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Species
Microstegium vimineum var. imberbe
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Japanese stiltgrass is native to Japan, Korea, China, Malaysia, India, and the Caucasus Mountains [59,71,128,141,220]. It has invaded portions of Asia where it is nonnative, extending its range into Pakistan, Nepal [72], and Turkey [178]. Japanese stiltgrass is nonnative in the United States and Mexico; Europe; Australia and New Zealand; Africa; South America; and islands of the Atlantic, Pacific, and Indian oceans [220].
In the United States, it is sporadically distributed throughout most of the East and in the Caribbean, from New York south to Texas, Florida, Puerto Rico, and the Virgin Islands [58,71,97]. Japanese stiltgrass was first noted in North America around 1918 in Tennessee [15,51], where it was probably introduced accidentally [51]. It was formerly used as packing material for imported Chinese porcelain, and discarded packaging material containing seeds might have been the source of introduction [214]. Japanese stiltgrass is rare in Florida and other parts of the Southeast [164,230] but is rapidly increasing in Maryland, New York, and other northern states [15,90,169]. It was introduced in New Jersey around 1959 and spread rapidly in that state in the 1990s and 2000s (review by [5]). Roads and waterways appear to be the primary corridors for population expansion [90]; see Site Characteristics and Impacts for information. Plants database provides a map of Japanese stiltgrass distribution in the United States.
Culm geniculate, about 2 mm in diameter, hard. Blade 7-8 cm long by 10 mm wide, hirsute on both surfaces; ligule rounded at the upper part, about 1 mm long, hispid on the back; sheath margins and sheath-mouth densely ciliate. Inflorescence of 3 racemes subdigitately arranged. Spikelets paired, monomorphic; the upper pedicellate, the pedicels nearly as long as the spikelet; the lower sessile 4.5-5 mm long; rachis and pedicel slender, ciliate on margins. Glumes subcoriaceous, as long as the spikelet, the lower linear-lanceolate, 2-keeled, shortly ciliate on keels, the upper deltoid, 1-keeled, acute, upper fioret minute, about 1-1.5 mm long; lemma linear, chartaceous, about 1 mm long, with an awn of about 3.5 mm long, arising from the tip of the lemma; palea membranous, lanceolate about 1.5 mm long. Caryopsis cylindrical, about 1.5 mm long; embryo 1/2 the length of the caryopsis.
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Within a growing season, Japanese stiltgrass increases vegetatively by tillering [30,90] and by stolons [90], sometimes forming dense, monospecific stands through vegetative spread [15]. Because Japanese stiltgrass is an annual, the vegetative shoots do not survive through the next growing season [68]. High vegetative biomass does, however, increase the likelihood of reproductive success by increasing photosynthate gain and thus the potential for high seed production. High light and other favorable conditions maximize vegetative growth [29].
More info for the terms: allelopathy, basal area, cover, density, fire management, forb, hardwood, interference, invasive species, liana, litter, mesic, natural, nonnative species, prescribed fire, presence, restoration, selection, shrub, tree
Impacts:
Invasiveness: Japanese stiltgrass can be highly invasive on disturbed sites [16]. Unpublished surveys from 1992 showed Japanese stiltgrass was the most frequently reported nonnative, invasive annual grass in The Nature Conservancy's US preserves [166]. Characteristics that contribute to Japanese stiltgrass invasion include [34,201]:
- rapid invasion of disturbed habitats
- annual life history
- reproductive plasticity in the face of varying environmental conditions
- high seed production
- rapid clonal growth
Compared to uninvaded sites, sites where Japanese stiltgrass is prevalent may show reduced ecosystem function and, on silvicultural sites, timber production may be less.
A 2003 review of vegetation surveys in the eastern United States revealed that Japanese stiltgrass was among the most commonly reported invasive species, and it was the most common invasive annual grass. It was most frequent on floodplains and in mesic forests [114]. It was ranked a high invasive threat in deciduous, coniferous, and mixed forests, grasslands, old fields, riparian zones, and freshwater wetlands of the Northeast [47], and it was ranked a high to moderately-high threat in red oak and eastern hemlock forests of Delaware Water Gap National Recreation Area [85]. As of 2000, the density of Japanese stiltgrass infestations in Dixon State Park, Illinois, ranged from 2.3 stems/m² to 16,706 stems/m² [68].
