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Photo by Leslie J. Mehrhoff, University of Connecticut, Bugwood.org |
GENERAL DISTRIBUTION:
Asiatic tearthumb has a limited distribution in North America. The distribution map provided by
Plants Database shows Asiatic tearthumb concentrated in the mid-Atlantic states, from Virginia north to New York and Connecticut and west to Ohio.
Asiatic tearthumb has also been documented in Massachusetts [33],
Rhode Island [35], Mississippi, Oregon, and British Columbia [26].
However, a 1994 review states that Asiatic tearthumb has not been reported west of the Rocky Mountains since 1954 [39], suggesting that western populations documented in the
past failed to persist.
Asiatic tearthumb is native to a wide area of eastern Asia, occurring from Japan west and south to the Philippines (review by [9]). In North America, Asiatic tearthumb was first collected in Oregon (1890), apparently transported in ship ballast. This population did not persist. In the mid 1930s, Asiatic tearthumb was introduced into a Pennsylvania nursery via contaminated seeds. All populations of Asiatic tearthumb in the mid-Atlantic states are traced back to this introduction (review by [9]), with plants throughout the region lacking genetic variation [44].
Asiatic tearthumb's spread in the mid-Atlantic states is largely attributed to the dispersal of its buoyant seeds along water drainages. Asiatic tearthumb spread is also facilitated by contaminated nursery stock [41], soil, or hay; or seed transported by logging equipment (review by [39]) or migratory birds ([41], review by [39]) (see Seed dispersal). Though Asiatic tearthumb spreads quickly in some areas [9], it appears that its establishment is limited by the need for seeds to undergo a period of cold stratification prior to germination. Therefore, it is unlikely that Asiatic tearthumb will establish in warm temperate regions of North America [24].
HABITAT TYPES AND PLANT COMMUNITIES:
In its native range, Asiatic tearthumb is commonly found along water or in moist areas
(review by [41]). In North America, Asiatic tearthumb's multiple means
of dispersal facilitate its establishment in a variety of plant communities, including riparian or lowland areas as well as upland sites. All plant community descriptions presented here are from the mid-Atlantic states.
Riparian or lowland plant communities: In the mid-Atlantic states, Asiatic tearthumb establishes along waterways [1,9,11,12,21] and wetlands [28], in swamps [31,41], and in moist woodlands [52]. Collection data from Maryland, Pennsylvania, and Washington, DC, documented Asiatic tearthumb along creeks, on low ground, in shrub swamps, and on wooded floodplains. Extensive stands of Asiatic tearthumb occurred in an alluvial black walnut (Juglans nigra) forest. Asiatic tearthumb was also reported flourishing along beaches and marsh strands in the estuaries of the upper Chesapeake Bay [41]. In Washington, DC, Asiatic tearthumb occurred in riparian deciduous forests dominated by boxelder (Acer negundo), red maple (A. rubrum), yellow-poplar (Liriodendron tulipifera), and American sycamore (Platanus occidentalis) [11]. In Pennsylvania, Asiatic tearthumb occurred on the edges of stands of the "globally rare" Darlington's glade spurge (Euphorbia purpurea), establishing in swamps bounded by upland forest. The swamp canopy was dominated by sweet birch (Betula lenta), red maple, yellow-poplar, black ash (Fraxinus nigra), and black tupelo (Nyssa sylvatica) [31]. In central New Jersey, Asiatic tearthumb occurred in moist woodlands containing sugar maple (A. saccharum), red maple, sweet birch, shagbark hickory (Carya ovata), bitternut hickory (C. cordiformis), and American elm (Ulmus americana) [52].
