Litter leachates transform soil bacterial composition enhancing nitrogen fixation in alpine meadow

Abstract

Litter leachates have the potential to considerably regulate biogeochemical cycles in terrestrial ecosystems. Yet the effects of litter leachates on the soil microbial composition have so far not been adequately evaluated. Litter leachates of Elymus nutans, Kobresia setchwanensis, Ligularia virgaurea, were sprayed onto alpine meadow to assess their effects on community structure. Specific functional genes of soil bacteria were also analyzed to explore their potential ecological functions. Results indicate that application of litter leachates to alpine meadow on the Qinghai-Tibet Plateau over three consecutive growing seasons, modifies plant communities and soil bacterial composition. Plant biomass, soil moisture, and C:N ratio of litter leachate treated soils were lower compared to the control, but soil microbial biomass carbon was greater. Increased plant and soil bacterial α-diversities were accompanied by alterations in soil physico-chemical properties and plant community structures, including higher soil bacterial β-diversity. Soil moisture, organic carbon, microbial biomass carbon, inorganic nitrogen, and C:N ratio being abiotic factors, were closely related to bacterial composition in the topsoil (0–20 cm), while plant biomass and diversity were the major biotic driving forces of soil bacterial composition in both topsoil and subsoil (20–40 cm). L. virgaurea litter leachate application increased soil nitrogen fixation potential, E. nutans and K. setchwanensis litter leachates reduced soil nitrification and denitrification however. These results indicate that litter leachates stimulate the nitrogen cycle in alpine meadow by altering bacterial composition and function of plants and soil bacteria. This ecologically significant contribution supports strategic application of litter leachates on alpine pasture.