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Species
Polygonum aviculare L. (1753)
IUCN
NCBI
EOL Text
Widely distributed in temperate and subtropical regions.
License | http://creativecommons.org/licenses/by-nc-sa/3.0/ |
Rights holder/Author | eFloras.org Copyright © Missouri Botanical Garden |
Source | http://www.efloras.org/florataxon.aspx?flora_id=110&taxon_id=200006713 |
More info for the terms: fire regime, fuel, prescribed fire
Fuels: As of 2010, little is known about the fuel characteristics of prostrate knotweed. The potential for prostrate knotweed to alter fuel characteristics likely varies by plant community. It is not clear whether the persistence of dead mats of vegetation or stems from year to year would represent an increased fuel load or fire hazard.
FIRE REGIMES: It is not known what type of fire regime prostrate knotweed is best adapted to. Results from a study in a northeastern Kansas tallgrass prairie suggest that annual prescribed fire is more favorable to prostrate knotweed than fire at 4-year intervals or no fire [143]. However, it is impossible to make valid generalizations from a single study from a single plant community. As the Fire Regime Table indicates, prostrate knotweed occurs in a wide range of North American plant communities that exhibit a full range of fire regime characteristics. It is also likely that prostrate knotweed occurs in plant communities and associated FIRE REGIMES not presented in this table. See the full Fire Regime Table for information on FIRE REGIMES of other plant communities of interest. The impacts of prostrate knotweed on these FIRE REGIMES are unknown.
Canada
Rounded National Status Rank: NNR - Unranked
United States
Rounded National Status Rank: NNR - Unranked
License | http://creativecommons.org/licenses/by-nc/3.0/ |
Rights holder/Author | NatureServe |
Source | http://explorer.natureserve.org/servlet/NatureServe?searchName=Polygonum+aviculare |
Distribution: Widely distributed in temperate and subtropical regions of both the hemispheres.
License | http://creativecommons.org/licenses/by-nc-sa/3.0/ |
Rights holder/Author | eFloras.org Copyright © Missouri Botanical Garden |
Source | http://www.efloras.org/florataxon.aspx?flora_id=5&taxon_id=200006713 |
More info on this topic.
More info for the terms: density, shrubs, succession
Prostrate knotweed establishes in early successional plant communities, though it may persist into later successional stages. Prostrate knotweed established in early succession on heavily eroded buttes in the Badlands region of western North Dakota [79]. In abandoned fields in Colorado, prostrate knotweed occurred in a full range of field ages, including fields abandoned 3 months prior to sampling, and fields abandoned for 62 years [77]. In blue grama and buffalo grass grasslands in eastern Colorado, prostrate knotweed dominated abandoned roads in the early stages of succession. Prostrate knotweed density was highest on roadbeds 2 years after abandonment. It occurred infrequently >5 years after road abandonment [126]. In mixed-grass prairies in southeastern Wyoming, prostrate knotweed was one of several annuals dominating the vegetation in the first years following plowing or scraping and was seldom observed 10 years after disturbance [124]. At mine sites in Wyoming, prostrate knotweed was a dominant species 1 to 4 years following plantings of native shrubs and grasses at one location [72] and established within 2 years of soil placement in another location [125]. Prostrate knotweed has also been reported at numerous sites in the first few years following fire [27,35,42,60,64,88,106,112,115,143,167]. See Plant response to fire for more information.
Several sources report a preference for open sites [50,116,160] and light is generally though to improve germination.
Prostrate knotweed establishes on disturbed sites, including logged areas [156], revegetating mine sites [72,125], scraped and plowed mixed-grass prairie [124], roads, hiking trails [93], ski runs [142], backcountry shelters [54], heavily eroded areas [77,79], exposed sand bars [90], and lake shores [168]. Prostrate knotweed is often associated with locations disturbed by domestic and wild animals. It tolerates trampling [113,160,168] and is found in areas heavily grazed by cattle [149] and bison [143,158]. In old fields in Germany, prostrate knotweed established in areas grubbed by wild boars [107]. Prostrate knotweed also commonly establishes in the highly disturbed areas surrounding black-tailed prairie dog towns [93,149].
