor), sycamore (Platanus occidentalis), pin oak (Q. palustris), black tupelo (Nyssa sylvatica), and eastern cottonwood (Populus deltoides ssp. deltoides) are typical of the black ash-American elm-red maple forests of northern Ohio and Indiana. In New England and eastern Canada, sweet birch (B. lenta), paper birch (B. papyrifera), gray birch (B. populifolia), silver maple, and black spruce (Picea mariana) are common. The cover type in New York is habitat for white ash (Fraxinus americana), slippery elm (U. rubra), rock elm (U. thomasii), yellow birch, black tupelo, sycamore, eastern hemlock (Tsuga canadensis), and bur oak (Q. macrocarpa) [104]. The black ash-American elm-red maple cover type in northern Wisconsin and the Upper Peninsula of Michigan is dominated by black ash. On very poorly drained sites, stands are almost pure black ash, and black ash is considered a climax species [39].

Northeastern U.S. and eastern Canada: Black ash is common to many deciduous, coniferous, and mixed lowland forest types in the eastern U.S. and Canada.

In the northern Great Lake states, the greatest black ash biomass production is reported for elm-ash-maple (Ulmus-Fraxinus-Acer spp.) forests. Black ash biomass yields are 2nd greatest in northern white-cedar (Thuja occidentalis) forests and 3rd greatest in balsam fir forests [113]. Tamarack (Larix laricina), balsam fir, northern white-cedar, and red maple are found with black ash in lowland spruce-fir forests of New England, the Great Lake states, and the boreal region of Canada [12,42]. Black spruce-speckled alder (Alnus rugosa) communities are typical of water-logged soils in eastern Canada, the northern Great Lake states, and Maine [31]. Red spruce (P. rubens)-balsam fir vegetation types extending as far south as West Virginia and as far north as maritime provinces of Canada may include black ash trees [52].

Black ash usually comprises less than 20% of the basal area in sugar maple (Acer saccharum)-dominated vegetation in the Great Lake states, New York, New England, Ontario, Quebec, and portions of the Appalachians. In eastern Canada, black ash occupies sugar maple-yellow birch habitats [48]. In northern Wisconsin, upper Michigan, southern Ontario, and southern Quebec black ash is a "less common associate" of the eastern hemlock-yellow birch vegetation type that grades into black ash-American elm-red maple forests on wetter sites [47].

In wet calcareous mixed woods of the maritime provinces, black ash is dominant, and eastern white-cedar and red maple are both typical. These forests occur on poorly drained organic soils. In the early 1800s, black ash occurred in these forests with 6.5% frequency, but in 1993 the frequency of ash was less than 1%. Land clearing, wetland drainage, and tree harvest practices of European settlers are at least partially responsible for the decline in black ash habitat [78].

Illinois: Black ash is common in Illinois' seep and swamp vegetation where silver maple and green ash (F. pennsylvanica) are also typical [75].

Michigan: In northern Lower Michigan, seasonally flooded black ash-alder (Alnus spp.) swamps experience extreme daily and seasonal temperature changes. Black ash also occupies hardwood swamps where basswood (Tilia americana) and northern white-cedar are typical. Hardwood swamps are also seasonally flooded but do not occur in frost pockets. The basal area of black ash in black ash-alder swamps is 7.1±13.1 (s) m²/ha and in hardwood swamps is 6.1±6 m²/ha [145].

In the Indian Bowl area of southwestern Michigan, black ash occurs in tamarack swamps, thought to be an earlier stage of succession to southern hardwood forest. The Indian Bowl is frequently flooded, has organic soils high in calcium, and occupies elevations of 600 to 750 feet (183-229 m) [68]. On the Isle Royale, black ash occurs in 40-year-old paper birch-aspen (Populus spp.)-white spruce (Picea glauca) stands that revegetated burned areas after a late July fire in 1963 [54].

Minnesota: In Voyageurs National Park, researchers recognize 2 vegetation types dominated by black ash. The black ash-elm/trillium (Trillium ssp.) type occupies moist sites, with deep nutrient-rich soils. This type is uncommon but is considered climax. The black ash/yellow marsh marigold (Caltha palustris) habitat type is a climax type on sites that are better drained than those occupied by black ash-elm/trillium [72]. Buell and Bormann [24] recognize a stable basswood-balsam fir-black ash vegetation type on poorly drained sites of Minnesota's Red Lake Indian Reservation.

In the Lake Agassiz Peatlands of Minnesota, black ash dominates the overstory of swamp forests that lie on peatland edges and receive mineral-rich water. Other typical species may include northern white-cedar, tamarack, black spruce, and speckled alder [55]. In the Boundary Waters Canoe Area, black ash occurs with low frequencies in balsam fir-paper birch and red maple-quaking aspen (Populus tremuloides)-paper birch communities [88].

