Our bodies my provide sustenance for other life (much the same way food does for us) but that doesn't make us "still alive" or "living in another form" any more than it does for an orange after I've eaten it.

Plus not all biological forms end up feeding other life, some of it breaks down into hydrocarbons and becomes coal or other petroleum products :P

I don't define life as the soul of the psychological construct. If so then I would have to argue that someone who is brain dead is "dead". This isn't the case since clearly the body is still functioning (thus living).