Ailanthus altissima

• INTRODUCTORY
• DISTRIBUTION AND OCCURRENCE
• BOTANICAL AND ECOLOGICAL CHARACTERISTICS
• FIRE ECOLOGY
• FIRE EFFECTS
• MANAGEMENT CONSIDERATIONS
• REFERENCES

INTRODUCTORY

AUTHORSHIP AND CITATION FEIS ABBREVIATION SYNONYMS NRCS PLANT CODE COMMON NAMES TAXONOMY LIFE FORM FEDERAL LEGAL STATUS OTHER STATUS
	Photo courtesy of David J. Moorehead, Forestry Images

The Eastern and Southern regions of the U.S. Forest Service rank tree-of-heaven in Weed Category 1: an exotic species known to be invasive and persistent throughout all or most of the Regions. Weed Category 1 species can spread into and persist in native plant communities, displacing native species and posing a demonstrable threat to plant communities. Use of tree-of-heaven is prohibited on National Forest System Lands [159,160].

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

A century after the North American introductions, tree-of-heaven is most common in its initial centers of distribution: the Northeast and California. In the East, it is invasive from New England south to the mid-Atlantic states [45,125]. Tree-of-heaven is frequently found in the Midwest, becoming uncommon in the Great Plains and the South. It is weakly invasive in the Great Plains [58,138] and is rare south of North Carolina in the Southeast and South [39,125,174]. In the West, tree-of-heaven is common in California and locally frequent in Oregon and Washington [45,71]. In California tree-of-heaven occurs in the Bay Area, the Central Valley, and in foothill counties with a history of gold mining [72,81]. In the Pacific Northwest it grows along waterways, including banks of the Snake and Columbia rivers [71]. In the Southwest it occurs in riparian zones and mesic canyons [154]. Plants database provides a map of tree-of-heaven distribution in the United States.

Tree-of-heaven has established in temperate climates throughout the world. Its earliest introductions may have been in Japan and Korea, where it is probably not native [101]. It was introduced in Europe in the 1700s. and became widespread there [88,155]. Introductions in Argentina, Australia, and Africa followed, using seed from European trees [72,74].

Because of its scattered and disjunct distribution in North America, tree-of-heaven occurrence is not well documented for all plant communities where it may occur [112]. The following lists are not restrictive, but include plant communities where tree-of-heaven is a known invader.

On the Georgia Piedmont, tree-of-heaven is an important species in early successional loblolly pine (Pinus taeda)-black oak-white oak forests. Flowering dogwood (Cornus florida), yellow-poplar (Liriodendron tulipifera), Chinese privet (Ligustrum sinense), and winged elm (U. alata) are common associates [27].

Tree-of-heaven is invasive in riparian zones of the Southwest and elsewhere [69,142]. In the middle Rio Grande Basin of New Mexico, tree-of-heaven occurs in Fremont cottonwood-Rio Grande cottonwood-sandbar willow (Populus fremontii-P. deltoides var. wislizenii-Salix  exigua) bosques along with nonnative, invasive Siberian elm (U. pumila) and white mulberry (Morus alba) [48]. Tree-of-heaven has invaded arroyos of the Sandia National Laboratory, New Mexico, associating with Siberian elm, saltcedar (Tamarix ramossima), Apache plume (Fallugia paradoxa), and fourwing saltbush (Atriplex canescens). Upland, it associates in Colorado pinyon-oneseed juniper (Pinus edulis-Juniperus monosperma) stands with Gambel oak (Quercus gambelii) and Siberian elm [108].

BOTANICAL AND ECOLOGICAL CHARACTERISTICS

GENERAL BOTANICAL CHARACTERISTICS RAUNKIAER LIFE FORM REGENERATION PROCESSES SITE CHARACTERISTICS SUCCESSIONAL STATUS SEASONAL DEVELOPMENT
	Photo courtesy of Chuck Bargeron, Forestry Images

Tree-of-heaven is a nonnative, deciduous tree. It may reach 60 to 70 feet (18-21 m) in height, 80 feet (24 m) in crown width, and 3 feet (0.9 m) in trunk diameter at maturity [35,53,165]. The champion tree is in Tennessee, and reaches 67 feet (20 m) in height, 64 feet (19 m) in spread, and 20.6 feet (6.3 m) in diameter [73]. Trees may be shrubby when suppressed or regularly pruned [52]. Tree-of-heaven has smooth, thin bark and a straight bole. Branches are brittle and self-pruning. The large, malodorous leaves are pinnately compound, with prominent glands on the back of each leaflet. Surface-to-volume ratio of leaves is high: leaflets range from 15 to 41 in number, and total leaf length may reach 3 feet (1 m) [35,52,53,165]. Leaf stipules have nectaries that excrete sugars [14].

Most flowers are unisexual, but some trees may have perfect flowers [176]. The inflorescence is a 0.3- to 0.6-foot (10-20 cm) panicle with 6- to 8-mm-long flowers. Staminate flowers have a strong, objectionable odor. Fruits grow in clusters of 1-seeded, dry schizocarps with wings. They are 2.5 to 5 cm in length and propeller-shaped, resembling maple (Acer spp.) fruits [35,52,69,70,77,79,131,172]. A fruit cluster contains hundreds of seeds [88] that average 0.6 × 0.25 cm in size [5] and 27 mg in mass [107].

Roots are shallow, widely spreading, and capable of sprouting [112]. Young trees have a taproot and several large laterals [123,129,130], although the taproot may diminish with tree age [112]. Ramets do not have taproots. In dry, rocky soil or beneath pavement, trees grow long horizontal roots that do not branch until more favorable soil is found [123,129,130]. Roots near the trunk thicken with age, serving as storage organs. Most roots occur in the upper 18 inches (46 cm) of soil. Deep roots send out smaller roots that grow near the soil surface; adventitious shoots generally arise from these shallow roots [112].

Investigations of tree-of-heaven in China give little clue as to the species' natural growth habit. Tree-of-heaven grows in a densely populated area of China where no wildlands are left. As valued ornamentals, mature trees-of-heaven in China are pruned to aesthetically pleasing, single-stemmed forms. Sprouts are harvested for firewood and medicinal uses [74,130].

Life span: Tree-of-heaven is typically short lived, with an average life span of 30 to 50 years [88,112]. Cloning from root sprouts can extend ramet life hundreds of years [78]. Sprouts from the 1st tree-of-heaven in North America, planted in Philadelphia's Bartram Botanical Garden 1784, still exist today [23].

Physiology: Tree-of-heaven appears to be allelopathic [32,97,100,109,111,115]. Chemical extracts from the leaves, barks, roots, and seeds have inhibited germination and growth of other species in the laboratory [64,65,66,97]. Allelopathic chemicals (ailanthone and other compounds identified in [5,6,32,109]) are most concentrated in roots, with young ramets producing more toxins than older trees [64,97]. Reciprocal transplant experiments [25] may help determine the degree of tree-of-heaven allelopathy under natural conditions.

Open-grown trees-of-heaven are highly efficient at photosynthesis, and store large quantities of photosynthate in stems and roots [14,17,18,103,110]. Foliar nectaries appear to maintain carbohydrate balance during growth and flower initiation by excreting photosynthates [15].

Tree-of-heaven is sensitive to ozone pollution [55]; however, it is highly tolerant of most industrial pollutants [110,133]. In a highly polluted area of Armenia, tree-of-heaven showed the least damage and best growth of 8 urban tree species (Derojan, as cited in [45]).

Breeding system: Tree-of-heaven is mostly dioecious. Rarely, either bisexual trees or trees with both bisexual and unisexual flowers are found [35,52,78,112,176].

As with most species with wind-dispersed seed, tree-of-heaven appears to have a relatively uniform genetic system, with most diversity occurring among rather than within populations [46,130]. Because North American tree-of-heaven populations originated from only 3 introductions [35,72,155,169], they may be even less genetically diverse than native Asian populations. A comparison of seedlings germinated from seed collections from 5 locations across the United States and 5 locations across China showed significant differences in height growth (p=0.01), root:shoot ratios (p=0.05), and leaf area (p=0.05) among United States and Chinese seedlings. Populations from the United States were taller, allocated relatively less biomass to roots than stems, and had greater leaf areas, compared to Chinese populations [46]. In a common garden study comparing seedling populations within the United States, Feret and others [47] found California populations were significantly (p=0.01) taller than eastern populations. Seed width and biomass were correlated with latitude (t=0.96), with northern populations having the widest, heaviest seeds. Feret [45] found some tree-of-heaven seed and seedling growth characteristics of provenances from the East and California appeared random, and were not correlated (nor appeared best adapted) to site or geographic location. He reported significant differences between North American and Chinese tree-of-heaven provenances for seed and seedling characteristics. Contrary to expectations, allozyme analysis showed no evidence of inbreeding depression in North American provenances compared to native Chinese provenances.

Pollination: Tree-of-heaven is pollinated by a variety of nectar- and pollen-feeding insects [120]. Although disagreeable to humans, the strong odor of male flowers attracts honey bees, beetles, and other insects [112].

Seed production: Tree-of-heaven produces many small, light seeds. Flower, fruit, and seed production begin early. Six-week-old seedlings have flowered in the greenhouse [44], and 1-year-old saplings and 2-year-old root sprouts have been observed with fruit [78,88,147]. Trees in California produce viable seed by 10 years of age [78]. Best seed production is from 12 to 20 years of age [112]. In France, which has a climate similar to California, 1.6- to 3.3-foot-long (0.5-1 m) root sprouts produced seeds [14]. Mature female trees may produce several hundred inflorescences in a year. Hunter [78] reports 5-year production of a female tree in Martinez, California, as 150, 183, 219, 439, and 56 inflorescences. An individual flower contains hundreds of seeds, so individual trees can produce 325,000 or more seeds per year [14,78]. Illick and Brouse [80] estimated that a small, 12-inch-diameter (30-cm) tree in Pennsylvania produced over a million seeds. Most seed are viable, even those that overwinter on the tree and disperse in spring [78,102]. Repeated top-kill lowers seed production [112].