Surveys show that as of 2008, Japanese stiltgrass occupied about 650,000 acres (260,000 ha) in the Southeast [127], and it was most invasive in Tennessee, North Carolina, and northwestern South Carolina [126]. It is ranked a high invasive threat in upland grasslands and oak-hickory woodlands and a potentially high threat in wet grasslands and palmetto (Arecacae) prairies [187]. In the southern Appalachian region, 8 of 35 federal, state, and private agencies ranked Japanese stiltgrass among their greatest ongoing or potential management problems (behind kudzu (Pueraria montana var. lobata) and multiflora rose) [106]. It was the most frequent (23%) of any nonnative species found in a 2006 survey of riparian forests in North Carolina [213]. Surveys in mixed-hardwood communities in the Blue Ridge Mountains of North Carolina also found Japanese stiltgrass was the most frequent nonnative invasive species, occurring in 100% of watersheds and 84% of plots [104]. In Oak Ridge National Environmental Research Park, Tennessee, Japanese stiltgrass was ranked the most "aggressively invasive" nonnative species based on distribution, abundance, relative difficulty of control, and ability to exclude native plant species. Japanese honeysuckle and Chinese privet were ranked 2nd and 3rd, respectively [48]. Japanese stiltgrass reportedly replaced existing ground vegetation in 3 to 5 years on sites in Great Smoky National Park [185], and it has formed "extensive and dense" infestations in Natural Areas and Parks, managed forests, wetlands, riparian areas, and rights-of-way in Alabama and adjacent states [4].
Because Japanese stiltgrass is an annual, its productivity is more closely tied to yearly climate fluctuations than that of perennial herbaceous species. Annual variations in Japanese stiltgrass productivity can have important effects on forest understory species composition and diversity. On a sweetgum site on the Oak Ridge National Environmental Research Park, Japanese stiltgrass produced 64% as much biomass in a wet year compared to a dry year [19]. Using a model, Holcombe [80] predicts a gain of 51,400 miles² (133,000 km²) in Japanese stiltgrass cover in North America due to climate change.
Ecosystem function: Japanese stiltgrass is associated with changes in ecosystem function, including altered soil characteristics, changes in soil microfaunal composition, lowered plant and animal species diversity, and altered stand structure. These changes may interfere with growth and establishment of native and other invasive nonnative species. Japanese stiltgrass has also been implicated as being allelopathic. Sites with Japanese stiltgrass may also have less coarse woody debris and more fine fuels than uninvaded sites; this is discussed in Fuels.
Soil and soil microfauna changes: Japanese stiltgrass may alter ecosystem function on forest floors and in forest soils [51,53,99,100,101,102,103] by affecting litter layers, soil composition, and species composition of soil microfauna. For example, Kourtev and others [100] reported that Japanese stiltgrass-invaded areas in New Jersey had thinner litter and organic soil layers than sites without Japanese stiltgrass; they attributed these changes to high densities of nonnative earthworms on sites with Japanese stiltgrass. Sites invaded by Japanese stiltgrass have also shown lower levels of soil carbon, nitrogen, and net ammonification [102]; dissimilar soil enzymes; and had significantly higher soil pH compared to uninvaded areas [99,101,103,122]. In white oak forests of New York, Japanese stiltgrass-invaded sites had thinner organic soil horizons, higher soil pH values, and higher levels of available soil nitrate than adjacent uninvaded sites [51]. In a chestnut oak-black oak-red maple forest, an eastern white pine plantation, and an old field in Tennessee, soil beneath Japanese stiltgrass litter had significantly higher pH and phosphorus levels and lower aluminum levels than soil beneath litter from uninvaded plots, regardless of plant community type. Overall, soil invertebrate richness was lower in Japanese stiltgrass litter than in uninvaded litter in all community types, although Japanese stiltgrass litter housed more mite species than litter from uninvaded plots. The authors surmised that in Japanese stiltgrass litter, overall diversity of forest-floor invertebrates may decrease, but mite populations may increase [122]. In white oak and American beech forests of New Jersey, soil microbial communities differed in species composition in Japanese stiltgrass-invaded and uninvaded areas, and nonnative earthworms were more common on Japanese stiltgrass sites compared to uninvaded sites [100,102]. Kourtev and others [99] warn that such drastic changes to soils will likely persist and may encourage reinvasion by Japanese stiltgrass or invasions by other nonnative species.
Japanese stiltgrass may alter soil nutrient cycling [42,43,43,188], although some claim the already altered nutrient status of disturbed sites favors Japanese stiltgrass establishment [79]. In a North Carolina wetland undergoing restoration, sites dominated by Japanese stiltgrass appeared to have decreased nitrogen cycling compared to sites where Japanese stiltgrass was removed. Decomposition and nitrogen release from Japanese stiltgrass litter was about half that of litter of native groundlayer species, and species richness was significantly less on invaded plots than on plots where Japanese stiltgrass was controlled [42,43]. DeMeester [43] concluded that compared to native species, Japanese stiltgrass "is clearly superior in capitalizing resources and suppressing other vegetation". In oak-pine forest in Whitehall Experimental Forest, Georgia, carbon apparently cycled more quickly sites with Japanese stiltgrass than on sites without Japanese stiltgrass. Plots with Japanese stiltgrass showed reduced total organic carbon (24% decline, P<0.09), particulate organic matter (34% decline, P<0.08), mineralizable carbon (a measure of microbially-available carbon; 36% decline, P<0.01), and microbial-biomass carbon (72% decline, P<0.05). The authors suggested that Japanese stiltgrass may accelerate carbon cycling and deplete carbon levels in southern oak-pine forests [188]. In mixed-hardwood and oak-hickory forests of West Virginia, interior forest plots with Japanese stiltgrass had significantly lower soil carbon levels than plots without Japanese stiltgrass (P=0.07) [87].
