I'm posting on behalf of a friend who has a Chinese elm which recently
started shedding leaves. The foliage is very sparse compared to its
appearance this time last year. The only cause we can think of is
overwatering or that perhaps it needs repotting. There doesn't seem to
be any obvious signs of pests or disease.

I've scanned a small pictu

www.ivy32.demon.co.uk/bonsai.html

Does anyone have any suggestions as to what is wrong?