How old is the vegetation on Rangitoto Island?

[First paragraph(s)...]
The gently sloping basaltic base of Rangitoto Island in Auckland Harbour shows stages in colonization by pohutukawa (M etroszderos excelsa) and the scoria cone above is covered with incipient pohutukawa forest. During a statistical investigation it became necessary to take the age of this vegetation into consideration in order to complete the picture.
Though the vegetation of Rangitoto is unique and has been said to be the most important in New Zealand little has been written about it. Kirk's three-page account of 1878 (T.N Z.I.) is the longest. Most writers emphasize the slow progress of colonization that had gone on for hundreds or thousands of years. The present thesis is that the vegetation has developed mainly since the white man came to New Zealand, this conclusion being based on the following lines of evidence: