More info for the terms:
adventitious,
association,
basal area,
climax,
constancy,
cotyledon,
cover,
cover type,
density,
dioecious,
fire frequency,
forest,
frequency,
fruit,
habitat type,
hardwood,
litter,
mesic,
natural,
phanerophyte,
relative density,
relative dominance,
root crown,
seed,
sere,
shrub,
shrubs,
stratification,
succession,
swamp,
tree,
woodlandGreen ash is recognized as a dominant species in
the following vegetation classifications:
AR: [259]
GA: [306]
KS: [181]
NE: [7]
MA: [166]
MD: [49]
MN: Voyageurs National Park [176]
MO: [80]
MT: [128,129,133,134,183]
ND: [106,107,131,213]
NY: [234]
OK: [142]
SC: [306]
TX: Trinity River floodplain [217]
WY: [65]
Custer National Forest of ND, SD, and MT [130]
Great Plains: [35,132]
MB: [53]
PQ: [293]
Green ash is a component of many vegetation and cover types across its range.
The sugarberry-American elm (Celtis laevigata-Ulmus americana)-green ash cover type is found in southern
forests from eastern Texas east to the Gulf Coast region and north to the major
river floodplains of southern Illinois. This cover type occupies clay or silt loam soils and
is considered successionally "long-term." Pure stands of green ash are occasional
on moist flats or in shallow sloughs [
159]. On low flats and sloughs of the
Mississippi River floodplain, this type is typical after heavy cutting or
fire. Other important associated species include dwarf hackberry (C.
tenuifolia), water hickory (Carya aquatica), and willow oak (Quercus phellos) [
221].
Western U.S.: Green ash is restricted to riparian areas in the westernmost portion of its range.
Montana
: In central and eastern Montana, the green
ash/chokecherry (Prunus virginiana) habitat type is common. This type is typical
on older terraces of the Missouri River and commonly lines sections of the
Yellowstone, Powder, Tongue, Milk, and Little Missouri rivers [
133]. Lesica [
183]
recognizes a green ash-American elm/chokecherry vegetation association in which boxelder
(Acer negundo) and Rocky Mountain juniper
(Juniperus scopulorum) can occur. Quaking aspen (Populus tremuloides)
may occur in the early
successional stages. Associated shrubs include American plum (Prunus americana) and
Saskatoon serviceberry (Amelanchier alnifolia) [
133,
183].
Wyoming: Green ash occurs in riparian areas of
Wyoming in the boxelder-green ash-American elm/common snowberry (Symphoricarpos albus)
community type. Other species common in this vegetation type are bur oak (Q. macrocarpa),
hophornbeam (Ostrya virginiana), and cutleaf coneflower (Rudbeckia laciniata) [
65].
Colorado: Green ash, American elm, and
boxelder are typically present as minor species and contribute less than 1%
coverage on the Arkansas and South Platte river drainages of eastern Colorado.
The dominant species are plains cottonwood (Populus
deltoides ssp. monilifera) and peachleaf willow (Salix
amygdaloides). Saltcedar (Tamarix chinensis) often forms a dense
subcanopy or shrub layer on the Arkansas River floodplain
[
187].
North-central U.S. and south-central Canada: In many forest cover types of the northern Great Plains and the Great Lakes regions, green ash
is important. Green ash is typical in the bur oak cover type in the Black Hills
of South Dakota and Wyoming where interior ponderosa pine (Pinus ponderosa
var. scopulorum), American elm, and plains cottonwood are common as well
[
87]. In the northern Great Plains, green ash commonly invades the cottonwood (Populus
spp.) forest cover type as succession
advances beyond the pioneer stages [
173]. In the sugar maple-basswood (Tilia
americana) cover type of western Wisconsin and central Minnesota,
green ash, hackberry, bitternut hickory (Carya cordiformis), and several
oak (Quercus spp.) species occur together [
111]. Green ash is also a major associate
of the silver maple (Acer saccharinum)-American elm cover type that occurs
in central U.S. forests and Canada's Great Lakes-St. Lawrence forest region.
This type is considered "subclimax" along river bottoms and
floodplains [
222]. Along the Red, Assiniboine, Souris, and other rivers of Manitoba and eastern
Saskatchewan, green ash is an important component of maple-elm-ash floodplain communities [
33].
Manitoba: The eastern deciduous forest of
Manitoba has a canopy dominated by green ash, American elm, and boxelder and a shrub-dominated
understory of beaked hazelnut (Corylus cornuta), chokecherry, and
American cranberrybush (Viburnum opulus var. americanum).
This forest is predominant on nutrient-rich basic substrates [
53].
Green ash is also typical of flooded and nonflooded woodlands surrounding Lake Manitoba. The
forest nearest to the lake is often flooded in the spring and supports a mixture of
green ash, shining willow (Salix lucida), peachleaf willow, and sandbar
willow (S. interior). Forests beyond these rarely flood and are dominated by
balsam poplar (Populus balsamifera),
quaking aspen, green ash, boxelder, black willow (S. nigra), and American
hazelnut (C. americana) [
189].
North Dakota: Green ash is a dominant species in several upland
hardwood habitat types of southwestern North Dakota. The green ash-American
elm/chokecherry habitat type occupies mesic sites with gentle slopes and loam to
silt loam soils [
107]. The green ash/chokecherry vegetation type occupies
intermittent drainages and narrow draws with slopes of up to 40% and
soils containing more than 35% clay. The green ash/common snowberry vegetation is restricted to floodplains
and tributaries of the Little Missouri River. The clay content of these soils is
often 30% to 59%. The eastern cottonwood (P. deltoides)-green ash community
type occurs on Missouri River floodplains. It is considered a
mid-seral type that develops into the green ash/common snowberry type [
106].
In west-central North Dakota, green ash-box elder forests are typical in river valleys
of the Knife River Indian Villages National Historic Site [
61].
Green ash is common in upland draws, valley bottoms, and
moderately steep north- and east-facing slopes of the Badlands. Green
ash-dominated vegetation abuts mixed-grass prairies in the uplands and cottonwood
and silver sagebrush (Artemisia cana) in the valleys.
American elm trees commonly occur with green ash in the northern
Badlands. Boxelder and Rocky Mountain juniper are occasional associates in the
bottomlands. Quaking aspen is present in disturbed stands that
have experienced fire or die-off in the past. Bur oak associates with green ash
north of the Killdeer Mountains [
213].
Minnesota: Managers in Voyageurs National Park
recognize a rare ash-elm/trillium (Trillium spp.) vegetation type. Canopy
dominants in this type are black ash (Fraxinus nigra), green ash, and
American elm. Ash-elm/trillium habitats are moist with deep, nutrient-rich soils [
176].
Wisconsin: Green ash, swamp white oak (Q. bicolor),
and common buckthorn (Rhamnus cathartica) are
important in floodplain forests of southeastern Wisconsin's eastern
ridges and lowland provinces. These species dominate soils with neutral pH
that are typically moist throughout the growing season and experience spring
flooding at intervals of every 2
to 3 years [
85].
Along the lower 230 miles (370 km) of the Wisconsin River floodplain that includes
100-year-flood regions, river birch (Betula nigra), silver maple, black
ash, green ash, eastern cottonwood, swamp white oak, black willow, and American
elm are consistently found together [
285].
Nebraska: Green ash is a subdominant
species of dry bur oak-bitternut hickory forests along the Missouri River
and northern red oak (Q. rubra var. rubra)-American basswood climax forests in eastern Nebraska.
The green ash-American elm forest type is also found on most of Nebraska's river floodplains.
