Our Japanese Maple appears to be drying out and leaves are falling. It is well established (10 years) and a good size. We recently experienced a 3 day heat wave. The tree faces west and gets afternoon sun. Could the sun and heat have caused this? Is there anything we can do to strengthen the tree?
If it's the heat wave (and japanese maples don't like heat) then the best you can do is to keep the area watered and mulch around (but not touching) the tree. Don't give up hope though if it sheds leaves this year, trees have this mechanism to protect themselves and it will probably be OK next year.