Changes in soil chemistry and microfaunal composition associated with soil disturbances tend to favor Japanese stiltgrass. Across Fairfax County, Virginia, riparian sites in zones changing from rural to urban had increased sediment deposition, increased available soil phosphorus, and decreased soil nitrogen compared to rural riparian zones. In aboveground Japanese stiltgrass tissues, phosphorus content increased with urbanization, while the nitrogen:phosphorus ratio decreased. The authors suggested that disturbances and changes in soil nutrient levels enhanced the suitability of urbanizing riparian zones as Japanese stiltgrass habitat [79]. Nonnative earthworms may also favor Japanese stiltgrass invasion. In sugar maple and oak-hickory forests of New York and Pennsylvania, biomass of nonnative earthworm species was positively associated with Japanese stiltgrass and 2 other nonnative species, garlic mustard and Japanese barberry. Nonnative earthworm biomass was negatively correlated with leaf litter volume (r= -0.58, P<0.001) [140]. Several studies show that deep litter, which is more typical of early- than late-successional forests, discourages Japanese stiltgrass establishment [32,120,194] (see Germination and Seedling establishment and plant growth). Nuzzo and others [140] suggest that nonnative earthworm species, rather than Japanese stiltgrass, may be driving changes in ecosystem function—such as reduced native plant diversity—in forest communities of the eastern United States, and that nonnative earthworms may facilitate establishment of nonnative plant species.
Japanese stiltgrass may favor insect guilds that use the ground layer as habitat. In a harvested white oak-yellow-poplar forest in Tennessee, there was significantly greater cover of all insect guilds (herbivores, omnivores, carnivores, and scavengers) on sites with than without Japanese stiltgrass (P≤0.05), probably because there was 2.5 times more plant cover on sites with Japanese stiltgrass. Measurements were taken at the end of the growing season (mid-October) [119].
Diversity and stand structure:
Plant species diversity: Sites with Japanese stiltgrass tend to have lower native and total plant species diversity than sites without Japanese stiltgrass [2,3,21,41,68,87,223]. In an oak-yellow-poplar forest in Tennessee, density (r²=0.80, P<0.001) and diversity (r²=0.31, P=0.02) of native woody species was less in Japanese stiltgrass-infested compared to uninfested sites. The authors suggested that regeneration of woody species in southern forests will likely be reduced with Japanese stiltgrass invasion [146]. In a bottomland box elder-yellow-poplar-sycamore forest in Indiana, plots tilled and sown with native herbs and Japanese stiltgrass had significantly different groundlayer species composition than plots tilled and sown with only native herbs. Japanese stiltgrass plots showed 43% lower groundlayer species richness and 38% lower diversity than plots without Japanese stiltgrass. There was a strong negative correlation between Japanese stiltgrass presence and biomass of the sown native herbs (P<0.0001 for all variables) [61,63]. In urban riparian forests of North Carolina, Japanese stiltgrass presence was negatively correlated with presence of white oak, hickories, flowering dogwood, and mapleleaf viburnum (Viburnum acerifolium) (P<0.05). The authors found that light and high soil nutrient levels were positively associated with cover of nonnative species in general (P<0.05), and they suggested that Japanese stiltgrass is competitively excluding woody species in urban riparian forests of the eastern United States [213]. In sweetgum-sycamore and loblolly pine-white oak-sweetgum forests of Mississippi, Japanese stiltgrass presence was significantly associated with low species richness, and Japanese stiltgrass production was less in species-rich plant communities than in species-poor communities (P<0.001) [21]. In mixed hardwood and oak-hickory forests of West Virginia, interior forest plots with Japanese stiltgrass had significantly lower herb, liana, and shrub diversity (P=0.03) and tree seedling richness (P=0.02) and diversity (P=0.07) than plots without Japanese stiltgrass [87]. In surveys within Chesapeake and Ohio Canal National Historic Park, Maryland, plots with Japanese stiltgrass had greater native species diversity than plots without Japanese stiltgrass until August, when Japanese stiltgrass overtopped associated groundlayer species. After that, native species diversity was greater on plots without than with Japanese stiltgrass [2,3].
