Not trying to be argumentative, but, I have dug up old slab piles that I know where covered up in the 1940's and found slabs of wood intact and not nearly decomposed. While I do believe limbs and logs will eventually decay, I doubt I would live long enough to reap the benefit. On the other hand, wood chips, notably Ramail wood chips, contain 75% of a trees nutrients and will decompose much faster than logs or tree limbs. Ramail wood chips differ from the bagged wood chip products you buy from retail stores. ramail chips are the small limbs, twigs, mostly bark, of a tree. Hardwood bark being prefered instead of pine bark. Trees removed and then chipped with the bulk of the trunk material removed is much better than saw dust or nutrient poor large dia woods. I used to have the local power company dump all their wood chips on my property. I would get a 100 or so truck loads at a time. Thats a lot of chips. I would pile the chips as high as I could and then take my FEL and turn the piles every couple of months. This kept the piles hot and decomposing. I used these chips in my garden and for erosion control on steep slopes. I even managed to sell a lot for mulch. Properly composed wood chips; would turn those 100 truck loads into about 10 truck loads of composted material.
As for adding the chips to my garden, I never incorporated the chips into the soil during growing season. This reduces the nutrient tieup and robbing nutrients from the growing plants, I used the chips as a mulch, which you already know the benefits of, and after harvest I would then till the mulch material into the soil. This way the mulch was in direct contact with the soil and the sun during growing season yet not in a situation to where its decay could tie up nutrients needed for a productive garden, This method also speeds up the soil building process of applying qood materials to the soil. One other thing to consider when burying logs or wood chips, anything deeper than about 6-7 inches will create anaerobic conditions, starving the good microbes and slowing down the decomposition of the wood products.