Seed dispersal: The winged fruits are easily and widely dispersed by wind [39,88]. Water and machinery also disperse seeds [124]. In the laboratory, Matlack [107] reported the following dispersal characteristics for tree-of-heaven seed collected in Delaware (data are means and 1 standard deviation):

Distance traveled was significantly greater (p<0.05) compared to seed of 37 other wind-dispersed species [107]. On Staten Island, New York, tree-of-heaven seedlings volunteered on a restored landfill site planted to native woody species. A year after restoration plantings, tree-of-heaven count on fifty 10 × 30 meter plots totaled 65 seedlings, the 6th highest among 32 naturally regenerating taxa. Distance to the nearest seed-bearing tree-of-heaven was 299 feet (70 m) [137].

In Ithaca, New York, new tree-of-heaven seed clusters often fell and dispersed in clumps, resulting in patches of closely related seedlings. Seeds dispersed individually as the fruit clusters disintegrated over the winter [123].

Seed banking: Seeds retain dormancy for less than a year, so seeds do not build up long-term seed banks [79,93]. Tree-of-heaven does establish temporary soil seed banks from on- and off-site sources of seed [176]. In Tennessee, for example, Dobberpuhl [37] found viable tree-of-heaven seed in the soil seed bank. There were no trees-of-heaven in the overstory.

Germination: Hand-collected, freshly dried tree-of-heaven seed yields 60% to 85% germination in the laboratory [112,165]. Hunter [78] reports 30% germination of seeds that overwintered on the tree and dispersed in spring. Tree-of-heaven embryos are dormant, and stratification improves germination rates [56,78,112]. Seed can germinate in highly compacted soil [130], and is salt tolerant. Studies of eastern hardwood species found roadside salt does not appreciably affect tree-of-heaven germination; native oak and birch seed is far more adversely affected by salt [13]. The tree-of-heaven embryo is well equipped for rapid growth. Although it lacks an endosperm, it has 2 large cotyledons with stored oils [52,92,105,112,176]. Litter has both negative and positive effects on germination. In eastern deciduous forests, oak (Quercus spp.) leaf litter has been shown to delay tree-of-heaven germination and increase mortality, but not affect subsequent biomass of surviving seedlings [41]. Litter may have positive effects on tree-of-heaven germination and establishment by reducing competition from herbaceous species [42].

Seedling establishment/growth: Although seed production is prolific, tree-of-heaven seedling establishment is infrequent on many sites [124]. Dry climate may limit tree-of-heaven recruitment in the Great Plains and the arid West [45,124]. Even so, tree-of-heaven has successfully expanded its range through seed spread [89,128,137,139], and seedling establishment appears to be more common than indicated in general literature [88,147]. For example, in a root excavation study, Knapp and Canham [89] found initial tree-of-heaven recruitment in New York eastern hemlock forest gaps was from off-site seed, not root sprouts.

Whether initial regeneration is accomplished from seed or by cloning, once established, tree-of-heaven growth is extremely rapid. It may be the fastest-growing tree in North America [89,127]. Both the species' common and scientific (Ailanthus, sky-tree) names refer to its ability to attain height quickly [35,165]. Seedlings attain 3.3 to 6.6 feet (1-2 m) in their 1st year [112]. Growth of tree-of-heaven seedlings relative to native sweetgum (Liquidambar styraciflua) and nonnative Norway maple seedlings 2 years after planting in a New York City common garden was [123]:

Saplings average an additional meter of height growth per year for at least 4 years [1]. Relatively rapid growth continues for pole-sized trees: in New York, pole-size trees-of-heaven growing in canopy gaps gained 2 to 4 mm of radial growth annually, the highest rate recorded for the 6 tree species measured (the other 5 species were native) [89]. In a New England survey, tree-of-heaven reached 33 to 49 feet (10-15 m) in height and 3.7 to 4.3 inches (9-11 cm) dbh in 30 years [1]. Growth is fastest in California trees, which are typically 35 to 63 feet (10-20 m) high by 12 to 20 years of age [79]. Growth slows greatly after age 20 to 25, with height increases of 3 inches (7.6 cm) or less per year [80]. Once established, tree-of-heaven density increases by root sprouting. One ramet may occupy over an acre (0.4 ha). Sprout growth slows to several centimeters per year if sprout stems become shaded [79]. In West Virginia, Kowarik [91] reported an average growth rate of 0.36 foot/year (0.11 m) for tree-of-heaven sprouts suppressed in the understory of an oak (Quercus spp.)-sugar maple forest.

Cattle, deer, and small rodent browsing may retard tree-of-heaven establishment and growth [122]. Browsing effects probably vary by site and animal density. In a New York oak-hickory woodland, Forgione [49] found no significant differences in tree-of-heaven seedling establishment on open plots and plots exclosed to white-tailed deer.

Asexual regeneration: Tree-of-heaven sprouts from the roots, root crown, and bole [45,98]. Although tree-of-heaven reproduces well from seed, sprouting is the more common method of regeneration [88]. In Ithaca, New York, 42% of 1-year-old, excavated tree-of-heaven stems were seedlings, and 58% were root sprouts [123]. Young trees, cut to the root crown before bark becomes thick and corky, often sprout from both the root crown and roots [88,147]. Bole damage promotes root, root crown, and bole sprouting [78,88]. Death or injury of the main stem usually results in prolific root sprouting [112]. Top-growth damage is not necessary for root sprouting to occur, however. Even as seedlings, trees-of-heaven produce horizontal roots capable of sprouting [23]. Root sprouting is an uncommon regeneration strategy for woody species (e.g., see FEIS reviews on quaking aspen and Sierra mountain misery (Chamaebatia foliolosa)), but it is a powerful strategy for species employing it. Roots have more nutrient- and photosynthate-storing capacity than rhizomes, conferring better protection from aboveground disturbances such as fire, and a more vigorous sprouting response after top-kill has promoted sprouting by removing apical dominance [84,85].

With tree-of-heaven's spreading root system, root sprouts may appear as far as 50 to 90 feet (15-27 m) from the parent stem [80,88,147]. Sprouts of all types (root, root crown, or bole) generally grow faster than seedlings. In the East, average rate of growth is reported as 6 feet (1.8 m) per year for bole sprouts, 2.7 feet (0.8 m) for root sprouts, and 1.3 feet (6.5 m) for seedlings [80]. Root sprouts in California may exceed 3.5 feet (1 m) in their 1st year [78]. During drought, tree-of-heaven pulls stem water into roots and begins stem die-back. Stem die-back may be extensive during extended droughts, but tree-of-heaven typically survives drought by sprouting from the roots when there is sufficient water to support new growth. Frost die-back and regrowth is common in tree-of-heaven's northern limits [45].

On the Himalayan foothills of India, trees-of-heaven with root crown girths between 12 and 16 inches (30 and 40 cm) showed greatest root sprout production following road construction. Trees in the largest-diameter class did not produce sprouts. Mean sprout production was [96]:

Tree-of-heaven has been termed "the most adaptable and pollution tolerant tree available" [36]. Highly tolerant of industrial gases, dust, and smoke, tree-of-heaven is common on disturbed sites, especially alleyways, roadsides, and fence rows [35,53,58,114,174]. In wildlands, tree-of-heaven occurs on disturbed sites, open woodlands, and riparian zones [58,71,150,169]. In the Southwest, tree-of-heaven invades canyons, arroyos, and riparian zones including the banks of the Rio Grande [3,108]. After Hurricane Camille, it was associated with debris avalanche chutes in Virginia [76]. Tree-of-heaven occurrence in an oak-hickory forest of West Virginia was also associated with disturbance [75]:

Soils/topography: Tree-of-heaven tolerates a wide range of soil conditions [39,112]. For example, in oak-hickory woodland of Sussex County, New Jersey, tree-of-heaven occurs in permanently swampy, ridgebottom soils of an abandoned Boy Scout camp [10]. At the other moisture extreme, large, water-storing roots enable tree-of-heaven to tolerate dry, rocky soils and extended drought. Even seedlings show drought tolerance, often volunteering in pavement cracks and other dry sites [57,156]. In Kansas, mature eastern redcedar and tree-of-heaven showed best survivorship to the drought of 1934 compared to associated tree species [149].

Tree-of-heaven also tolerates a range of nutrient conditions. Best growth occurs on nutrient-rich, loamy soils such as those in the Central Valley of California, but tree-of-heaven tolerates nutrient-poor soils [45,88,112,176]. In reclamation studies, tree-of-heaven tolerated acid mine spoils better than calcareous spoils, and grew on low-phosphorus soils [112]. Tree-of-heaven can grow on soils as low as 4.1 pH, in soluble salt concentrations of 0.25 mmhos/cm, and in soils with phosphorus levels as low as 1.8 ppm [128]. It tolerates compacted soils [123].

Tree-of-heaven's spreading root system permits establishment and growth on cliff faces and other steep inclines [4].

Climate: Tree-of-heaven is the only species in its genus that tolerates cold climates [74]. Climate within tree-of-heaven's North American distribution varies widely, from subtropical and wet in Florida, arid in the Great Plains and Great Basin, to cold and wet in the Northeast. Tree-of-heaven tolerates as little as 14 inches (360 mm) of annual precipitation under 8 months of drought in the arid West, and as much as 90 inches (2,290 mm) annual precipitation in the Appalachian Mountains. Annual mean maximum and minimum temperatures are 15 and 97 ^oF (-9 and 36 ^oC). Large, water-storing roots confer drought tolerance. Extreme cold and prolonged snow cover restrict its occurrence to lower slopes in mountainous regions, as seedlings are not cold resistant. Tree-of-heaven may be able to colonize cold regions that experience several successive years of mild climate [112].

Elevation: Tree-of-heaven grows from 4,900 to 5,900 feet (1,500-1,800 m) elevation in China [163]. It is reported at the following elevations in the western United States:

Tree-of-heaven rarely occurs in closed-canopy, late-successional hardwood forests (e.g., [18]), but can establish in closed-canopy and old-growth forest canopy gaps (e.g., [89]) such as those created by woolly adelgid [121] or gypsy moth defoliation, windstorms [76], or possibly fire. For example, tree-of-heaven occurred in 2 of 4 avalanche debris chutes surveyed 10 years after Hurricane Camille, but did not occur in adjacent, undisturbed hardwood forest in Nelson County, Virginia [76]. Its growth rate is such that tree-of-heaven can reach the surrounding canopy rapidly, without further need of disturbance [89]. Besides its genetic capacity for growth, its relative unpalatability compared to associated hardwood species may confer further growth and successional advantage to tree-of-heaven in eastern hardwood forests with dense white-tailed deer populations [49,89].