Animal species diversity and stand structure: In areas with dense white-tailed deer populations, Japanese stiltgrass and white-tailed deer interactions may be altering forest structure, with attendant changes to wildlife populations. White-tailed deer avoid grazing Japanese stiltgrass because it is unpalatable (see IMPORTANCE TO LIVESTOCK AND WILDLIFE). Heavy white-tailed deer browsing of palatable woody species can result in dense cover of Japanese stiltgrass and little woody species regeneration [10,75,221]. Royo and Carson [176] termed this phenomenon a "recalcitrant understory"; such understories can persist for decades, altering forest structure and successional pathways. Baiser and others [10] postulated that in eastern deciduous forests, decreases in bird guilds that nest on the ground, the understory, or the midstory may be partially due to decline of under- and midstory woody species that are subject to heavy white-tailed deer browsing and replacement of the woody species by Japanese stiltgrass. The authors found that from 1980 to 2005, breeding bird guilds using lower forest layers averaged greater population declines than bird species using the canopy for breeding, and the only bird species with increased populations were those nesting in the canopy. This general decline occurred for both resident and neotropical bird species that nest below the canopy. Among these guilds, eastern wood-pewees (midstory nester) and black-billed cuckoos (ground or understory nester) showed greatest declines in abundance [10].
Interference: Japanese stiltgrass may negatively impact establishment and growth of native species. For example, in hardwood floodplain forests of north-central Mississippi, Japanese stiltgrass interfered with growth of native slender woodoats (Chasmanthium laxum), whitegrass, and white oak seedlings. Density of the native species was negatively correlated with that of Japanese stiltgrass (P≤0.03) [22]. Japanese stiltgrass may interfere with production of forage species on rangelands [111].
Japanese stiltgrass may competitively exclude midstory species from germination and establishment sites. Based on germination and shade manipulation experiments conducted in a loblolly pine-red oak-black oak/flowering dogwood/mayapple (Cornus florida/Podophyllum peltatum) forest in Virginia, Shaw [181] suggested that Japanese stiltgrass may interfere with recruitment of midstory species such as eastern redbud (Cercis canadensis) and flowering dogwood (Cornus florida). There were significantly more eastern redbud (Cercis canadensis) germinants on plots without Japanese stiltgrass than on plots with Japanese stiltgrass (P<0.001). There were also more flowering dogwood germinants on plots without Japanese stiltgrass, but on all plots, recruitment of flowering dogwood was too scant for statistical analyses [181].
Silvicultural implications: Japanese stiltgrass is identified as a potentially serious competitor on productive timber sites in the Southeast [12,172,184]. It is implicated in reducing growth of timber species and associated species growing under the canopy. Because it is a tall grass that can form thick lawns, it often overtops and excludes native species. On the Hutcheson Memorial Forest, height of Japanese stiltgrass ranges from 10 to 40 inches (30-100 cm), far taller than most tree seedlings and forest herbs [8]. In red oak-green ash forests of New Jersey, survival of planted red oak and American ash seedlings was less on sites with Japanese stiltgrass than on sites where Japanese stiltgrass was removed (P<0.0001), but survival of associated red maple was not significantly affected by Japanese stiltgrass. Relative growth rates of red oak and American ash were significantly reduced on plots with Japanese stiltgrass (P<0.0001). Overall herbaceous species richness was less on plots with than on plots without Japanese stiltgrass (P=0.02). The author speculated that Japanese stiltgrass interference and white-tailed deer browsing (deer density range: 58-77/km²) have a synergistic, negative effect on oak and ash regeneration in New Jersey forests [8] (see Animal species diversity for more information). On an oak plantation in southwestern Tennessee, Japanese stiltgrass presence was negatively correlated (r= -0.82) with growth of northern red oak seedlings. Four silvicultural treatments were tested: clearcut (all stems >6 inches (20 cm) diameter removed); 2-aged selection cut (harvest to retain a stand basal area of 15 to 20 feet²/acre of residual oaks, hickories, and yellow-poplar); high-grade cut (all stems >14 inches (36 cm) DBH removed); and a control no-cut treatment. Mean biomass gain of Japanese stiltgrass was greatest with a 2-aged selection cut and least with the no-cut control [144]:
Japanese stiltgrass productivity (lb/acre) by silvicultural treatment in a Tennessee oak plantation [144] | |||
2-aged | Clearcut | High-grade | No cut |
3,100 | 1,800 | 550 | 220 |
In a harvested white oak-yellow-poplar forest in Tennessee, Japanese stiltgrass mean stem length and number of nodes increased as canopy cover decreased, while soil temperature and moisture increased as Japanese stiltgrass cover increased. Leaf area of red maple and yellow-poplar was less in plots with than without Japanese stiltgrass, likely because Japanese stiltgrass outcompeted the hardwoods for soil moisture. Measurements were made at the end of the growing season (mid-October) [119].