Upland plant communities: Asiatic tearthumb may establish in upland plant communities in the mid-Atlantic states, including upland hardwood forests [1,9,24,52], conifer plantations [24,52], shrubby thickets [41,52], and disturbed open areas [12,24,41,52]. In West Virginia, Asiatic tearthumb established at the edge of disturbed forests dominated by silver maple (A. saccharinum) [9]. In Pennsylvania and Virginia, Asiatic tearthumb occurred along the edges of disturbed forests, man-made meadows, hiking paths, or roads. It established in both monospecific stands or was integrated with other vegetation, including native plants like goldenrod (Solidago spp.) and American pokeweed (Phytolacca americana) and a number of other nonnative species like garlic mustard (Alliaria petiolata) and Canada thistle (Cirsium arvense). In areas where it dominated, it grew over other nonnatives including multiflora rose (Rosa multiflora), Japanese honeysuckle (Lonicera japonica), and common reed (Phragmites australis) [12]. Collection data from Maryland, Pennsylvania, and Washington, DC, documented Asiatic tearthumb in gullies, blackberry (Rubus sp.) thickets, and woodland borders [41]. In Maryland, Asiatic tearthumb occurred in clearings in logged hardwood forests [1]. In Pennsylvania, Asiatic tearthumb occurred in conifer plantations and mixed hardwood forests with white oak (Quercus alba), water oak (Q. nigra), northern red oak (Q. rubra), chestnut oak (Q. prinus), red maple, yellow-poplar, mockernut hickory (Carya tomentosa), shagbark hickory, and pignut hickory (C. glabra). Asiatic tearthumb also established in open areas such as fallow fields, clearcuts, and utility rights-of-way [24]. In central New Jersey, Asiatic tearthumb occurred in several fragmented plant communities, including open hardwood forests, abandoned conifer plantations, and shrub thickets. Open hardwood forests contained white ash (F. americana), yellow-poplar, black walnut, northern red oak, black cherry (Prunus serotina), and flowering dogwood (Cornus florida). Abandoned conifer plantations contained white spruce (Picea glauca) and eastern white pine (Pinus strobus). Shrub thickets contained Allegheny blackberry (R. allegheniensis) and the nonnatives multiflora rose and Russian-olive (Elaeagnus angustifolia). Asiatic tearthumb was also reported in successional fields, along forest edges, and in the center and edges of large forest canopy gaps [52]. In New Jersey, Asiatic tearthumb established in the full shade of a closed-canopy red maple-black tupelo forest (D. Snyder personal observation cited in [45]).
Botanical description: This description covers characteristics that may be relevant to fire ecology and is not meant for identification. Keys for identification are available (e.g., [27,39]).
| Asiatic tearthumb is a glaucous, branching, vine-like herb. It grows from an herbaceous base that may become woody with age [41]. Vines may grow 10 to 12 feet (3-4 m) long [9] and climb or recline on other plants [41]. The angles of stems, petioles, and the principal veins on the undersurface of leaves have recurved prickles. Asiatic tearthumb leaves are distinctively triangular, 0.4 to 3 inches (1-8 cm) long, and light green, though they may appear reddish when young. Asiatic tearthumb has apetalous flowers that are borne in axillary or terminal fascicles and are well concealed among the upper leaves. The fruits are metallic blue in color, subglobose, fleshy, and berry-like, 4 to 6 mm in diameter. The solitary achene is black, spherical, and about 3.5 mm long [41]. |  |
Photo by Leslie J. Mehrhoff, University of Connecticut, Bugwood.org |
Asiatic tearthumb roots are fibrous and shallow ([36], reviews by [3,27]).
Asiatic tearthumb is generally considered an annual [3,9,27,39,51,58], though some sources report it as a perennial [3,41,58]. One source reports that Asiatic tearthumb behaves like an annual in North America (review by [58]) though it grows as a perennial in mild areas of its native range [56].
Raunkiaer [40]
life form:
Therophyte
SEASONAL DEVELOPMENT:
In the mid-Atlantic states, Asiatic tearthumb seeds germinate in early April (review by [37]).
Seedlings are established by late April (review by [39]),
reaching 4 to 8 inches (10-20 cm) in height by early May [21].
Flowering begins in early June or July. Fruits are produced from early August until plants die
in mid-October (review by [3]). Fruits ripen from September to
November (review by [39]). Dead stems may persist for as long as a year [24].
Pollination and breeding system: Asiatic tearthumb usually reproduces via self-fertilization ([14,22], reviews by [44,58]), though outcrossing occasionally occurs (review by [44]). One study reported bumblebees visiting Asiatic tearthumb flowers in Delaware, though the authors noted that insect pollination was not required for seed set [22].
Seed production: Asiatic tearthumb seed production is highly variable. In Pennsylvania, seed production averaged 7.85 seeds/plant one year and 39.35 seeds/plant another year [23]. At field sites in Delaware, Asiatic tearthumb plants produced approximately 3,500 seeds/plant by the end of the growing season [22]. An increase in light availability appears to improve seed production [22,24]. In Delaware, Asiatic tearthumb plants in field cages produced >2,200 seeds in full light but <400 seeds in the shade (unpublished data cited in [22]). In New Jersey, seed production was limited by drought [52].