Tree-of-heaven also occurs in middle old-field succession. It is not reported in very early old field succession, but was found in Pennsylvania old fields that were abandoned approximately 20 years before the old field survey. At 20 years, hardwoods were forming a 23- to 39-foot (7-12 m) canopy over the old fields. Tree-of-heaven was common in these early hardwood stands [86]. Once established, tree-of-heaven can spread into the surrounding understory by root sprouts, which grow slowly but persist under low light conditions [91].

Tree-of-heaven is intolerant of deep shade [18,49,61,91]. Seed plantings in New Jersey plant communities showed best tree-of-heaven establishment was in an open-grown herbaceous community, with intermediate establishment in an eastern redcedar/little bluestem woodland (Juniperus virginiana/Schizachyrium scoparium) and least establishment in a closed-canopy oak-hickory forest. Mortality rate was over 90% for experimentally planted tree-of-heaven seed planted under a closed-canopy oak-hickory forest [49]. Similarly, mortality of naturally established tree-of-heaven seedlings under an oak (Quercus spp.)-maple sugar canopy in West Virginia was 100%. Although tree-of-heaven cannot successfully regenerate from seed under its own canopy [91], it does produce under-canopy sprouts [67,78,91]. Without canopy-opening disturbance, under-canopy sprouts remain suppressed and grow slowly [61,78,91]. For example, in a mid-successional mixed oak-hickory forest in southern Illinois, tree-of-heaven was scarce, with 2.5 stems/ha, relative dominance of 0.1%, and relative importance of 0.4% [99]. Tree-of-heaven does not photosynthesize efficiently in shade [17,18]. Bourdeau and Laverick [18] found high light compensation points for tree-of-heaven in the laboratory.

Tree-of-heaven's reputed allelopathy may slow succession in plant communities where it is invasive [64,88]. Concentration of allelopathic chemicals is highest in young tree-of-heaven stands [23,97]. Seasonally, toxins are greatest in spring and decline as the growing season progresses. Allelopathic chemicals are present in all portions of the tree, but are most concentrated in roots. The litter is also allelopathic. For example, slash (Pinus elliottii) and Monterey pine (P. radiata) seed germination is inhibited by fresh tree-of-heaven litter. The allelopathic effect dwindles through the growing season. By fall (when pine seeds would not normally germinate), pine seed germination is no longer inhibited by tree-of-heaven litter [168].

The following table shows tree-of-heaven phenological events by state and region:

FIRE ECOLOGY

• FIRE ECOLOGY OR ADAPTATIONS
• POSTFIRE REGENERATION STRATEGY

Flammability of tree-of-heaven is not reported in the literature as of this writing. Its growth habit and stand structure suggest that once ignited, tree-of-heaven stands probably burn easily. The trees have large, finely divided leaves [35,52,53,131,165] that provide a surface-to-volume ratio favorable for ignition and burning. The trees produce prodigious litter, not only from the large leaves, but also from broken branches in all size classes. Downed woody fuels are common in tree-of-heaven stands. The brittle branches break easily even when green, and branch die-back from drought or frost is common [78,80].

Fire regimes: Tree-of-heaven is native to a long-settled, densely populated region of China. Although its pharmacological use is mentioned in early Chinese writings, early references about its ecology have not been found [74]. Its native fire regime is lost to prehistory. Its ability to sprout from photosynthate-storing roots and establish from off-site, wind-dispersed seed; its extraordinarily rapid growth rate; early age of seed production; and its appearance in early successional plant communities in North America (see Botanical and Ecological Characteristics) suggest tree-of-heaven has been subject to evolutionary pressures of frequent, stand-replacement disturbances. Tree-of-heaven shows flooding tolerance [10], but its consistent association in upland habitats may indicate a past association fire-prone ecosystems.

In North America, tree-of-heaven has invaded ecosystems where, for the most part, historic fire regimes are no longer functional (e.g., see [7,126,170,173]). It is difficult to assess how tree-of-heaven may further alter historic fire regimes in ecosystems and plant communities where it is present. It may encourage fire spread in eastern hardwood forests, since its propensity to self-prune and grow in thickets can alter historic stand structure. Its impact in the arid West, where tree-of-heaven growth is more restricted to mesic sites and riparian zones [78], is even more difficult to judge. Further information, especially on postfire response of tree-of-heaven, is needed on how tree-of-heaven affects fire regimes in North America.

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

Tree-of-heaven probably establishes from seed after fire. Its seed disperses easily by wind [39,88,147], and tree-of-heaven is known to establish from seed in early successional, disturbed environments other than burns [18,88,89,121] (see Successional Status). Further information is needed on tree-of-heaven's ability to establish from seed in postfire environments.

MANAGEMENT CONSIDERATIONS

• IMPORTANCE TO LIVESTOCK AND WILDLIFE
• OTHER USES
• IMPACTS AND CONTROL

Palatability/nutritional value: Although browsed, tree-of-heaven is not reported as preferred browse for ungulate species [49]. The bark and leaves contain saponins, quassinoids, and other bitter compounds that may discourage consumption [6,66,100,165]. Small animal use of tree-of-heaven is largely unknown. One old-field study in New York showed white-footed mice preferred browsing eastern white pine, sugar maple, and white ash over tree-of-heaven. The same study noted meadow voles preferred tree-of-heaven seedlings over eastern white pine seedlings [122]. Further research is needed on animal use of tree-of-heaven.

Tree-of-heaven is a fairly good source of protein. Nutritional content  (%) of tree-of-heaven browse in Pakistan was as follows [9]:

The seeds are a good source of fatty oils [16]. Seed collected in the U.S. had 56% fatty oil and 23% protein content [6]. Kapoor and others [82] identified palmitic, oleic, and lineleic as the major fatty acids.

Cover value: No information is available on this topic.

Tree-of-heaven is a bioindicator of ozone pollution. When subjected to heavy ozone concentrations, the leaves show spotting damage and drop off  [55]. Conversely, tree-of-heaven tolerates high levels of sulfur and mercury pollution, concentrating mercury in its leaves ([92] and references therein). It has been used to rehabilitate mine spoils in the East. Tolerant of saline soils and low pH, tree-of-heaven shows better growth on mine spoils compared to native species [128]. Due to its tendency to spread on disturbed sites, however, it is not recommended for rehabilitation [77,95].

Possibly allelopathic, tree-of-heaven extracts have reduced germination and growth of other weed species. Tree-of-heaven extracts have potential use as herbicides [32,100].

The species has a long history of folk medicine and cultural use in Asia [74]. It is used as an astringent, antispasmotic, anthelmintic, and parasitide. In powdered form it is a narcotic, with depressant effects similar to tobacco (Nicotiana spp.). Fresh stem bark is used to treat diarrhea and dysentery; root bark is used for heat ailments, epilepsy, and asthma.  The fruits are used as an emmenagogue and to treat ophthalmic diseases. Leaves are an astringent and used in lotions for seborrhea and scabies [5,74]. Laboratory studies show tree-of-heaven has a potential role in modern medicine. Pharmacological research is focusing on possible use of tree-of-heaven extracts for treating cancer, malaria, and HIV-1 infection [5,20,26,119].

Wood Products: Tree-of-heaven wood resembles ash (Fraxinus spp.) wood in appearance and quality. It is easily worked with tools and glue, and takes a finish well. Tree-of-heaven wood properties are summarized in Alden [2] and Moslemi and Bhagwat [117]. Berchem and others [11] and Adamik and Brauns [1] provide information on properties and potential uses of tree-of-heaven wood fiber. Zasada and Little [176] provide information on tree-of-heaven cultivation.

Tree-of-heaven is an important timber and fuelwood tree in China, and is planted for timber and afforestation in New Zealand, the Middle East, eastern Europe, and South America [8,74,144,163,176].

Other products: In China, tree-of-heaven is grown commercially as a host for Attacus cynthia, a silkworm that produces coarse, durable silk [74,165]. Tree-of-heaven is a food for honey bees worldwide. Initially bad-tasting, tree-of-heaven honey ages to a high-quality, flavorful product [29,112].

There is controversy about tree-of-heaven's invasiveness. Some authors note that although tree-of-heaven established in North America over 100 years ago, it has not spread to many sites that appear to be good habitat for the species [117]. Tree-of-heaven seems most invasive in disturbed eastern hardwood ecosystems [18,86,88,89,91,121]. Tree-of-heaven was 1st collected in North Carolina in 1911; it has now established in at least 48 counties in that state [125]. Tree-of-heaven appears less invasive in the arid West. It is an important pest species in California [72], invading disturbed mesic areas and riparian zones where water relations allow seedling establishment. It has not invaded closed-canopy forests [45,78]. Outside mesic areas, Hunter [78] considers it "only potentially invasive, and also potentially eradicable" in California.

Socio-economic - In developed areas, tree-of-heaven roots can damage buildings and foundations [74]. The rapidly growing, extensive root system also allows the tree to establish on steep to vertical inclines including roofs and cracked walls, which are damaged if seedlings are not promptly killed [4,139]. Tree-of-heaven roots damaged the walls and roof of the 800-year-old Sé Velha of Coimbra Cathedral in Portugal after establishing in the wall mortar and clay roof tiles [4]. The water-seeking roots can stop up sewer lines and invade wells and cisterns, damaging infrastructures and giving potable water an unpleasant taste [31,74].

Tree-of-heaven sap causes a dermatitis reaction in some people. The pollen can cause an allergic reaction [34].

Control: Effective tree-of-heaven control requires vigilance due to its strong sprouting ability and prolific seed production. Roadways and trails are the usual corridor for tree-of-heaven infestations [21,24,75]. For example, in a West Virginia study tree-of-heaven occurrence was heaviest along interstate freeways (I-79 and I-68) [75]. Fortunately, roadside and trail invasion makes accessibility, early detection, and treatment relatively easy [21].

