I have been finding that if you mulch to heavily you will killout grasses and smaller plants in general reducing the yeild. I now only mulch heavy on problem areas. On good patches I try to sprinkle well broken bits that don't damage the plants. Chickens dig too much if I put the mulch on thick, the smaller plants cant get a hold this way. I think that in a semi-forest the leaves that fall provide enough mulch. Also sunny areas can handle more mulch perhaps because the chickens don't spend as much time there due to the lack of bugs in the hotter dryer areas. Big plants on the other hand like beans or squash love loads of mulch. On the big ones I like to use solid layers of dry manure when its hard like a board nothing is getting through that. I only do a small area around each plant or group of plants. That way I hardly reduce the yeild of hey and stuff but I get a good crop of dummy food(grains) too.