Answer: Mulch is a good thing! In my experience, any organic mulch will do including all those you mentioned plus more such as half finished compost, straw, wood chips, cardboard and even newspaper. There are a few cautions which come immediately to mind, however. Grass clippings treated with herbicide should not be used; manure should be well aged; colored inks should be avoided; pine needles used in great quantity may acidify the soil; fresh bark or other fresh green "woody" mulches may require additional nitrogen be added. (A year of aging is a good idea, but you already know that from the perennial garden.) They will all benefit the soil structure in time as they break down, and they will all do the job. By running basic soil tests (and observing the plants) you will be able to compensate for any side effects the different mulches may cause. I would feel comfortable using the bark.
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