Seed dispersal: Asiatic tearthumb seeds are dispersed in several ways. Water dispersal is common ([9,14], reviews by [27,37,39]). Asiatic tearthumb's large, blue fruits have a waxy perianth that repels water and promotes floating; fruits retain buoyancy for 7 days [14]. Asiatic tearthumb seeds are also dispersed by birds ([14,52], reviews by [27,39]), and mammals (reviews by [27,39]), including chipmunks, squirrels, and white-tailed deer (review by [27]). Ants may disperse seeds short distances (review by [27]). Seeds may also be transported by logging equipment or in the rootballs of nursery stock (review by [38]). Seeds that remain on the parent plant may by dispersed when dead stems are moved in control efforts [18] or when Asiatic tearthumb stems are transported while attached to nursery plants (review by [38]).
Seed banking: Asiatic tearthumb seeds may persist in the soil seed bank for several years; one review suggests that seeds persist for up to 4 years [3]. In New Jersey, wild-collected seeds were buried 1 inch (2 cm) below the soil surface in December. Seeds were removed at intervals over 3 years and placed in a germination chamber. Germination was highest after 1 year of burial (96.3%) but was still substantial after 3 years of burial (32.6%) [52]. In Pennsylvania, Asiatic tearthumb seeds were buried in an old field and a 55-year-old red pine (Pinus resinosa) plantation. Over 2 years, seeds were removed at intervals and germinated in a laboratory. After 2 years, 50% to 95% of the seeds were viable, with higher viability in seeds from the red pine plantation compared to those from the old field. Germination rates were higher 18 months after burial compared to 6 months after burial [24].
Asiatic tearthumb seeds may be present in the soil seed bank even when established Asiatic tearthumb stands are not present in the immediate vicinity. In Pennsylvania, sites with existing populations of Asiatic tearthumb had abundant Asiatic tearthumb seeds in the soil seed bank, but seeds were also sometimes found in areas adjacent to established Asiatic tearthumb stands or in areas sharing no common border with Asiatic tearthumb stands [24].
Germination: Asiatic tearthumb seeds need moisture ([24,58], reviews by [22,39]) and cold stratification ([14,24,39,58], review by [22]) to germinate. Several sources suggest that Asiatic tearthumb seed germination improves in the presence of litter (e.g., leaves, decayed organic matter, brush) that keeps the soil moist ([36], reviews by [37,38]); however, laboratory tests in Virginia found no significant change in germination rates with varying moisture levels [14]. Seeds collected throughout eastern North America needed cold-wet stratification for 4 to 19 weeks to break dormancy, and germination rates improved as stratification time increased. Growth chamber germination rates for wild-collected Asiatic tearthumb seeds following cold-wet stratification averaged 52.4% and ranged from 11% to 86% [58]. In laboratory germination tests in Pennsylvania, Asiatic tearthumb seeds responded favorably to cold-wet stratification. A minimum of 6 weeks was needed for germination. Seeds germinated over a wide temperature range (50 to 68 °F (10-20 °C)) but germination was more consistent at 50 °F (10 °C) than at 68 °F (20 °C). Germination rates were highest (52.9%) at 50 °F (10 °C) after 6 weeks of stratification [24].
Scarification may improve germination rates ([8,24,39], review by [22]) and allow germination at a wider range of temperatures. In laboratory germination tests in Pennsylvania, acid scarification improved germination in weeks 6 to 12 of the trials [24]. In laboratory germination tests in Virginia, an 8-week cold stratification treatment was not required in acidic (pH 3.5) environments, whereas it was required in environments with higher pH. The author hypothesized that acidic litter in field settings could act as a scarifying agent and improve germination [14]. Though one source suggested that scarification may occur when seeds are ingested by mammals and birds (F. Johnson personal communication cited in [39]), ingestion by captive songbirds did not improve germination of Asiatic tearthumb seeds collected in Virginia [14].
Disturbance may not impact Asiatic tearthumb germination. In New Jersey, a field study found no significant difference in Asiatic tearthumb seedling emergence in disturbed (removal of vegetation and loosening of the top 2 inches (5 cm) of soil) and undisturbed sites. Across 3 habitat types (forest, forest edge, successional fields), seedling emergence averaged 61.3% [52].
Seedling establishment and plant growth:
Seedling establishment: Asiatic tearthumb seedlings may establish in high densities; in Asiatic tearthumb monocultures in Pennsylvania, seedling densities exceeded
500/m² (unpublished data cited in [22]).
