Time evolution of the mean value of the surface density of planetesimals in the feeding zone for a disk 6 times more massive than the MMSN. For the case without planetesimal fragmentation (red solid curve), the total surface density corresponds to planetesimals of radius 0.1 km. This is not the case when planetesimal fragmentation is considered (solid black curve). However, the total surface density is dominated by the surface density of planetesimals of 0.1 km (dashed red curve). (Color version online.)