Tree dying from the bottom

[Iowaraised]

I will start by saying I know nothing about trees  I am not even sure if this is a pine or evergreen. Starting a few years ago, the very bottom branches started dying and not producing cones or needles. It has gradually gone up through more branches. I am in eastern Iowa.  Another tree has started the same, on just one side of it. And another that is a few feet away is completely fine, full and absolutely beautiful. This is at a location I rent at and I know the owners would elect to just cut them down. I am hoping to save them. Last summer some weeds grew up through the tree as well. Any suggestions would be very welcome!

[nepia]

I can't be sure but it looks like the soil level has been raised around the trunks.  That's not a good thing to do and can often result in a slow death; lack of oxygen to the roots, decay of the bark followed by infection of the live tissue underneath