Let me say first off, that I am not an attorney. But, I do know that in my state, or other states, that the value of a cemetery plot is considered as "real property", and is considered the same as owning a piece of property that you would have a house or other property on. Cemetery plots can be worth quite a bit of money, and you should have a deed to the property, similar to a deed to a house or other real property.
If you check out California laws
, pertaining to inheritance, I am sure you will be able to find an answer to your question, but I do know that here where I am, the property, such as you describe, if passed on to a descendent, would be considered to be a taxable asset.
There are very many good experts in our group, that I am sure will be able to give to you a specific answer to your question.
Take care and good luck!