Seedling survival may be higher in moist, light areas compared to dry, shaded areas. In New Jersey, one study examined seedling survival in 3 habitat types (forest, forest edge, and successional fields). Wild-collected seeds were stored over the winter and planted in field sites in the spring. Of the seedlings that emerged, overall survival was low (4.3%) but was highest in successional fields (11.3 %), low in forest edge (1.7%), and nonexistent in the forest interior. Soil moisture and light were highest in the field, followed by the edge, then the forest. Primary cause of seedling death appeared to be desiccation [52]. In Pennsylvania, one author observed that seedlings germinating in the understory of mixed hardwood forests did not produce fruit and eventually died by summer [24].
Plant growth: Asiatic tearthumb plants exhibit rapid growth (review by [3]), growing up to 6 inches (15 cm)/day (review by [45]) and up to 33 feet (10 m)/year [23].
Increased availability of light, moisture, and nutrients may improve Asiatic tearthumb growth. In Maryland growth chamber experiments, seedlings from wild-collected seeds were exposed to several light and water treatments. Plants exposed to both high light and water developed 2.25 times the biomass compared to plants exposed to high light and low water, and 10 times the biomass of plants exposed to low light and either high or low water (P<0.05). Plants exposed to both high water and light had the greatest leaf area (P<0.05). Plants exposed to high light had higher growth rates than those exposed to low light (P<0.05) and also exhibited the greatest root mass; at harvest, root mass of high-light plants averaged 0.4 ounces (1.3 g), while low-light plants averaged 0.004 ounces (0.1 g) [1]. Another series of growth chamber experiments compared total biomass, root to shoot ratio, leaf weight ratio, and height of Asiatic tearthumb seedlings at 4 resource combinations: high light-high nutrient, high light-low nutrient, low light-high nutrient, low light-low nutrient. Both high nutrient (P<0.01) and high light (P<0.05) treatments led to a significantly greater reproductive biomass. Manipulating nutrient and light levels led to changes in the allocation of resources to root or vegetative growth; low nutrient levels led to an increase in root growth over vegetative growth, while low light levels led to an increase in vegetative growth over root growth [52].
Vegetative regeneration: Asiatic tearthumb does not regenerate vegetatively in North America (review by [39]). In areas of China experiencing mild weather and lacking frost, there are reports of roots growing from the stem nodes of perennial Asiatic tearthumb plants. It was suggested that these plants may eventually establish as separate plants [56].
SITE CHARACTERISTICS:
Sources report Asiatic tearthumb establishing on a wide range of sites, though reviews suggest that it establishes best in areas with high light [34]
and moisture [1,38],
and abundant plant litter [1,34,37,38].
Asiatic tearthumb establishes in disturbed areas [1,3,13,38,41,54],
particularly those associated with human activity, such as roadsides [1,3,13,23,27,38,41,51], railroad tracks
[9,27], ditches [3,38,41,51],
nurseries and orchards [3,27,38,51],
powerline rights-of-way [3,27],
regenerating logged areas [27,34,51],
hedgerows [1,54], recreational areas [3],
woodpiles [38], and open fields [3,13,23,27,38].
Asiatic tearthumb also establishes along forest edges
[3,13,27,38,41],
in openings in forested areas [1,3,9,38],
on eroded banks [41], and in thickets [27,38,41],
gullies [41], and meadows [27,39].
Climate: In North America, Asiatic tearthumb is limited to areas with a temperate climate that experience cold winters (review by [58]). It is sensitive to freezing, with the first hard frost killing plants (F. Johnson personal communication cited in [39]). Asiatic tearthumb has been observed growing as a perennial in frost-free areas of China [58], leading one source to suggest the potential for Asiatic tearthumb to expand its distribution to areas in North American with warm climates, like Florida [39]. However, other sources suggest that the need for cold stratification for germination precludes such a range expansion [24].
Soils: As of this writing (2010) there was little information available regarding soil preferences of Asiatic tearthumb. In Maryland, Asiatic tearthumb established on gravelly loam [1]. In Pennsylvania, Asiatic tearthumb established on shallow, well-drained, channery loam [34]. In Virginia, Asiatic tearthumb grew in areas with pH ranging from 5.5 to 6.4 [14]. A review [27] states that Asiatic tearthumb prefers soil high in organic matter. Most sources suggest that Asiatic tearthumb prefers moist conditions ([18,42,51], reviews by [13,38]), though it can tolerate low soil moisture (reviews by [13,27]). In Maryland, field sites where Asiatic tearthumb occurred had soil moisture content ranging from 15% to 40% [1]. Some sources suggest that moist, well-drained sites are preferred [42,51].
