That's a cable cut. They cut all the trees and bush, so that they could run power lines unobstructed through all this wilderness. If you follow one of these cuts to a high-resolution area, you will actually be able to see the power pylons yourself. Just like here for example: http://maps.google.com/maps?&ll=45.435752,-62.887808&spn=0.0,0.0&t=k&hl=en