The Responses Of AM Fungi Warming And Nitrogen Addition And Their Feedbacks On Songnen Grassland

Arbuscular mycorrhizal fungi(AM fungi) can form mutualistic symbioses with most plant species and play a key role in determining plant community structure and productivity, and the community composition of AM fungi are influenced by global change. However, the effects of climate change on AM fungi species community composition and development, and their feedbacks on plant community are not well understood. We measured the influences of warming and nitrogen(N) addition on AM fungi species composition and development, and tested their feedbacks on aboveground plant community structure and productivity in Songnen grassland. The main results and conclusions are present as the followings:(1) N addition reduced the diversity and richness of AM fungi, and suppressed AM fungi spore density and hyphal length; warming had no impact on AM fungi species composition, but reduced spore density and diameter increased extramatrical hyphal lengths.(2) Rotation treatment suppressed the development of AM fungi including spore density, mycelia density and mycorrhizal colonization of five species. Static advanced the flowering times of mycorrhizal plant species such as Chloris virgata in warming and N addition treatment while delayed nonmycorrhizal plant such as Suaeda corniculata. Meanwhile plant height of Setaria viridis and Chloris virgata in static treatment under warming and N addition were increased which may just the opposite of what the Suaeda corniculata be. Rotation significantly decreased the aboveground biomass of Leymus chinensis in warming and N addition treatment but increased that of Suaeda corniculata; however, static highly increased the aboveground of Leymus chinensis and decreased Suaeda corniculata in warming and N addition treatment at the same time.(3) AM fungi highly improved plant species diversity and richness whether in warming or N addition treatment, AM fungi all increased the relative abundance and aboveground biomass of Gramineae forage Leymus chinensis and reduced the relative abundance and aboveground biomass of Chenopiodiaceae weed Suaeda corniculata, significantly. Moreover, AM fungi highly increased total aboveground biomass in warming and N addition treatments.In summary, our results suggest that although global warming and N deposition can affect the species composition or suppress development of AM fungi, AM fungi still play a vital role in increasing plant diversity, productivity and ecosystem stability. The result highlights that AM fungi might can reduce the threats of grassland degradation and productivity reduction caused by climate change in temperate meadow ecosystem.