What's the best wood for stair landing ?

[ddel]

Hi all, 

I am restoring some old stars with 1 landing (U stairs). I am curious what type of wood I should get for:

1) For decking top side. 

2) for the base of the lading.

This landing always get the rain and that's why it is dying first. I will also be grateful if someone know what the best option is for stairs pieces are as well ?