SUCCESSIONAL STATUS:
Asiatic tearthumb is an early successional species (review by [3]).
Disturbance: Asiatic tearthumb frequently establishes on disturbed sites ([9,18], reviews by [3,14]) or in open areas (reviews by [3,13]). In its native range, it is largely restricted to riparian areas where frequent flooding creates open and disturbed areas for continuous population establishment [23]. Along the Delaware River, Asiatic tearthumb populations survived frequent flooding, including a 100-year flood [21]. In eastern Pennsylvania, Asiatic tearthumb established the season after severe floods deposited a thick layer of sandy silt on the floodplain, burying well-established forbs and grasses. Many weed species established following the flooding event. Asiatic tearthumb dominated the weed community the 1st postflood year, but was restricted in dominance the following year and subsequently failed to establish [18]. In North America, Asiatic tearthumb establishes well in areas that have been treated with herbicides targeting other nonnative species (review by [27]). It also establishes well in forests following clearcutting (W. Mountain and L. McCormick personal communications cited in [39]).
Light: Asiatic tearthumb prefers full sun ([42,45,52], reviews by [27,39,51]). Plant growth [1,52], seedling survival [52], and seed production [24] may be higher in areas with more light compared to areas with more shade. Nevertheless, Asiatic tearthumb can also establish in shaded areas ([1,9,14,45], reviews by [3,13,27,39,51]). In Maryland, Asiatic tearthumb established in areas experiencing substantial shading for at least part of the day, with insolation at canopy level ranging from 7% to 60% of full light [1]. In Virginia, streamside populations of Asiatic tearthumb experienced 32% to 100% light [14]. In New Jersey, Asiatic tearthumb plants reproduced in the full shade of a closed-canopy red maple-black tupelo forest (D. Snyder personal observation cited in [45]). Plants establishing in shaded conditions often use the structure of other vegetation to reach areas where light is readily available ([14], review by [3]). In Maryland, Asiatic tearthumb established in hardwood forest openings and spread into the forest understory a distance of approximately 23 feet (7 m) [24].
Successional role: Asiatic tearthumb may influence the successional trajectories of native plant communities where it establishes, particularly in areas where the dense, tangled mats of Asiatic tearthumb vines lead to changes in native plant cover or diversity (see Impacts). Because Asiatic tearthumb can either establish in monospecific stands or be integrated with other vegetation [12], its impact on plant community succession probably varies by location.
FIRE EFFECTS:
Immediate fire
effect on plant: As of this writing (2010), no information was available about the immediate effects of fire on Asiatic tearthumb. It is likely that fire would kill entire plants.
Information was also lacking on fire effects on Asiatic tearthumb seeds. One source reported that Asiatic tearthumb seeds expand like popcorn when heated in a microwave (R. Westbrooks personal
communication cited in [39]).
Postfire regeneration strategy [46]:
Ground residual colonizer (on site, initial community)
Initial off-site colonizer (off site, initial community)
Fire adaptations and plant response to fire:
Fire adaptations: As of 2010,
there was no published information regarding Asiatic tearthumb adaptations to fire. The information presented here is inferred from reported botanical traits.
In general, Asiatic tearthumb appears to possess few adaptive traits for surviving fire or establishing after fire. It does not regenerate vegetatively (See Vegetative regeneration), so on-site plants would likely be killed. The consumption of litter by fire would likely create dry conditions that would inhibit Asiatic tearthumb seed germination and establishment, despite other conditions (full sun, disturbance (see Successional status)) or botanical traits (persistence in the seed bank, long-distance seed dispersal) that may appear conducive to Asiatic tearthumb establishment in burned areas. It is possible that Asiatic tearthumb seeds present in the soil seed bank or dispersed from off-site sources could germinate in moist, burned riparian zones or as upland site conditions change during postfire succession.
Plant response to fire: As of 2010 there were no studies available documenting the response of Asiatic tearthumb to fire.