New York: Black ash is common in swamps and on floodplains of New York. In the Adirondacks, black ash occurs in black spruce swamps. Small northern white-cedar, tamarack, and red maple trees also populate these sites [10]. Red maple dominates the hardwood swamps in poorly drained depressions with inorganic soils throughout New York. Black ash, American elm, swamp white oak, butternut (Juglans cinerea) and/or bitternut hickory (Carya cordiformis) may also associate with red maple hardwood swamps. Green ash, red maple, slippery elm, American hornbeam (Carpinus caroliniana), and northern white-cedar may associate with black ash in lowland sites along the Hudson River. Along rivers and lake shores of central and western New York where conditions are uniformly wet and seasonal water fluctuations are low, silver maple-ash swamps are common. Silver maple often makes up 70% of the canopy cover, but black ash, green ash, and white ash are also typical [97]. Huenneke [60] describes black ash in the eastern hemlock-yellow birch-red maple wet vegetation type near Cayuga Lake.

Ohio: Black ash is a dominant species in closed-canopy lowland forests at an average elevation of 860 feet (262 m) in central Ohio; other common species are American elm, honey-locust (Gleditsia triacanthos), and pin oak [16]. Braun [20] describes black ash in northern coniferous forests, eastern hemlock-pine (Pinus spp.)-northern hardwood forests, and beech-maple forests of Ohio. On poorly drained sites that are part of northwestern Ohio's Black Swamp, black ash occurs with silver maple, green ash, American elm, bur oak, and shellbark hickory (Carya laciniosa) [17]. In swamp forests of west-central Ohio's Cedar Bog, northern white-cedar, red maple, black ash, and yellow-poplar (Liriodendron tulipifera) dominate the overstory [27].

Pennsylvania: Black ash occurs in the pin oak-sweet gum (Liquidambar styraciflua) forest cover type in Gettysburg National Military Park and Eisenhower National Historic Site in south-central Pennsylvania [144].

Vermont: In eastern hemlock-northern hardwood forests of central Vermont, sugar maple, beech, white ash, and yellow birch dominate the canopy, but black ash, basswood, eastern hemlock, and American elm also populate the canopy [18].

Wisconsin: In the black ash-yellow birch-eastern hemlock hardwood swamps of Wisconsin's northern lowland forests, black ash is a mid-sized tree (45-70 feet (14-21 m)) with a narrow crown [30]. In northern white-cedar-balsam fir-black ash swamps of northern Wisconsin, black ash is most important on compacted organic soils that are inundated for much of the growing season [25]. Winget and others [140] describe black ash, northern white-cedar, and yellow birch communities on very poorly drained, black muck soils in northern Wisconsin where even in mid-summer the ground water is just 12 inches (3 cm) beneath the soil surface. Black ash is occasional in southern Wisconsin's elm-ash savannah that is restricted to wet meadow sites. Important canopy species include silver maple, river birch (B. nigra), green ash, and swamp white oak [21].

Manitoba: Black ash is now the dominant overstory species in hardwood and mixed hardwood forests of Manitoba that were dominated by American elm in the past. Boxelder (Acer negundo) often dominates the subcanopy layer. This community occurs along small stream floodplains on deep, loamy-clay soils with poor to very poor drainage [146].

In the early 1970s, black ash colonized the Portage la Prairie grassland area of Manitoba. While this area experiences periodic spring flooding, it does not support the wet conditions most often associated with the distribution of black ash. The successful establishment of black ash in prairie grasslands suggests that high moisture levels are not the only factor limiting the range of black ash. Other tree species associated with the Portage la Prairie include bur oak, American elm, green ash, and red-osier dogwood (Cornus sericea ssp. sericea) [102].

BOTANICAL AND ECOLOGICAL CHARACTERISTICS

• GENERAL BOTANICAL CHARACTERISTICS
• RAUNKIAER LIFE FORM
• REGENERATION PROCESSES
• SITE CHARACTERISTICS
• SUCCESSIONAL STATUS
• SEASONAL DEVELOPMENT

Black ash is a native tree described by some as the "slenderest broadleaf tree in the forest" [26]. Black ash is normally a small tree just 40 to 60 feet (12-18 m) tall but can reach 90 feet (27 m) in height [26,59]. Branches do not appear until high up on the trunk; tall trees may be without branches for up to 50 feet (15 m) [26,118]. The narrow trunk is rarely more than 2 feet (0.6 m) in diameter and is often leaning or bent [59]. Black ash bark is soft with shallow grooves that give a scaly or flaky appearance [20,51,59,118]. The shallow, spreading black ash root system makes this species prone to windthrow [39,59]. Fine roots that measure between 0.1 and 0.4 mm in diameter are long and rarely branch [23]. A discussion of black ash mycorrhizal root associations is available [80], as is an in-depth investigation of the microscopic appearance of black ash roots that may be useful in identification [23].

