More info for the terms: cover, litter
Information about site characteristics where goutweed is invasive in North America is limited (2009). Information on sites where goutweed occurs comes primarily from European studies.
Climate: Goutweed occurs in temperate climates (see General Distribution). In Europe, mean precipitation on sites where goutweed occurred ranged from 19.5 [70] to 32.8 [26] inches (495-832 mm). Mean annual temperature was typically around 44 °F (7 °C), except where goutweed occurred in central Sweden, where average annual temperatures were as low as 42 °F (5.6 °C) [59].
Elevation: As of this writing (2009) no information is available on goutweed's elevational distribution in North America. Publications from Europe indicate that goutweed occurs at altitudes from 31 feet (10 m) [90] to nearly 3,488 feet (1,063 m) [33,45]. In one study from Sweden, goutweed was most common at altitudes from 1,030 to 1,120 feet (315-340 m) [33].
General habitat and moisture: Available evidence suggests that goutweed prefers moist conditions and may tolerate saturated soils. In the northeastern United States, goutweed is associated with moist sites [28]. In the upper Great Lakes region goutweed occurs on moist, well-drained soils [15]. In Australia, goutweed growth is "most prolific" in moist conditions and semishade (review by [14]). One review indicated that goutweed survives "very wet" conditions [72], and in Sweden, goutweed occurred on a site that was regularly flooded by an adjacent stream [33].
Leuschner and Lendzion [49] investigated microhabitat conditions for various herbaceous species in a beech forest in Germany and speculated that goutweed's occurrence was most influenced by relatively low soil moisture. On sites where goutweed occurred (i.e., open and sheltered valley sites, shallow and steep north-facing slopes) moisture content ranged from 33.2% to 36.4%; moisture content ranged from 25.2% to 28.1% on sites where goutweed was absent (i.e., rapid drying south-facing slopes) [49].
Microclimate and soil variables at 6 sites in a beech forest in Germany from March to May [49]
Variable
Valley North-facing slopes South-facing slopes open sheltered shallow steep shallow steep Goutweed cover (%) 15-25 15-25 3-5 1-3 0 0 Temperature (°C) 13.1 11.4 12.1 12.7 15.3 16.2 Relative humidity (%) 69.3 89.4 76.5 74.4 64 59.6 Vapor pressure deficit of air (Pa) 527 153 363 385 669 750 Photosynthetic active radiation (µmol/m²/s) 451 434 305 339 470 508 Soil moisture (volume %) 34.7 36.4 36.1 33.2 28.1 25.2 pH 7.3 7.1 7.2 7.4 7.3 7.3
In North America, goutweed is associated with anthropogenically influenced habitats like roadsides and the sides of buildings [74,76]. In Canada, goutweed has escaped cultivation primarily to roadsides and "waste places" in southwestern British Columbia and from southern Manitoba to Nova Scotia [62,75]. Goutweed occurs in grasslands, forests, roadsides, "waste places", and gardens in the upper Great Lakes region [15] and in Michigan, it occurs on forest borders [92]. On 1 site in Illinois, it occurred in a shaded ravine [82]. In Connecticut, goutweed occurs in floodplains and on the edges of wildlands (review by [13]). In Vermont it occurs in riparian and upland forests (review by [91]), and in Massachusetts it occurs on uplands, wetlands, and on floodplains (review by [95]). In North Carolina and South Carolina, the all-green type of goutweed occurs on the edges of bogs [71].
Goutweed occurs on similar sites throughout Europe. It occurs in managed or abandoned grasslands [83,84] or in fields where mowing or grazing has occurred [26,65,66]. Its occurrence has been associated with gardens [6]. It occurs in wildlands, especially in open forests, forest edges [39,67,83,88], and riparian areas [83,88].
Substrate: In regions outside North America, goutweed is considered a nitrophilous species ([42,53,83,88], Ellenberg 1979 cited in [22]). Soil pH, however, may influence goutweed's distribution more than nitrogen concentrations [23,90].
Available evidence from Europe indicates that goutweed occurs in soil pH ranging from 3.1 [24] to 9 [94], but several publications indicate it is most commonly found in weakly acidic [23,24,33,61,66] to weakly basic soils ([49,102], Ellenberg and others 1992 cited in [89]). In Sweden, goutweed occurred in a forest on sites with soil pH from 4.0 to 7.0. Over a 30- to 35-year period, goutweed cover increased more rapidly on sites where pH was >6.5 than in more acidic soils [22]. In a greenhouse, goutweed occurred in soil pH ranging from 3.17 to 4.5 but was most frequent on soils in the higher portion of that range (less acidic) [23]. In Britain, goutweed's nitrogen uptake was greatest in soils of pH 7 [3]. Two publications from Europe indicate that goutweed occurs on limestone [49,93].
Information on other substrate characteristics associated with goutweed is patchy. In Belgium, goutweed occurred in a flat, low-lying forest on sandy loam and silty loam. A layer of sandy clay occurred at approximately a 3-foot (1 m) depth and impeded drainage [90]. In Sweden, goutweed occurred in soils covered with a thin layer of litter that persisted from autumn to spring and decomposed by summer. There was no or only a thin layer of humus below the litter layer [21].