FUELS AND FIRE REGIMES:Fire regimes: It is not known what type of fire regime Asiatic tearthumb is best adapted to. The literature contains few descriptions of plant communities where Asiatic tearthumb occurs. It is common in riparian areas in many parts of North America, and fire regimes in riparian areas are often related to fire regimes of adjacent upland communities. Asiatic tearthumb also occurs in upland areas. Thus fire regimes for plant communities with Asiatic tearthumb could be quite variable. See the Fire Regime Table for further information on fire regimes of plant communities in which Asiatic tearthumb may occur. Find further fire regime information for the plant communities in which this species may occur by entering the species name in the FEIS home page under "Find Fire Regimes".
FIRE MANAGEMENT CONSIDERATIONS:
Potential for postfire establishment and spread: Postfire establishment and spread of Asiatic tearthumb have not been documented as of 2010. The establishment of Asiatic tearthumb following fire is likely limited by the consumption of litter and consequent lack of moisture in burned areas. However, the frequent
dispersal of Asiatic tearthumb seed via waterways suggests that Asiatic tearthumb could establish in burned areas adjacent to riparian zones, particularly if those burned areas exhibit high moisture. It is also possible that seeds present in the soil seed bank could germinate several years following fire, once conditions conducive to germination develop on
the site. Asiatic tearthumb plants adjacent to burned areas could possibly spread into the burned areas, taking advantage of high-light conditions there. However, none of these responses have been documented in the literature (2010).
Preventing postfire establishment and spread: Preventing invasive plants from establishing in weed-free burned areas is the most effective and least costly management method. This can be accomplished through early detection and eradication, careful monitoring and follow-up, and limiting dispersal of invasive plant seed into burned areas. Asiatic tearthumb's ability to persist in the soil seed bank for several years and/or long-distance seed dispersal suggest that long-term monitoring of burned areas may be necessary to prevent Asiatic tearthumb establishment. Other recommendations for preventing postfire establishment and spread include:
For more detailed information on these topics see the following publications: [2,4,15,49].
Use of prescribed fire as a control agent: Because Asiatic tearthumb appears to have few adaptations for surviving fire (see Fire adaptations), it is likely that prescribed fire would kill Asiatic tearthumb plants. It is possible that Asiatic tearthumb seeds present in the soil seed bank or dispersed from off-site sources may establish following prescribed fire, but short-term establishment rates may be limited by the need of Asiatic tearthumb seed for moisture to germinate. The persistence of Asiatic tearthumb seeds in the seed bank suggests that seeds could germinate as postfire conditions change.
Altered fuel characteristics: One review suggests that Asiatic tearthumb, along with several other nonnative species, may reduce the flammability of some sites, largely through the production of "succulent, almost nonflammable vegetation" [10]. In sites dominated by Asiatic tearthumb, this characteristic could limit the ability of managers to use prescribed fire to promote the regeneration of desirable native species (Gorman personal communication 2005 cited in [10]).
FEDERAL LEGAL STATUS:
None
OTHER STATUS:
Asiatic tearthumb is listed as a noxious weed in several states. Information on state-level noxious
weed status of Asiatic tearthumb is available at Plants Database.
IMPORTANCE TO WILDLIFE AND LIVESTOCK:
Palatability and/or nutritional value: The
prickly foliage of Asiatic tearthumb is not attractive to herbivorous mammals [10].
However, more than 30 species of herbivorous insects were found on Asiatic tearthumb foliage in
Virginia and Pennsylvania [12]. Asiatic tearthumb fruits are consumed
by birds, mammals, and insects (review by [27]).
Cover value: No information is available on this topic.
OTHER USES:
Asiatic tearthumb fruits are edible to humans and have a high potassium content (review by [12]). Asiatic tearthumb has been used in China as an herbal medicine for the relief of fever, inflammation,
cough, and swelling (review by [58]). It has also been used
to treat snakebites and dysentery (review by [7]).
Asiatic tearthumb extracts may reduce blood sugar levels and inhibit cancer cell growth
(review by [58]). Extracts from the whole plant have been used for insect pest control in China
(review by [57]).
|
IMPACTS AND CONTROL: Impacts: Several reviews report that Asiatic tearthumb populations may reduce the abundance and diversity of native plants [3,13,45], largely through the formation of dense, tangled mats of vegetation [9,36]. These mats are thick enough to kill herbaceous vegetation underneath [36], and may even negatively impact other rapidly growing nonnative species like Japanese honeysuckle [9,36]. In laboratory germination experiments, extracts from Asiatic tearthumb had allelopathic qualities [7]. |
 |
Photo by Leslie J. Mehrhoff, University of Connecticut, Bugwood.org |
Asiatic tearthumb may establish in both dense monocultures ([14,24,28,34], review by [19]) and mixtures with other plant species [24,28]. In Pennsylvania, Asiatic tearthumb dominance ranged from 30% to 90% in a variety of site types, including hardwood forests, conifer plantations, and old fields [24]. In some areas of Pennsylvania, Asiatic tearthumb stems reached a density of 300 stems/m² [23]. Asiatic tearthumb stands in New Jersey covered 1 acre (0.4 ha) or more [45].