The perfect and/or unisexual black ash flowers are described as tightly packed panicles or racemes and arise from leaf scar axils produced the previous year [20,51]. The opposite leaves are 10 to 16 inches (25-40 cm) long and pinnately compound [51,59,110,118]. Leaflets often occur in groups of 9 but may number 7 or 11. They measure 2 to 8 inches (5-20 cm) long by 0.6 to 2.4 inches (1.5-6 cm) wide [20,51,59,118,121]. The black ash fruit is a sometimes twisted samara most often containing 1 seed but sometimes containing 2 or 3 seeds [20,51,110]. The fruit measures 1 to 1.5 inches (2.5-4 cm) long and is produced in clusters [59,112,118,121]. Often fruits have a spicy odor [112].

Life span: Black ash is a long-lived tree with a relatively rapid growth rate [122]. Heinselman [57] suggests that the typical life span of black ash is 150 years. However, many black ash trees on the edges of Lake Duparquet in northwestern Quebec were over 200 years old, and the oldest tree in the area was 319 years old [127]. In northeastern Minnesota, several black ash trees in relatively pure stands were 250 year old. At 100 years old, black ash trees can be between 39 and 75 feet (12-23 m). Height is not well correlated with age when trees are more than 80 to 100 years old [71].

Breeding system: Black ash can produce perfect or separate male and female flowers [20,51]. Hosie [59] suggests that male, female, and bisexual flowers can occur on a single tree. In the northeastern U.S., the smallest tree to flower was 3 inches (8 cm) in diameter [142].

Pollination: Ashes are wind pollinated [142].

Seed production: Large viable seed crops are produced intermittently by black ash. The ability to produce seed occurs when trees are 30 to 40 years old [57]. In a review, Sims and others [112] report that good crops of seed are produced at 1- to 8-year intervals. Similarly, Sutherland and others [122] suggest 5 or more years pass between good black ash seed production. For 25 years, researchers monitored black ash seed production in northeastern Wisconsin. They found that seed production was 61% to 100% of full crop for 28% of this time but was less than 36% of full crop for 68% of the time [49]. In 2 years of seed collection in southeastern Michigan, researchers collected a total of 98,032 seeds from 42 different species. During the course of this study black ash failed to produce any "potentially viable seed" [83].

Seed dispersal: The timing of fruit shed and weather conditions can affect the dispersal distances for black ash seed. Sutherland and others [122] report that winds can transport seeds 328 feet (100 m) or more away from the parent tree. Curtis [30] called winter-shed fruits "ice boats" and suggested that long-distance dispersal is likely under these conditions. No actual distances were reported.

Seed banking: Several researchers report that black ash seeds can remain viable for up to 8 years under natural conditions [112,122].

Germination: The germination of black ash seed is a multistage process of stratification and scarification that often takes 2 to 3 years under natural conditions [30,112]. The embryo is immature when seeds are shed and requires warmth and moisture to fully develop. When fully ripe, the embryo is still dormant and requires a cold, moist period to break dormancy. Seeds germinate best on peat or mineral soils with high organic content [30] and can germinate in litter or when covered by 0.5 to 0.75 inch (1-2 cm) of soil [39].

Steinbauer [116] conducted in-depth studies of black ash seed germination. He found that at the time of seed shed the embryo is differentiated into the hypocotyl, epicotyl, and cotyledons, but the embryo is just 1/2 to 2/3rd the size of the seed. Embryos attain maximum size (0.5 inch (14 mm)) after 2 to 3 months at 68 °F (20 °C). Germination does not immediately follow and is likely delayed by mechanical restrictions of the endosperm, suberized layer, and/or seed coat. The digestion process necessary for germination is most efficient after 2 to 3 months at 41 °F (5 °C). Higher temperatures (68-86 °F (20-30 °C)) allow the embryo to break mechanical barriers and germination begins [116]. In the laboratory, maximum germination (87%) of black ash seed occurred after seeds were ripened in peat moss for 18 weeks at 70 °F (21 °C) and then exposed to 39 °F (4 °C) temperatures for 24 weeks [133,134].

