Question: Why don't tree's shrink or get smaller when they grow old like humans?

Alexis Barr answered on 18 Jun 2013:

Oooh – this is a tough one. Humans shrink during the course of each day because between the vertebrae in our spines are 23 jelly-like disks that are like shock absorbers. As we stand all day, they become compressed, lose water and we shrink a little in height. When we lie flat at night the disks reabsorb water and we regain height. As we age, the disks are not as good at reabsorbing water and so we can permanently shrink.
Trees slow their growth as they age but they don’t shrink. There is a theory that trees have a maximum height because above that height they struggle to transport water from the roots to the top of the tree. Instead the trunk gets wider as they add more rings.