If I were to hazard a guess I would say that this is all done in the printing. The appearance reminds me of a split grade print in which diffusion is used in a part of the hard exposure. Beyond that some quite noticeable edge burning and high contrast. But then again, this may be the second time that I have been wrong today.
I read an interview with him in Camera Arts two years ago. He shoots everything with a 35mm Nikon SLR, and then does extensive darkroom manipulation including diffusion, bleaching and all other sorts of orange-light legerdemain. Cool stuff, isn't it?