Other nonnative species: Japanese stiltgrass may outcompete other nonnative herbs and woody species. Miller and others [127] compared the relative competitive abilities of Japanese stiltgrass and garlic mustard in greenhouse and field experiments. In the greenhouse, they found that in both shaded conditions and open sunlight, Japanese stiltgrass gained more aboveground biomass and had higher rates of photosynthesis than garlic mustard. In the field, Japanese stiltgrass seedlings also gained more biomass and had higher rates of photosynthesis than garlic mustard; additionally, it suffered less mortality and insect herbivory (P<0.001 for all variables). The authors concluded that in eastern forests, Japanese stiltgrass has greater potential than garlic mustard for spread on both open and shaded sites [127].
In a sweetgum plantation in Tennessee, Japanese stiltgrass outcompeted Japanese honeysuckle for light, gaining more height growth and biomass than and shading out Japanese honeysuckle when the 2 species were grown together. Watering increased Japanese stiltgrass's interference with Japanese honeysuckle growth. Since Japanese stiltgrass is an annual, Japanese stiltgrass's negative effect on Japanese honeysuckle growth may decrease as Japanese honeysuckle matures and gains height [18].
Allelopathy: In the laboratory, the inhibitory effect of Japanese stiltgrass extracts on germination of radish (Raphanus sativus) seed was strong enough (β= -0.37) that the authors suspected Japanese stiltgrass may be allelopathic. They called for field studies testing Japanese stiltgrass's possible allelopathy [160].
Control: Control of Japanese stiltgrass is difficult and requires multiple treatments [48]. In order to locally control this annual, seed-banking grass, repeated annual efforts must be made to prevent flowering and seed set until the seed bank is exhausted [68]. Japanese stiltgrass resembles native white grass, so proper identification of Japanese stiltgrass before control measures are undertaken is advised [125]. Shaw [181] writes that "M. vimineum is proving to be an enigma for scientists because it can grow and succeed in a wide range of habitats. This plasticity makes M. vimineum a difficult weed (in terms of preventing) its invasion and/or (controlling the) spread of existing patches".
Several researchers stress the importance of controlling Japanese stiltgrass along roadsides and trails in order to prevent its invasion into forest interiors [36,117,131]. Because Japanese stiltgrass seed production, cover, and rate of spread were significantly greater along roadsides than within oak-hickory and maple-beech-birch forest interiors of West Virginia, Huebner [86] also recommended making control of Japanese stiltgrass along roadsides a priority.
In all cases where invasive species are targeted for control, no matter what method is employed, the potential for other invasive species to fill their void must be considered [24]. 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 [116].
Prevention: 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 [104,183,183] (for example, avoid road building in wildlands [204]) and monitoring several times each year [91]. 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 [78]. Monitoring efforts are best concentrated on the most likely sites of invasion, particularly along potential pathways for Japanese stiltgrass invasion: waterways, roadsides, and adjacent old fields and woodlands. Periodically surveying to detect new invasions is recommended [206]. The Center for Invasive Plant Management provides an online guide to noxious weed prevention practices.
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 [206]. Nord and others [137] suggested that Japanese stiltgrass invasion may be prevented if disturbed sites are kept free of Japanese stiltgrass seed and stolons (by, for example, cleaning logging or other equipment coming into disturbed sites), and that disturbed plant communities are likely to become less vulnerable to Japanese stiltgrass over time. The rate of Japanese stiltgrass population expansion decreased with time since disturbance on their Pennsylvanian oak-hickory-eastern white pine forest study sites [137]. See the Guide to noxious weed prevention practices [206] for specific guidelines in preventing the spread of weed seeds and propagules under different management conditions.
Swearingen [191] stresses that preventing the introduction of Japanese stiltgrass into uninfested areas, and early control of small infestations, should be a priority. Removing Japanese stiltgrass plants late in the growing season, before Japanese stiltgrass seed set but after seed set of most associated species, is recommended [68,215]. Once established, Japanese stiltgrass requires major, long-term eradication and restoration efforts. The Nature Conservancy [201] reports high potential for successful control and management of Japanese stiltgrass if it is detected and controlled in the early stages of invasion, but they report only moderate potential for Japanese stiltgrass control and large-scale wildland restoration in areas where Japanese stiltgrass is already well established. Tu [201] provides a contact list of managers who have used control measures (successful or not) on Japanese stiltgrass in Natural Areas.
Fire: For information on the use of prescribed fire to control this species, see Fire Management Considerations.
