Have you scratched around in the mulch near the trunk or topsoil where any roots may be? Could be a fungal infection that started when tissue/bark cracked in a freeze, and then the drought progressively weakened the plant further.

My Dicksonia spp. leaves turned brown with the freeze, but I left them to help protect the tree, and eventually cut them off. Are there any grass or other roots invading the trunk? If so, carefully cut them off, and keep them off.
These ferns are heavy feeders, but I do not use chemical fertilizers. I use worm castings, washed seaweed (from the beach), composted manure, or manure 'tea' (either the water the composted manure has been sitting in, or the manure itself), or 'kitchen and leaf' compost as a dressing, with mulch. After several years, the mulch breaks down, adding to the compost. Don't let the mulch or compost touch the 'bark'. My tree fern is back and looks healthy...hope your's will be, soon. I don't know if these ferns have any diseases here, but it pays to be on the lookout.

I'll prune back the dying branches tonight after it cools off (haha). There is invasion by grasses near the tree. I'll also remove that and fertilize.

I'd hate to lose the tree. They are so pretty and lush when in good health. I saw some today at Tropical Ranch, and although losing leaves, they looked 90% better than mine does.

I'll carefully inspect the lower trunk after I pull back the grass stems. We do not weedwack near it. I hand-pull weeds/grasses near trunks. My chickens kick the mulch away, and the grass invades rapidly.

Thanks for your helpful ideas!

Lisa

Japanese Fern Tree isn't really a tree fern. It called that because the foliage resembles ferns.

Mine is shedding leaves right now also, but it does have new foliage. I think I let it get a little too dry. I am growing it in a large container in my patio.