Downhill piling is a seasonal problem, and bare roots are not a problem in the right season, except pine trees; You don't know the season for changing mud. Elms turn to mud in severe cold (plants hibernate). Even if a large number of roots and branches are cut off, they will revive and grow as quickly as spring comes. If you change the mud now, if it has been planted in the pot for a long time and can still keep the mud ball, you won't be afraid, or you will be in trouble. I suggest you put the pile in the shade, keep it ventilated and breathe freely, and spray water on the tree several times a day to stop watering the mud. Pour some rooting water on it and do your best. It should still be saved. Check the answer details on bonsai art online community website >>