What happens when "male piggies" die in the novel, Xenocide?

When ordinary male piggies die, their corpses turn into brothertrees. Brothertrees resemble fathertrees except they do not retain their consciousness or memories from their second life. Brothertrees are very much like the hive queen's drones, when piggies need tools, weapons or building materials, the brothertrees fashion them from their own bodies. Thus the piggies have little need to industrialize.