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Ulex europaeus (tree, shrub)  |
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General Impact
Ulex europaeusis is a major weed in five countries (R. Hill, pers. Comm.). It is extremely competitive, displaces cultivated and native plants, and alters soil conditions by fixing nitrogen and acidifying the soil (Egunjobi, 1969; Grubb and Suter, 1970). It creates an extreme fire hazard due to its oily, highly flammable foliage and seeds, and abundant dead material. It not only increases the risk of fire, but also produces a hotter fire than most weeds (MacCarter and Gaynor 1980, In IPM, 2000). This fire risk increase threats on the margins of native vegetation (R. Hill, pers. Comm.).
Because of various characteristics of the plant, the soil is often bare between individual gorse plants, which increases erosion on steep slopes where gorse has replaced grasses or forbs. Spiny and mostly unpalatable when mature, gorse reduces pasture quality where it invades rangeland. Gorse understory in forests interferes with cultural operations, increasing pruning and thinning costs (Balneaves and Zabkiewicz 1981. In IPM, 2000), and can interfere with the growth of conifer seedlings (Clements et al., 2001). It excludes grazing animals from rangelands and pasture (Richardson and Hill, 1998; Tulang, 1992).
Location Specific Impacts:Australia 
Agricultural: Gorse provides shelter to agricultural pests such as rabbits. It also increase the risk of wildfires, reduces access and reduces stocking rates (Agriculture and Resource Management Council of Australia and New Zealand, 2000).
Economic/Livelihoods: Gorse impacts on forestry by competing with young seedlings. There are potential impacts on tourism as gorse infestations reduce the natural attraction of the area (Agriculture and Resource Management Council of Australia and New Zealand, 2000).
Ecosystem change: Gorse threatens open grasslands by changing them to thorny shrublands, with potentially large effects on native flora (Agriculture and Resource Management Council of Australia and New Zealand, 2000).
Interaction with other invasive species: By building up soil nitrogen levels, gorse allows for the establishment of other weedy species (Agriculture and Resource Management Council of Australia and New Zealand, 2000).
Modification of nutrient regime: Gorse builds up soil nitrogen levels and causes acidification of soil (Agriculture and Resource Management Council of Australia and New Zealand, 2000).
Other: Gorse plays a role in minimising soil erosion, and if controlled an alternative would need to be found. Beekeepers also claim gorse is an important source of pollen for their hives in autumn and spring (Agriculture and Resource Management Council of Australia and New Zealand, 2000).
Reduction in native biodiversity: Gorse has the potential to effect native flora, especially understorey species. It is increasingly becoming a threat as an environmental weed in national parks, reserves, riparian areas and bushland margins (Agriculture and Resource Management Council of Australia and New Zealand, 2000). Tasmania (Australia)
Agricultural: Gorse provides shelter to agricultural pests such as rabbits. It also increase the risk of wildfires, reduces access and reduces stocking rates. A recent estimate suggested gorse was costing Tasmanian primary producers around $1M in lost production (Agriculture and Resource Management Council of Australia and New Zealand, 2000).
Economic/Livelihoods: Gorse impacts on forestry by competing with young seedlings. There are potential impacts on tourism as gorse infestations reduce the natural attraction of the area (Agriculture and Resource Management Council of Australia and New Zealand, 2000).
Ecosystem change: Gorse threatens open grasslands by changing them to thorny shrublands, with potentially large effects on native flora (Agriculture and Resource Management Council of Australia and New Zealand, 2000).
Interaction with other invasive species: By building up soil nitrogen levels, gorse allows for the establishment of other weedy species (Agriculture and Resource Management Council of Australia and New Zealand, 2000).
Modification of nutrient regime: Gorse builds up soil nitrogen levels and causes acidification of soil (Agriculture and Resource Management Council of Australia and New Zealand, 2000).
Other: Gorse plays a role in minimising soil erosion, and if controlled an alternative would need to be found. Beekeepers also claim gorse is an important source of pollen for their hives in autumn and spring (Agriculture and Resource Management Council of Australia and New Zealand, 2000).
Reduction in native biodiversity: Gorse has the potential to effect native flora, especially understorey species. It is increasingly becoming a threat as an environmental weed in national parks, reserves, riparian areas and bushland margins (Agriculture and Resource Management Council of Australia and New Zealand, 2000). Garry Oak Ecosystems (Canada) (Canada)
Habitat alteration: Gorse is extremely competitive and displaces native plants, often creating a shrub layer where none existed previously. Established patches of gorse can produce a large amount of acidic litter that inhibits the germination and growth of many native grasses and other plants.
Modification of fire regime: The high oil content of gorse creates a risk of hotter than normal fires, with the potential for damage to oaks and other native vegetation.
Modification of nutrient regime: Gorse also ‘fixes’ atmospheric nitrogen, creating soil conditions that favour other non-native species. The soil is often bare between gorse plants, which could increase erosion on slopes that were once covered with native grasses and forbs. Gulf Islands (Canada)
Reduction in native biodiversity: Gorse threatens native plant communities. Vancouver Island (Canada)
Reduction in native biodiversity: Gorse threatens native plant communities. Vancouver Island (Canada)
Reduction in native biodiversity: Gorse threatens native plant communities. Poland
Competition: Several species of native plants are reportedly affected. The scale of impact of this species is weak Hawaii (Hawai‘i) Is. (United States (USA))
Modification of nutrient regime: A field survey conducted in 2004 has identified ecological features of the landscape, which distinguish gorse infestations from the surrounding uninfested periphery. The soils within the gorse infestation are more acidic and depleted of basic cation nutrients. Furthermore, gorse retains higher concentrations of these nutrients compared to the kikuyu grass (Pennesitum clandestinum) swards ubiquitous throughout the site. With a capacity for symbiotic nitrogen fixation, gorse also retains higher nitrogen contents than kikuyu grass. Sample populations of Bradyrhizobium were isolated from populations of gorse and adjacent populations of the endemic canopy legume koa (Acacia koa) for genetic comparisons. Bradyrhizobium isolated from gorse and koa share matching genetic fingerprints. This determines that the exotic and endemic legumes of this location interact with the same indigenous bradyrhizobia populations. Based on these results, soil acidification, nutrient depletion and symbiotic nitrogen fixation are competitive advantages for gorse in this volcanic landscape.
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