Norway Maple (Invasive Exotic Plants of North Carolina)

Norway Maple

Acer platanoides

Summary ⁵

Acer platanoides (Norway maple) is a species of maple native to eastern and central Europe and southwest Asia, from France east to Russia, north to southern Scandinavia and southeast to northern Iran. It is part of the Acer family, or the Maple family.

Ecological threat in the united states ⁶

Norway maple forms monotypic populations by displacing native trees, shrubs, and herbaceous understory plants. Once established, it creates a canopy of dense shade that prevents regeneration of native seedlings. Although thought to have allelopathic properties (meaning that the plant releases toxins that inhibit or prevent the growth of other plants), research has not been able to confirm this.

Impacts and control ⁷

More info for the terms: competition, density, fire management, hardwood, natural, presence, shrubs, tree

Impacts: Impacts of Norway maple on communities and ecosystems in North America derive from its apparent competitive superiority, especially on forested sites with a cool, moist, rich, shaded environment (see Site Characteristics). Potential effects of Norway maple invasion include reduced abundance and diversity of native species and alteration of forest community structure.

Norway maple negatively impacts sugar maple/American beech forests of the northeastern United States by dominating the seedling layer and displacing shade tolerant native species [62,64]. In a New Jersey Piedmont mixed hardwood forest, Norway maple seedlings reached densities of 40,500 stems/acre (100,000 stems/ha) or 0.9 stems/ft2 (10 stems/m2) [59]. Norway maple seedlings and saplings appear to be strong understory competitors beneath native species such as sugar maple [31].

Norway maple may outcompete sugar maple for understory dominance in eastern deciduous forests by exhibiting superior growth. In a Pennsylvania mixed hardwood forest from 1987 to 1991, Norway maple saplings displayed an average annual height growth increment that was nearly twice that of nearby sugar maple [25]. Kloeppel and Abrams [25] demonstrated how differences in growth may be attributable to physiological characteristics. When daily mean net photosynthesis on a mass basis was compared for saplings of both species at comparable sites throughout a single growing season, values were consistently higher for Norway maple than for sugar maple. Light response curves revealed Norway maple saplings had significantly (P<0.05) higher maximum photosynthetic rates than those of sugar maple, even though saplings of both species had similar respiration rates and light compensation points. Nitrogen and phosphorus use efficiencies were also significantly (P<0.05) higher in Norway maple than in sugar maple on 2 sampling dates. Norway maple saplings also maintained significantly (P<0.05) higher rates of instantaneous water use efficiency than sugar maple saplings at the same site, indicating greater drought tolerance in Norway maple. In addition, average leaf longevity was 12 days longer for Norway maple compared with sugar maple, which probably also contributed to the apparent competitive differences between the 2 species. While these observations represent a single growing season at a single site, they indicate Norway maple may be able to outcompete sugar maple for understory dominance in eastern forests where sugar maple was previously the dominant late-successional species [25].

Presence of Norway maple in the overstory of northeastern forests may lead to reduced woody species diversity. Norway maple canopy trees appear to be more successful at excluding interspecific woody regeneration than canopy sugar maples [31]. In a New Jersey Piedmont mixed hardwood forest, understory/overstory species relationships were assessed to determine impacts of Norway maple canopy trees on understory species diversity. Although understory species composition was similar beneath Norway maple, sugar maple, and American beech canopies, understory richness was significantly lower beneath Norway maple than beneath sugar maple or beech. Norway maple seedlings comprised 83% of stems and 98% of woody seedlings beneath Norway maple trees [59]. Dense shade provided by Norway maple canopies appears to substantially inhibit woody seedling regeneration, including even Norway maple seedlings [31]. There is concern that Norway maple may alter forest structure by shading out other native understory plant species, such as shrubs and spring ephemeral herbs [55], although data supporting this assertion are lacking.

The impact of invasive Norway maple in forested natural areas is likely to be closely related to seed source proximity [1]. While Norway maple doesn't require edge habitat to successfully establish, its spread into previously uncolonized forest habitats is accelerated where adjacent development with landscape plantings provides a substantial seed source. Conversely, large unfragmented forest tracts may become colonized by Norway maple more slowly [59].

More research is needed to determine the nature and extent of risk posed by Norway maple invasion to native plants, plant communities, and ecosystems throughout North America. For example, Norway maple has been identified as a threat for invading conifer forests of west-central Montana [29].

Control: While removal of overstory Norway maple trees is necessary to end immediate recruitment of Norway maple seedlings, pre-existing Norway maple seedlings and saplings are likely to be abundant and should be removed to enhance growth and survival of native species and to eliminate potential future Norway maple seed sources. Control efforts may require removal of Norway maple trees outside the immediate vicinity of a treatment area due to the influx of seeds from relatively distant sources [61].