However, it is most well developed on larger river floodplains [
7].
In the bottomlands of Lost Creek in the Schultz
Prairie of south-central Nebraska, green ash occupies savannah-like riparian
vegetation. Associated canopy species may include bur oak, white mulberry
(Morus alba), and/or silver maple. Roughleaf dogwood (Cornus drummondii)
and American bittersweet (Celastrus scandens) are characteristic of the
understory. A decreased fire frequency in this prairie region is thought to have
facilitated an expansion of woody vegetation [
240].
North-central Nebraska's Niobrara River valley
supports hardwood communities where green ash is dominant. Other typical
hardwood species include bur oak, basswood, boxelder, hophornbeam,
black walnut (Juglans nigra), and American elm [
163].
Illinois: In Vermilion County's Horseshoe
Bottom Nature Preserve, silver maple, green ash, and black ash dominate all
diameter classes in swamp communities [
180]. Along
the Oakwood Bottoms Greentree Reservoir of the Shawnee National Forest, green ash
occurs in pin oak-cherrybark oak (Q. palustris-Q.
pagoda) communities. This vegetation type is restricted to old fields [
281].
Indiana: Green ash populates poorly drained sites in the
old-growth Ginn Woods of east-central Indiana. Other species of the Ginn Woods
include silver maple, red maple (A. rubrum), shellbark hickory (Carya laciniosa),
American sycamore (Platanus occidentalis), and eastern cottonwood [
18].
South-central U.S.: Abandoned agricultural fields and floodplains are typical green ash habitat in the
south-central plains and coasts. Hook [
145] describes green ash in
association with the baldcypress (Taxodium distichum) cover type
of the coastal plains. In the lower Midwest states, green ash is considered
important in the sassafras-common persimmon (Sassafras albidum-Diospyros virginiana)
cover type. Green ash commonly invades this pioneer
type on old-field sites with deep soils [
17].
Kansas: In the eastern portion of Kansas, the green ash-American
elm-hackberry vegetation type occurs in temporarily flooded
forests. Green ash is also a common component of the pecan (C. illinoensis)-hackberry
forests found in the Cherokee lowlands, Glaciated
Regions, and the Osage Cuestos area. The eastern cottonwood-black willow
floodplain forests and bur oak-Shumard oak (Q. shumardii)-bitternut
hickory/Indian woodoats (Chasmanthium
latifolium) communities also provide green ash habitat [
181].
Missouri: Green ash is a component of Boone
County's old-growth Schnabel Woods, where some trees are as old as 205 years.
Since the last study of this area, 40 years ago, green ash
importance has declined, however. The dominant canopy species of the Schnabel
Woods is sugar maple (A. saccharum), and other canopy species include
northern red oak (Q. rubra), white oak (Q. alba), chinkapin oak
(Q. muehlenbergii), basswood, and slippery elm (Ulmus rubra) [
235].
In floodplain forests of northern Missouri's Dissected Till Plains, green ash
dominates several forest types. In the black willow-green ash forest type, green
ash has an importance value of 77. Green ash importance is just over 20 in the
silver maple-American elm-green ash and oak-green ash-river birch forest types.
Researchers indicate that green ash is well represented in the sapling stage and
will likely remain in the area long term if there are no
major disturbances [
80].
Oklahoma: The green ash-American
elm and American elm-slippery elm-sugarberry-hackberry-green ash vegetation
associations are widespread throughout Oklahoma. In the Red River drainage, the
green ash-cedar elm-(Ulmus crassifolia)-sugarberry vegetation type is
typical, and the loblolly pine (Pinus taeda)-green ash-American
elm/longleaf woodoats (C. sessiliflorum) community is common on floodplains
and Coastal Plain swamps [
142].
Arkansas: Along the Cache River floodplain of
northeastern Arkansas, the Texas red oak (Q. texana)-green ash vegetation type
populates low-lying areas. Sites
occupied by this community may be flooded 90 to 100 days of the year [
259].
Texas: Simpson [
257] describes green ash in
piney woods, Gulf prairies, marshes, post oak (Q. stellata) savannahs, blackland prairies,
Cross Timbers, Rio Grande floodplains, and the Rolling Plains of eastern Texas.
In the Big Thicket National Preserve of southeastern Texas, green ash is common
in flatland hardwood forests between the
Trinity and Neches rivers where standing water is typical after heavy rains.
Other species associated with this habitat are swamp chestnut oak (Q. michauxii),
willow oak (Q. phellos), laurel oak (Q. laurifolia), and loblolly pine [
194].
In low flood plains of the Roy E. Larsen Sandylands Sanctuary, green ash
associates with water tupelo (Nyssa
aquatica), sweetgum (Liquidambar styraciflua), baldcypress, and red
maple [
195].
Louisiana: Green ash is widely distributed in the
Cat Island Swamp of Feliciana Parish. In the swamp, sugarberry and baldcypress are the most
conspicuous canopy species but water tupelo, overcup oak (Q. lyrata), and
pecan are also found [
77].
Southeastern U.S.: Along the Gulf and Atlantic coasts and in the interior southeastern states, green ash associates
with many vegetation types. The overcup oak-water hickory forest type is green
ash habitat on floodplains and back water basins of the Gulf
and Atlantic coast states and in Tennessee and southern Illinois. Sugarberry, American elm,
water locust (Gleditsia aquatica), red maple, and/or
Texas red oak are also typical of these forests [
158]. In the coastal plains
states, green ash is occasional in the baldcypress forest cover type [
145].
On islands and levees of southern Louisiana and southwestern Mississippi, green
ash associates with sugarberry and American elm in the live oak cover type [
88].
Kentucky: In old-growth woodlands of Pennyroyal
Plain, green ash is important in the subcanopy and understory. The common upper
canopy vegetation of this area is dominated by a mix of shagbark hickory (Carya ovata),
red maple, slippery elm, sweetgum, pin oak, swamp chestnut oak,
and southern red oak (Q. falcata) [
60].
Virginia: The hardwood forests of Virginia's lower Coastal Plain
characteristically include green ash, American elm, red maple, cherrybark oak,
swamp chestnut oak, willow oak, and/or
laurel oak [
58].
Tennessee: Green ash is an occasional species
in wet and moist bottomland hardwood forests of the Natchez Trace State Forest,
State Resort Park, and Wildlife Management Area of western Tennessee.
Wet bottomland hardwood forests occupy poorly drained sites with moderate to
high soil fertility. Other wet bottomland forest species include red maple,
sweetgum, willow oak, and black willow. Moist bottomland hardwood forest
canopies are diverse and may include yellow-poplar (Liriodendron tulipifera),
sweetgum, white oak, loblolly pine, and/or red maple. Soils
in moist bottomland forests are well drained, and soil fertility remains moderate to high [
258].
North Carolina: Along the expansive floodplain of Tyrrell
County's Scuppernong River, an assortment of bald cypress, loblolly pine, swamp tupelo
(N. biflora), sweetgum, red maple, and green ash
typically dominate the overstory. Occasionally water tupelo and Atlantic white-cedar
(Chamaecyparis thyoides) are found [
208].
South Carolina: The laurel oak-green ash and swamp
chestnut oak-green ash floodplain forest types are common in Congaree Swamp
National Park of central South Carolina [
306].
Mississippi: Sharkey County is home to the Green Ash Research
Natural Area. The vegetation of this area is dominated by Texas red oak, green ash,
and American elm. There are old-growth green ash trees between 200 and 250 years old in the area [
78].