Some sources report prostrate knotweed occurring in disturbed areas but not in adjacent undisturbed plant communities. In southern Nevada, prostrate knotweed established on ski runs but did not spread into surrounding forests [142]. In deciduous riparian forests in southeastern Arizona, prostrate knotweed was present in the soil seed bank in areas that had some human disturbance but was absent from the seed bank in undisturbed areas [120].
Though examples of prostrate knotweed spreading from disturbed areas into undisturbed areas are lacking in the literature (2010), some sources report it occurring in adjacent disturbed and undisturbed areas, suggesting that such spread is possible. Prostrate knotweed occurred both along roadsides and in the interior of ponderosa pine forests in Arizona, though populations were more dense and occurred more frequently along roadsides [60]. In the northern Rocky Mountains, prostrate knotweed occurred in both disturbed areas (e.g., ditch banks and logged areas) as well as nearby undisturbed areas (e.g., subalpine meadows) [156].
Rounded Global Status Rank: GNR - Not Yet Ranked
License | http://creativecommons.org/licenses/by-nc/3.0/ |
Rights holder/Author | NatureServe |
Source | http://explorer.natureserve.org/servlet/NatureServe?searchName=Polygonum+aviculare |
More info for the terms: density, natural
Seedlings: A weed identification guide reports that prostrate knotweed seedlings grow slowly [150]. Prostrate knotweed seedlings may reach high densities, though as of this writing (2010) there were no quantitative descriptions of seedling densities in natural plant communities. In experimental winter wheat (Triticum sp.) fields in Spain, prostrate knotweed seedling density was 3 times higher in tilled than untilled fields (P<0.05), exceeding 100 seedlings/m². A few new seedlings were observed after precipitation events in all tillage systems and precipitation appeared to increase survival [152]. In laboratory experiments, high salinity appeared to improve the growth of prostrate knotweed seedlings [130]. In garden experiments in Pennsylvania, a fungal rust caused the mortality of an entire seedling population [71].
Mature plants: One flora describes prostrate knotweed as "vigorous" [121]. In dense lawns of Bermuda grass, prostrate knotweed patches increased 5 feet (1.5 m) in diameter in a growing season [1]. In garden experiments in Pennsylvania, prostrate knotweed had a higher survival rate in plots where it was planted with native species than where it was planted in monocultures (P<0.05) [71]. In the deserts of Death Valley National Monument, prostrate knotweed survival and reproduction was limited by precipitation and/or soil moisture [59].
Canada
Rounded National Status Rank: NNA - Not Applicable
United States
Rounded National Status Rank: NNA - Not Applicable
License | http://creativecommons.org/licenses/by-nc/3.0/ |
Rights holder/Author | NatureServe |
Source | http://explorer.natureserve.org/servlet/NatureServe?searchName=Polygonum+aviculare |
More info for the term: bisexual
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., [32,46,47,48,61,73,98,99,109,116,138,154,165,169]). For a key to the prostrate knotweed subspecies recognized in North America, see: [32].
Prostrate knotweed is generally considered an annual [32,65,69,99,160], though some sources report it as occasionally perennial [44,70,116].
Prostrate knotweed plants exhibit highly variable architecture depending on both genetic and environmental factors [32]. In general, prostrate knotweed is a mat-forming plant [65], with mats reaching 4 to 48 inches (10-122 cm) in diameter [113]. Prostrate knotweed stems are prostrate to erect, 2 to 80 inches (6-200 cm) long. Leaves are alternate and vary in size and shape, but are generally ovate. Inflorescences are axillary cymes with 2 to 6 flowers. Flowers are bisexual [32]. Prostrate knotweed fruits are one-seeded nuts [105]. Seeds are achenes, 1.7 to 4.0 mm long [32]. | |
Prostrate knotweed has a taproot [32,65,116]. Taproots of mature prostrate knotweed plants in alluvial soil reached depths of 30 inches (70 cm). Dense horizontal secondary roots were distributed in the upper 5 to 10 inches (15-25 cm) of soil (Kutschera 1960 cited in [32]). On sand dunes in the deserts of Death Valley National Monument, prostrate knotweed taproots penetrated approximately 5 inches (13 cm) in the soil and roots exhibited very little lateral spread (approximately 1 inch (3 cm)). Ten plants had an average root to shoot ratio of 0.09 [59].
