What I can tell you is that purple Japanese maples go to green when there is too much shade. Fall coloration in more shade will also be less-intense.

I have no clue what too much dog urine does to a Japanese maple. Two years of constant urination on/around the same tree is likely not to do it any good though.

Dax

The maple tree is in a somewhat shaded corner of the house. However, it's been there forever and it's been red every year but this year.

In St. Louis our WET spring, hot fairly dry late summer, and desert dry and beautifully warm October fall colors have been all over, some good, some bad, some still looking like summer.

Anything unusual in your area?

I'll bite that different trees color differently in different PH soils and all the urine changes the PH.

Also are the trees shading your maple still growing providing more shade every year or are they past peak and in decline?

Any chance of moving the puppy around?

As for weather, I don't think this year is any different than years past, maybe a touch cooler if anything.
As for the pH issues, that's what I'm thinking is the issue as some flowers bloom different colors according to pH.
As for the shading of the maple, it's actually shaded by a corner of my house as the sun crosses over the house - no trees involved.
If there is no harm done, then I guess we'll just leave things be. However, IF there is harm, we could find another spot. It's just that it's the most convenient area for all involved, especially in the winter when it snows.

Super-explanation.

Dax

Thank you for the info. We do have the sprinkler going daily in that area, but I guess I'll have it go a bit longer.