I work in Alabama in a POwerhouse for a saw mill that runs 24/7.
Ihave a second job to make ends meet and have been doing both for longer than a year.My question is can my supervisor change my schedule so he does not have to pull a shift and force me to quit my other job legally?

Unless you have a bona fide contract that specifies that you will work exactly these hours and no other, your employer can change your hours any time he wants. If that means you have to quit your other job, that's a shame but it's perfectly legal. Your other job is not his problem.