More info for the term: pericarp
Prostrate knotweed seeds require moist-cold stratification for germination [9]. One source suggests that achenes produced in different seasons (summer and autumn) are fundamentally different in their dormancy and germination characteristics, but most studies do not specify which type of seed was tested. Personal observations of the authors suggested that the small, summer achenes have a strong primary dormancy and may constitute the persistent seed bank. These seeds must undergo a moist-cold stratification at 35 °F to 54 °F (1.6 °C-12 °C) for 12 to 110 days to break dormancy. In contrast, autumn achenes are larger, have a weak innate dormancy, and are capable of germinating immediately if exposed to temperatures of 70 °F to 80 °F ( 20-25 °C). If temperatures are lower, they germinate in the spring in a single flush at temperatures as low as 40 °F (5 °C). The authors suggested that most germination studies likely refer to summer seeds [32].
Temperature: Low winter temperatures release seed dormancy while high summer temperatures reinforce dormancy [9,10,11,34]. In laboratory experiments, prostrate knotweed seeds required a 40 °F (5 °C) treatment in the dark to germinate. Optimum germination (100%) was obtained after a 90-day cold-stratification at 40 °F (5 °C) [83].
Moisture: Prostrate knotweed seed germination is favored by moisture [11,28]. Laboratory germination tests showed that seeds exposed to low moisture had low germination (<5%) and showed no response to light treatments. Fluctuating soil moisture improved germination rates. Seeds exposed to constant moisture at 35 °F (1.6 °C) had low germination rates (<5%) while those exposed to fluctuating soil moisture had higher germination rates (approximately 40%). Fluctuations in soil moisture also improved germination rates of seeds kept in the dark, suggesting that such fluctuations may allow prostrate knotweed seeds to bypass the light requirement for germination in some situations. The authors suggested that deeply buried seeds would not be exposed to such moisture fluctuations [11].
Light: While some sources report that prostrate knotweed seeds require light to break dormancy [10,11], one study suggests that light is not required but improves germination rates. In laboratory germination tests in Kentucky, prostrate knotweed seeds exposed to several thermoperiods germinated from January to June, at rates of 70% to 90% for seeds exposed to light, and 1% to 26% for seeds kept in the dark [7].
Depth: Seed burial depth may influence germination rates, though results from experiments are not consistent. A review states that most seedlings emerge from the top 1 inch (3 cm) of soil and emergence declines with depth of burial [32]. In growth chamber experiments, shallow burial (<0.5 inches (1.25 cm) increased germination while deep burial (1 to 4 inches (2.5-10 cm)) decreased it [66]. In contrast, other laboratory experiments showed that germination rates were higher for prostrate knotweed seeds buried from 5.5 to 6 inches (14-15 cm) compared to those buried at depths ranging from 0 to 4 inches (0-10 cm). Dormancy was induced earlier for seeds closer to the soil surface than those buried at various depths beneath the soil. The authors suggested that dry conditions near the soil surface could induce dormancy [34].
Disturbance: Soil disturbance and scarification may improve germination rates. In field experiments using potted seeds in Ireland, germination began in late February, peaked in April, and ceased by the end of May. Soil disturbance in March increased seed germination (from 4% to 21%), though germination still ceased by the end of May. Soil disturbance at times other than late March or early April had no impact on seed germination, nor did it impact the timing of seedling emergence the following year. Mechanical or sulfuric acid removal of the pericarp increased germination rates [34].
Salinity: The impacts of salinity on germination are not clear. In laboratory experiments, exposure of prostrate knotweed seeds to highly saline conditions led to higher germination rates; germination rates were higher at electrical conductivities of 200 mS/m and 250 mS/m compared to electrical conductivities ranging from 0 to 150 mS/m (P=0.05) [130]. Other laboratory experiments also showed prostrate knotweed seeds to be moderately salt tolerant; the cumulative germination percentage of seeds decreased as salinity increased, though some seeds did germinate at the highest salinity (300 mM NaCl) [83]. In contrast, germination of seeds removed from saline soils in Ohio varied little in relation to soil salinity, and laboratory trials showed germination rates decreasing with increasing salinity [58].