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NITROGEN LEACHING FROM GORSE - STUDY BY G.N. Magesan Hailong Wang
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https://cdn.boprc.govt.nz/media/33673/SCION-090803-Nitrogenleachinggorse.pdf
GORSE AS AN ENVIRONMENTAL WEEDGorse is regarded as an environmental weed because of its invasiveness, potential for spread, and economic and environmental impacts. The main biological features contributing to its weed status are its vigorous growth, N fixation ability, prolific seed production, longevity of seeds in the soil, and its sprouting ability after cutting or fire. Gorse has high photosynthetic efficiency and annual dry matter accumulation and can live to an age of 46 years in New Zealand. In pastoral and bushland areas, gorse is increasingly becoming a threat as it reduces the potential for grazing by cattle and sheep, provides shelter for pests, and increases the risk of bushfires because of its flammability. In plantation forests gorse can reduce the height and diameter of forest trees, increase the cost of site preparation and make access for pruning and thinning operations difficult and therefore more expensive. The bushes grow up with the trees, compete with them for nutrients and minerals, particularly boron and phosphorus, and therefore can cause a wide variation in the growth rates of individual trees and consequently an overall decrease in stand quality and growth rates. Gorse can rapidly invade dry and disturbed areas by suppressing and inhibiting
The ability of the seed to resist fire and the ability of the plant to resprout have led to gorse's dominance in many pioneer successions throughout the country. The ability to produce large seed banks helps gorse to persist in many areas. The combination of competitive and defensive characteristics of gorse may allow it to remain dominant in an area. Only when the gorse ages, its canopy becomes more open. The resulting increase in light beneath the canopy, the canopy's stabilizing effect on moisture and temperature fluctuations, and the fertile litter all provide favourable conditions for the germination of native shrub seedlings. Since its introduction, gorse has colonised around 900 000 ha or approximately 3.6% of New Zealand as a weed of forestry land, agricultural land, and parks and reserves. However, this figure may be much larger due to the length of time gorse seed can remain dormant in the ground. Once the land is suitably disturbed, a flush of gorse regeneration soon follows. Soil solution sampling and analysis indicated nitrate concentration in soil solutions below the rooting zone under mature gorse stands remained at levels relatively above drinking water standards for most of the year, although it decreased during the winter drainage period. Nitrogen supply has been maintained by continued inputs of nitrogen rich gorse litter fall. As a result, a considerable amount of nitrate has leached below the rooting zone.Study demonstrates that gorse stands are producing biologically active nitrogen and releasing nitrate to groundwater, which may then enter the lakes. To protect lake water quality, we recommend that effective methods be developed to eliminate gorse in the Rotorua lakes catchment areas. Wikipedia Introduction to New ZealandIntroduced from Western Europe in the very early stages of European settlement, it was recorded by Charles Darwin during his voyage through New Zealand waters in 1835 as growing in hedges in the Bay of Islands. Its spread and development as a weed in New Zealand's temperate climate was rapid, but settlers failed to recognise the threat; gorse seed continued to be imported and plantings deliberately established into the 1900s. Problems The introduction resulted in large spreading infestations over hundreds of hectares, peaking in the late 1940s. It was recognised as a threat as early as 1861 with the Provincial Council in Nelson passing an act to prevent the planting of gorse hedges. The seed can lie dormant on the ground for up to 50 years, germinating quickly after the adults have been removed. Unfortunately, most methods of removing adult gorse plants, such as burning or bulldozing them, create the ideal conditions for the gorse seeds to germinate and total eradication with current technology seems impossible. Gorse is now one of the most widely recognised agricultural weeds in New Zealand. It covers 700,000 hectares (1,700,000 acres) at varying densities — a total of 5% of the land area of New Zealand when excluding existing indigenous forest, vegetated sub-alpine and alpine areas.[4] Gorse became New Zealand's most costly weed to control, an estimated $22 million per annum by the early 1980s.[5] Biological control Current research areas are: active management of control agents, development of a bio herbicide, and the use of modelling. Biological pest control of gorse has been investigated since the 1920s. Seven different agents have been released in New Zealand. Results have been mixed, but in general neither the seed-feeding nor foliage-feeding insects are doing enough damage to be viable as a stand-alone control agent. MASSEY UNIVERSITY has on its data base as follows:Gorse is considered by many to be New Zealand’s worst scrub weed. It was originally introduced to New Zealand as a hedge species, but now occupies large areas of hill-country, reducing the area available for grazing by livestock on pasture land. It also causes severe competition with young forest trees, and makes access to forests difficult for pruning and thinning operations. Over summer, foliage of gorse can become quite dry, making gorse stands susceptible to fire. This creates risks of damage to forests and also houses in areas such as Wellington situated close to stands of gorse. Large quantities of seeds with tough outer coats are formed by gorse each year, allowing the species to re-establish quickly once a fire has been through a stand. Gorse does so well in New Zealand that it flowers twice a year, unlike in Europe from where it originates. However, some people consider gorse to have its uses, as it can act as a nursery plant to allow native trees to get established, and it does stop steep hillsides from eroding by covering them in dense vegetation.