Posttreatment monitoring and retreatment is essential for this root-sprouting, rapidly growing species (see Regeneration Processes). Treated areas should be checked once or twice a year, with any new sprouts or seedlings retreated (cut, sprayed, or pulled) as soon as possible so that roots do not have time to build up carbohydrate reserves and grow larger. Plan on several treatments a year. Initially, summer treatment is desired to impact trees when their root reserves are low. Establishing a thick cover of native trees or grass helps shade out tree-of-heaven and discourages regrowth. Targeting female trees-of-heaven for control helps slow seed dissemination [72]. Monitoring should continue for at least a year after tree-of-heaven sprouting appears controlled [79]. Hoshovsky [72] reviews best application methods for many of the tree-of-heaven control methods discussed below.

As an early seral, potential invasive with wind-dispersed seed, tree-of-heaven may show up on sites where treatments for other invasive weeds have created open, disturbed conditions. Whenever there is a nearby tree-of-heaven seed source, disturbed sites require monitoring and follow-up treatments to prevent tree-of-heaven invasion and spread. For example, tree-of-heaven and Norway maple seedlings invaded a New Jersey site after Norway maple removal treatments (cutting mature trees and hand-pulling Norway maple seedlings). Tree-of-heaven was not present on study plots prior to Norway maple removal [171]. Further information and research are needed to recognize undisturbed sites at risk for tree-of-heaven invasion [72].

Prevention: The most efficient and effective method of managing invasive species is to prevent their invasion and spread [145]. Preventing the establishment of nonnative invasive plants in Natural Areas is achieved by maintaining healthy natural communities and by conducting aggressive surveying and monitoring several times each year. Monitoring efforts are best concentrated on the most disturbed areas in a site, particularly along potential pathways for tree-of-heaven invasion: roadsides, parking lots, fencelines, trails, and waterways. The Center for Invasive Plant Management  provides an online guide to noxious weed prevention practices.

Integrated management: A combination of complementary control methods may be helpful for rapid and effective control of tree-of-heaven. Integrated management includes not only killing the target plant, but establishing desirable species and discouraging nonnative, invasive species over the long term.

Physical/mechanical: Mechanical treatments including cutting or girdling are a good 1st step in controlling tree-of-heaven. Cutting encourages both stump and root sprouts, so follow-up treatments are required. Cut stems before flowering to prevent seed spread, cutting at the ground level to prevent bole sprouts. Depending on bole size, mechanical tools including loppers, machetes, brush cutters, and power saws can be used on tree-of-heaven [79]. Sprouts can be controlled by further cutting treatments or herbicides [72,79,95]. Unless the treatment area is heavily shaded, it usually takes 5 or more years of follow-up treatment to control sprouts [72].

In small areas, seedlings can be controlled by hand pulling. Seedlings quickly develop extensive root systems, so the entire root needs to be removed to prevent sprouting. It is easiest to remove the entire seedling root when soils are softened by rain [95]. Top-growth of seedlings and root sprouts is similar, but root sprouts are connected by large, pre-existing lateral roots. Tree-of-heaven seedlings can sometimes be distinguished without digging by their cotyledons (if still present), trifoliate 1st leaflets, and thinner stems compared to the thicker stems and variable number of leaflets found on sprouts [79]. Grubbing roots may be effective for saplings [157]. Except for small infestations, grubbing roots is seldom practical for mature trees or well established tree-of-heaven colonies. The root systems are extensive and nearly impossible to entirely remove, and even a small root fragment can produce root sprouts [72,79].

Fire: Fire has limited use in controlling tree-of-heaven, but may be useful for spot treatment. Instead of using mechanical or chemical methods to kill stems, a flame thrower or weed burner can heat-girdle tree-of-heaven boles. As with all top-kill methods, tree-of-heaven sprouts after heat-girdling [28].

Hunter [79] recommends against using fire to control tree-of-heaven colonies, speculating that burning is likely to promote vigorous sprouting. To date (2004), broadcast burning has not been attempted on tree-of-heaven, probably in large part for fear that a top-killing fire compounded by the nutrient flush that follows will result in dense postfire sprouting. Small-scale research is needed to compare long-term efficacy of fire vs. other methods in controlling tree-of-heaven.

Biological: As of this writing (2004), there are no biological control agents approved for tree-of-heaven [157]. As a disease-resistant, unpalatable species, tree-of-heaven may be a poor candidate for biological control. Containing quassinoid compounds that inhibit development of most insect larvae and retard rotting [66], it is resistant to insect predation, root-feeding nematodes, and fungi [1,45,54,68,112,140]. Leaf-browsing lepidoptera (Atteva punctella and Samia synthia) damage tree-of-heaven [112,113], but usually inflict more damage to more palatable associated species such as wild cherries and plums (Prunus spp.). Asiatic garden beetles (Maladera castenea) feed on tree-of-heaven, but also damage numerous desirable plant species. Although cattle and deer browsing may reduce tree-of-heaven [78,152], large mammalian browsers may prefer associated species to tree-of-heaven. Tree-of-heaven is less susceptible to root rots (Phymatotrichum spp.) than many native hardwoods. Two crop-infesting fungi, Verticillium dahliae and Fusarium oxysporum, have been isolated from dead and dying tree-of-heaven in the Northeast. These fungi may be candidates for fungal control of tree-of-heaven if strains affecting only Ailanthus species can be isolated [112,135].

Plant competition is not a reliable method of control. With 1 of  the fastest growth rates of any tree in North America [89], tree-of-heaven will probably grow faster and outcompete whatever native species co-occur or are planted with it [79,89,91]. Maintaining a healthy overstory can help minimize invasive potential for tree-of-heaven [145].

Chemical: Herbicides may provide initial control of a new invasion or a severe infestation, but are rarely a complete or long-term solution to invasive species management [22]. Herbicides are more effective on large infestations when incorporated into long-term management plans that include replacement of weeds with desirable species, careful land use management, and prevention of new infestations. Control with herbicides is temporary, as it does not change conditions that allow infestations to occur in the 1st place (e.g. [175]). See The Nature Conservancy's Weed control methods handbook for considerations on the use of herbicides in Natural Areas and detailed information on specific chemicals.

Systemic herbicides (e.g., triclopyr and glyphosate), which kill roots, currently provide the best chemical control for tree-of-heaven. Dicamba, imazapyr, and methsulfuron methyl have also provided tree-of-heaven control [72,95,147]. Applying herbicides late in the growing season, when tree-of-heaven is fully leafed out and translocating nutrients to the roots, is the only effective way to kill the roots [72,166]. Aerial spraying may be indicated when there are large thickets without nontarget species, or as a follow-up treatment to other control methods. In mixed stands, aerial application of herbicides will probably have a greater impact on nontarget species that lack tree-of-heaven's ability to root sprout. When trees-of-heaven are interspersed with nontarget trees, the foliage, stumps, or basal bark of individual trees can be treated with herbicides. The stems can be cut, with immediate application of  triclopyr or glyphosate to the stump. Coating the lower bole with herbicide, or girdling the stem and injecting the bole cuts with herbicide spray (hack-and-squirt), is also effective [72,95,147,157]. Basal bark herbicide treatment (imazapyr or triclopyr) is most effective in late winter or early spring before trees begin to leaf out, although summer application also works [158]. Swearingen and Pannill [152] provide information on applying foliar and basal bark chemicals to trees-of-heaven in wildlands.

In Shenandoah National Park, low-volume basal application of herbicides (triclopyr, picloram, imazapyr, and combinations) gave better tree-of-heaven control than cutting. At posttreatment year 2,  a shift toward native herbs had occurred on plots where tree-of-heaven was controlled, while nonnative herbs including garlic mustard (Alliaria petiolata) and burdock (Arctium minus) were more prevalent on plots where tree-of-heaven density remained high. Mean tree-of-heaven density at posttreatment year 2 was [21]:

Chemical control programs targeting herbaceous species may unintentionally increase tree-of-heaven, depending upon the herbicides used. In West Virginia, diuron, simazine, and terbacil treatments for rough pigweed (Amaranthus retroflexus), barnyard grass (Echinochloa crus-galli), and other herbaceous weeds  in an apple (Malus sylvestris) orchard successfully reduced most herbaceous weeds; however, tree-of-heaven and tall fescue (Festuca arundinacea) dominated plots treated with diuron and simazine. Terbacil alone gave best control of tree-of-heaven [158].

Cultural: No information is available on this topic.

Ailanthus altissima: REFERENCES

1. Adamik, Karl; Brauns, Friedrich E. 1957. Ailanthus glandulosa (tree-of-heaven) as pulpwood. Part II. Tappi. 40(7): 522-527. [46739]

2. Alden, Harry A. 1995. Hardwoods of North America. Gen. Tech. Rep. FPL-GTR-83. Madison, WI: U.S. Department of Agriculture, Forest Service, Forest Products Laboratory. 136 p. Available: http://www.fpl.fs.fed.us/documnts/fplgtr/fplgtr83.pdf [2004, January 6]. [46270]

3. Allen, Craig Daniel. 1989. Changes in the landscape of the Jemez Mountains, New Mexico. Berkeley, CA: University of California Berkeley. 346 p. Dissertation. [42116]

4. Almeida, M. T.; Mouga, T.; Barracosa, P. 1994. The weathering ability of higher plants. The case of Ailanthus altissima (Miller) Swingle. International Biodeterioration and Biodegradation. 33(4): 333-343. [45754]

5. Ansari, S. H.; Ali, M. 1999. Recent developments in the chemistry of Ailanthus altissima. Hamdard Medicus. 42(3): 58-63. [46264]

6. Ansari, S. H.; Ali, M. 2003. Two new phytosterols from Ailanthus altissima (Mill) Swingle. In: Bernath, J.; [and others], eds. Proceedings of the international conference on medicinal and aromatic plants; 2001 July 8-11; Budapest, Hungary. In: Acta Horticulture. 597: 91-94. [46145]

7. Arno, Stephen F. 2000. Fire in western forest ecosystems. In: Brown, James K.; Smith, Jane Kapler, eds. Wildland fire in ecosystems: Effects of fire on flora. Gen. Tech. Rep. RMRS-GTR-42-vol. 2. Ogden, UT: U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station: 97-120. [36984]

