This card was made at a recent card class I went to run by Jo French see her blog here. She demoed how to do the sunset and hills technique using sponges to bring the colours in. I think from memory I used Pumpkin Pie, Daffodil Delighy and Early Espresso Stampin Up Inkpads.
The hills were done by tearing some paper and using this as a template, moved around to make the hills different.
The tree stamp is one that I have had for years and is not branded but you can get a very similar one from Stampin Up in the Lovely as a Tree set.
The Thanks so Much sentiment is from a retired Stampin Up set.