Seedling establishment/growth: Black ash seedlings establish under canopy shade on a variety of soils [122]. In a review, Sims and others [112] report that seedling growth is rapid. Seedlings may reach 2 inches (5 cm) in the first 2 weeks of growth. In 1 year, seedlings are often 6 inches (15 cm) tall. Seedling survival is reportedly best at 45% to 50% full sun conditions [112]. While seedlings can establish under a canopy, they will eventually need canopy release for long-term survival [122]. Curtis [30] reports that high densities of black ash seedlings are rare [30]. Others suggest that grass and brush growth on the site can disrupt successful establishment [39].

Bell [11] monitored the growth and mortality rates for an average of 6 black ash trees along Hickory Creek in Illinois. Over the 18 years of the study, the average mean annual growth rate was 3.8±3 (s) mm/year and mortality was 3%±2.2%/year.

Researchers followed the establishment and survival of black ash, green ash, and white ash seedlings in open meadows and in upland and lowland young, successional, and closed-canopy forests of central Ohio. Ashes made up 69.9% of the 2,553 seedlings monitored. Significantly more (p≤0.05) ash seedlings emerged on lowland sites. Average ash seedling production was 241±21(s _x) new seedlings/100 m²/year from 1984 to 1993. In 1988 and 1990, seedling production peaked at approximately 800 to 1,000 new seedlings/100 m². Production in 1988 and 1990 was significantly greater (p≤0.05) than for any other year. Peak production was not correlated with any observed annual or seasonal climate events, and the authors suggest that production peaks related to black ash's masting behavior. The average life span of ash seedlings was 5 to 7 months. The seedling population produced in June of 1990 was 916. By October of the same year, 66.7% were dead; by May of 1991, 96.6% were dead. Survivorship was likely affected by white-tailed deer browsing; deer occurred in densities of 0.6 to 0.7 animal/ha in the area [16].

Potential changes in growth: Several factors may affect the growth rate and/or growth form of black ash. In open canopy conditions, black ash exhibits a broader canopy than trees grown in closed-canopy forests [26]. The growth rate of black ash is slower on sites with organic peat and muck soils. Trees are just 30 to 45 feet (9-14 m) after 50 years of growth and only 50 to 60 feet (15-18 m) in 100 years [39]. Immature plants severely browsed by white-tailed deer may develop a shrubby growth form. A single year free of browsing pressure, however, is enough to allow production of a leader branch [30].

Asexual regeneration: Vegetative reproduction is common following damage or top-kill [30]. In reviews, black ash is described as a "vigorous sprouter" following fire, browsing, or cutting. Sprouts are produced from adventitious buds located on the sides of stumps or root crowns [39,112]. Black ash produces 7 to 17 stem sprouts when cut [77].

Asexual vs. sexual regeneration: Along Lake Duparquet in northwestern Quebec, researchers studied numerous characteristics of black ash's sexually and asexually produced plants. In this region, sprouts have higher and more constant mortality rates than seedlings, and sexually reproduced stems reach older ages and produce larger diameters than sprouts. Seedlings more often than sprouts reach canopy height. However, on exposed flooded sites, new (1st-year and older) seedlings experience higher mortality than sprouts, and vegetative reproduction predominates. Likely, the more developed sprout root system allows for a more rapid growth rate and an increased tolerance to flooding. Successful black ash seedling establishment requires periods free of prolonged, intensive flooding [127], but xeric conditions are not tolerated either [128].

Soils: Black ash grows on moist to wet, deep, fertile, mineral or organic soils [26]. Mottles and gleys are typical of soils supporting black ash (referenced in [112]). Soils associated with the black ash-American elm-red maple cover type are wet mucks or shallow peat soils that are frequently acidic with mid-levels of nutrients [104]. In hardwood and mixed hardwood vegetation types of Manitoba, black ash dominates the overstory. This vegetation occupies deep, fine, loamy-clay soils with poor to very poor drainage along small river floodplains [146].

Excessive moisture is tolerated by black ash [62], and growth is considered best on sites receiving moving, aerated water with soil pH values between 4.4 and 8.2 [143]. On Quebec's Lake Duparquet floodplain, where black ash occurs in pure stands, flooding records from 1915 to 1991 indicate that flooding occurs between April 7 and July 13. Flooding conditions last an average of 24 days and range between 0 and 65 days [127].

Several areas report more specific soil characteristics for black ash habitats. In southeastern Wisconsin, the relative importance of black ash is significantly ( p<0.05) greater on basin sites than floodplain sites. The basin site soils had significantly lower (p<0.0001) pH and significantly higher organic matter, calcium, and magnesium levels than floodplain soils [38]. In the Lake Agassiz Peatlands of Minnesota, black ash grows in rich swamp forests where the pH is 6 to 6.5, calcium and magnesium concentrations are high, and the moderately decomposed peat layer can be 1 to 6 feet (0.3-1.8 m) deep [55]. Northern Lower Michigan's black ash-alder swamps have an organic matter depth of 16±9 (s) inches (40±22 cm). The pH is 7.3±0.5 (4 inches (10 cm) below soil surface) and calcium and magnesium concentrations are 55.8±7.2 ppm and 20.6±3 ppm, respectively [145]. In alder swamps of Chippewa County, Michigan, where black ash occurs, soils are described as black mucks. These soils have a 10- to 11-inch- (26-28 cm) deep organic layer, pH levels between 6.4 and 6.8, and dissolved oxygen levels of 1.9/mg to 2.0/mg. These alder swamps remained wet until mid-July during the study [92].

