When the skater is on the straight part of the track his strides are wider than on the curved part of the track. The reason for this is because on the curved part of the track it is easier to steer around the turn if he keeps the lateral distance between his strides small. However, the trade-off is that he can't go as fast around a turn as he can on the straight part of the track.
In short track speed skating the radius of the turn is quite small. This introduces considerable "lean" of the skaters towards the inside of the turn, due to centripetal acceleration. As a result, short track speed skaters can't do much skating around the turns. They must mostly ride the turns using the momentum gained on the straight part of the track. The picture below shows speed skaters as they go around a turn.