Prunus cerasifera "Nigra"dead?

I have just noticed that the Prunus Cerasifera Nigra at the bottom of our garden has no leaves at all. It is a young tree - we've had it for about 3 years. It had full blossom in Spring and the usual amount of leaves until... (don't know when they fell off) The ends of the twiggy branches are brittle and snap, but the thicker branches seem OK. Is it dead/dying - or is it just reacting to the very dry year we've had?

 

Mine does that every year and I am in a near-permanent dry location in Algarve. I just give it a light haircut to freshen it. Currently I have leaves on the lower half and none on he top (mine is in a pot).

 

Really useful to know - thanks Victoria.