These methods of Japanese stiltgrass control are discussed below:
- Physical or mechanical control
- Biological control
- Cultural control
- Chemical control
- Integrated management
- Comparisons of different control methods
Physical or mechanical control: Hand-pulling, mowing, tilling, and flooding can help control Japanese stiltgrass. Hand-pulling controls small Japanese stiltgrass infestations [48]. Japanese stiltgrass is shallow-rooted and prefers moist soils; hence, it is usually easy to pull [43,191]. Hand-pulling is most effective in late summer (August-September) [38,191], when plants are tall and branched. Plants pulled before seed set can be left on site; plants with fruits should be bagged and removed. Hand-pulling disturbs the soil, and is likely to create microsites favorable for germination of soil-stored Japanese stiltgrass seed. Late summer pulling is advantageous because soil-stored seed does not have a long enough growing season to establish. Pulling in July or earlier is not recommended. Hand-pulling needs to be continued until the seed bank is exhausted, which may take several years [191,201]. Floodplains and other sites subject to continual replenishment of the seed bank require hand-pulling treatments indefinitely [201]. Japanese stiltgrass rapidly invaded newly contoured streambanks in a wetland undergoing restoration in North Carolina. Hand-pulling for 3 years reduced Japanese stiltgrass (59% vs. 80% cover on weeded and unweeded plots, respectively), but Japanese stiltgrass rapidly invaded the year after weeding stopped [43].
Mowing is recommended late in the growing season (August-September), when plants are flowering but before seed set. Because Japanese stiltgrass is an annual, late-season mowing curtails growth. Early-season mowing does not control Japanese stiltgrass because 1) seed-banked seeds can still establish and produce a new crop of seeds by the end of the growing season, and 2) plants cut in early summer respond with new growth and flower production soon after cutting [44,191,215].
Tilling also reduces Japanese stiltgrass [201]. Soil must be tilled late in the growing season to avoid establishment of soil-stored seed. Tilling may not be appropriate in Natural Areas and may damage desirable plants.
Flooding for 3 straight months, or intermittent inundation, may kill Japanese stiltgrass plants. It may not kill soil-stored seed [201].
Biological control: Japanese stiltgrass has few natural predators and pathogens in North America [34]. No biological control agents were available for Japanese stiltgrass control as of 2010 [191,201]. Biological control of invasive species has a long history that indicates many factors must be considered before using biological controls. Refer to these sources: [211,227] and the Weed control methods handbook [203] for background information and important considerations for developing and implementing biological control programs.
Cultural control: Little information was available on cultural control of Japanese stiltgrass as of 2010, but one study demonstrates how native-species planting after control treatment helped control Japanese stiltgrass. In a 3-year study in a native cane (Arundinaria gigantea) wetland in Palo Verde National Park, Costa Rica, Japanese stiltgrass became dominant on plots where nonnative Chinese privet had been removed and cane was not planted. However, cane became dominant on plots where it was planted after Chinese privet removal, and overall plant species diversity increased compared to plots where Chinese privet was removed but cane was not planted (P≤0.05 for all variables) [143].
Chemical control: Herbicides may provide initial control of a new invasion or a severe infestation, but used alone, they are rarely a complete or long-term solution to invasive species management [26]. Herbicides are most 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 the conditions that allowed the invasion to occur (for example, [231]). See The Nature Conservancy's [203] Weed Control Methods Handbook for considerations on the use of herbicides in Natural Areas and detailed information on specific chemicals.
Extensive infestations of Japanese stiltgrass can be controlled with systemic herbicides [191]. Herbicides may be the only practical method to effectively control large infestations. Glyphosate may control Japanese stiltgrass [38], but since glyphosate is a nonselective herbicide, care must be taken to avoid drift onto desirable native species. The University of Tennessee reported good control of Japanese stiltgrass on their Ames Plantation, but they also reported that managing for a desirable plant community after Japanese stiltgrass was controlled was "difficult". The University found good control of Japanese stiltgrass with imazameth [201]. Because imazameth is selective for only a few plant species, it killed Japanese stiltgrass plants without killing associated native herbaceous species. Sethoxydim and fluazifop are grass-specific herbicides reported as giving some control for Japanese stiltgrass (Tu 2005 personal communication cited in [202]). See these references for further information on using herbicides to control Japanese stiltgrass: [56,74,95,121,163,163,201,229].
Integrated management: A combination of complementary control methods may be helpful for rapid and effective control of Japanese stiltgrass. Integrated management includes not only killing the target plant, but also establishing desirable species and discouraging nonnative, invasive species over the long term. Japanese stiltgrass control is rarely successful with only one method of control [147], but a combination of control methods may be effective. Unfortunately, few studies on using integrated management to control Japanese stiltgrass had been reported as of 2010.
The best way to prevent large Japanese stiltgrass infestations is to control small patches. Small patches of Japanese stiltgrass in Great Smoky Mountains National Park have been controlled through a combination of herbicides, mowing, and hand-pulling (Johnson 2001 cited in [48]). Prescribed fire may be used in combination with other control methods for Japanese stiltgrass. For example, burning can be used to help reduce litter and standing plant biomass prior to herbicide application for Japanese stiltgrass control [201].
