It looks like surgical sutures, possibly emergency medical work done on-site in an attempt to prevent greater tissue loss and maybe to tie off major veins and arteries that were damaged. This picture looks like it was taken in medical quarters after the patient had been brought in. But it could just as easily be remnants of whatever the patient was wearing on that foot that have been blown into the wound, or even singed grass...
I'd say you nailed it. Good job