Alabama: Green ash is typical of bottomland communities
that line small streams in the lower Alabama Piedmont. Sweetgum and red maple
are often found with green ash in these narrow floodplains with
moderately well-drained soils [
114].
Georgia: The swamp chestnut oak-green ash vegetation type
is common on high-elevation floodplains in Georgia's Piedmont province.
The red maple-green ash type is common in Georgia and occupies lower elevation
floodplains. The sweetgum-laurel oak-green ash vegetation type is rare and occupies moderately
wet to dry alluvial floodplains near Savannah [
306].
Florida: Green ash is associated with several forest
communities on the Apalachicola River floodplain of northwestern Florida. Other species occurring
with green ash include sugarberry, water oak (Q. nigra), red maple, and planertree
(Planera aquatica). Researchers estimate that within this 175 mi²
(454 km²) floodplain 14,200 tons (12,900 tonnes) of ash leaf litter (predominantly Carolina ash
(Fraxinus caroliniana) and green ash) falls annually [
89].
Northeastern U.S. and southeastern Canada: Swamps and floodplains are typical green ash habitats in the northeastern United
States and southeastern Canada. Green ash is common in mature
sassafras-common persimmon forest types that occur in the
mid-Atlantic states. Green ash replaces this pioneer type on upland and
lowland old fields with deep soils [
17].
Quebec: Green ash is a dominant canopy species in
silver maple-green ash forests in the Lac des Deux-Montagnes area. This
forest type occurs at elevations between 65.6 and 73.5 feet (20-22.5 m)
on imperfectly or poorly drained soils. Red-osier dogwood (Cornus sericea
ssp. sericea) and riverbank grape (Vitis riparia) dominate the shrub layer of silver
maple-green ash forests. Green ash is also typically present in northern red oak and eastern
white pine (Pinus strobus) forests that occupy well-drained soils at elevations of
79 to 98 feet (24-30 m) [
293].
Massachusetts: The overstories of many small river
floodplain forests in eastern Massachusetts are green ash dominated. The silver
maple-green ash-pin oak vegetation type is typical of small tributaries of the Connecticut
and Nashua rivers where flooding occurs. This type also occurs on island edges
in the Merrimack River. Green ash is present but less common in the red maple-silver
maple-swamp white oak and silver maple-green dragon (Arisaema dracontium)
vegetation types [
166].
New York: Green ash and black ash are
codominants in the silver maple-ash forest type that is common along
ravines and floodplains at the southern edge of Cayuga Lake in Tompkins
County. In this vegetation type, silver maple contributes up to 70% of the total
canopy coverage, and green and black ash together make up 5% to 15% cover [
154].
Ohio: On poorly drained sites that are part of northwestern Ohio's Black
Swamp, green ash occurs with silver maple, black ash, American elm, bur oak,
and shellbark hickory [
39].
Maryland: Green ash is a dominant species in the
American sycamore-green ash-box elder-silver maple vegetation type
characteristic of bottomlands in the Piedmont and Appalachian provinces. Along
the Pocomoke River, green ash occurs in the abundant baldcypress vegetation
association often together with red maple and sweetgum. Green ash also occurs in
river birch-American sycamore vegetation in bottomlands and along shorelines of the
Potomac River [
49].
BOTANICAL AND ECOLOGICAL CHARACTERISTICS SPECIES: Fraxinus pennsylvanica
©Kitty Kohout,
Wisconsin State Herbarium
GENERAL BOTANICAL CHARACTERISTICS:
This description provides characteristics that may be relevant to fire ecology,
and is not meant for identification. Keys for identification are available
[44,47,62,84,108,109,110,124,155,177,206,227,249,257,269,272,294,297,304,312,317].
Green ash is a deciduous tree with high branches and a slender growth form. It grows to 100 feet (40 m) in the
southern part of its range but is typically half that
height in the northern portion of its range [84,110,124,167,269]. Some research
indicates height differences across the east to west range of this species as well.
Trees found in New York are typically greater than 100 feet (30 m) tall, while
those in South Dakota rarely exceed 49 feet (15 m) [1]. South Carolina's state
champion green ash tree grows in the bottomland hardwood floodplain forest of Congaree National Park and was last measured in 2002. This tree was 143 feet
(43.6 m) tall, and had a crown spread of 96 feet (29 m) and a
circumference of 181 inches (460 cm) [263]. The 2004-2005 National Tree Register
reports that the national champion green ash
tree grows in Cass County, Michigan, and is 95 feet (29 m) tall, 259 inches (658
cm) in circumference, and has a 95-foot (29 m) canopy spread. This tree was
last measured in 1995 [11].
The trunk of green ash trees is large and straight [
269]. When subjected to
prolonged periods of flooding, trunks may become enlarged
at the base [
110]. Under dry conditions, the outer bark is
between 5 and 7 mm thick at breast height, while the inner bark
measures a thickness of 1.5 to 2.5 mm [
211].
Green ash leaves are opposite, odd-pinnately compound, and measure between
4.3 and 12 inches (11-30 cm) long by 3 to 7.1 inches (8-18 cm) wide [
110,
124].
Commonly there are 5 to 9 leaflets that are typically 2 to 4 inches (6-10 cm)
long and 2 to 5 cm wide. Though thin, leaflets are "firm and leathery" [
269].
Flowers appear before the leaves and are borne on old wood [
110,
304]. Female flowers are
short, dense panicles with 200 to 300 flowers per panicle [
269]. Trees as small as
20 to 30 feet (6-8 m) tall with dbh of 3 to 4 inches (8-10 cm) have produced flowers
[
167]. However, abundant flowers are not produced until trees are approximately 8 to 10 inches
(20-30 cm) in diameter (review by [
93]). The fruit is a single-seeded, winged
samara measuring 10 to 15 mm long [
108,
269]. Seeds are small [
308].
The rooting habit of young and adult green ash trees has been investigated by
several researchers. Lateral roots are long with few branches. Fine lateral
roots average 0.25 to 0.55 mm in diameter [
48]. The rooting depth of green ash
on fine-textured soils is described as shallow, between 5 and 10 feet (2-3 m).
Although the root system is considered extensive,
green ash trees may topple with high winds (reviews by [
226,
301]). In East
Brunswick, New Jersey, 2- and 3-year-old green ash saplings were planted and
excavated 3 years later. Maximum root spread for the saplings was 1.68 times
their driplines, and crown and trunk diameter were significantly (p=0.01) correlated
with root spread [
103]. In eastern Nebraska, researchers examined the
root depth and spread of several green ash trees representing a range of ages. A
3-year-old green ash tree in Lancaster County had roots that extended approximately
5 feet (2 m) deep and spread 8 feet (2 m) in diameter. A 24-year-old tree from
Pawnee County had a root spread of a
little over 30 feet (9 m) and a depth of more than 8 feet (2 m). In Merrick County, a
45-year-old green ash tree had roots that spread 44 feet (13 m) and extended 10 feet
(3 m) deep [
266]. For information on green ash mycorrhizal associations and their
effect on green ash growth and/or resource acquisition, see [
12,
14,
15,
45].
Male and female trees: Green ash is
dioecious.
Morphological differences between male and female green ash trees were studied
in Winnipeg, Manitoba. From a sample of 45 green ash trees between 15 and
45 years old, researchers found that the crown of male trees was generally
rounder, broader, and
fuller than female tree crowns [
233]. However, from 6 male and 6 female
green ash trees in the same area between 254 and 373 inches (644-948 cm)
tall, researchers found that female trees had significantly greater shoot
length (p=0.04), greater lateral shoot length (p=0.0005), and a greater number of lateral shoots (p=0.007) than male
trees [
74].
