I have seen it often suggested that organic mulches such as wood chip and bark from conifers is acidic. The pH is a measure of the amount (the negative log of the concentration)of hydrogen ions and this measurement must be done in a liquid. You cannot measure the pH of a solid unless you dissolve it in water. As most of the solid from wood chip and bark is insoluble in water, it is virtually impossible to measure the pH of these materials.
The woody chippings or bark could be giving off substances that acidify the soil solution as they decompose. However, neither pine bark nor pine chippings have been found to have any effect on soil pH. (Tahboub, Lendemann and Murray 2008) There is no significant change in soil pH for wood chip incorporated into soil measured over a three year period. Bare soil is more likely to have a low pH (be acidic) than organic mulches. Shredded bark and woodchip have been found to be the least acidifying of the organic mulches.
Regardless, wood chip could be shaken up in water and the resultant solution tested. This should be done with distilled water or deionised water to make sure that you are testing the pH of the dissolved substance not the pH of the water. Tap water contains a lot of substances although it usually has a neutral pH of around 7.
Now, I haven't tested the pH of woodchip solution, however I would conjecture that it would be fairly neutral or possibly slightly alkaline. There are some that suggest that the phenolic substances secreted by the above ground structures of a plant may be acidic. I don't know.
What I am going to do is test the soil beneath an estimated 2000 year old yew tree. The tree is in my local nature reserve. There is nothing growing under the tree within about a 50 food diameter.
I would suggest that the pH of the soil is no different from the rest of the wood so I will take samples from outside the yew trees influence as well as under its canopy. After 2000 years of falling litter surely it would have affected the soil underneath it.
My suggestion is that there will be no difference between the soil pH from beneath the canopy of the yew tree and the soil from outside the canopy.
The fact that there is no build up of litter under the tree would suggest to me that some invertebrates, such as worms, are feeding on the organic matter from the tree. Worm's preferred habitat is one with a neutral or alkaline pH.
Usually scientific consensus is pretty solid, however sometimes explanations that purport to be scientific are merely based on hearsay and anecdote and need to be challenged by experiment.