I have a Harry Lauder Walking Stick Tree and the lower leaves are drying out and turning brown?

Question:the tree is about 8 years old, it is planted in Cleveland Ohio, I have never experienced this in the past.

Answers:
I don't know about this plant in particular, but in general the same holds true for most plants:
If the leaves at the top turn brown or yellow and fall off, it's not getting enough water.
If the leaves at the bottom or middle turn brown or yellow and fall off, then it's getting too much water.
One additional bit of information: Some plants go through growning spurts; when this happens, the lower leaves and branches die off so that the plant can direct all the nutrients to the new growth. Check to see if it has a lot of new growth at the top and/or at the ends of the oldest branches.