Adaptations to flooding:
Green ash trees tolerate flooding through a variety of physiological
and morphological adaptations.
Researchers have observed shoot lenticels, adventitious roots, increased lateral
root production coupled with decreased downward root growth, and succulent roots
with large air spaces [
199]. Oxidation of the rhizosphere,
accelerated anaerobic respiration in secondary roots, and the growth of new
secondary roots
are important flood adaptations as well [
146,
278].
Phenotypic variation:
Green ash trees exhibit a
high level of phenotypic variation, and many researchers have
highlighted differences in the
growth rate, survival, drought tolerance, appearance, and cold tolerance of
green ash seedlings grown from seed collected in northern vs. southern and
eastern vs. western locations. Seed collected from similar latitudes in New
York, Ohio, Illinois, Nebraska, and South Dakota represented a gradient of
decreasing annual precipitation. Drought resistance of the
seedlings increased from east to west locations when grown in a common
location. South Dakota seedlings had small, thick leaves, while New York
seedlings' leaves were thin and large [
1]. A similar study compared 6-month to
1-year-old seedlings grown in a common area from seed collected from 39
different locations in the Great Plains. Researchers observed an
increase in drought tolerance,
decrease in size of parent trees, and an increase in the percentage of trees
with dark green foliage as location of the seed varied from south to north and
east to west locations [
202].
Growth rates decreased and winter hardiness
increased in green ash trees grown from seed collected in more northerly
latitudes. Green ash seed was collected from the Coastal Plain region of North
and South Carolina and from the Mississippi River valley from southern Illinois
to southern Louisiana and Mississippi. Five and ten years following
planting in a common location, green ash trees from northern seed grew
slower than those from southern seed [
303].
Twenty seedlings collected from 9 eastern United States and Canada locations
grown in a common nursery were easily sorted into 2 distinct groups.
Northern seedlings collected from Maine, Michigan,
Wisconsin, Ontario, and Minnesota grew slowly, dropped leaves early in the fall,
and resisted winter kill. Southern seedlings collected from South Carolina,
North Carolina, and Virginia had rapid growth rates, retained their leaves until
late fall, and suffered more damage with cold winter temperatures. The length of
stem damage from winter cold was 0.1 inch (0.3cm) and 5.7 inches (14 cm)
in the northern and southern seedlings, respectively [
314].
RAUNKIAER [228] LIFE FORM:
Phanerophyte
REGENERATION PROCESSES: Green ash reproduces both through seed production and
vegetative sprouting [
250]. Two studies in Montana investigated sexual and asexual
regeneration of green ash. In east-central Montana, studies in 17 green ash
stands from 6 sites revealed that both vegetative regeneration and
seed production were important to regeneration. The stands were
uneven aged, suggesting an irregular recruitment pattern. On average 33% of green ash
trees had live basal sprouts, and the likelihood of finding sprouts was greater
for large-size trees than small trees.
The average density of seedlings was 10 plants/100 m² in all
stands, but 9 of 17 stands had 0 to 1 plants/100 m². Stands with
a greater number of seedlings typically had a more uneven age distribution than
those without seedlings. Likely vegetative regeneration, which is typically
coupled with periodic disturbances such as drought, fire, or logging, created the
more even-aged communities [
184].
In a postfire study, Lesica [
185] found heavy reliance on
vegetative regeneration and decreased production of seedlings by green ash trees
recovering from fire. Green ash woodland sites in eastern Montana that burned in
August or September between 1988 and 1998 were studied in 2001. There were more
sprouts, fewer seedlings, and more dead trees on burned sites
compared to unburned sites. Likely fire killed green ash seed on or
near the soil surface,
restricting seedling recruitment to seed producing trees, many of which
were killed in the fires. The average number of sprouts, seedlings, and dead
trees on unburned and 3- to 13-year-old burned sites is presented below. Data
were collected from 0.025-ha circular plots [
185].
Population attribute (mean) Burned Unburned
Sprouts 4.3 1.3
Diameter of sprouts (mm) 1.56 0.84
Seedlings 1.8 8.1
Dead trees 1.43 0.14
Pollination: Flowers are wind pollinated [
22,
167].
Male flowers mature earlier than female flowers, and female flowers are
receptive from the time of bud opening to the time the stigma withers. Female
receptiveness lasts 7 to 10 days for individual trees and 2 to 3 weeks for populations [
277,
315].
Some have observed green ash trees just 7 years old and 12 feet (3.7 m) tall flowering,
but typically flowering occurs after trees reach 3 to 4
inches (8-10 cm) in diameter and/or a height of 20 feet (6 m) [
316].
The majority of pollen produced travels 25 to 50 feet (7.6-15 m)
from the source tree. Wright [
313] counted the number of pollen grains
from open-grown green ash trees at increasing distances from the source tree. The
number of pollen grains from white and green ash trees was 2,502, 1,110, 110,
and 2 from stations 25, 50, 150, and 400 feet (7.6, 15, 45.7, and 122 m)
from the source tree, respectively. However, because of collection
technique limitations, the author suggests that
these numbers may incorporate an error factor of 2 or 3 [
313].
Breeding system: Green ash trees are dioecious [
110,
124,
269]. With male and female flowers on separate,
wind-pollinated trees, outcrossing is mandatory and the potential for genetic
exchange is great.
Seed production: Ash trees exhibit a masting behavior [
38]. Sutherland and others [
273] suggest that
ash trees produce good seed crops every 5 or more years, while others suggest that
good seed crops are produced every year by green ash [
308]. Wright [
316] reported a
high percentage of male and female flowers each year and a high percentage of
annual seed production by female trees.
In the Philadelphia area, green ash trees monitored from 1947 to 1951
revealed that a large number of flowers did not necessarily dictate a large number of
seeds, but greater than 33% of observed green ash trees produced large seed
crops for 2 or 3 sequential years [
315]. Along the north shore forest margin
of Quebec's St. Lawrence estuary, green ash seed production was high even when
many trees showed signs of damage from ice and debris flows [
179].
In forest fragments of southeastern Michigan, researchers monitored seed
rain from May through February for 2 years. The basal area of green ash averaged
3 m²/ha in the forests. Over the 2-year period, 73% of the
2.7 ft² (0.25 m²) seed traps received green ash seed rain, and an average of
60 green ash seeds were produced/m²/year. The number of seeds trapped was greater
in areas with a greater density of mature green ash trees [
198].
Seed dispersal: Green ash seeds are primarily dispersed by wind but movement by water is
also likely [
10,
167]. Animals cache ash seed [
72], which may subsequently
germinate and establish.
Dispersal distance: The dispersal distance of green ash seeds is
dependent on season and time since seed shed. Seeds shed in the winter
potentially move great distances from the source on frozen surfaces; seeds
dropped in the fall typically rest near the parent tree [
280]. Sutherland and others [
273]
report that ash seeds may travel 300 feet (100 m) or more from the parent tree.
The natural invasion of a reforestation project in
the Tensas River National Wildlife Refuge was evaluated 6 years following Texas
red oak and water oak plantings. The frequency of green ash volunteers
was 61.9%, and green ash tree size averaged 13 inches (3.3 cm) dbh. The
distance of planted fields
ranged from 423 to 2,100 feet (129-640 m) from forested edges. Most green ash plants occurred on
plots within 850 feet (259 m) of the forested edge. The density of green ash in
nearby forested areas was not reported [
197].