The establishment of Asiatic tearthumb at one site in New Jersey led to the demise of a population of the state-endangered manyflower flatsedge (Cyperus lancastriensis) in less than a decade (D. Snyder personal observation cited in [45]). In Pennsylvania, Asiatic tearthumb establishing on the edges of stands of the "globally rare" Darlington's glade spurge has led to some concern over how it will impact Darlington's glade spurge in the future [31]. Asiatic tearthumb completely killed dense stands of Japanese honeysuckle, American black elderberry (Sambucus canadensis) and blackberry in a Pennsylvania nursery [36]. In Virginia, sites with established Asiatic tearthumb populations experienced a reduction in vascular plant species richness over a 1-year period. The author suggested that the early spring emergence and rapid growth of Asiatic tearthumb promoted its establishment and spread, even allowing it to limit the persistence of perennial species [14].
Asiatic tearthumb establishment has several other potential impacts. One review suggests that the changes in plant communities resulting from Asiatic tearthumb establishment could reduce food availability and degrade habitat for wildlife [3]. In recently harvested forests, Asiatic tearthumb establishment limits forest regeneration by shading or growing on top of tree seedlings (W. Mountain and L. McCormick personal communications cited in [39], reviews by [3,27]). In commercial forests where Asiatic tearthumb has impacted tree regeneration, costs ranging from about $60 to $500/ha may be incurred for site preparation, weed management, and labor to replant seedlings (Charles Brown personal communication cited in [56]). Asiatic tearthumb presents similar problems in orchards and nurseries (review by [27]). The tangled mats of Asiatic tearthumb may impede the movement of heavy machinery (R. Westbrooks personal communication cited in [39]) or restrict human access to recreational areas [28].
Control: In all cases where invasive species are targeted for control, the potential for other invasive species to fill their void must be considered, no matter what control method is employed [5]. Control of biotic invasions is most effective when it employs a long-term, ecosystem-wide strategy rather than a tactical approach focused on battling individual invaders [32]. Information presented in the following sections may not be comprehensive and is not intended to be prescriptive in nature. It is intended to help managers understand the ecology and control of Asiatic tearthumb in the context of fire management. For more detailed information on the control of Asiatic tearthumb, consult the references cited here or local extension services. For reviews of control recommendations for Asiatic tearthumb, see the following sources: [37,39,58].
Fire: For information on the use of prescribed fire to control Asiatic tearthumb see Fire Management Considerations.
Prevention: To prevent establishment of Asiatic tearthumb, several reviews recommend maintaining wide streamside forest buffers in riparian areas and stable vegetative cover in upland areas (i.e., not creating gaps or disturbances) [3,13,58].
It is commonly argued that the most cost-efficient and effective method of managing invasive species is to prevent their establishment and spread by maintaining "healthy" natural communities [32,43] (e.g., avoid road building in wildlands [48]) and by conducting monitoring several times each year [25]. Managing to maintain the integrity of the native plant community and mitigate the factors enhancing ecosystem invasibility is likely to be more effective than managing solely to control the invader [20]. Weed prevention and control can be incorporated into many types of management plans, including those for logging and site preparation, grazing allotments, recreation management, research projects, road building and maintenance, and fire management [49]. See the "Guide to noxious weed prevention practices" [49] for specific guidelines in preventing the spread of weed seeds and propagules under different management conditions.
Cultural control: Similar to prevention measures, cultural methods of Asiatic tearthumb control include supporting the integrity of existing plant communities, such as maintaining wide streamside forest buffers in riparian areas and stable vegetative cover in upland areas [3,13,58].
