If I saved dead oak and maple tree leaves and put them in my cactus pots come spring will decomposing leaves fertilize them or hurt them?

Oak is fine but really no fertilize effect. Maple leaves contain tannin. Which is a plant killer. It stops bottom plants competing with the maple tree. Compost after two years is ok. Compost hummus holds moisture and may not be the best idea. Be sure to use palmice or perlite to aid drainage.