For the base :
A metal plate ( 12 th scale)
For the dome :
Plastic bottle cap or something similar. Try to
find something that is really clear.
A press stud to glue on the top ( optional)
Glue a piece of dried bark to the plate. You can also use a piece of wood or a stone or whatever you like.
Use some green paint ( I used my watercolors) to add a bit of a moss effect to your tree bark base.
I also added some green fluffy bits.
I used a lot of different bits of greenery for this project. I always find the most intersting ones at http://www.minikitz.com/
They have stuff that looks like tiny plants and grasses, stretchy vine which is great to make trees with and lots more.
I little bit of the stretchy vine material ( see above) made lovely greenery for the tree. Just lightly glue on top of the basic tree.
Decorated the base with some mini gravel and some flower foam and more greenery in different shades of green.
In the end I used a different bottle cap for the dome. Here is the final version .