The big trunk is a Rimu – a much prized protected species of podocarp which was extensively logged in the past.  Massive trees in climax forest.  But look at the size of the smaller tree growing around the rimu trunk. This is a Rata vine, which growns from the top down – windblown seeds settle in the top of the tree and send roots down to the ground.  This one may eventually strangle the rimu, or more likely will be there as a tree in its own right when the rimu dies.

Northern rātā (Metrosideros robusta), is a huge forest tree endemic to New Zealand. It grows up to 25 m or taller, and usually begins its life as a hemiepiphyte high in the branches of a mature forest tree; over centuries the young tree sends descending and girdling roots down and around the trunk of its host, eventually forming a massive, frequently hollow pseudotrunk composed of fused roots.

But there is a second epiphyte – the large diagonally curving one which I think might be Passifloria tetrandra – also attached to the tree.  Normally seen as a slender vine about 3/4 in thick in the forest, this one has been in place for many years and is now huge.

Epiphytes and vines are fascinating – here’s a reference to much, much more if you want:

http://nzetc.victoria.ac.nz/tm/scholarly/tei-Bio28Tuat02-t1-body-d1.html

and another pdf:

http://www.nzepiphytenetwork.org/uploads/1/9/4/7/19475779/c_bryan_-_new_zealands_vascular_epiphyte_vines_and_parasites.pdf