Elevation: Very few areas report black ash elevation tolerances. Kudish [70] indicated that black ash occurs between 100 and 2,800 feet (31-853 m) in the Adirondack uplands of New York. In a review, researchers suggest that black ash occupies sites from sea level to the highest elevations in the northern part of its range; in the southern portion of black ash's range it is restricted to elevations above 2,000 feet (610 m) [143].

Weather: Black ash grows in regions with continental climates. Wright [143] described black ash habitats as humid, receiving between 20 and 45 inches (510-1,140 mm) of precipitation annually, having average low January temperatures of 0 to 32 °F (-18 to 0 °C), reaching an average high temperature of 70 °F (21 °C) in July, receiving annual snowfall levels of 30 to 100 inches (760-2,540 mm), and typically having 80 to 180 frost-free days [143].

Some suggest that weather events during the previous and current year's growing season of black ash are significantly (p<0.05) related to radial growth. In the Lake Duparquet region of northwestern Quebec, researchers found that April and May temperatures and August precipitation in the previous year positively affected radial growth in black ash. However, precipitation in the previous April, May, June, and October was negatively associated with radial growth. In the same growing year, April temperature and June precipitation were positively correlated with radial growth, but July precipitation was negatively correlated with black ash radial growth [125]. Information was slightly different when flooded and nonflooded sites were compared. On floodplain sites, growth was not generally affected by temperature, but precipitation in the previous year's August and June and the current year's December positively affected radial growth. On nonflooded sites, radial growth was negatively correlated with the previous year's August temperatures and the same year's May temperatures. The aforementioned relationships were significant (p<0.05) [126].

Black ash does not represent a climax species in all cases. In mixed stands on moderately drained mineral soils black ash is regarded as a "sub-climax" species [112]. The black ash-American elm-red maple cover type is a "temporary climax" that typically succeeds to tamarack-black spruce communities but is subsequently replaced by northern white cedar [104]. Based on black ash's environmental tolerances, Graham [50] suggests it cannot be a climax species in eastern hemlock-hardwood forests of Michigan's Upper Peninsula. Because black ash does not often reproduce in thick layers of decaying material and is only moderately shade tolerant, it cannot be a climax species in eastern hemlock-hardwood forests.

Shade relationships: Reviews of black ash indicate that initially black ash is moderately shade tolerant but with increasing age, shade tolerance decreases [39,112]. Erdmann and others [39] suggest that seedlings develop best under 45% to 50% of full sunlight conditions.

Several researchers rated black ash's shade tolerance. Rudolf [105] gives black ash a shade tolerance rating of 2.4 on a scale that rates extremely shade-intolerant aspens a 0.7 and extremely shade-tolerant eastern hemlocks a 10. Kaminski and Jackson [62] rate black ash a 4 on a 10-point scale in which 1 corresponds to a complete intolerance of shading.

Response to disturbances: Powerful storms that blow down or damage trees are the most common disturbance in black ash forest habitats. Little is reported on fire, harvesting, or livestock grazing in these habitats. Black ash typically increases following events that provide openings in the canopy.

One and two years following the 1998 ice storm in northern New York, researchers observed black ash damage but did not find obvious changes in diameter distribution [103]. A July wind storm in 1983 in Minnesota's Anoka and Isanti counties caused substantial mortality in both eastern white pine (Pinus strobus) and northern pin oak (Quercus ellipsoidalis) forests. In both forest types, black ash density and basal area initially decreased following the event, but by the 7th poststorm year, black ash basal area and density exceeded prestorm measurements. A summary of the changes in black ash density and basal area is provided below [8]:

Following the widespread mortality of American elm trees in deciduous swamp communities of southeastern Michigan, researchers tracked changes in forest composition. Five to ten years after losing the American elm trees, black ash, red maple, and yellow birch became important overstory and understory species [9].

The following studies suggest that black ash is a resilient and opportunistic species regardless of disturbance type.

