3.2 | Plant biomass
There were many significant differences on the final shoot biomass of each species in the effects of the interaction between home or away (redcedar) soil types and the main effects of whether the soil was live or sterilized (Table 2). Root biomass and total biomass results generally aligned with those of shoot biomass (see Appendix Figures 2, 3 and Tables 2, 3).
Plant-soil feedbacks where soil conditioned by redcedar suppressed shoot biomass were not detected for either C4 grass species in the study. A. gerardi shoot biomass in live home soils showed a strong negative feedback (estimate = -1.3, p < 0.001) when compared to the biomass of samples grown in sterile home soils. Shoot biomass of A. gerardi grown in live home soils was less than its biomass when grown in redcedar soils that were live (estimate = -1.6, p < 0.001) or sterile (estimate = -1.5, p < 0.001). No significant effects or interactions were found when modeling shoot biomass as a function of growth in home or away soils and soil sterilization status.
The C3 grasses in this experiment showed strong negative feedbacks when grown in redcedar soil (Figure 3). However, the shoot biomass of B. inermis did not show any significant feedback when growth between live and sterile home soils (estimate = -0.10, p = 0.93) was contrasted. Shoot biomass of B. inermis was reduced when grown in live (estimate = 0.99, p < 0.001) or sterile (estimate = 0.71, p < 0.001) redcedar-soils in comparison to shoot biomass in live home soils. Similarly, shoot biomass of B. inermis was reduced when grown in live (estimate = -1.1, p < 0.001) or sterile (estimate = 0.80, p < 0.001) redcedar soils in comparison to shoot biomass in sterile home soils. Shoot biomass ofB. inermis did not differ when grown in live or sterile redcedar-conditioned soils (estimate = -0.28, p = 0.29). The shoot biomass of P. smithii grown in home live or sterile soils did not differ (estimate = -0.28, p = 0.50). Shoot biomass of P. smithiigrown in sterile away soils was reduced significantly when compared to live (estimate = 0.62, p = 0.017) or sterile (estimate = -0.91, p < 0.001) home soils. Shoot biomass of P. smithii was reduced when grown in live redcedar soils when compared to live (estimate = -0.93, p < 0.001) or sterile (estimate = -1.2, p < 0.001) home soils. Shoot biomass of P. smithii did not differ when grown in live or sterile redcedar-conditioned soils (estimate = -0.30, p = 0.44).