Sometime during the winter a lorry drove over the grass, leaving tracks, outside the building where I work. I've just noticed this morning that the grass on the tracks is green and new while all the undriven-on grass is still brown. Why is this? The only explanation I can come up with is that the driven on grass was killed or damaged and the new shoots need to get in an early start so as to be able to compete for light with the surrounding grass. Anybody know any better?