Researchers indicate that in northern Lower Michigan an increased presence of black ash and red maple is typical during the secondary succession of wet, bog sites following cutting or fire [45,46]. On a 1st order stream near Duluth, Minnesota, the selective removal of quaking aspen trees by American beavers increased the importance of black ash in the area [61]. Researchers visited upland swamp forests of northeastern Indiana 20 and 53 years after domestic livestock grazing was discontinued. Livestock grazed with "medium to heavy intensity" until 1930 in the area. Black ash did not appear on grazed sites in the 20th postgrazing year but was found in the 53rd postgrazing year. By 1984, the density of black ash on previously grazed sites was 93.9 stems/ha. In nearby ungrazed oak-hickory forests, black ash density was 89.0 stems/ha in 1931, 19.8 stems/ha in 1951, and 19.8 stems/ha in 1984. This study suggests that livestock grazing may prohibit successful black ash establishment [7].

Community change over time: Several have monitored the species composition changes in black ash communities and many have speculated about future changes in black ash forests. The succession of flood plains in north-central United States forests begins with the establishment of shade-intolerant, flood-tolerant pioneers (cottonwoods (Populus spp.) and willows (Salix spp.)). These species are later replaced by more shade-tolerant, flood-tolerant species (ashes and elms). The latest successional communities are dominated by American beeches, basswoods, and white oaks that tolerate heavy shade and flooding [107].

In the Cedar Bog fen of west-central Ohio, researchers assessed age class associations, population structure, density-diameter curves, and life history information that suggested black ash and red maple would increase but remain subdominant to northern white-cedar for the "foreseeable future" [27].

In a 30-year study of Connecticut's mixed hardwood forests, muck soil sites showed an increased abundance of black ash over time. Trees were aged between 25 and 40 years old when monitoring began. In 1927, there were 6 black ash trees/acre, and in 1957 there were 12 trees/acre [89]. Forty years of monitoring in the Indian Bowl area of Berrien County, Michigan, revealed similar increases in black ash. The percentage of total stems belonging to black ash more than doubled over the course of the study. The tamarack swamps that black ash occupied in Indian Bowl had organic soils high in calcium, occupied elevations between 600 and 750 feet (183-229 m), and were relatively free of human-caused disturbances. The increases in black ash at 10-year intervals are provided below. Increases in black ash occurred with general increases in the total number of stems per acre, suggesting black ash increases rather than other species decreases explains black ash's increased percentage of total stems [68,117].

In northern Lower Michigan, researchers monitored changes during 40 years of secondary succession on 2 lowland sites. Severe disturbances (logging and burning) occurred in the area from 1870 to the early 1920s. At the time of plot establishment, the oldest trees were 10 to 15 years old. One site was a mixed conifer swamp on poorly drained organic soils dominated by northern white-cedar, black spruce, and balsam fir. The other site occurred on a flat, moist sandy plain dominated by quaking aspen. Here the water table varied from a few inches above the soil surface to 30 inches (76 cm) below. The basal area of black ash in mixed conifer-dominated sites in 1981 was lower than in 1938. In the quaking aspen-dominated forests, the basal area of black ash increased substantially from 1938 to 1981. The comparisons between different sites and communities makes assigning the changes in black ash basal area to any single site or community characteristic difficult. The results of this study are summarized below [106]:

In an old-growth, central hardwood forest of east-central Indiana, changes in vegetation composition were compared over a span of 60 undisturbed years. Bur oak trees in the forest were 201 to 306 years old. Black ash density (number of stems/plot) decreased from 1926 to 1986, a change that researchers attributed to increased shading in the forests [4].

FIRE ECOLOGY

• FIRE ECOLOGY OR ADAPTATIONS
• POSTFIRE REGENERATION STRATEGY

Fire regimes: There are widely different fire frequencies reported for black ash habitats, and often times black ash occupies small niches that may or may not burn when most of the forested area experiences fire. Tubbs [130] considers fires rare in the northern hardwood forests of the north-central United States. Wade and others [135] report that the black ash forest cover type burned in mixed and stand replacing fires at 35- to 200-year frequencies. However, on poorly-drained sites within northwestern Ohio's Black Swamp, where black ash occurs, the estimated fire return interval is greater than 600 years [17].

Bergeron [13] reconstructed the presettlement fire regime for boreal forests along the lakeshores and on islands of Lake Duparquet in northwestern Quebec from early historical records and fire scar data. In these boreal forests, the fire cycle has increased since the late 1800s. Ash forests occurred only on lakeshores and made up 6.7% of the area surveyed. The last fire in ash forests occurred an estimated 183 years prior to the study [13].

Black ash is typical of boreal forests surrounding the Great Lakes. These forests experience "short fire return interval crown fires and/or severe surface fire regimes." Fires occur at 50- to 100-year intervals and are typically large (1,000-10,000 acres). Extreme drought conditions are necessary to fuel fires and occur at 20- to 30-year intervals. Heinselman [57] suggests that the fire return interval increases in more eastern forests that receive higher levels of precipitation.

