No easy way, but you could either:
1 – Use clippings cart to create two new trees, then remove the original. Not easy.
2 – (my preferred) – try GEDsplit.exe from http://www.rootsweb.ancestry.com/~gumby/ged.html IIts old but shoulld still work. It’s a couple of years since I used it, but not hard once you get the hang of it.