8. Ashraf, Mohammad, Rehman, Sham-ur. 2001. A short note on the vegetative propagation of Ailanthus and Prosopis. The Pakistan Journal of Forestry. 51(1): 85. [46216]

9. Azim, A.; Khan, A. G.; Ahmad, J.; Ayaz, M.; Mirza, I. H. 2002. Nutritional evaluation of fodder tree leaves with goats. Asian Australian Journal of Animal Science. 15(1): 34-37. [46153]

10. Barringer, Kerry; Pannaman, Laura. 2003. Vascular plants of the Fairview Lake watershed, Sussex County, New Jersey. Journal of the Torrey Botanical Society. 130(1): 47-54. [46143]

11. Berchem, T. E.; Moslemi, A. A.; Sutula, P. R. 1972. Fiber length in the wood of tree-of-heaven. Wood Fiber. 4(3): 234-235. [46455]

12. Bernard, Stephen R.; Brown, Kenneth F. 1977. Distribution of mammals, reptiles, and amphibians by BLM physiographic regions and A.W. Kuchler's associations for the eleven western states. Tech. Note 301. Denver, CO: U.S. Department of the Interior, Bureau of Land Management. 169 p. [434]

13. Bicknell, Susan H.; Smith, William H. 1975. Influence of soil salt, at levels characteristic of some roadside environments, on the germination of certain tree seeds. Plant and Soil. 43(3): 719-722. [46740]

14. Bory, G.; Clair-Maczulajtys, D. 1980. Production, dissemination, and polymorphism of seeds in Ailanthus altissima. Revue Gererale de Botanique. 88(1049/1051): 297-311. [45847]

15. Bory, G.; Clair-Maczulajtys, Danielle. 1986. Composition of nectar and role of extrafloral nectaries in Ailanthus glandulosa. Canadian Journal of Botany. 64(1): 247-253. [46147]

16. Bory, G.; Clair-Maezulajtys, D. 1989. Lipid content and fatty acid composition of seeds of Ailanthus altissima (Mill) Swingle (Simaroubaceae). Indian Journal of Plant Physiology. 31(1): 12-16. [46745]

17. Bourdeau, Philippe F. 1958. Photosynthetic behavior of sun- and shade-grown leaves in certain tolerant and intolerant tree species. Bulletin of the Ecological Society of America. 39(3): 84. Abstract. [46134]

18. Bourdeau, Philippe F.; Laverick, Miriam L. 1958. Tolerance and photosynthetic adaptability to light intensity in white pine, red pine, hemlock and ailanthus seedlings. Forest Science. 4(3): 196-207. [46152]

19. Bourke, C. A. 1996. Lack of toxicity of Ailanthus altissima (tree-of-heaven) for goats. Australian Veterinary Journal. 74(6): 465. [45850]

20. Bray, D. H.; Boardman, P.; O'Neill, M. J.; Chan, K. L.; Phillipson, J. D.; Warhurst, D. C.; Suffness, M. 1987. Plants as a source of antimalarial drugs. 5. Activities of Ailanthus altissima stem constituents and of some related quassinoids. Phytotherapy Research. 1(1): 22-24. [46125]

21. Burch, Patrick L.; Zedaker, Shepard M. 2003. Removing the invasive tree Ailanthus altissima and restoring natural cover. Journal of Arboriculture. 29(1): 18-24. [45788]

22. Bussan, Alvin J.; Dyer, William E. 1999. Herbicides and rangeland. In: Sheley, Roger L.; Petroff, Janet K., eds. Biology and management of noxious rangeland weeds. Corvallis, OR: Oregon State University Press: 116-132. [35716]

23. Call, Lara J. 2002. Analysis of intraspecific and interspecific interactions between the invasive exotic tree-of-heaven (Ailanthus altissima (Miller) Swingle) and the native black locust (Robinia pseudoacacia L.). Blacksburg, VA: Virginia Polytechnic Institute. 80 p. Thesis. [45299]

24. Call, Lara J.; Nilsen, Erik T. 2003. Analysis of spatial patterns and spatial association between the invasive tree-of-heaven (Ailanthus altissima) and the native black locust (Robinia pseudoacacia). The American Midland Naturalist. 150(1): 1-14. [45002]

25. Callaway, Ragan M.; Walker, Lawrence R. 1997. Competition and facilitation: a synthetic approach to interactions in plant communities. Ecology. 78(7): 1958-1965. [27660]

26. Chang, Young-Su; Woo, Eun-Rhan. 2003. Korean medicinal plants inhibiting to human immunodeficiency virus type 1 (HIV-1) fusion. Phytotherapy Research. 17(4): 426-429. [46074]

27. Cowell, C. Mark. 1993. Environmental gradients in secondary forests of the Georgia Piedmont, U.S.A. Journal of Biogeography. 20: 199-207. [24132]

28. Cozzo, Domingo. 1972. Initial behavior of Ailanthus altissima in experimental plantation. Revista Forestal Argentina. 16(2): 47-52. [46731]

29. Dalby, Richard. 2000. Minor bee plants in a major key: tamarisk, ailanthus and teasel. American Bee Journal. 140(1): 60-61. [43996]

30. Davies, P. A. 1935. Ecology of Ailanthus altissima thickets. Transactions, Kentucky Academy of Science. 7: 21. [46730]

31. Davies, P. A. 1942. The history, distribution, and value of Ailanthus in North America. Transactions, Kentucky Academy of Science. 9: 12-14. [45812]

32. De Feo, Vincenzo; De Martino, Laura; Quaranta, Emilia; Pizza, Cosimo. 2003. Isolation of phytotoxic compounds from tree-of-heaven (Ailanthus altissima Swingle). Journal of Agricultural and Food Chemistry. 51(5): 1177-1180. [46076]

33. DeMars, Brent G.; Runkle, James R. 1992. Groundlayer vegetation ordination and site-factor analysis of the Wright State University Woods (Greene County, Ohio). Ohio Journal of Science. 92(4): 98-106. [19823]

34. Derrick, Elizabeth K.; Darley, Charles R. 1994. Contact reaction to the tree of heaven. Contact Dermatitis. 30(3): 178. [45520]

35. Diggs, George M., Jr.; Lipscomb, Barney L.; O'Kennon, Robert J. 1999. Illustrated flora of north-central Texas. Sida Botanical Miscellany, No. 16. Fort Worth, TX: Botanical Research Institute of Texas. 1626 p. [35698]

36. Dirr, Michael A. 1990. Manual of woody landscape plants: their identification, ornamental characteristics, culture, propagation and uses. Champagne, IL: Stipes Publishing Company. 1007 p. [46754]

37. Dobberpuhl, J. 1980. Seed banks of forest soils in east Tennessee. Knoxville, TN: University of Tennessee. 219 p. Thesis. [46755]

38. Duchesne, Luc C.; Hawkes, Brad C. 2000. Fire in northern ecosystems. In: Brown, James K.; Smith, Jane Kapler, eds. Wildland fire in ecosystems: Effects of fire on flora. Gen. Tech. Rep. RMRS-GTR-42-vol. 2. Ogden, UT: U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station: 35-51. [36982]

39. Duncan, Wilbur H.; Duncan, Marion B. 1988. Trees of the southeastern United States. Athens, GA: The University of Georgia Press. 322 p. [12764]

40. Eyre, F. H., ed. 1980. Forest cover types of the United States and Canada. Washington, DC: Society of American Foresters. 148 p. [905]

41. Facelli, Jose M. 1994. Multiple indirect effects of plant litter affect the establishment of woody seedlings in old fields. Ecology. 75(6): 1727-1735. [23541]

42. Facelli, Jose M.; Pickett, S. T. A. 1991. Indirect effects of litter on woody seedlings subject to herb competition. Oikos. 62(2): 129-138. [46146]

43. Fairweather, Stephen E.; Cavanaugh, Cecile M. 1990. Identification, restoration, and maintenance of historic woodlots at Gettysburg National Military Park. Tech. Rep. NPS/MAR/NRTR - 90/049. Philadelphia, PA: U.S. Department of the Interior, National Park Service, Mid-Atlantic Region. 123 p. [17985]

44. Feret, Peter P. 1973. Early flowering in Ailanthus. Forest Science. 19(3): 237-239. [45855]

45. Feret, Peter P. 1985. Ailanthus: variation, cultivation, and frustration. Journal of Arboriculture. 11(12): 361-368. [46741]

46. Feret, Peter P.; Bryant, Richard L. 1974. Genetic differences between American and Chinese ailanthus seedlings. Silvae Genetica. 23(5): 144-148. [45518]

47. Feret, Peter P.; Bryant, Richard L.; Ramsey, James A. 1974. Genetic variation among American seed sources of Ailanthus altissima (Mill.) Swingle. Scientia Horticulturae. 2(4): 405-411. [46124]

48. Finch, Deborah M.; Wolters, Gale L.; Yong, Wang; Mund, Mary J. 1995. Plants, arthropods, and birds of the Rio Grande. In: Finch, Deborah M.; Tainter, Joseph A., eds. Ecology, diversity, and sustainability of the Middle Rio Grande Basin. Gen. Tech. Rep. RM-GTR-268. Fort Collins, CO: U.S. Department of Agriculture, Forest Service, Rocky Mountain Forest and Range Experiment Station: 133-164. [26190]

49. Forgione, Helen M. 1993. Limits to the establishment and growth of tree-of-heaven explored. Restoration & Management Notes. 11(1): 70-71. [22459]

50. Frankel, Edward. 1999. A floristic survey of vascular plants of the Bronx River Parkway Reservation in Westchester, New York: compilation 1973-1998. Journal of the Torrey Botanical Society. 126(4): 359-366. [37376]

51. Garrison, George A.; Bjugstad, Ardell J.; Duncan, Don A.; Lewis, Mont E.; Smith, Dixie R. 1977. Vegetation and environmental features of forest and range ecosystems. Agric. Handb. 475. Washington, DC: U.S. Department of Agriculture, Forest Service. 68 p. [998]

52. Gleason, Henry A.; Cronquist, Arthur. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. 2nd ed. New York: New York Botanical Garden. 910 p. [20329]

