How do mycorrhizal suppression and plant functional group loss affect plant communities in Inner Mongolia Steppe?

AimsAlthough many studies have investigated how biodiversity loss impacts ecosystem functioning, we still have little understanding of how it interacts with arbuscular mycorrhizal fungi (AMF) to affect plant communities in natural grasslands. Here, we conducted a removal experiment to examine how AMF suppression and plant functional group (PFG) removal affect above-ground productivity and community composition in a grassland, and to determine whether AMF alter the compensation ability of the remaining plants. LocationInner Mongolian grassland, China. MethodsWe suppressed AMF activities by applying Topsin((R))-M as a soil drench and selectively removed PFGs to give three treatments (no removal, removal of C-3 grasses and removal of both C-4 grasses and forbs). We then measured various plant, soil and AMF parameters for each treatment combination. ResultsThe addition of Topsin-M effectively reduced mycorrhizal root colonization across all of the PFG removal treatments. Furthermore, above-ground productivity was significantly impacted by both the presence of AMF and the removal of PFGs. When C-3 grasses were removed, neither C-4 grasses nor forbs compensated for the biomass decline, and the presence of AMF did not affect their compensation ability. Conversely, C-3 grasses could completely compensate for the removal of both C-4 grasses and forbs, but the presence of AMF reduced their compensation ability. The removal of both C-4 grasses and forbs dramatically increased the shoot P content of C-3 grasses but AMF slightly decreased this. In contrast, AMF significantly increased the plant P content of C-4 grasses and forbs across all three PFG removal treatments. ConclusionOur results highlight the importance of AMF in structuring natural above-ground productivity under various biodiversity loss scenarios, and indicate that AMF will be able to modify vegetation dynamics in response to the future loss of plant diversity.