Recruitment of Coprosma wallii at Paengaroa Mainland Island

H Parkinson
A B S T R A C T This study examined recruitment of the threatened shrub Coprosma wallii at Paengaroa Mainland Island, Mataroa, New Zealand. This is the first comprehensive survey of recruitment of C. wallii seedlings in the North Island. Superficially, Paengaroa appears to offer ideal conditions for C. wallii seedling recruitment. However, the population at Paengaroa appeared to have a scarcity of seedlings and young plants. The present study quantified seedling density and determined which
more » ... ors might be hindering seedling recruitment. An intensive search was made for seedlings around 21 mature female C. wallii plants: 9 inside the main reserve and 12 on adjacent land that was exposed to weed control. Seedlings were present in four of these plots, with the numbers of seedlings per plot ranging from 1 to 50. The distribution of seedlings strongly suggests that germination and growth take place in areas of disturbance and high light levels, as there were very few seedlings in parts of the forest that were established, with low disturbance and dappled light. It is concluded that C. wallii requires a number of conditions for germination, including high light levels, ground disturbance, moisture and fertile soils. Recommendations are made for further monitoring of seedling recruitment including quantitative measurement of environmental drivers; adaptive management to improve recruitment through spray trials, planting of cultivated seedlings and pulsed grazing regimes; the inventory of a third population; and use of dendrochronlogy to establish population age structures.