Factors Influencing Future Canopy Composition at Tiromoana Bush, North Canterbury, New Zealand
Degree GrantorUniversity of Canterbury
Degree NameMaster of Forestry Science
The purpose of this study was to investigate seedling recruitment beneath kanuka forest at Tiromoana Bush, North Canterbury. The regeneration of broadleaved tree species is evident throughout Tiromoana Bush. This research aimed to quantify the biotic and abiotic factors influencing the distribution of small and large seedlings of canopy tree species, their relative growth rates, their survival, abundance and composition throughout the forest understorey of Tiromoana Bush. Tiromoana Bush is a forest restoration area of 410 hectares adjacent to the Kate Valley landfill. To determine the future tree species composition at Tiromoana Bush, seedling recruitment, growth and survival was quantified through remeasuring tagged seedlings in 26 permanent vegetation monitoring plots located in the major forest patches at Tiromoana Bush. In addition, seedling data from 78 temporary vegetation survey plots established in three major forest patches were used to assess the influence of different factors on seedling abundance. At Tiromoana Bush, the most common canopy tree species as seedlings in the permanent vegetation monitoring plots was mahoe followed by fivefinger. Mahoe seedling density was significantly affected by canopy openness, distance to seed sources, light index, shrub cover and slope, but not by aspect, basal area and time. For fivefinger, seedlings increased in abundance with time, but the difference was not statistically significant. The relative growth rate of mahoe in the 20-49cm height class (in which most seedlings occurred) was significantly affected by shrub cover, light index and canopy vii openness. Mahoe seedling recruits were significantly affected by light index and canopy openness. Survivability of mahoe was affected by aspect. For fivefinger, individual relative growth rates were significantly affected by canopy openness and light index. Similar results were found for tree species seedlings present in the temporary survey plots provided with mahoe and fivefinger again the most common species, followed by kohuhu. Light index significantly affected golden akeake small seedlings as well as canopy openness. Light index significantly affected ngaio large seedling distribution. Aspect was the only significant factor for kohuhu large seedling distribution. Distance from seed sources significantly affected fivefinger small seedling distribution as seedlings are dependent upon dispersal away from the parent trees. Slope significantly affected the distribution of red matipou small seedlings. The most important environmental attribute influencing seedling abundance is light. This is evident in both the permanent seedling monitoring plots and the temporary vegetation survey plots. Based on data from the temporary vegetation survey plots, mahoe, fivefinger and kohuhu are most abundant suggesting that these three canopy tree species will dominate the forest canopy at Tiromoana Bush once the kanuka starts to senesce.