How to create backup from symbolic links?

Use the -h tar option. From the man page:

-h, --dereference
    don't archive symlinks; archive the files they point to

If the links are all in the root directory you can have the shell dereference them and pass to tar as arguments. For example if you have /backup/source/a and /backup/source/b, both of which are symlinks pointing to the real directory, something like the following would work

tar -cf /path/to/backup.tar /backup/source/*/