Here's another shot of the tree.

The spotty stuff n the trunk is lichen. Indicates the air in your region is good quality.

The thinning of the tree's canopy is due to something else. Might have a Certified Arborist or two out for an onsite evaluation.

I winder if chlorine splash could be an issue. I hear it affects some species more than others.

FWIW, last year REALLY was terrible here and the trees have not fully recovered. In fact I dunno if many ever will. Yours looks young for that type of fatalistic view though.

I think it is some kind of fastigate hornbeam, but I don't know what the problem is. It might be from the pool though.

how LARGE A TRANSPLANT WAS IT??/

DAm caps button... lol

ken

Thanks for the responses... Not sure how big of a transplant it was... we bought the house 2 years ago and the tree was here when we moved in.

Regarding the pool, I don't think that's the problem because the pool doesn't get much usage, and there's another tree identical to this tree immediately behind where I'm taking the picture from that is doing fine. It's just as close to the pool and it's near the shallow end that gets more use than the deep end.

At least I know the lichen isn't the problem.

Kevin

at the base of the trunk... can you see a root flare ??? .. see link ....

if not.. dig around gently.. and find out how deeply its telephone poled ...

can we see a pic of both trees together... and a bigger overview ...

stabbing around in the dark here ...

ken

Here is a link that might be useful: is there a root flare

Look at the very bottom of the trunk in the second pic. Looks like white shelf fungi. If so, tree was probable planted too deep and/or some other transplant cultural problem. If those are shelf fungi, remove the tree and replace. It will not recover. Take a close up picture and we can be more sure.

Arktrees

Maybe catapillars eating the leaves? I have some on my trees, BT would take care of it, but it is the end of the season, so I haven't been in a rush to spray now.

Thanks for the replies... I don't think it's catapillers because the other tree looks fine. Also, I think the thinning is caused by branches dying and falling off, rather than just leaves missing.

I've added a few more photos. I checked and the root flare is visiible on the healthy tree, but not the unhealthy tree. Could that be causing the problem? If so, if I scapped some of the mulch/dirt away from the base, would that fix the problem?

Also, no mushrooms or fungus, as you can see in the newer pictures.

Kevin

Here's a picture of the tree, facing the other direction, with the good tree in the background.

Here's a picture of the healthy tree, with the problem tree in the background. You can see the root flare on the healthy tree.

I'm no expert but it looks like the tree is suffocating. It must have been planted too deeply to begin with then the mulch dressing is really finishing it off. If it were me I would remove the mulch and rake away some of the top soil almost to the point were the feeder roots are visible and as far out as the drip line. Then I would put a light top coating of wood chips (not shredded which could compact) over the top. This might seem drastic but you have nothing to lose since it looks like if you don't do something you'll probably lose the tree anyway.
The tree looks like some kind of Poplar. Very pretty. I love the conical shape. Perfect for the space. It would be a shame to have to get rid of a tree like that.