The last picture is known as a The Baobab Tree.
Some great links left by hitmewithit in the comments.
Arborsculpture - Wikipedia
Axel Erlandson - Wikipedia
Arborsmith Studios - Axel Erlandson Tree Circus
Pooktre Tree Shapers
And thanks to anonymousfor Bonfante Gardens Family Theme Park
And thanks to Becky form Pooktre for the following links
Circus Trees by Axel N Erlandson
Tree shaping - Wikipedia
A few more sent in by email