Comparisons of different control methods: A comparison of 5 Japanese stiltgrass control methods in North Carolina suggest hand-pulling or a grass-specific herbicide are good choices for Japanese stiltgrass control. The control treatments were: 1) season-long hand-pulling, 2) fall mowing, 3) a single application of glyphosate in fall, 4) selective hand-pulling of only Japanese stiltgrass, or 5) fenoxaprop (a grass herbicide) application once or twice a year as needed. Fall treatments were done before Japanese stiltgrass was flowering. These treatments were conducted for 3 consecutive years on 2 sites. On the Duke Forest site, Japanese stiltgrass dominated the ground layer of a loblolly pine plantation and was interfering with growth of loblolly pine regeneration. On the Schenck Memorial Forest site, Japanese stiltgrass and sweetgum seedlings dominated the ground layer of a white ash-American elm forest. After 3 years, all treatments reduced Japanese stiltgrass cover and presence in the seed bank compared to control plots. There were no significant differences in Japanese stiltgrass cover among treatments, but native plant recruitment and species richness were highest with selective hand-pulling of Japanese stiltgrass or fenoxaprop applications. Because it reduced recruitment of native woody species the most, glyphosate was considered the least effective for restoration purposes [93,96].
Some Japanese stiltgrass control treatments serve overall restoration objectives better than others. On 3 mixed-hardwood forest sites in southern Indiana, hand-pulling Japanese stiltgrass promoted cover of native grasses better than a postemergent herbicide (fluazifop) the 1st year after treatments, while either hand-pulling or postemergent herbicide best promoted forb cover. However, Japanese stiltgrass invaded hand-pulled areas the spring after treatment. Both pre- and postemergent herbicide prevented Japanese stiltgrass reinvasion the spring after treatment, although postemergent herbicide promoted higher overall native plant diversity. Seeding with native species did not increase native plant diversity over that of unseeded plots in posttreatment year 2 (P<0.05 for all variables) [61,62].
According to the WeedUS Database, Japanese stiltgrass has been reported to be invasive in natural areas in 15 eastern states inculding Connecticut, Delaware, Georgia, Indiana, Kentucky, Maryland, Massachusetts, New Jersey, New York, North Carolina, Pennsylvania, Tennessee, Virginia, West Virginia, and Washington, DC.
Andropogon vimineus Trin., Mem. Acad. St. Petersb. VI. Math, Phys. Nat. 2: 268. 1832.
Microstegium vimmeum var. polystachum (Fr. & Sav.) Ohwi, Act. Phytotax. Geobot 11: 156. 1942.
Microstegium vimineum var. imberbe (Nees) Honda, Monogr., 408. 1930.
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More info for the terms: cover, density, hardwood, leaf area index (LAI), litter, shrub
Japanese stiltgrass may initially establish in large numbers, experience high seedling mortality, then form thick lawns via vegetative expansion of remaining plants. In southern Illinois, Japanese stiltgrass established at a mean density of 43 seedlings/m². Plant mortality was greatest (≥50%) during seedling establishment (mid-March), dropping to about 20% by July [68]. In central New Jersey, Japanese stiltgrass seedling density in March and April averaged 1,963 seedlings (SD 652)/m², and the seedlings averaged 2 to 6 inches (5-15 cm) in height [28]. Barden [12] estimated the number of plants produced from 1983 to 1986 on a 2-m² plot in North Carolina averaged 1,000 (in 1983), 256 (1984), 44 (1985), and 0 (1986), respectively. Density of Japanese stiltgrass on another 2-m² study plot on the North Carolina site averaged 857 (in 1984), 47 (1985), and 29 (1986) [12].
Sunlight and moist soil increase the chances of Japanese stiltgrass establishment and favor its growth (review by [218]). Establishment and spread are limited in shaded environments [87]. On shaded sites, more carbon is allocated to leaves and aerial stems than to stolons [34] and flowers [87]. However, Japanese stiltgrass is well adapted to shady conditions. It can establish, grow, and produce some seed in as little as 5% of full sunlight [215].
In oak-hickory forests of West Virginia, Japanese stiltgrass was significantly taller along roadsides than within forest interiors; Japanese stiltgrass cover and spread were also higher along roadsides than in forest interiors [86]. On rural and wildland sites in New Jersey, seedling emergence, growth, and seed production of sown Japanese stiltgrass seed was significantly greater on an open lawn than in an interior red maple-shagbark hickory-sweetgum woodland (P<0.05). Japanese stiltgrass density on the lawn averaged 1,573 plants/m², while density in the interior woodland averaged 709 plants/m². Seed production was positively correlated with light (r²=0.06, P>0.05) but not with Japanese stiltgrass density or soil moisture [30].