Green ash colonization of the Ouchita Wildlife Management Area of
northeastern Louisiana resembled an "advancing front." Agriculture
was abandoned in the area in 1984. In May of 2000, green ash, although
not planted on the reclaimed site, was the most dominant woody
species in terms of basal area and density. The density of green ash
saplings was 800/ha within 30 feet (10 m) of the bordering forest edge
and 70/ha at 300 feet (80 m) from the edge [
28].
Seed banking: The length of time green ash seed remains viable in the soil likely
depends on site conditions including
temperature, flooding, and/or soil type. Sutherland and others
[
273] suggest that ash seeds are viable for up to 3 to 4 years
in the seed bank. However, no green ash seed germination from seed bank samples in baldcypress-green
ash swamps
along the Cache River of Illinois. Sampling was conducted in April of 1992 and 1993 in
9 intact swamp forests and 51 former swamp sites that have been farmed for the last
1 to 50 years. Under greenhouse conditions, no green ash seedlings emerged from the
swamp soil samples [
204]. As sampling and laboratory techniques can affect seed
bank study results [
26,
171], green ash may have been present in the seed bank
despite its failure to emerge in the greenhouse.
Germination: Green ash seed requires cold stratification to germinate. Seeds dispersed
in the fall and winter germinate the following spring [
22]. Taylor [
280]
indicates that approximately 50% of the green ash seeds shed in the
spring initiate germination with those that overwintered on the ground; the other 50%
initiate germination the following spring. The embryos of newly
fallen green ash seed are dormant. Temperatures near 40 °F (5 °C)
are optimal for endosperm digestion, and germination is encouraged at
daily temperatures alternating
between 70 and 90 °F (20-30 °C) [
268].
Green ash seeds can also germinate in flooded
conditions. Seed collected in the fall was stratified for 30 days and put in 2
inches (5 cm) of tap water. Thirty percent of immersed seeds germinated [
82].
Other research indicates that moisture affects seed viability
and germinability. In a plantation, 500 seeds from 3 green ash trees
were collected weekly from 31 August to 2 November 1970. Seeds slated for
germination testing were stratified for 90 days at 40 °F (5 °C). The
moisture content of other seeds
was evaluated following collection. Researchers found that seed
viability increased with maturity in
consecutive weekly harvests. They also found that seeds with greater
than 71% moisture content may not be
fully mature, but seeds with 9% to 19% moisture were likely
fully mature. The study also revealed that the moisture
content of green ash seeds was influenced by late fall precipitation [
70].
Seedling establishment/growth: Green ash seedlings establish best in partially shaded sites with moist soil or
litter [
209]. Researchers found more 1- to 5-year-old seedlings
grew under a partial canopy than in open- or closed-canopy
hardwood river bottom forests of southern Illinois. A greater
number of 1- and 2-year-old seedlings established on sites with low
(0.5 inch (1.3 cm)) litter depths than those with deeper litter (0.5-2
inches (1.3-5 cm)) [
151].
From controlled studies, researchers established
that ideal soil temperatures for green ash seedling growth are above
61 °F (16 °C). Green ash seedling growth increased with increasing soil temperatures
from 50 to 70 °F (8-20 °C). Exceedingly low
root zone soil temperatures adversely affected root growth and resource
partitioning [
13].
Green ash seedlings studied in 34 stands along North Dakota's Missouri River
floodplain occurred in all sampled stands but average density and frequency were
greatest on sites with "intermediate to high" nutrient levels [
161].
Flood tolerance of seedlings:
In southern Illinois, green ash
seedling survival and development were monitored in flooded and nonflooded conditions.
Seedlings developed "well past the cotyledon stage" were exposed to water
levels approximately 1 inch above the soil surface. No green ash seedlings died
after 60 days of flooding; green ash seedlings in saturated soils averaged 7.8
inches (19.9 cm) tall, while those in well-watered, well-aerated conditions
averaged 1.4 inches (3.5 cm) tall [
150]. However, no seedlings survived when green ash seedlings were
subjected to flooding levels 1 foot (0.3 m) above the soil surface [
149].
Seedling survival and growth:
Seedling establishment, survival, and growth
have been extensively studied. In central Ohio,
researchers followed the establishment and survival of black ash, green ash, and
white ash seedlings in open meadows and deciduous forests.
Ashes made up 69.9% of 2,553 seedlings monitored. Significantly more
(p≤0.05) ash seedlings
emerged on lowland than upland sites and in forests than open meadows. 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. 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 [
38].
Growth:
Green ash trees produce more than 1
growth flush per season [
135], and growth rates may
increase with flooding frequency. Johnson [
162] studied 34
stands along 80 river miles (100 km) of North Dakota's Missouri River.
From tree core analyses, Johnson estimated mean total radial tree growth at 26.8
mm for 17 green ash trees grown for 15 years during high flooding frequencies.
Trees grown for a 15-year period in the absence of flooding averaged 20.4 mm
total radial tree growth. From 14 trees,
Johnson estimated that the annual radial growth rate of green ash was 2.1 mm/year.
Asexual regeneration: Green ash is capable of producing root crown and epicormic sprouts,
and both are typical following disturbances.
Many report "prolific" and "vigorous" root
crown sprouting following fire, logging, or
other events that damage the trunk [
167,
183,
247,
248]. Epicormic sprouting is
common following lesser damage to branches. Observations
of green ash trees in Winnipeg, Manitoba, indicate that epicormic shoot
production may not only be stimulated through damage. Researchers
suspect that environmental and/or genetic cues may also signal epicormic shoot
production [
232].
The importance of vegetative sprouting following logging is illustrated in
the following 2 studies. On the Tombigbee River floodplain in Choctaw County,
Alabama, green ash trees were cut on 2 sites, 1 in early June and the other in
early October. A total of 83 green ash trees were cut and monitored following
logging. More than 50% of the stumps were sprouting 32 months after the fall
harvest, while less that 50% had sprouted by the 3rd postharvest year in the summer
harvest areas [
115]. Secondary succession of mixed-hardwood
forests in southeastern Virginia's Chowan River basin was studied following
logging. Forests were clearcut from 2 and 20 years before the study period and
allowed to regenerate naturally. Early coppice forests were dominated by red
maple and ash, primarily green ash [
265].
Flooding may also stimulate vegetative regeneration in green ash. The
north shore forest margin of Quebec's St. Lawrence estuary has experienced an increase
in the frequency of extreme flooding events in the 1950s and 1970s. Green ash trees damaged from these events regenerated
from the root crown and at the point of breakage on damaged stems [
179].
On an island in the Chippewa River near Eau Claire, Wisconsin,
96% of the counted green ash stems were sprouts. This finding may indicate a
reliance on asexual
regeneration on sites where the likelihood and/or frequency of
disturbance is high [
22].
SITE CHARACTERISTICS: Green ash is most often described in association with riparian areas,
floodplains, and swamps, but is also found in areas that periodically experience
drought conditions. In the Great Plains states, green ash is described on floodplains,
streambanks, lake margins, and ravines but is also typical on homesteads and in
shelterbelt and windbreak plantings [
124,
269,
294]. Moist to wet habitats are typical
green ash habitats described for the southeastern United States as well [
84,
110].
In Florida green ash is common on floodplains and calcareous river swamps [
62]. In
Michigan sites occupied by green ash are at least
seasonally wet [
297]. Green ash occurs on both wet and dry sites in Arkansas [
155].
Soils: Green ash tolerates a variety of soil types. Fertile, clay,
silt, and/or loam soils that range from poorly to well drained are the most common
generic descriptions of green ash soils [
10,
167,
167,
269].
