The tree primitives can be manipulated as a vetex object and then they most certainly can be exported. I have done it. I take them into bryce becasue I enjoy Bryces sky editor much more than cararra's. In C3 its just too much work trying to get a nice sky. What I discovered is that the trees exported from C3 through poser and into Bryce, is that the trees from C3 appear to render quicker than the preset trees in Bryce. They are far more sparse though.