The two dimensional aspect of the photos makes illustrating a height more challenging, but it looks like you have the bottom of the root flare pretty well pinned down (assuming the marks were indicating a position on the side of the trunk as opposed to the front). The top of the root flare is a little higher than the upper marks (again, assuming you meant to indicate a position on the side). The root flare is the area at the bottom of the trunk, just above the roots, where there is a noticeable increase in taper.

In the first picture, the top of the root flare (on the side) would be at the level in the picture corresponding to somewhere around the 4" mark on the ruler. At the front side, where your ruler is, it appears the root flare is just slightly above the higher red line.

I hope this makes sense. It's pretty simple, but I'm having a harder time than I thought I would putting it into understandable words.

You bet, from the side.

Your description makes sense...now that I have the visual going, I would say these trees are planted at the optimal depth.

My tree's (those aren't my images)start of the root flare is at ground level or if you were to compare against the pictures, ground level would be just below the top red lines.

next time something dies ... or if you have some rogue seedlings you are pulling out.. like little maples by the bazillions ....

hose them off.. and study the interface...

you will see.. they look like an entirely differing wood structure .... and for sure.. you will see where bark starts ... and in my mind.. bark rots.. so it should never be in the soil.. it needs air.. more than it needs damp soil ..

ken

next time something dies ... or if you have some rogue seedlings you are pulling out.. like little maples by the bazillions ....

hose them off.. and study the interface...

you will see.. they look like an entirely differing wood structure .... and for sure.. you will see where bark starts ... and in my mind.. bark rots.. so it should never be in the soil.. it needs air.. more than it needs damp soil ..

ken

Hmm. I know I posted on both your threads a day or so ago. So here's another try --

I suggest you stop worrying about planting depth, and start figuring out why the roots are dead (refer to the final picture, above), also whether or not the tree is still stable.

To determine the latter, I suggest you have a certified arborist who is qualified to evaluate potentially hazardous trees to take a look.

For anyone who is interested, OP's other thread is at http://forums2.gardenweb.com/forums/load/trees/msg062334126633.html?7

Here is a link that might be useful: OP's other thread

Never mind about the so-called other thread. I oopsed. (Hey. It happens.) - sigh -