Hi Tring, Yes, could be suffering from lack of water but luckily because they have been fairly dormant through the winter, my gut feeling is that you might just be lucky !! So, dont panic, just give plenty of water, especially around the crown and you should get some new leaves in the spring You didnt say how tall the trunk was ? but if it is dead, heres a little tip you might like to use. Quite a few tree ferns have been killed recently, even down here in Cornwall and what weve done which seems to be quite successful is this.
Buy a very small Dicksonia, make a 'basket' of fine chicken wire, lined with moss, place the 'basket on top of the old dead trunk and plant the new small plant in the basket. Keep well watered and quite quickly the roots will secure it to the trunk and give it a couple of seasons to establish and 'hey presto' a new tree fern (with a trunk).I know its a cheat but better than throwing the dead trunk out ?? they aint cheap !!
best wishes, lannerman