how to reload/refresh/reinit DynaTree?

Function the initialization:

function InitTree() {
   $("#tree3").dynatree({
       (...init params...)
   });
}

InitTree();

To reload data, call:

$("#tree3").dynatree("destroy");
InitTree();

look at the tree.reload() method, it should do what you are after.

see the docs here: http://wwwendt.de/tech/dynatree/doc/dynatree-doc.html#h8.2

as in the docs, the tree is the internal drawing of the tree, and you get it by calling the getTree command: $("#node").dynatree("getTree")

tree.reload(); is for data loaded dynamically as in Ajax. If you are working with ul/li lists and need to reload your tree, you have to do: $("#tree").dynatree("destroy"); before your regular dynatree creation code. The destroy parameter is not documented.