protected function _getRootNode( $sort = '+' )
	{
		$search = $this->createSearch();
		$search->setConditions( $search->compare( '==', $this->_searchConfig['level']['code'], 0 ) );
		$search->setSortations( array( $search->sort( $sort, $this->_searchConfig['left']['code'] ) ) );
		$nodes = $this->searchNodes( $search );

		if( ( $node = reset( $nodes ) ) !== false ) {
			return $node;
		}

		return null;
	}