The root block is with a placeholder texture instead of the normal dirt texutre. What is causing this problem is the Default 3D texture pack, is there a way to use it without causing this issue?

I know this is a trivial/too specific question, it's just that really like the texutre pack and the dynamic trees mod, i want to have both of them running at the same time. Sorry if i'm bothering.

This isn't directly an issue with DT. You need to work out how to edit a multipart model properly to allow for this. Assuming that's possible there are many places to ask for help in doing so - but an issue tracker isn't the place.