Question

what will happen if a saprotrophs disappear from the forest

Answer 1

Saprotrophs are those organisms which play a major role in the decaying of dead animals and plants. If the saprophytes disappears from the forest then the dead remains of animals and plants would remain, causing land degradation of the forest

Answer 2

Saprotrophs are organisms which turn dead plants and animals into humus. It also makes the soil fertile for the growth of plants. If they disappear from the forest, all the dead  bodies will keep accumulating and cause disturbance to other living beings.  It will affect the nutrient cycle.