The ability of the seed to resist fire and the ability of the plant to resprout have led to gorse's dominance in many pioneer successions throughout the country. The ability to produce large seed banks helps gorse to persist in many areas. The combination of competitive and defensive characteristics of gorse may allow it to remain dominant in an area. Only when the gorse ages, its canopy becomes more open. The resulting increase in light beneath the canopy, the canopy's stabilizing effect on moisture and temperature fluctuations, and the fertile litter all provide favourable conditions for the germination of native shrub seedlings. Since its introduction, gorse has colonised around 900 000 ha or approximately 3.6% of New Zealand as a weed of forestry land, agricultural land, and parks and reserves. However, this figure may be much larger due to the length of time gorse seed can remain dormant in the ground. Once the land is suitably disturbed, a flush of gorse regeneration soon follows. Soil solution sampling and analysis indicated nitrate concentration in soil solutions below the rooting zone under mature gorse stands remained at levels relatively above drinking water standards for most of the year, although it decreased during the winter drainage period. Nitrogen supply has been maintained by continued inputs of nitrogen rich gorse litter fall. As a result, a considerable amount of nitrate has leached below the rooting zone.Study demonstrates that gorse stands are producing biologically active nitrogen and releasing nitrate to groundwater, which may then enter the lakes. To protect lake water quality, we recommend that effective methods be developed to eliminate gorse in the Rotorua lakes catchment areas. Wikipedia Introduction to New ZealandIntroduced from Western Europe in the very early stages of European settlement, it was recorded by Charles Darwin during his voyage through New Zealand waters in 1835 as growing in hedges in the Bay of Islands. Its spread and development as a weed in New Zealand's temperate climate was rapid, but settlers failed to recognise the threat; gorse seed continued to be imported and plantings deliberately established into the 1900s. Problems The introduction resulted in large spreading infestations over hundreds of hectares, peaking in the late 1940s. It was recognised as a threat as early as 1861 with the Provincial Council in Nelson passing an act to prevent the planting of gorse hedges. The seed can lie dormant on the ground for up to 50 years, germinating quickly after the adults have been removed. Unfortunately, most methods of removing adult gorse plants, such as burning or bulldozing them, create the ideal conditions for the gorse seeds to germinate and total eradication with current technology seems impossible. Gorse is now one of the most widely recognised agricultural weeds in New Zealand. It covers 700,000 hectares (1,700,000 acres) at varying densities — a total of 5% of the land area of New Zealand when excluding existing indigenous forest, vegetated sub-alpine and alpine areas.[4] Gorse became New Zealand's most costly weed to control, an estimated $22 million per annum by the early 1980s.[5] Biological control Current research areas are: active management of control agents, development of a bio herbicide, and the use of modelling. Biological pest control of gorse has been investigated since the 1920s. Seven different agents have been released in New Zealand. Results have been mixed, but in general neither the seed-feeding nor foliage-feeding insects are doing enough damage to be viable as a stand-alone control agent. MASSEY UNIVERSITY has on its data base as follows:Gorse is considered by many to be New Zealand’s worst scrub weed. It was originally introduced to New Zealand as a hedge species, but now occupies large areas of hill-country, reducing the area available for grazing by livestock on pasture land. It also causes severe competition with young forest trees, and makes access to forests difficult for pruning and thinning operations. Over summer, foliage of gorse can become quite dry, making gorse stands susceptible to fire. This creates risks of damage to forests and also houses in areas such as Wellington situated close to stands of gorse. Large quantities of seeds with tough outer coats are formed by gorse each year, allowing the species to re-establish quickly once a fire has been through a stand. Gorse does so well in New Zealand that it flowers twice a year, unlike in Europe from where it originates. However, some people consider gorse to have its uses, as it can act as a nursery plant to allow native trees to get established, and it does stop steep hillsides from eroding by covering them in dense vegetation.
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