Litter apparently impairs Japanese seedling establishment [51,137,145]. In a landscape-level study of 3 white oak-sweet birch forests in New Jersey, sites with Japanese stiltgrass had less litter than adjacent uninvaded sites [51]. In an oak-yellow-poplar plantation in southwestern Tennessee, plots where litter was removed in winter experienced 4.5 times the invasion of Japanese stiltgrass compared to plots where winter litter was left intact (P<0.001). At the end of the growing season, Japanese stiltgrass on plots without litter had spread an average 5.45 feet (1.66 m), while Japanese stiltgrass spread on plots with litter averaged 1.20 feet (0.37 m). Japanese stiltgrass cover averaged 48% and 5% on plots without and with litter, respectively. The authors suggested that increased light as a result of litter removal favored Japanese stiltgrass germination and growth [145]. In a harvested white oak-yellow-poplar forest in Tennessee, Japanese stiltgrass spread was greater with litter removal or soil disturbance than on undisturbed sites [118,119]. Measured from plot edges, the distance at which 90% of Japanese stiltgrass plants occurred (P=0.02) and overall mean distance of Japanese stiltgrass spread (P=0.04) were significantly farther with litter removal than without. Outlier Japanese stiltgrass plants (those farthest from the population center) may be of greatest concern in terms of Japanese stiltgrass spread. The distance of outlier Japanese stiltgrass plants was significantly farther in litter-removal and soil-disturbance plots than control plots (P=0.02) The authors suggest that disturbing litter may increase Japanese stiltgrass invasion and spread in eastern hardwood forests, while leaving litter layers intact may slow Japanese stiltgrass invasion [118].
While litter may inhibit Japanese stiltgrass establishment, a greenhouse study suggests litter may not impede growth after seedlings establish. Using soils from oak-hickory and red maple forests of New Jersey, Ross [175] found that regardless of soil origin, leaf litter additions did not significantly decrease growth of established Japanese stiltgrass plants compared to soils without added litter. Additional greenhouse studies using soil from the 2 forests showed arbuscular mycorrhizae had no effect on Japanese stiltgrass growth. Japanese stiltgrass roots were susceptible to arbuscular mycorrhizal colonization, but Japanese stiltgrass height growth was similar with and without arbuscular mycorrhizal colonization [175].
Based on shade and litter manipulations in white oak-red oak-shagbark hickory, red maple-American elm, and white ash-yellow-poplar forests in New Jersey, Schramm and Ehrenfeld [179,180] suggested that deep litter, shade, or their interactions may limit Japanese stiltgrass spread (P=0.05 for all variables). Only seedlings with no litter or a litter layer one-half of average (~0.8 inch (2.2 cm)) showed "substantial" survivorship. There was a trend towards decreasing Japanese stiltgrass cover with increasing successional stage. Japanese stiltgrass was "effectively excluded" where American beech, a late-successional species that casts deep shade at maturity, dominated the canopy, while open, successional red maple- and white ash-dominated forests had 22% to 30% Japanese stiltgrass cover. Oak-hickory forest supported intermediate levels of Japanese stiltgrass (5-8% cover). Regardless of successional stage, there was a trend toward decreasing Japanese stiltgrass invasion with increasing stand size (r²=0.33) [180]. The authors suggested that generally, loss of the shrub layer due to heavy white-tailed deer browsing could accelerate Japanese stiltgrass spread [179,180]. Interactive effects of white-tailed deer and Japanese stiltgrass on stand structure and plant species composition are discussed further in Impacts; see Successional Status for further information on Japanese stiltgrass and shade.
Rauschert and others [168] present a model of Japanese stiltgrass population growth based on broadcast seeding experiments in an oak-hickory-eastern white pine forest in Pennsylvania.
Several other site characteristics, and stand structure, apparently affect Japanese stiltgrass regeneration. In North Carolina, Japanese stiltgrass regeneration was negatively correlated with high soil pH (5.5 vs. a median of 5.1); high levels of soil potassium, zinc, and calcium; high percent silt (18% vs. 10%); deep litter (8.6 vs. 5.5 cm); high cumulative PAR on an overcast day (0.72 vs. 0.57 mol/m²/day); and high leaf area index (LAI) of other species (1.3 vs. 0.7) [12]. In southern Illinois, reproductive success was correlated with soil conditions and canopy cover. Reproduction increased with increasing availability of soil cations and sand content and decreased with increased soil silt content and canopy cover (P<0.05 for all variables) [68].
Because it is similar in appearance to several native grasses, it is important to know how to recognize and differentiate stiltgrass from look-alikes. Look for asymmetrical leaves with a shiny midrib and the stilt-like growth form. Attention to new infestations should be a priority. Because it is shallow-rooted, stiltgrass may be pulled by hand at any time. If flowering, cut plants back using a mower, weed whip or other device to prevent seed production. For extensive infestations, herbicides are the most practical and effective method currently.
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Japan, Korea, China, Malaysia and India
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Source | http://www.efloras.org/florataxon.aspx?flora_id=2&taxon_id=200025707 |