there are some reasons that you want to export-import the trees
for example: selective backup, transfer tree data between databases etc

it is possible to export-import the trees by the use of these functions:
tree.tree_export(tree_name)
tree.tree_import_from_table(table_name)

with the first function you can export data
for example:
CREATE TABLE <TABLE_NAME> AS SELECT * FROM tree.tree.tree_export(<TREE_NAME>);
Or if you want to append records:
INSERT INTO <TABLE_NAME> SELECT * FROM tree.tree.tree_export(<TREE_NAME>);

with the second function you can import data
for example: 
SELECT tree.tree_import_from_table(<TABLE_NAME>);
(for importing data the trees must not exist inside the library);