The population structure of invading Pinus contorta stands in the central North Island, especially in Dracophyllum subulatum communities and its implications for management and control
1989
Zoete, T.
Various open Protected Natural Areas in the central North Island are currently being invaded by P.contorta. Control has proven troublesome and expensive. The autecology of undisturbed P.contorta in Te Papa, east of Taupo, was compared with the autecology of disturbed P.contorta at Rangipo, east of Tongariro National Park. Data were collected in belt transects through individual clusters of P.contorta as well as through the infested areas at large, except where the density of P.contorta was low. There, a T-square sampling method was used. Most spread of P.contorta occurs laterally along the fringe of P.contorta stands. However, seed transported by wind may establish outlier populations, thus enhancing the rate of spread. Large quantities of seed are produced by year 10, though some trees start shedding seed at year 7. The presence of P.contorta is promoted by low competition with the surrounding vegetation. Control by hand cutting and pulling was found to be sensitive to obscuring of P.contorta by high/dense native vegetation, slash and boulders. Seed banks were substantial after control, both in their potential to provide high numbers of regenerating individuals/ha immediately after control as well as to provide new recruitments of individuals for at least 5 years after control. The implications of the foregoing for management of protected Natural Areas were discussed with the aid of a number of scenarios. Current policies relevant to P.contorta control were found to be inadequate. A flow chart for efficient P.contorta control is proposed.
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