Thank you Mike and Eric. Apart from having a striking look, I think it works because all the white streaks are balanced within the context of the whole image. Shooting in-camera motion shots when there is white light shining through trees is notoriously difficult, because, more often then not, the white streaks often ruin the image by bringing attention to themselves at the expense of the rest of the image.
True. And here they really work as part of the composition.