From charcoal records collected in the Lake of the Clouds in the Boundary Waters Canoe Area, where black ash occurs, Swain [123] conservatively estimates the mean fire return interval for the past 1,000 years at 70 to 80 years and indicates that changes in the vegetation following fire were short lived (20-30 years).

From historic records including bearing trees, line descriptions, plat maps, and township summaries from Michigan's Lower Peninsula, the fire cycle in swamp forests where black ash is typical was an estimated 3000 years [136].

The following table provides fire return intervals for plant communities and ecosystems where black ash is important. For further information, see the FEIS review of the dominant species listed below.

FIRE EFFECTS

• IMMEDIATE FIRE EFFECT ON PLANT
• DISCUSSION AND QUALIFICATION OF FIRE EFFECT
• PLANT RESPONSE TO FIRE
• DISCUSSION AND QUALIFICATION OF PLANT RESPONSE
• FIRE MANAGEMENT CONSIDERATIONS

PLANT RESPONSE TO FIRE:
Black ash produces sprouts following fire [57]. Sprouting in black ash is considered "vigorous." Adventitious buds located at the sides of stumps or root crowns produce the sprouts [39,112].

DISCUSSION AND QUALIFICATION OF PLANT RESPONSE:
Very few studies assess the recovery of black ash on burned sites. This may be because the wet niches occupied by black ash do not burn often. Following a mid-May fire near Tower, Minnesota, in 1992, burned sites were compared to nearby harvested sites. Logged sites were within 9.3 miles (15 km) of the burned sites and matched burned sites "to the extent possible." The fire burned in quaking aspen-dominated woodlands, but fire severity was not reported. Black ash made up 13% of the total number of live trees on burned sites sampled in the summer of 1994. However, black ash was not among the 9 living species on logged sites. Without predisturbance data, it is not possible to say that black ash fared better on burned than logged sites [109].

In northern Cook County, Minnesota, an August wildfire burned in a 73-year-old jack pine (Pinus banksiana)-black spruce forest. Severity of the fire was not reported, but researchers noted that black ash was present in the forests before and after the fire. Researchers took no measurements or made no estimates of black ash's pre- or postfire distribution [6].

In riparian areas northeast of Thunder Bay, Ontario, the presence of black ash was a significant (p=0.05) indicator of sites adjacent to areas burned in 1999. The fire did little damage to riparian vegetation but "consumed" all but a few remnant trees in the upland boreal mixed woods and conifer-dominated forests. Black ash occurred on just 7% of sampled sites, so statistical significance may be related to the fire's clearing effect but may be what the authors describe as "a statistical artifact" [74].

MANAGEMENT CONSIDERATIONS

• IMPORTANCE TO LIVESTOCK AND WILDLIFE
• VALUE FOR REHABILITATION OF DISTURBED SITES
• OTHER USES
• OTHER MANAGEMENT CONSIDERATIONS

Native ungulates: Both moose and white-tailed deer utilize black ash. Utilization by moose increased with their population increases. During the dormant season (mid-September through mid-May), black ash is low preference browse for moose in the Lake Superior region [5]. On Isle Royale in Michigan, black ash made up 0.4% of available browse and made up 0.1% of moose winter diets [3]. After compiling findings from 13 browse surveys done in northern Ontario, Cumming [29] found that black ash comprised less than 1% of moose diets.

On Isle Royale in the sugar maple-yellow birch vegetation type, black ash comprised 2.4% of moose summer diets in 1946. The average degree of black ash browsing on the main island was 13% in 1945, 15% in 1948, 0 in 1950, 22% in 1961, 5% in 1965, and 9% in 1970. Decreased browsing from 1948 to 1950 corresponded to substantial moose die-off; moose populations were increasing from 1950 to 1961 [67].

Utilization of black ash by white-tailed deer likely depends on its availability. In reviews, Sims and others [112] consider black ash important white-tailed deer browse, and Erdmann and others [39] indicate that black ash seedlings and sprouts are readily browsed by white-tailed deer in the Great Lake states. However, in Cook County, Minnesota, and the Upper Peninsula of Michigan, black ash is not widely distributed in white-tailed deer wintering areas and is not important browse [2].

Studies indicate that black ash tolerates heavy browsing. Following heavy clipping (complete utilization of the season's growth) of stems in Cook County, Minnesota, black ash increased output by 19% by the time researchers clipped plants the next year. Output increased by over 300% in successive clippings. Both the number of twigs and the average length of twigs increased with clipping [2]. Erdmann and others [39] in a review suggest that black ash trees can withstand even heavy winter browsing.

