Fig. 3.

Path diagram showing rhizobial controls on average acacia growth and the difference in response of A. salicina and A. stenophylla. Soils from A. stenophylla generally have higher overall densities of rhizobia, particularly as measured by A. stenophylla, and lower phylotype richness. The increase in overall densities of rhizobia results in an increase in average acacia growth. The differential increase in rhizobia that colonize A. stenophylla but not A. salicina, and the reduction in rhizobial phylotype richness increase the growth of A. stenophylla relative to that of A. salicina, resulting in positive soil community feedback.