53. Godfrey, Robert K. 1988. Trees, shrubs, and woody vines of northern Florida and adjacent Georgia and Alabama. Athens, GA: The University of Georgia Press. 734 p. [10239]

54. Goor, A. Y.; Barney, C. W. 1968. Forest tree planting in arid zones. New York: Ronald Press. 409 p. [46759]

55. Gravano, Elisabetta; Giulietti, Valentina; Desotgiu, Rosanna; Bussotti, Filippo; Grossoni, Paolo; Gerosa, Giacomo; Tani, Corrado. 2003. Foliar response of an Ailanthus altissima clone in two sites with different levels of ozone-pollution. Environmental Pollution. 121(1): 137-148. [46737]

56. Graves, William R. 1990. Stratification not required for tree-of-heaven seed germination. Tree Planters' Notes. 41(2): 10-12. [46149]

57. Graves, William R.; Dana, Michael N.; Joly, Robert J. 1989. Influence of root-zone temperature on growth of Ailanthus altissima (Mill.) Swingle. Journal of Environmental Horticulture. 7(2): 79-82. [46130]

58. Great Plains Flora Association. 1986. Flora of the Great Plains. Lawrence, KS: University Press of Kansas. 1392 p. [1603]

59. Greenlee, Jason M.; Langenheim, Jean H. 1990. Historic fire regimes and their relation to vegetation patterns in the Monterey Bay area of California. The American Midland Naturalist. 124(2): 239-253. [15144]

60. Greller, Andrew M. 1977. A classification of mature forests on Long Island, New York. Bulletin of the Torrey Botanical Club. 104(4): 376-382. [22020]

61. Grime, J. P. 1965. Shade tolerance in flowering plants. Nature. 28(5006): 161-163. [46122]

62. Guyette, Richard; McGinnes, E. A., Jr. 1982. Fire history of an Ozark glade in Missouri. Transactions, Missouri Academy of Science. 16: 85-93. [5170]

63. Hanover, James W.; Wood, Bruce W.; Hart, John W.; Brissette, John C.; Dickmann, Donald I.; Stadt, Thomas J.; Lemmien, Walter A.; Kowalewski, Greg. 1978. Accelerated growth of hardwood seedlings. In: Central hardwood forest conference: Proceedings; 1978 November 14-16; West Lafayette, IN. West Lafayette, IN: Purdue University, Department of Forestry and Natural Resources: 370-388. [46133]

64. Heisey, Rod M. 1990. Allelopathic and herbicidal effects of extracts from tree of heaven (Ailanthus altissima). American Journal of Botany. 77(5): 662-670. [45477]

65. Heisey, Rod M. 1990. Evidence for allelopathy by tree-of-heaven. Journal of Chemical Ecology. 16(6): 2039-2055. [45481]

66. Heisey, Rod M. 1996. Identification of an allelopathic compound from Ailanthus altissima (Simaroubaceae) and characterization of its herbicidal activity. American Journal of Botany. 83(2): 192-200. [45475]

67. Heisey, Rod M. 1997. Allelopathy and the secret life of Ailanthus altissima. Arnoldia. 57(3): 28-36. [46157]

68. Hepting, George H. 1971. Diseases of forest and shade trees of the United States. Agric. Handb. 386. Washington, DC: U.S. Department of Agriculture. 658 p. [20880]

69. Hickman, James C., ed. 1993. The Jepson manual: Higher plants of California. Berkeley, CA: University of California Press. 1400 p. [21992]

70. Hitchcock, C. Leo; Cronquist, Arthur. 1973. Flora of the Pacific Northwest. Seattle, WA: University of Washington Press. 730 p. [1168]

71. Hitchcock, C. Leo; Cronquist, Arthur; Ownbey, Marion; Thompson, J. W. 1961. Vascular plants of the Pacific Northwest. Part 3: Saxifragaceae to Ericaceae. Seattle, WA: University of Washington Press. 614 p. [1167]

72. Hoshovsky, Marc C. 1988. Element stewardship abstract: Ailanthus altissima, [Online]. In: Invasives on the web: The Nature Conservancy wildland invasive species program. Davis, CA: The Nature Conservancy (Producer). Available: http://tncweeds.ucdavis.edu/esadocs/documnts/ailaalt.html [2004, January 9]. [46265]

73. Houge, Robert. 1998. Tree-of-heaven: Ailanthus altissima, [Online]. In: National Register of Big Trees. American Forests (Producer). Available: http://www.americanforests.org/resources/bigtrees/ [2004, January 6]. [46268]

74. Hu, Shiu Ying. 1979. Ailanthus. Arnoldia. 39(2): 29-50. [45755]

75. Huebner, Cynthia D. 2003. Vulnerability of oak-dominated forests in West Virginia to invasive exotic plants: temporal and spatial patterns of nine exotic species using herbarium records and land classification data. Castanea. 68(1): 1-14. [46144]

76. Hull, James C.; Scott, Ralph C. 1982. Plant succession on debris avalanches of Nelson County, Virginia. Castanea. 47(2): 158-176. [41715]

77. Hunter, Carl G. 1989. Trees, shrubs, and vines of Arkansas. Little Rock, AR: The Ozark Society Foundation. 207 p. [21266]

78. Hunter, John C. 1995. Ailanthus altissima (Miller) Swingle: its biology and recent history. California Exotic Pest Plant Council News. 3(4): 4-5. [45846]

79. Hunter, John. 2000. Ailanthus altissima (Miller) Swingle. In: Bossard, Carla C.; Randall, John M.; Hoshovsky, Marc C., eds. Invasive plants of California's wildlands. Berkeley, CA: University of California Press: 32-36. [46752]

80. Illick, Joseph S.; Brouse, E. F. 1926. The ailanthus tree in Pennsylvania. Bulletin 38. Harrisburg, PA: Pennsylvania Department of Forests and Waters. 29 p. [46734]

81. Jepson, Willis Linn. 1925. A manual of the flowering plants of California. Berkeley, CA: University of California Press. 1238 p. [19365]

82. Kapoor, N.; Bedi, K. L.; Tikoo, M. K.; Kapoor, S. K.; Sarin, Y. K. 1990. Some lesser known tree-borne oilseeds of India. Journal of the Oil Technologists Association of India. 22(3): 65-66. [46156]

83. Kartesz, John T. 1999. A synonymized checklist and atlas with biological attributes for the vascular flora of the United States, Canada, and Greenland. 1st ed. In: Kartesz, John T.; Meacham, Christopher A. Synthesis of the North American flora (Windows Version 1.0), [CD-ROM]. Chapel Hill, NC: North Carolina Botanical Garden (Producer). In cooperation with: The Nature Conservancy; U.S. Department of Agriculture, Natural Resources Conservation Service; U.S. Department of the Interior, Fish and Wildlife Service. [36715]

84. Keeley, Jon E. 1981. Reproductive cycles and fire regimes. In: Mooney, H. A.; Bonnicksen, T. M.; Christensen, N. L.; Lotan, J. E.; Reiners, W. A., tech. coords. Fire regimes and ecosystem properties: Proceedings of the conference; 1978 December 11-15; Honolulu, HI. Gen. Tech. Rep. WO-26. Washington, DC: U.S. Department of Agriculture, Forest Service: 231-277. [4395]

85. Keeley, Jon E. 1986. Resilience of Mediterranean shrub communities to fires. In: Dell, B.; Hopkins, A. J. N.; Lamont B. B., eds. Resilience in Mediterranean-type ecosystems. Dordrecht, The Netherlands: Dr. W. Junk Publishers: 95-112. [9826]

86. Keever, Catherine. 1979. Mechanisms of plant succession on old fields of Lancaster County, Pennsylvania. Bulletin of the Torrey Botanical Club. 106(4): 299-308. [41717]

87. Keller, Terry. 1993. Riparian zone plant ecology and hydrology in Aliso Creek, Chino Hills State Park, southern California. In: Keeley, Jon E., ed. Interface between ecology and land development in California: Proceedings of the symposium; 1992 May 1-2; Los Angeles, CA. Los Angeles, CA: The Southern California Academy of Sciences: 137-141. [21702]

88. Kentucky Exotic Pest Plant Council. 2001. Invasive exotic plant list, [Online]. Southeast Exotic Pest Plant Council (Producer). Available: http://www.se-eppc.org/states/KY/KYlists.html [2005, April 13]. [44948]

89. Knapp, Liza B.; Canham, Charles D. 2000. Invasion of an old-growth forest in New York by Ailanthus altissima: sapling growth and recruitment in canopy gaps. Journal of the Torrey Botanical Society. 127(4): 307-315. [46142]

90. Kowarik, Ingo. 1983. The acclimatization and phytogeographical behavior of the tree of heaven in the French Mediterranean area. Phytocoenologia. 11(3): 389-406. [46757]

91. Kowarik, Ingo. 1995. Clonal growth in Ailanthus altissima on a natural site in West Virginia. Journal of Vegetation Science. 6: 853-856. [45195]

92. Kozlowski, T. T. 2002. Physiological ecology of natural regeneration of harvested and disturbed forest stands: implications for forest management. Forest Ecology and Management. 158(1-3): 195-221. [42122]

93. Krussmann, Gerd; Wennemuth, Georg; Thon, Heinz Edgar. 1981. Die baumschule. 5th ed. Berlin: Parey. 565 p. [46761]

94. Kucera, Clair L. 1981. Grasslands and fire. In: Mooney, H. A.; Bonnicksen, T. M.; Christensen, N. L.; Lotan, J. E.; Reiners, W. A., tech. coords. Fire regimes and ecosystem properties: Proceedings of the conference; 1978 December 11-15; Honolulu, HI. Gen. Tech. Rep. WO-26. Washington, DC: U.S. Department of Agriculture, Forest Service: 90-111. [4389]

95. Kuchler, A. W. 1964. United States [Potential natural vegetation of the conterminous United States]. Special Publication No. 36. New York: American Geographical Society. 1:3,168,000; colored. [3455]

96. Lalhal, J. S.; Singh, Ombir. 1992. Sucker development in Ailanthus glandulosa Desf. Van Vigyan. [Dehra Dun, India: Journal of the Society of Indian Foresters]. 30(3&4): 179-180. [46155]