Several researchers have described the soils in green ash vegetation types;
soils are described below:
Vegetation type Area of focus Soil description
sugarberry-American elm-green ash major river floodplains from eastern Texas to Atlantic Coast
& southern Illinois clay or silt loams [
159]
green ash/chokecherry southwestern North Dakota >35% clay, pH 7.9-8.1
green ash/western snowberry southwestern North Dakota 30-59% clay, pH 8.0-8.3 [
106]
green ash/chokecherry central and eastern Montana clay loam to sandy loam, water table <1 m in drought [
133]
green ash-American elm western North Dakota pH 6.6-7, chemical ions in
order of decreasing concentrations¹: Ca>Mg>Fe>K>P>Na>Mn>Zn>Sr>Cu
[
300]
green ash/chokecherry northwestern South Dakota moderately fertile, P levels low, N moderately low, 4-20% organic matter, neutral pH
[
296]
¹
The green ash-American elm forest type when compared to other forest types in the area
had the highest organic matter, total N, and replaceable Ca and Mg levels [
300].
On the Missouri River floodplain of North Dakota,
green ash dominates soils with high clay content. Green ash seedlings
and saplings display wide ecological tolerances with respect to soil
nutrients, organic matter, and water capacity [
162]. In eastern Texas, soils
supporting green ash are heavy limestone clays, acidic sands, or sandy loams
receiving ample water [
257].
Plantations, shelterbelts, and reclaimed farmlands:
Many have studied the relationships between soils
and green ash growth in plantations, shelterbelts, and reclaimed agricultural
areas. Soil analysis of a 6-year-old green ash plantation
on the Neches River terrace in Tyler County, Texas, revealed a positive
correlation between green ash height and pH of the A1
horizon. The pH of the A1 horizon ranged from 4.14 to 6.35 and accounted for 94.6% of the
variation in green ash tree height, which ranged from 4.5 to 18.1 feet (1.4-5.52
m). Green ash height and fine soil materials at a
depth of 2.5 feet (0.76 m) were negatively correlated. Correlations were reported
as significant (significance levels not reported) [
307].
In shelterbelts of Swift County, Minnesota, green ash survival and growth
were monitored
for 5 years on 3 different soils. Green ash survival was "excellent"
regardless of soil type. However, trees planted on
excessively drained, droughty, sandy loam soils grew slowly, while trees on
silty, clay loam, calcareous soils with poor drainage grew best. Cloudy and
rainy weather
during the establishment period likely enhanced survival rates [
55].
On abandoned farmlands of southwestern Quebec, green
ash seedling survival and growth were compared on sites with
stony littoral, sandy beach, dry-mesic moraine, mesic moraine, morainic ridge,
and wet marine soils. Green ash survival was greater than 70% on all
sites; however, height growth was best on nutrient-rich, fine-textured, well-drained
dry-mesic moraine soils. Green ash displayed wide ecological tolerances of the
soils studied, which ranged from rapidly to imperfectly drained with sand
contents of 31% to 86% and clay contents of 7% to 26% [
63].
Flooded soils:
Green ash is flood tolerant, but
studies indicate that green ash is more common on temporarily flooded sites.
The elm-ash-cottonwood forest type is
common along rivers and streams in the north-central states, and the forest
dominants reportedly tolerate
flooding for up to 50% of the growing season [
209]. In lowland forests of
southern Ontario, green ash constancy was 90% on temporarily flooded sites, 70%
on sites located 49 feet (15 m) inland from ponds, and 30% on mounds in ponds that
were raised above water level [
92]. In the Piedmont of Georgia, researchers indicate
that green ash "rapidly succumbs" to continued inundation during the growing
season [
94]. In lower hardwood swamp forests and backwaters or flats, green ash
is typical on sites where flooding is not continuous [
250].
Controlled experiments found reduced growth in green ash seedlings
grown in flooded conditions. Flood levels were 2 inches
(5 cm) above the soil surface and lasted for 32 days. The relative growth
rate of green ash leaves was 46% of well-watered controls.
Root and stem growth of flooded seedlings were 6% and 73% of controls,
respectively. The net photosynthetic rate of flooded green ash seedlings
was 50% of controls by flood-day 8 and 30% by flood-day 32 [
123].
Elevation: Below are the few areas that report elevational tolerances
for green ash:
Area Elevation
Colorado >6,000 feet [
120]
western North Dakota
(green ash-American elm type) 1,890-3,200 feet [
300]
central and southern Texas >3,000 feet [
257]
Utah "lower" elevations [
304]
West Virginia "low" elevations [
272]
southern Appalachians > 3,000 feet [
84]
Climate: The wide range occupied by
green ash implies a wide tolerance of climatic conditions. In a review of
green ash, Kennedy [
167] reports that green ash grows in humid to subhumid
environments with average annual precipitation levels between 15 and 59.8
inches (380-1,520 mm), low average January temperatures of -0.4 to 55 °F
(-18 to 13 °C), mean July temperatures from 64
to 81 °F (18-27°C), and an average number of 120 to 280 frost-free days.
In a 2-year study in the Little Missouri Badlands of North Dakota, where
green ash grows, minimum and maximum temperatures reached -35 °F (- 31°C) and 105
°F (41 °C), respectively, and annual precipitation averaged 15.75 inches (400
mm) [
318]. The climate described for green ash habitats in southeastern
Texas is much milder. Reported minimum and maximum temperatures were 51.1
°F (10.6 °C) and 81.7 °F (27.6 °C), respectively, and annual precipitation
averaged 52 inches (1,320 mm) in the Big Thicket National Preserve. However,
the frequency of
tropical storms and hurricanes in this region can be high [
194]. A temperate
climate regime is reported for the northern shore of Quebec's St. Lawrence
estuary, which supports an almost pure green ash stand. From 1960 to 1988, the
mean annual precipitation was 38.9 inches (987 mm), 9.1 inches (231 mm) of which
was snow. The average January temperature was 10.9 °F (-11.7 °C), and the mean
July temperature was 67.1 °F (19.5 °C) [
179].
Drought tolerance:
Although overwhelmingly described as a riparian, floodplain species, green ash
has survived drought conditions in several areas. In southeastern South Dakota,
green ash survival was 63% over a 5-year period (1934-1939) that included 2 years
described as "the most severe droughts ever to visit" the area.
The author cautioned that
green ash should not be planted on upland sites with fine-textured soils,
suggesting an increased likelihood of green ash tree mortality
during drought conditions on these sites [
191].
Green ash trees in windbreaks of western Minnesota suffered
severe drought conditions in 1934.
By the end of that summer, just 8% of
green ash trees were dead or dying. However, in western Kansas,
green ash mortality was 33% at the end of a 4-year-long drought. Trees
investigated were all mature, established green ashes [
8].
Cold tolerance:
Green ash survival is
consistently high in shelterbelt plantings of the northern Great Plains, where
winters can be severe. However, green ash may suffer slightly increased
winterkill with age, injury from late-spring frosts, and occasional broken
stems from drifting snow [
100]. Green ash seedlings grown from seed
collected in Wisconsin were exposed to low
temperatures and stomatal closure was measured. Green ash seedlings exposed to 3
days of 37 °F (3 °C) temperatures had increased stomatal closure with each successive
day. Treatments of 43 to 48 °F (6-9 °C) did not produce the same response,
suggesting that 37 °F (3 °C) is below green ash's cold tolerance [
172].