Other large mammals: Black ash habitats are used seasonally by both American black bears and bobcats. The presence of black ash may indicate valuable feeding sites for American black bears in the Great Lakes region. The lowland grasses and herbaceous vegetation associated with black ash swamps are a primary early spring (April-May) food [99,100]. Lovallo and Anderson [79] found that female bobcats selected lowland deciduous forests as habitat in northwestern Wisconsin in the summer and the winter. Black ash and alder (Alnus spp.) dominated the lowland forests.

Small mammals: American beavers, rabbits, and other small mammals occasionally feed on black ash bark and stems. In Michigan's Upper Peninsula, American beavers infrequently utilized black ash as a winter food source; however, in North Dakota the small twigs and bark of black ash are preferred by American beaver [76]. On Mantioulin Island, Ontario, snowshoe hare use of black ash was low in the winter season. Five percent of available stems were browsed [34]. In a guide to growing black ash in the Maritime Provinces, authors suggest the use of poison-grain mouse-bait stations in plantations to discourage mice from girdling stems [77].

Birds: Although few studies highlight specific links between birds and black ash, it is likely that the wetland habitats occupied by black ash are attractive to many bird species. It is also likely that birds feed on black ash seeds. Black ash was one of many species investigated in a caloric content study of seeds eaten by birds [66]. In Aitkin County, north-central Minnesota, 2 of 14 located great gray owl nests were found in black ash trees [115]. Black ash habitats are important ruffed grouse roosting and brooding areas. Ruffed grouse used black ash-dominated swamp hardwoods as winter habitat. Swamp hardwoods made up 19% of the winter habitat use (number of plots with roosts/total number of plots of this cover type), and an average of 1.3 roosts/plot were found in black ash-dominated swamps. In the hot summer months, swamps are important brood habitat [36].

Amphibians: Researchers found several frog species in balsam fir-black ash forests of Itasca State Park, Minnesota. Researchers found a total of 855 frogs throughout the 5 years of field studies conducted in mid-August. Of the 855 frogs, 270 occurred in the balsam fir-black ash habitat type. Microclimates, vegetation type and coverage, as well as potential escape areas likely affected habitat choice. The frog species found in the balsam fir-black ash habitat type are shown below [81]:

Palatability/nutritional value: Nutritional contents are reported for black ash seed, wood, and litter. Black ash seed collected near Champaign, Illinois, from November through March of 1954 to 1959 contained an average of 5,625 gram-calories/gram [66]. Researchers in Wisconsin found that the in-vitro dry matter digestibility of black ash wood was 17% and bark was 45%. Free sugars and sugars after hydrolysis made up 6.5% and 10%, respectively, of the carbohydrates in black ash extract [84]. Fresh black ash litter collected over a 2-year period from a marginal fen in Minnesota's Cedar Creek Natural History Area contained 4,376 g cal/g dry weight and 4,714 g cal/g ash-free weight. The dominant trees in the study area were 35 to 45 years old. The nutrient content of the fresh black ash litter is summarized below [96]:

In a review, Blinn and Buckner [15] report the following foliar nutrient levels for black ash:

Cover value: Black ash-red maple hardwood swamps are important winter range for white-tailed deer in northern Wisconsin and typically support high deer numbers [25]. A study of bobcat food availability suggests that lowland deciduous habitats dominated by black ash of northwestern Wisconsin are home to several rodent species. In lowland deciduous forests, 3.9 voles, 0.87 mice, 0.87 shrews, and 0.87 chipmunk were captured per 100 trap nights [79].

Black ash wood splits into slats easily, making it ideal for basketry [59]. Native people of northeastern Canada and the United States historically and currently use black ash in basket making. Black ash basketry is common in Maine, New Brunswick, Nova Scotia, and New York. The Passamaquoddy, Penobscot, Maliseet, Micmac, and Mohawk people utilize black ash in their baskets [108].

Wood Products: The wood from black ash trees is not particularly strong and is used mainly for indoor furnishings. Black ash wood is moderately heavy; 1 air-dried cubic foot weighs 34 pounds [26]. The grain is coarse, sapwood is almost white, and heartwood is dark in older trees [26,59]. Wood is used in making cabinets, veneer, paneling, short tool handles, baskets, and indoor furniture [26,59,131]. Treated black ash wood is also used for posts. A study found, however, that oil-treated posts outlast untreated posts. Trees cut in the spring were peeled, air dried to 15% to 25% moisture content, and treated with 5% pentachlorophenol oil solutions. Posts soaked in oil for 24 hours lasted 33 years, while untreated posts lasted just 4.5 years [64].

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