MD, I agree with you that most of this is fine, but one big quibble I have is salient in my mind...
Evidence: Actually, many studies
have demonstrated that woody
mulch materials increase nutrient
levels in soils and/or associated plant
foliage. My hypothesis is that a zone
of nitrogen deficiency exists at the
mulch/soil interface, inhibiting weed seed
germination while having no influence
upon established plant roots below
the soil surface. For this reason, it is
inadvisable to use high C:N mulches in
annual beds or vegetable gardens where
the plants of interest do not have deep,
extensive root systems.
I would include perennial beds as well as I have witnessed backward growth from wood chip application first hand in several perennials (once had hosta dwindle from massive three foot across to a foot in two seasons) Plus most C/N counts I see find perennials and veggies at about the same needs. SO let's throw perennials in too. SO it's fine as long as we don't use it on annuals, perennials, and veggies...that's somewhat limiting, but not even vaguely surprising to me...
High carbon inputs (like wood chips) tend to make fungal, therefore acidic soils (yes, I know what the good doctor said, but she is talking about a small amount as amendment, not a forest woodland soil). High nitrogen inputs like grass and herbaceous materials tend to make bacterial, therefore more base soils...
We need both for good veggie and perennial and annual growth, but they like it a bit more to the bacterial side of things (F/B ratio of .75 to 1) Here we come with a load of wood chips, which shifts the biology toward the fungal end of things (both by innoculating and providing more suitable environment). Not a big problem until we start to get an F/B around 2, then we have unsuitable ratios for crops, but suitable for shrubs. Around 5 it is only suitable for trees...
It is not so much that the bacteria for wood breakdown NEED N as much as it is they ARE N (carbon combines with nitrogen to make amine groups, which combine to make amino acids, which combine to make proteins, which combine to make bacteria, protozoans, etc.) As that population gets bigger, they need more protein, thus more N, and they steal it and keep it (stingy little bacteria). We could release that N by providing a lot of bacterial predators (protozoa) to eat bacteria and poop nitrogen, but where could we find them?
That's right, compost. And for just that reason I only use uncomposted wood chips around trees and shrubs; just safer. Compost them for a while and the predators have shown up already, so the lock-up effect is already mitigated somewhat.
We are just learning (actually we were learning lots until chemicals showed up and everybody decided soil was just somwhere to put the roots) how nature does fertilization and it is a lot more complicated than we thought it was (I one asked Elaine Ingham how much we knew about soils and she shot back "A lot less than we know about our oceans". This from the Mike Dirr of soil biology). Living soil just works better than dead soil, and I wanted to give you all a peek into that world, and just why certain things behave as they do. SO... good question, and it all comes back to the soil, greens and browns, and working with Mother, not against her...