Dormant 1-year-old twigs collected from an area near Greenville, Mississippi,
and a site in St. Paul, Minnesota, were used to evaluate the freezing resistance
of green ash. Researchers defined freezing resistance
as the lowest temperature at which no injury occurred. Green ash bud and cortex
xylem tissue from Mississippi resisted freezing at temperatures of -20 °F (-30
°C) and -40
°F (-40 °C), respectively. Bud and cortex xylem tissue from Minnesota resisted
temperatures of -40 °F (-40 °C) and -90 °F (-70 °C), respectively [
243].
SUCCESSIONAL STATUS: Green ash is described as a pioneering, early successional, mid-successional,
subclimax, climax, and old-growth species in the literature.
In American beech (Fagus grandifolia)-sugar maple forests of
southern Indiana, green ash is an
early, open-field colonizing species that is later replaced by
American beech and sugar maple
[
309]. The hackberry-elm-ash (Celtis-Ulmus-Fraxinus spp.)
vegetation type occupying low flats and sloughs of the
Mississippi River floodplain is considered temporary and typically
follows heavy cutting and/or fire events [
221]. Green ash appears
early in the successional development of alluvial soils, sometimes as a pioneer
or as a replacement to cottonwood, quaking aspen, and/or black
willow communities [
167]. The quaking aspen-green ash community type on
floodplains of the Missouri River is a mid-seral type that is later replaced by
the green ash/western snowberry type [
106].
The cases in which green ash is labeled a late-successional or climax
species are equally abundant. In the successional development of Nebraska's river
floodplains, green ash is identified as a late-seral species [
7].
The sugarberry-American elm-green ash cover type
is identified as persistent by several authors [
159,
250].
Studies of 34 stands along 80 river miles (100 km) of North Dakota's Missouri River
floodplain revealed an increased importance of green ash with
increased substrate depth and increased stand age [
162].
Along rivers and streams of the north-central states, the elm-ash-cottonwood
forest type is considered subclimax [
209].
After studying a sere along the Yellowstone River from Glendive to Sidney,
Montana, researchers categorized green ash as a climax species [
40]. Green
ash also occurs in the old-growth Schnabel Woods of Boone County, central
Missouri. However, the importance of green ash
has declined over the last 40 years in the area [
235]. Kindscher and Holah [
169]
report that green ash importance increases with increasing stand age in
plains cottonwood-hardwood gallery forests of the Great Plains, and a dense
layer of green ash saplings is common in old-growth stands.
Shade tolerance:
Green ash is often described as moderately shade tolerant. Shade tolerance, however,
decreases with increasing age of green ash trees [
159,
250].
Several have studied green ash seedling growth under shaded conditions.
Growth and morphological differences were apparent in 2-year-old green ash
seedlings grown under different levels of shading. After 5 weeks, seedlings in 4%,
8%, and 100% of full sun ceased to grow, but growth continued in 20% and 40% of
full sun. Leaf thickness
increased linearly with decreased shading. Trees in heavy shading had poorly
developed crowns, reduced height growth, and fewer and smaller branches. The growth
rate of trees grown in moderate shade and full sun conditions exceeded that of
trees grown in heavy shade [
25].
Findings were similar for nursery-grown green ash seedlings subjected to full
sun and shade treatments in Lincoln, Nebraska. Comparisons of seedlings grown in
full sun and shade (18% full sun) revealed that leaf blade area was larger and
leaves were thinner on shade-grown trees. Relative growth rate (pretreatment
growth rate/posttreatment growth
rate) was 1.27 in shade and 2.85 in full sun [
196].
General disturbance:
Green ash easily colonizes
disturbed sites when a seed source is available. In a study of green ash
ecology, Taylor [
280] reported that green ash frequency increased as the amount of
disturbed area increased. In the Opinicon Lake area of
southeastern Ontario, succession was monitored in 2 hay fields abandoned in 1970. Half of one field was ploughed in
1975. On 3 sides, fields were bordered by forests dominated by American elm, white ash, green ash, and sugar
maple. In all plots, the occurrence of green ash was 54% for all years (1976-1994).
Researchers indicated that green ash seed was likely wind dispersed; birds or small
mammals may have also aided dispersal by caching seed [
72].
Canopy release:
Many studies indicate increased green ash growth in forest openings. Sites in several
mixed-hardwood forests of southeastern Virginia's Chowan River basin were
clearcut 2 to 19 years prior to study and allowed to regenerate naturally.
Regeneration in the mixed-hardwood forests was dominated by ash, primarily green ash, and red maple. Most early regeneration was due to sprouting [
265]. Green ash
was also identified as the species that most quickly colonized forest openings
in an extensive study of 34 stands along 80 river miles (100 km) of North Dakota's
Missouri River floodplain [
162].
In the Little Missouri National Grasslands of southwestern North Dakota's
Custer National Forest, canopy removal experiments were monitored for 7
years in degraded green ash-dominated woody draws. Sites that had 40% of
the overstory canopy removed were compared to those with no removal.
Green ash tree heights were significantly (p=0.04)
greater on sites with partial canopy removal for the 3rd, 4th, 5th, and 6th
posttreatment years [
291]. Harvesting 40% of the trees in the area also
stimulated green ash sprouting and seedling growth. Seedling height was greater
on harvested than unharvested sites, and within the harvested sites
increases were greater
on sites closed to grazing [
41].
Green ash increased in importance following harvests in
oak-dominated, mixed bottomland hardwood forests
along the Tombigbee River floodplain in Choctaw County,
Alabama. Before harvesting in the summer and
fall of 1992, green ash made up 5% of the preharvest stems. Following harvest,
green ash contributed 22% to the total number of stems in the area
[
116].
Secondary and old-growth forest comparisons:
Green ash is found in both secondary and old-growth forests. Researchers
compared 2nd-growth (<150 years old) and old-growth (>150 years old) forests
in the Wayne National Forest of southeastern Ohio. Green ash was present as a canopy
species in only 2nd-growth forests, as a sapling in most forests over 70
years old, and as a seedling in all forest age classes sampled [
112]. On Horseshoe Lake Island in
Alexander County, Illinois, green ash was most important in old-growth forests.
Old-growth stands had been relatively undisturbed, while 2nd-growth stands
were undisturbed for just the last 75 years [
239].
Researchers predicted that green ash would "gradually diminish" from the
approximately 100-year-old bottomland forests in Virginia's Meherrin River
in Greensville County [
251].
Floodplain succession:
The patterns of green ash succession
on alluvial floodplains are similar for many different rivers and
regions. Green ash typically invades pioneer communities early in succession
and remains in mature floodplain communities. Along a sinuous section
of the Bogue Chitto River in Washington Parish, Louisiana, green ash
occurred on the youngest
surfaces referred to as the herb-forest transition zone and the oldest surfaces
on the upper floodplain margin or the cut bank of the upstream river bend
[
238]. Studies of a sere along the Yellowstone River from
Glendive to Sidney, Montana, suggest green ash is a climax species.
Newly formed river sandbars
were populated by quaking aspen and willow (Salix spp.) communities.
Willows died out approximately 20 years
following establishment. After about 100 years, quaking aspen declined and
shrubs, primarily Wood's rose (Rosa woodsii) and western snowberry,
increased in importance. Green ash colonized young quaking aspen
communities, persisted through the shrub-dominated stage, and was common as a
seedling in subsequent communities. The researcher expected green ash seedlings
would replace decadent green ash adults, and thus green ash is likely a climax
species [
40].
