A double whammy - it's a 10 shot multiple exposure overlaid with a single shot of the same scene. The D300 is a magical device - in camera overlays and in camera multiples all rolled into one.
The dogwood/redbud multiple that was the PAD on the 21st - http://www.pbase.com/ed_k/image/95943148 - intrigued me so I did a little experimenting today. This PAD is one result.
Another attempt is at - http://www.pbase.com/ed_k/image/95995461 - and today's PAD is just a portion of this same tree.