97. Lawrence, Jeffrey G.; Colwell, Alison; Sexton, Owen J. 1991. The ecological impact of allelopathy in Ailanthus altissima (Simaroubaceae). American Journal of Botany. 78(7): 948-958. [15283]

98. Lepart, J.; Debussche, M. 1991. Invasion processes as related to succession and disturbance. In: Groves, R. H.; Di Castri, F., eds. Biogeography of Mediterranean invasions. Cambridge: Cambridge University Press: 159-177. [46742]

99. Lhotka, John M.; Zaczek, James J. 2003. Effects of scarification disturbance on the seedling and midstory layer in a successional mixed-oak forest. Northern Journal of Applied Forestry. 20(2): 85-91. [44594]

100. Lin, Lee-Juian; Peiser, Galen; Ying, Bai-Ping; Mathias, Kristina; Karasina, Faina; Wang, Zhan; Itatani, Joyce; Green, Laddie; Hwang, Yih-Shen. 1995. Identification of plant growth inhibitory principles in Ailanthus altissima and Castela tortuosa. Journal of Agricultural Food Chemistry. 43(6): 1708-1711. [45851]

101. Little, Elbert L., Jr. 1979. Checklist of United States trees (native and naturalized). Agric. Handb. 541. Washington, DC: U.S. Department of Agriculture, Forest Service. 375 p. [2952]

102. Little, Silas. 1974. Ailanthus altissima (Mill.) Swingle ailanthus. In: Schopmeyer, C. S., technical coordinator. Seeds of woody plants in the United States. Agric. Handb. 450. Washington, DC: U.S. Department of Agriculture, Forest Service: 201-202. [7503]

103. Marek, M. 1988. Photosynthetic characteristics of Ailanthus leaves. Photosynthetica. 22(2): 179-183. [46744]

104. Marler, Marilyn. 2000. A survey of exotic plants in federal wilderness areas. In: Cole, David N.; McCool, Stephen F.; Borrie, William T.; O'Loughlin, Jennifer, comps. Wilderness science in a time of change conference--Volume 5: wilderness ecosystems, threats, and management; 1999 May 23-27; Missoula, MT. Proceedings RMRS-P-15-VOL-5. Ogden, UT: U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station: 318-327. [40580]

105. Marshall, P. E.; Kozlowski, T. T. 1973. Cotyledon inactivation and early seedling development. American Journal of Botany. 60(4): 25-26. [46135]

106. Martin, William C.; Hutchins, Charles R. 1981. A flora of New Mexico. Volume 2. Germany: J. Cramer. 2589 p. [37176]

107. Matlack, Glenn R. 1987. Diaspore size, shape, and fall behavior in wind-dispersed plant species. American Journal of Botany. 74(8): 1150-1160. [28]

108. McAllister, C.; Beckert, H.; Abrams, C.; Bilyard, G.; Cadwell, K.; Friant, S.; Glantz, C.; Mazaika, R.; Miller, K. 1996. Survey of ecological resources at selected U.S. Department of Energy sites, [Online]. U.S. Department of Energy (Producer). Available: http://homer.ornl.gov/oepa/guidance/risk/ecores.pdf [2004, January 21]. [46457]

109. McFarland, Lisa. 1996. Isolation and characterization of seed germination inhibitors from Ailanthus altissima. Orono, ME: University of Maine. 214 p. Thesis. [45752]

110. McTavish, Hugh. 1988. A demonstration of photosynthetic state transitions in nature: Shading by photosynthetic tissue causes conversion to state 1. Photosynthesis Research. 17(3): 247-254. [46141]

111. Mergen, Francois. 1959. A toxic principle in the leaves of Ailanthus. Botanical Gazette. 121(1): 32-36. [45478]

112. Miller, James H. 1990. Ailanthus altissima (Mill.) Swingle ailanthus. In: Burns, Russell M.; Honkala, Barbara H., tech. coords. Silvics of North America: Vol. 2. Hardwoods. Agriculture Handbook 654. Washington, DC: U.S. Department of Agriculture, Forest Service: 101-104. [46753]

113. Mohanadas, K.; Verma, R. V. 1984. A new host record for Atteva fabriciella (Lepidoptera: Yponomeutidae) a pest of Ailanthus. Journal of Tree Science. 3(1/2): 128. [45521]

114. Mohlenbrock, Robert H. 1986. [Revised edition]. Guide to the vascular flora of Illinois. Carbondale, IL: Southern Illinois University Press. 507 p. [17383]

115. Moradshahi, A.; Yaghmaee, P.; Ghadiri, H. 2002. Allelopathic potential of tree of heaven (Ailanthus altissima Swingle). Iran Agricultural Research. 21(1): 27-38. [46154]

116. Morrison, Peter H.; Swanson, Frederick J. 1990. Fire history and pattern in a Cascade Range landscape. Gen. Tech. Rep. PNW-GTR-254. Portland, OR: U.S. Department of Agriculture, Forest Service, Pacific Northwest Research Station. 77 p. [13074]

117. Moslemi, A. A.; Bhagwat, S. G. 1970. Physical and mechanical properties of the wood of tree-of-heaven. Wood and Fiber. 1(4): 319-323. [46128]

118. Myers, Ronald L. 2000. Fire in tropical and subtropical ecosystems. In: Brown, James K.; Smith, Jane Kapler, eds. Wildland fire in ecosystems: Effects of fire on flora. Gen. Tech. Rep. RMRS-GTR-42-vol. 2. Ogden, UT: U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station: 161-173. [36985]

119. O'Neill, M. J.; Bray, D. H.; Boardman, P.; Phillipson, J. D.; Warhurst, D. C. 1985. Plants as sources of antimalarial drugs. Part 1. In vitro test method for the evaluation of crude extracts from plants. Planta Medica. 1985(5): 394-398. [46131]

120. Orians, G. H.. 1986. Site characteristics favoring invasions. In: Mooney, Harold A.; Drake, James A., eds. Ecology of biological invasions of North America and Hawaii. Ecological Studies 58. New York: Springer-Verlag: 133-148. [17513]

121. Orwig, David A.; Foster, David R. 1998. Forest response to the introduced hemlock woolly adelgid in southern New England, USA. Journal of the Torrey Botanical Club. 125(1): 60-73. [44642]

122. Ostfeld, Richard S.; Manson, Robert H.; Canham, Charles D. 1997. Effects of rodents on survival of tree seeds and seedlings invading old fields. Ecology. 78(5): 1531-1542. [46148]

123. Pan, Elizabeth; Bassuk, Nina. 1985. Effects of soil type and compaction on the growth of Ailanthus altissima seedlings. Journal of Environmental Horticulture. 3(4): 158-162. [45476]

124. Parsons, W. T.; Cuthbertson, E. G. 1992. Noxious weeds of Australia. Melbourne: Indata Press. 692 p. [45830]

125. Patterson, David T. 1976. The history and distribution of five exotic weeds in North Carolina. Castanea. 41(2): 177-180. [21454]

126. Paysen, Timothy E.; Ansley, R. James; Brown, James K.; Gottfried, Gerald J.; Haase, Sally M.; Harrington, Michael G.; Narog, Marcia G.; Sackett, Stephen S.; Wilson, Ruth C. 2000. Fire in western shrubland, woodland, and grassland ecosystems. In: Brown, James K.; Smith, Jane Kapler, eds. Wildland fire in ecosystems: Effects of fire on flora. Gen. Tech. Rep. RMRS-GTR-42-vol. 2. Ogden, UT: U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station: 121-159. [36978]

127. Petrides, G. A.; Peterson, Roger Troy. 1986. A field guide to North American trees and shrubs: Northeastern and north-central United States and southeastern and south-central Canada. 2nd ed. Boston: Houghton Mifflin Co. 428 p. [46760]

128. Plass, William T. 1975. An evaluation of trees and shrubs for planting surface-mine spoils. Res. Pap. NE-317. Upper Darby, PA: U.S. Department of Agriculture, Forest Service, Northeastern Forest Experiment Station. 8 p. [46129]

129. Rabe, Elizabeth P.; Bassuk, Nina. 1984. Adaptation of Ailanthus altissima to the urban environment through analysis of habitat usage and growth response to soil compaction. Hortscience. 19(3): 572. [Abstract]. [45852]

130. Rabe, Elizabeth Pan. 1985. Distribution and growth response of Ailanthus altissima in the urban environment. Ithaca, NY: Cornell University. 87 p. Thesis. [45753]

131. Radford, Albert E.; Ahles, Harry E.; Bell, C. Ritchie. 1968. Manual of the vascular flora of the Carolinas. Chapel Hill, NC: The University of North Carolina Press. 1183 p. [7606]

132. Randall, John M. 1997. Defining weeds of natural areas. In: Luken, James O.; Thieret, John W., eds. Assessment and management of plant invasions. Springer Series on Environmental Management. New York: Springer-Verlag: 18-25. [41098]

133. Rank, B. 1997. Oxidative stress response and photosystem 2 efficiency in trees of urban areas. Phytosynthetica. 33(3-4): 467-481. [45848]

134. Raunkiaer, C. 1934. The life forms of plants and statistical plant geography. Oxford: Clarendon Press. 632 p. [2843]

135. Riffle, Jerry W.; Peterson, Glenn W., technical coordinators. 1986. Diseases of trees in the Great Plains. Gen. Tech. Rep. RM-129. Fort Collins, CO: U.S. Department of Agriculture, Forest Service, Rocky Mountain Forest and Range Experiment Station. 149 p. [16990]

136. Ripple, William J. 1994. Historic spatial patterns of old forests in western Oregon. Journal of Forestry. 92(11): 45-49. [33881]

137. Robinson, George R.; Handel, Steven N. 1993. Forest restoration on a closed landfill: rapid addition of new species by bird dispersal. Conservation Biology. 7(2): 271-278. [22062]

138. Root, Thomas W. 1985. Addition to the vascular flora of Rock Island County, Illinois. Transactions, Illinois Academy of Science. 78(3-4): 281-284. [37532]

139. Santamour, Frank S., Jr. 1983. Woody-plant succession in the urban forest: filling cracks and crevices. Journal of Arboriculture. 9(10): 267-270. [45849]