Along the Missouri River of southeastern South Dakota, the 1st established woody
vegetation is a black willow-sandbar willow community that is
soon invaded by quaking aspen. The black willow-quaking aspen community persists for
nearly 15 years before willow trees begin to die. More mesic conditions
prevail after the loss of willows. Quaking aspen growth deteriorates about 50
years following establishment. With the loss of quaking aspen, green ash, American elm, and
boxelder dominate the floodplain [
311]. Another reach of the Missouri
River floodplain in North Dakota, extending from the Garrison Dam to the Oahe
Reservoir, has also been well studied. On recent alluvial deposits, quaking aspen
and peachleaf willow are pioneers. Green ash and boxelder are 1st to reach tree
size in the eastern cottonwood-peachleaf willow forests and persist
in intermediate- and old-aged
stands as well. The oldest trees in the study area were 300 to 350 years old,
and green ash seedlings occurred in stands of all ages [
161].
Using aerial photographs, ring counts, and/or stem cross sections,
researchers reconstructed and evaluated forest floodplain succession on the
Republican River of Clay County, Kansas. First to invade floodplain alluvium
were sandbar willow, peachleaf willow, and quaking aspen; these species
established on 1- or 2-year-old substrates.
Within 10 years, red mulberry (Morus rubra), American elm, green ash,
and boxelder appeared.
Hackberry established when the floodplain surface was 10 to 30
years old. Sandbar willow survived only about 10 years, peachleaf willow survived for
approximately 30 years, and quaking aspen died within 100 years of establishment. In
100- to over 150-year-old stands, American elm
and hackberry dominated, but green ash was present as well. Below is the average
basal area of green ash
in different-aged stands [
31]:
Stand age (years) 0-10 (n=8) 10-30 (n=17) 30-60 (n=7) >60* (n=7)
Trees <6 cm dbh <0.005 0.03 0.03 0.06
Trees >6 cm dbh 0 0.03 1.84 1.41
*Within the >60-year-old-stands, 2 were over 100 years old, 1 was 120 years
old, and 1 was 150 years old.
Flooding: In a review, Hook [
144] classified green
ash as
moderately flood tolerant. This tolerance rating suggests that green ash can
develop from a seedling to a mature tree in soils that are waterlogged
approximately 50% of the time. Winter, spring, and/or early summer flooding
are most typical in green ash habitats. For more information on the
survival and growth of green ash seedlings grown in flooded conditions, see the
Seedling establishment/growth discussion above.
Eighteen years of vegetation change were monitored in Hickory Creek
streambank forests of northeastern Illinois. Green ash
dominated the frequently flooded lowland sites from the streambank margin to 3
feet (1 m) above bank level. The researcher described green ash as "very flood
tolerant." Over the course of the 18-year-study, the relative density of green
ash decreased but relative dominance increased [
30].
Within the Montezuma National Wildlife Refuge of central New York,
researchers compared 2 seasonally flooded sites to a nonflooded control site.
The eastern pool was flooded in the spring from mid-March to mid- or late July.
The western pool was
flooded from mid-September to mid-November. Vegetation was surveyed in 1965
(before flooding of the western pool
and 1 year following flooding of the eastern pool), in 1979 (2 years after the end
of flooded conditions), and in 1995 (18 years after discontinued flooding in the
area). Researchers found that in 1995 the density of saplings in the eastern and
western pools was 30 to 90/ha, respectively, but was 270/ha in the
control area. Sapling
cores suggested that the majority of sapling recruitment occurred from 1967 to
1973, indicating lower recruitment levels in times of flooding. Green ash density and
basal area are provided below for the flooded and nonflooded periods [
76].
Site
East-
flooded 1964-1977
West-
flooded 1966-1977
Control
year density
(trees/ha ± s x) basal area (m²/ha) density basal area density basal area
1965 160 ± 7 ---- 140 ± 0 ---- ---- ----
1979 170 ± 47 8.2 ± 2.4 190 ± 38 5.8 ± 1.8 330 ± 92 6 ± 2.2
1995 170 ± 30 9.3 ± 3.0 ---- 8.7 ± 3.0 530 ± 138 4.7 ± 1.4
Extreme weather events:
Typically a majority of
green ash trees survive the high winds and/or ice that accompany extreme
weather events. In eastern Ontario, the mortality of
62 green ash trees (>3.9 inches (9.9 cm) dbh) was 24.2% for 1996 to 1998
(after ice storms). Mortality was 4.4% from 1999 to
2000, and no green ash trees died in 2001. Damaged trees died relatively quickly [
147]. In a "50- to 100-year"
ice storm event that deposited ice 0.8 inch (2 cm)
thick on branches of bottomland forests species in western New York's Till Plain,
the average green ash crown damage was just 10% [
246].
Following Hurricane Hugo, researchers evaluated the damage to mixed
bottomland hardwood species in Congaree Swamp National Park of South
Carolina. Winds exceeded speeds of 96.3 miles/hour (155 km/h) in
forests that had been relatively undisturbed for the previous 100 years. In
slough areas, 4 of 29 sampled green ash trees were uprooted; in bottomland
sites, just 2 of 41 green ash trees were uprooted [
225]. The
number of recruits, defined as number of individuals to reach 2 cm dbh,
increased significantly (p<0.05) following Hurricane Kate in
old-growth southern mixed hardwood forests
north of Tallahassee, Florida. There were 2 prehurricane (1978 to 1984) green ash
recruits and 11 posthurricane (1985 to 1992) recruits.
Increased recruitment was likely facilitated by the overstory mortality that
followed the high wind speeds of 99 miles/hour (160 km/h) over areas with soils saturated
by the storm [
27].
SEASONAL DEVELOPMENT: Green ash produces flowers before leaves [
304]. The process from
the start of inflorescence bud growth to fruit set takes 3
years for green ash trees, and on average 1/3rd of the flower buds initiated
produce flowers [
231]. In a review, Farmer and Pitcher [
93] report that male
trees flower almost every year, while female trees flower every 2 to 5 years.
From a 5-year study of 5 green ash trees in the Quetico-Superior
Wilderness Center of
northeastern Minnesota, Ahlgren [
6] reported an "abrupt" increase in
stem expansion with an "extreme" rise in temperature. Green ash bud swell
coincided with flowering but occurred only after temperatures had reached 70
°F (20 °C) or more. The 1st trees leafed out on 10 April, and the last trees
to leaf out did so on 3 June. The earliest trees to shed their leaves did
so on 19 September, and the latest trees dropped leaves on 3 October [
6].
In Ithaca, New York, researchers found that green ash
seedlings initiated root growth in mid- to late May when temperatures were between
54 and 59 °F (12-15 °C); root growth ceased in the fall when
temperatures were 40 to 50 °F (6-8 °C) [
135]. In Manitoba, Remphrey
[
230] reports that shoot growth begins sometime from mid-April to early
May. Green ash leaf fall is typically earlier
than other associated species including maples (Acer spp.),
elms, plums (Prunus spp.), alders (Alnus spp.), and
oaks [
308].
Below are the reported fruiting and flowering dates
for green ash:
State or region Flowering dates Fruiting dates
Florida spring [
62,
317] ----
Illinois April-May [
206] ----
north-central Texas February-March [
79] ----
West Virginia April-May [
272] ----
Blue Ridge province April-May [
312] ----
Carolinas April August-October [
227]
Great Plains April-May [
124] ----
New England ---- 2July -25
September [
249]
north-central Plains mid-April August-September [
269]
Quetico-Superior Wilderness Center of northeastern Minnesota 1st flowered on 23 April;
last initiation of flowering on 25 May* Seeds fell 3 October** [
6]
*Based on a 5-year-long study of 5
trees; tree age and site occupied varied.
**Based on a single year of study.
