Prairie and most sun-loving flower species developed in landscapes without many trees. A thick layer of leaves or worse, wood chips, is not only shortening the lives of these plants but also prevents the development of healthy biodiversity in and above the soil. A thriving landscape is like a happy mixed community, and shouldn’t look like a prison or a museum for isolated plant species.
Mulches can be helpful if you have a lot of unwanted species. Once the invasives or unwanted plant species are smothered, remove the mulch bit by bit so your good plants can expand and inter-seed. The denser you plant your plants the easier they will win the competition.