Because removal of Norway maple from a site may entail removing a large proportion of existing plant biomass, drastic changes in site conditions and species composition may result. While such efforts will hopefully benefit native species, there is also substantial risk of facilitating invasion by other nonnative plant species. Removal of overstory Norway maple trees in a New Jersey forest dominated by Norway maple and sugar maple resulted in invasion by new or newly conspicuous nonnatives, including tree of heaven (Ailanthus altissima), Japanese barberry (Berberis thunbergii), winged burning bush (Euonymus alata), Japanese honeysuckle (Lonicera japonica), and garlic mustard (Alliaria petiolata) [61].

As of this writing, there is very little information concerning control methods for Norway maple in North America.

Prevention: No information

Integrated management: No information

Physical/mechanical: Research was conducted in a 75- to 80-year old New Jersey forest, dominated in all strata by sugar maples and Norway maples, to determine the effects of a) removal of overstory Norway maples, and b) removal of Norway maple seedlings, on Norway maple and sugar maple seedling banks. Felling or girdling of canopy and subcanopy Norway maple trees significantly (P = 0.003) reduced new recruitment of Norway maple seedlings 2 years after treatment. While sugar maple seedling recruitment did not change significantly (P > 0.05) during this period, overall density of sugar maple seedlings was significantly (P = 0.007) higher. Increased sugar maple seedling density was apparently due to enhanced survivorship of older seedlings, stemming from diminished competition with Norway maple seedlings. In contrast, removal of Norway maple seedlings had no significant (P = 0.12) effect on sugar maple seedling density, and merely resulted in rapid recolonization by newly germinated Norway maple seedlings. Soil disturbance resulting from seedling removal treatments was presumed to enhance germination of Norway maple seeds in the seed bank. It was further speculated that had uprooting of overstory trees been included in the canopy removal treatments, further recruitment of Norway maple seedlings would have occurred [61].

Overstory and subcanopy Norway maple trees that are cut down may resprout from stumps. Larger overstory trees are less likely to produce sprouts that survive for more than a few years, but saplings and subcanopy trees may require further clipping to ensure mortality [61].

Fire: See Fire Management Considerations.

Biological: No information

Chemical: No information Cultural: No information

Habitat characteristics ⁸

As of this writing, there is very little published information describing the ecological range of Norway maple in North America. Because Norway maple is commonly mentioned as a congener of sugar maple in eastern North America [1,25,31,59,60,61,64], and because of their taxonomic similarity, it is likely that the two species share a similar ecological range in this region. (See sugar maple for relevant information.)

In Europe, Norway maple occurs within a climatic range characterized by maximum and minimum growing degree days (accumulated temperatures above 5 Â°C) of 2600 and 1150, respectively [41]. Within this range, it generally occurs in lowland areas, wide river valleys, and low mountain habitats. Norway maple is usually found as individuals or small groups in European mixed forests, and does not form pure stands over large areas [36].

Norway maple grows best on moist, "adequately" drained, deep, fertile soils. It is intolerant of low soil nitrogen conditions and is rare on acidic (pH near 4) soils. Norway maple makes "suboptimum" growth on sandy soils or soils high in lime or clay content, and does not tolerate high evapotranspiration or prolonged drought. Conflicting reports assert that it is rare on poorly drained soils, yet it reportedly can tolerate flooding for up to 4 months [36,41].

Northern distribution of Norway maple in North America is probably limited by cold temperatures. Variation in cold tolerance may be related to genetic source, since many cultivars of Norway maple have been developed for this trait. Seedlings can survive temperatures to at least -12 degrees Fahrenheit (-24 Â°C), although substantial twig tissue damage can occur. Insulation provided by early-winter snow may reduce seedling damage from cold temperatures [43]. Overwintering flower buds may be killed by prolonged exposure to cold temperatures. In Russia, damage to bud scales and loss of isolated buds have occurred after exposure for 1 hour at temperatures between 23 and 27 degrees Fahrenheit (-5 to -3 ÂºC) and loss of all buds noted below 23 degrees Fahrenheit (-5Âº). Open flowers are more sensitive than buds and may be susceptible to late-season frost. Exposure to temperatures < 27 degrees Fahrenheit (-3 ÂºC) for only 15 minutes produced necrosis in the stigma of the style, and 30 minutes of exposure killed entire flowers [28].

Sources and Credits

(c) lyee, some rights reserved (CC BY-NC), uploaded by lyee
(c) Marylise Doctrinal, some rights reserved (CC BY-NC-ND), http://www.flickr.com/photos/30257481@N03/4097992082
(c) Isa, some rights reserved (CC BY-NC), uploaded by Isa
(c) Mike R, some rights reserved (CC BY-NC), uploaded by Mike R
Adapted by Kate Wagner from a work by (c) Wikipedia, some rights reserved (CC BY-SA), http://en.wikipedia.org/wiki/Acer_platanoides
(c) Unknown, some rights reserved (CC BY-NC-SA), http://eol.org/data_objects/22733935
Public Domain, http://eol.org/data_objects/24640639
Public Domain, http://eol.org/data_objects/24640632

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Norway Maple

Summary 5

Ecological threat in the united states 6

Impacts and control 7

Habitat characteristics 8