140. Santamour, Frank S., Jr.; Riedel, Louise G. H. 1993. Susceptibility of various landscape trees to root-knot nematodes. Journal of Arboriculture. 19(5): 257-259. [46140]

141. Sapsis, David B. 1990. Ecological effects of spring and fall prescribed burning on basin big sagebrush/Idaho fescue--bluebunch wheatgrass communities. Corvallis, OR: Oregon State University. 105 p. Thesis. [16579]

142. Schwartz, Mark W.; Porter, Daniel J.; Randall, John M.; Lyons, Kelly E. 1996. Impact of nonindigenous plants. In: Status of the Sierra Nevada. Sierra Nevada Ecosystem Project: Final report to Congress. Volume II: Assessments and scientific basis for management options. Wildland Resources Center Report No. 37. Davis, CA: University of California, Centers for Water and Wildland Resources: 1203-1218. [28977]

143. Seymour, Frank Conkling. 1982. The flora of New England. 2nd ed. Phytologia Memoirs 5. Plainfield, NJ: Harold N. Moldenke and Alma L. Moldenke. 611 p. [7604]

144. Shafiq, Muhammad; Nizami, M. I. 1986. Growth behaviour of different plants under gullied area of Pothwar Plateau. The Pakistan Journal of Forestry. 36(1): 9-15. [46127]

145. Sheley, Roger; Manoukian, Mark; Marks, Gerald. 1999. Preventing noxious weed invasion. In: Sheley, Roger L.; Petroff, Janet K., eds. Biology and management of noxious rangeland weeds. Corvallis, OR: Oregon State University Press: 69-72. [35711]

146. Shiflet, Thomas N., ed. 1994. Rangeland cover types of the United States. Denver, CO: Society for Range Management. 152 p. [23362]

147. Southeast Exotic Pest Plant Council, Tennessee Chapter. 2001. Invasive exotic pest plants in Tennessee, [Online]. Athens, GA: University of Georgia; Southeast Exotic Pest Plant Council (Producer). Available: http://www.se-eppc.org/states/TN/TNIList.html [2004, February 12]. [46747]

148. Stickney, Peter F. 1989. Seral origin of species comprising secondary plant succession in Northern Rocky Mountain forests. FEIS workshop: Postfire regeneration. Unpublished draft on file at: U.S. Department of Agriculture, Forest Service, Intermountain Research Station, Fire Sciences Laboratory, Missoula, MT. 10 p. [20090]

149. Stiles, Elsa Horn; Melchers, Leo E. 1935. The drought of 1934 and its effect on trees in Kansas. Part I: Meteorological conditions, 1934. Kansas Academy of Sciences. 38: 107-127. [46732]

150. Strausbaugh, P. D.; Core, Earl L. 1977. Flora of West Virginia. 2nd ed. Morgantown, WV: Seneca Books, Inc. 1079 p. [23213]

151. Stromberg, Mark R.; Kephart, Paul; Yadon, Vern. 2001. Composition, invasibility, and diversity in coastal California grasslands. Madrono. 48(4): 236-252. [41371]

152. Swearingen, Jil; Pannill, Phil. 2003. Fact sheet: Tree-of-heaven Ailanthus altissima (Mill.) Swingle, [Online]. In: Weeds gone wild: Alien plant invaders of natural areas. The Plant Conservation Alliance's Alien Plant Working Group (Producer). Available: http://www.nps.gov/plants/alien/fact/aial1.htm [2004, January 9]. [46267]

153. Tajchman, Stanislaw J; Fu, Hailiang; Kochenderfer, James N.; Chunshen, Pan. 1995. Spatial characteristics of topography, energy exchange, and forest cover in a central Appalachian watershed. In: Gottschalk, Kurt W.; Fosbroke, Sandra L., eds. Proceedings, 10th central hardwood forest conference; 1995 March 5-8; Morgantown, WV. Gen. Tech. Rep. NE-197. Radnor, PA: U.S. Department of Agriculture, Forest Service, Northeastern Forest Experiment Station: 297-314. [25870]

154. Tellman, Barbara. 1997. Exotic pest plant introduction in the American Southwest. Desert Plants. 13(1): 3-10. [27408]

155. Tellman, Barbara. 1998. Stowaways and invited guests: how some exotic plant species reached the American Southwest. In: Tellman, Barbara; Finch, Deborah M.; Edminster, Carl; Hamre, Robert, eds. The future of arid grasslands: identifying issues, seeking solutions: Proceedings; 1996 October 9-13; Tucson, AZ. Proceedings RMRS-P-3. Fort Collins, CO: U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station: 144-149. [29294]

156. Trifilo, P.; Raimondo, F.; Nardini, A.; Lo Gullo, M. A.; Salleo, S. 2004. Drought resistance of Ailanthus altissima: root hydraulics and water relations. Tree Physiology. 24: 107-114. [46736]

157. Tu, Mandy; Hurd, Callie; Randall, John M., eds. 2001. Weed control methods handbook: tools and techniques for use in natural areas. Davis, CA: The Nature Conservancy. 194 p. [37787]

158. Tworkoski, Thomas J.; Welker, William V.; Vass, George D. 2000. Weed community changes following diuron, simazine, or terbacil application. Weed Technology. 14(1): 197-203. [46077]

159. U.S. Department of Agriculture, Forest Service, Eastern Region. 2004. Eastern Region invasive plants ranked by degree of invasiveness, [Online]. In: Noxious weeds and non-native invasive plants. Section 3: Invasive plants. Milwaukee, WI: Eastern Region (Producer). Available: http://www.fs.fed.us/r9/wildlife/range/weed/Sec3B.htm [2004, February 16]. [46748]

160. U.S. Department of Agriculture, Forest Service, Southern Region. 2001. Regional invasive exotic plant species list, [Online]. In: Regional Forester's list and ranking structure: invasive exotic plant species of management concern. In: Invasive plants of southern states list. Southeast Exotic Pest Plant Council (Producer). Available: http://www.se-eppc.org/fslist.cfm [2003, August 25]. [44944]

161. U.S. Department of Agriculture, Natural Resources Conservation Service. 2007. PLANTS Database, [Online]. Available: http://plants.usda.gov/. [34262]

162. U.S. Department of the Interior, National Park Service, Shenandoah National Park. 2003. Nature & science: Non-native species, [Online]. U.S. Department of the Interior, National Park Service (Producer). Available: http://www.nps.gov/shen/pphtml/subenvironmentalfactors28.html [2004, January 21]. [46456]

163. Udvardy, L. 1998. Spreading and coenological circumstances of the tree of heaven (Ailanthus altissima) in Hungary. Acta Botanica Hungarica. 41(1-4): 299-314. [46454]

164. Vermont Agency of Natural Resources. 1998. Invasive exotic plants of Vermont: A list of the state's most troublesome weeds. Vermont Invasive Exotic Plant Fact Sheet Series. Waterbury, VT: Department of Environmental Conservation; Department of Fish and Wildlife, Nongame and Natural Hertiage Program. 2 p. In cooperation with: The Nature Conservancy of Vermont. [38461]

165. Vines, Robert A. 1960. Trees, shrubs, and woody vines of the Southwest. Austin, TX: University of Texas Press. 1104 p. [7707]

166. Virginia Department of Conservation and Recreation, Division of Natural Heritage. 2003. Fact sheet: Tree-of-heaven (Ailanthus altissima (Miller) Swingle)., [Online]. In: Invasive alien plant species of Virginia. Virginia Native Plant Society (Producer). Available: http://www.dcr.state.va.us/dnh/fsaial.pdf [2003, November 6]. [45525]

167. Virginia Department of Conservation and Recreation, Division of Natural Heritage. 2003. Invasive alien plant species of Virginia, [Online]. Virginia Native Plant Society (Producer). Available: http://www.dcr.state.va.us/dnh/invlist.pdf [2005, June 17]. [44942]

168. Voigt, Garth K.; Mergen, Francois. 1962. Seasonal variation in toxicity of Ailanthus leaves to pine seedlings. Botanical Gazette. 123(4): 262-265. [46735]

169. Voss, Edward G. 1985. Michigan flora. Part II. Dicots (Saururaceae--Cornaceae). Bull. 59. Bloomfield Hills, MI: Cranbrook Institute of Science; Ann Arbor, MI: University of Michigan Herbarium. 724 p. [11472]

170. Wade, Dale D.; Brock, Brent L.; Brose, Patrick H.; Grace, James B.; Hoch, Greg A.; Patterson, William A., III. 2000. Fire in eastern ecosystems. In: Brown, James K.; Smith, Jane Kapler, eds. Wildland fire in ecosystems: Effects of fire on flora. Gen. Tech. Rep. RMRS-GTR-42-vol. 2. Ogden, UT: U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station: 53-96. [36983]

171. Webb, Sara L.; Pendergast, Thomas H., IV; Dwyer, Marc E. 2001. Response of native and exotic maple seedling banks to removal of the exotic, invasive Norway maple (Acer platanoides). Journal of the Torrey Botanical Society. 128(2): 141-149. [42560]

172. Welsh, Stanley L.; Atwood, N. Duane; Goodrich, Sherel; Higgins, Larry C., eds. 1987. A Utah flora. The Great Basin Naturalist Memoir No. 9. Provo, UT: Brigham Young University. 894 p. [2944]

173. Wright, Henry A.; Bailey, Arthur W. 1982. Fire ecology: United States and southern Canada. New York: John Wiley & Sons. 501 p. [2620]

174. Wunderlin, Richard P. 1998. Guide to the vascular plants of Florida. Gainesville, FL: University Press of Florida. 806 p. [28655]

175. Youtie, Berta; Soll, Jonathan. 1990. Diffuse knapweed control on the Tom McCall Preserve and Mayer State Park. Unpublished report (prepared for the Mazama Research Committee) on file at: U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station, Fire Sciences Laboratory, Missoula, MT. 18 p. [38353]

176. Zasada, John C.; Little, Silas. 2002. Ailanthus altissima (P. Mill.) Swingle ailanthus. In: Bonner, Franklin T., tech. coord. Woody plant seed manual, [Online]. Washington, DC: U.S. Department of Agriculture, Forest Service (Producer). Available: http://wpsm.net/Ailanthus.pdf [2004, January 6]. [46269]

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