They acknowledge it :

> “there would be a need to differentiate effects from human decomposition with those from other animals' decomposition.”

But then :

> However, there could be subtle differences in how plants respond to the decomposition of different kinds of mammals.

I really think it's a long shot and the number of false positive would make the technique impractical, unless you know there's a human body in this forest and you want to exhaust all possibilities to find it.