Nitrogen (N) deposition and arbuscular mycorrhizal (AM) fungi have a big impact on plant community structure and ecosystem functioning. The interactive effects of AM fungi and N addition on grassland communities are still unclear. It might be large because a number of studies indicate that N deposition influence the activity and composition of AM fungal communities. To test the influence of AM fungi and N addition on grassland stability and functioning, a 5-year in situ experiment was conducted in a temperate meadow in northeast China.
This study included two factors, with and without N addition, and with and without AM fungal suppression. In the N addition treatment, plots received ammonium nitrate (10 g m-2 yr-1). The abundance and activity of AM fungi was suppressed every two weeks using benomyl. The emissions of N2O and CH4, plant species composition, plant productivity and biomass stability were measured.
Results/Conclusions
AM fungi significantly decreased the emissions of N2O and CH4 under N addition. The reduction of N2O could partly be explained by accelerated the mineralization of soil N and increased plant N uptake by AM fungi. The decrease of CH4 emission might be related to the acceleration of litter decomposition caused by AM fungi. N addition strongly reduced plant species diversity and evenness, but increased aboveground biomass and N2O emission. Under N addition, AM fungi did not affect plant species diversity and richness, but significantly altered the functional groups coverage and increased plant productivity and biomass stability. AM fungi did not affect plant diversity and richness which might be related to the community composition. In the studied ecosystem, the dominant species Leymus chinensis (Poaceae) has lower mycorrhizal dependence.
In conclusion, AM fungi play key roles in reducing the negative effect of AM fungi on ecosystem sustainability by reducing N2O and CH4 emissions, increasing plant productivity and biomass stability under N addition in a temperate meadow ecosystem.