What can I use as a weighted base for a large paper mache tree I'm making? It can't be too heavy or too light.?

I've endeavored to build a life-size paper mache tree as a decoration for my bedroom, complete with painted tin birds hanging from the branches to appear as if they are in mid-flight. The only problem I've come across so far, in planning it out, is what should I use for the base of the tree. I think it has to be somewhat weighted so that the tree never falls over, but the weight can't be so heavy that I won't be able to move the tree around when it's finished. Also, whatever base I use has to be suitable for the project. The branches and trunk of the tree are going to be bendable wire on the inside and paper mache on the outside. So, the wire would have to attach to the base of the tree too. Perhaps I could weld it? I don't think any kind of glue would suffice, as that wouldn't be very stable. Also, the branches of the tree won't fit through the doorways of the house I'm living in. Could there be some way to make them detachable? Maybe, some sort of system to screw them in and out of place at the top of the tree...?