A representation of the mechanisms discussed in the text
that affect soil and plant diversity, and which contribute to feedbacks
on diversity between the two sets of organisms. Direct
mechanisms are represented by solid lines and indirect mechanisms
are represented by dashed lines. Soil diversity is split into
the three general categories of organisms discussed: Soil Mutualists
(such as mycorrhizal fungi and rhizobia), Soil Antagonists
(including pathogens, root herbivores, etc.), and the Soil Food
Web and Decomposer community.