Posted: Mon Jan 12, 2015 5:49 am
by fooman
Hi Don,

A quick perusal of Dawson & Lucas' "Native Trees of New Zealand", using a criterion of tree >= 5 m, there are approximately 210 tree species in NZ (I lost count a bit towards the end) and the outlying islands (including subtropical Kermadacs to Sub- Antarctic Auckland Islands). This includes 18 conifer species (2 more are shrubs), 6 tree ferns, and the rest angiosperms (including one palm, a number of palm-like cordyline and dracophyllum species) as well as more normal looking trees. Large genera include 25 Coprosma tree species (plus another 30 shrubs), 23 Olearia trees (plus 9 shrubs), 15 Pittosporum (plus 6 shrubs) and 12 Pseudopanax.

The book had more species than above, but they were described as "shrub to small tree" less than 5 m. Their criteria for a tree was a woody species more than 4 m in height, with a single trunk or substantial woody limbs. The book doesn't have a numerical breakdown, but the vast majority of species are 5-15 m tall. There are approx 35 tree species considered emergent or canopy trees (20+ m). The rest are sub-canopy.

I do remember reading a paper about NZ tree species height evolution. Most species evolved from shrub-like plants, and there was little competition for light. The emergent species didnt block a lot of light so height was not required as a trait.

The book states in total that NZ has ~2300 species of angiosperms, conifers and ferns in 268 000 sq km (~100,000 sq miles), 80% of which are endemic.