Looks like the kolban tree control is not fully implemented, you can achieve this by calling clearing out the values of the tree and calling destroy of the tree and then calling this.load();
Make a copy of the tree control and on the chang() handler put the following code
try {
this._tree._itemNodesMap = {};
// reset the state of the rootNode
this._tree.rootNode.state = "UNCHECKED";
// Nullify the tree.model's root-children
this._tree.model.root.children = null;
// remove the rootNode
if (this._tree.rootNode) {
this._tree.rootNode.destroyRecursive();
}
var treeObject = dijit.byId("mytree");
if (treeObject){
treeObject.destroy();
}
this.load();
} catch(error){
alert(error);
}
} catch(error){
alert(error);
}