The spread of lodgepole pine (Pinus contorta, Dougl.) in New Zealand

Lodgepole pine (Pinus contorta, Dougl.) was introduced to New Zealand in about 1880. It is the most vigorous naturally regenerating introduced conifer, which has led to large areas of unwanted spread or 'wildings'. Wildings threaten existing indigenous flora and fauna, visual landscape and land use values. The area affected by all conifer natural regeneration is estimated at 150,000 ha of which approximately two thirds is lodgepole pine. Control operations have been undertaken in New Zealand since the 1960s. The high 'weed' potential of lodgepole pine, coupled with its low grower and market acceptance in New Zealand, means that the species is seldom planted nowadays. Lodgepole pine spreads more Vigorously than other introduced conifers as it cones earlier, is capable of producing seed and wildings at higher altitudes, and has lighter seed allowing dispersal over wide areas. Spread occurs most readily on ungrazed land with low vegetation density, and is least likely to occur in intact, dense vegetation, or where intensive grazing is practiced. Direction and distance of spread from parent trees is predictable. Most wildings occur initially as fringe spread within 50 m downwind of parent trees. Distant spread (measured in kilometers) is usually associated with trees on take-off sites exposed to the wind, such as hilltops and ridges. Spread commonly occurs in 'waves', about once every 5 years for fringe spread, and once every 10-20 years for distant spread. Research on seed production, dissemination and the factors influencing seedling establishment has resulted in the development of strategies for the prevention and control of spread. The major aspects to consider for new plantings are siting, planting design and surrounding land management. Where large areas of spread exist, containment is often the most practical recommendation. Eradication is by burning, hand pulling (small seedlings only), felling and application of chemicals to stumps or foliage. Lodgepole pine was the first conifer to attract significant adverse attention due to its propensity for natural regeneration, but concern about the spread of introduced conifers is now general, especially in the hill and high country grasslands of the eastern South Island. This concern has been promoted by new 'effects-based' resource management legislation which is currently being implemented by territorial authorities. (C) 2001 Elsevier Science B.V. All rights reserved.