Several factors involved.... root depth, mulch depth, climate. I found that when mulch was really needed to hold in soil moisture the mulch dried out, as did the top couple of inches of soil, thus killing the fungus inbetween wet periods. Without the mulch, soil drying would have been much worse. Newspaper under wood chips would restrict fungal growth, so tht is an option too.
I have problems with low nitrogen here and there for a couple of reasons tied into using clay soil that has just recently been turned into a garden. It is very easy to see that the plants are not growing and have a bit of yellow on the lower leaves. I just give them a shot of shot of nitrogen. They perk up in a couple of days. It is much easier to deal with the low nitrogen than problems associated with not mulching (dry soil, weeds).