Why does ash alkalinize the soil, when wood chips do not?

It is well known that ash is strongly alkaline; why is this so, when the wood or other material it is derived from is not?

If I spread a foot of wood chips over a piece of land, it wouldn't alkalinize it; if anything, it might have a slight acidifying effect. Over time, the  carbon in the wood chips will escape into the air as carbon dioxide, and the minerals (calcium, potassium, etc.) will be left in the soil.

If I burned that same foot of woodchips to ash, the carbon would burn off as carbon dioxide, leaving an ash of minerals; when this ash is applied, it alkalinizes the soil.

The eventual outcome seems to be the same; decomposition is just slow burning. Why does one route alkalinize the soil, and the other does not?

Two related questions: is this because, when people apply ash, they are applying a far higher level of these minerals than they would feasibly be able to apply in wood chips?

Over time, will the alkalinizing effects of the ashes be neutralized in the soil, returning the pH back to what it would have been if the wood was applied without burning?

While I don't actually know as such, here's my best guess: it depends which specific salt the minerals are part of at the moment. For instance, potassium in ash is in the form of potassium carbonate (alkaline) or if the fire was very hot, potassium hydroxide (very alkaline). The corresponding acid of potassium carbonate is carbonic acid, a very weak acid. The corresponding acid of potassium hydroxide is water, which is not really an acid at all. If there are stronger acids (like carboxylic acids) present, the potassium will be found in the form of less alkaline salts. Wood probably contains quite a lot of various carboxylic (and other) acids, so in wood, the potassium will not be very alkaline at all, and the metabolism of the fungi and bacteria decomposing a pile of wood chips will produce a whole bunch more organic acids. Fire, on the other hand, burns away the vast majority of the carbon in the wood, including all the carboxylic acids, leaving the more alkaline salts.

Wood undergoes a chemical reaction when it is burned. Potassium in the wood combines with oxygen and carbon during the burn to produce potassium carbonate, which is left in the ashes along with other minerals, predominantly calcium. Wood ash can be up to 30% calcium. Carbonates neutralize acids, raising ph. When ash is added to the soil, the carbonates will neutralize acids in the soil, but also the calcium in the ash raises ph as well. Sandy acid soils like ours here in New Hampshire always have a calcium deficiency and wood ash is a valuable resource for mitigating this.