Physical or mechanical control: Physical or mechanical methods may effectively control Asiatic tearthumb, though such methods are complicated by the potential for human injury from Asiatic tearthumb's sharp prickles (review by [13]). Hand-pulling is practical for small populations; plants are shallow-rooted and easy to pull (reviews by [3,37]). After seedlings emerge, they can be removed with a hoe (review by [37]). Hand-pulling of seedlings should be done prior to prickles hardening (review by [3]). Mowing or cutting plants with a scythe may be effective (reviews by [37,39]); repeated mowing and trimming may prevent flowering and reduce or eliminate seed production (review by [3]). All physical and mechanical control methods are most successful when done prior to seed set (reviews by [3,37,39]), generally in September and November (review by [39]). Following physical or mechanical treatments, clearing treated areas of debris or decaying plant material is recommended to inhibit Asiatic tearthumb seed germination from the soil seed bank (reviews by [3,38,39]).
Biological control: Biological control of invasive species has a long history that indicates many factors must be considered before using biological controls. Refer to these sources: [53,55] and the Weed Control Methods Handbook [47] for background information and important considerations for developing and implementing biological control programs.
As of 2004, the Asiatic tearthumb weevil, a native of China, was approved by the USDA for biocontrol of Asiatic tearthumb [22,28]. Adult Asiatic tearthumb weevils feed on foliage while larvae feed within stems at nodes. Damage from Asiatic tearthumb weevils may cause enough damage to limit seed production [28]. In some areas, Asiatic tearthumb populations have completely collapsed 1 to 2 years following introduction of Asiatic tearthumb weevils [21]. For information on the success of the Asiatic tearthumb weevil as a biocontrol agent, see the following sources: [21,28]. For information on fungal associates that could be used as Asiatic tearthumb biological control agents, see [58].
Chemical control: Herbicides are effective in gaining initial control of a new invasion or a severe infestation, but they are rarely a complete or long-term solution to weed management [6]. See the Weed Control Methods Handbook [47] for considerations on the use of herbicides in natural areas and detailed information on specific chemicals.
Herbicides are generally considered effective at controlling Asiatic tearthumb [17,34,37], though the common establishment of Asiatic tearthumb in riparian areas may limit the use of herbicides. For information regarding the use of both pre- and postemergent herbicides to control Asiatic tearthumb, see the following sources: [17,34].
Integrated management: No information is available on this topic.
The following table provides fire regime information that may be relevant to Asiatic tearthumb habitats based on descriptions in available literature. Follow the links in the table to documents that provide more detailed information on these fire regimes.
| Fire regime information on vegetation communities in which Asiatic tearthumb may occur. This information is taken from the LANDFIRE Rapid Assessment Vegetation Models [30], which were developed by local experts using available literature, local data, and/or expert opinion. This table summarizes fire regime characteristics for each plant community listed. The PDF file linked from each plant community name describes the model and synthesizes the knowledge available on vegetation composition, structure, and dynamics in that community. Cells are blank where information is not available in the Rapid Assessment Vegetation Model. | |||||||
|
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| Northeast | |||||||
| Vegetation Community (Potential Natural Vegetation Group) | Fire severity* | Fire regime characteristics | |||||
| Percent of fires | Mean interval (years) |
Minimum interval (years) |
Maximum interval (years) |
||||
| Northeast Grassland | |||||||
| Northern coastal marsh | Replacement | 97% | 7 | 2 | 50 | ||
| Mixed | 3% | 265 | 20 | ||||
| Northeast Woodland | |||||||
| Oak-pine (eastern dry-xeric) | Replacement | 4% | 185 | ||||
| Mixed | 7% | 110 | |||||
| Surface or low | 90% | 8 | |||||
| Northeast Forested | |||||||
| Northern hardwoods (Northeast) | Replacement | 39% | >1,000 | ||||
| Mixed | 61% | 650 | |||||
| Northern hardwoods-eastern hemlock | Replacement | 50% | >1,000 | ||||
| Surface or low | 50% | >1,000 | |||||
| Appalachian oak forest (dry-mesic) | Replacement | 2% | 625 | 500 | >1,000 | ||
| Mixed | 6% | 250 | 200 | 500 | |||
| Surface or low | 92% | 15 | 7 | 26 | |||
| Beech-maple | Replacement | 100% | >1,000 | ||||
| *Fire Severities— Replacement: Any fire that causes greater than 75% top removal of a vegetation-fuel type, resulting in general replacement of existing vegetation; may or may not cause a lethal effect on the plants. Mixed: Any fire burning more than 5% of an area that does not qualify as a replacement, surface, or low-severity fire; includes mosaic and other fires that are intermediate in effects. Surface or low: Any fire that causes less than 25% upper layer replacement and/or removal in a vegetation-fuel class but burns 5% or more of the area [16,29]. |
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