Abstract

Plant litter can influence many fundamental ecosystem functions during decomposition. However, the mechanism of litter diversity effects on belowground ecological processes remains unclear, especially with regard to soil C and the N cycle in alpine ecosystems. In this study, we incubated the litter of four alpine steppe species (SP: Stipa purpurea, CM: Carex moorcroftii, LP: Leontopodium pusillum, AN: Artemisia nanschanica) alone or in mixture with soil. The litter-mixing experiment was conducted to determine the effects of litter diversity on soil C and N dynamics in an alpine steppe in Northern Tibet. Litter treatments significantly enhanced CO2 and N2O emissions and decreased CH4 immobilization in general; soil organic C, total N, water soluble organic C, water soluble organic N, microbial biomass C, microbial biomass N, and urease activity were also enhanced, while soil total inorganic N was decreased by litter treatments. Plant species richness poorly affected soil C and N dynamics, while litter chemical structure, such as C, N, lingin:N, phenol:N, cellulose, and cellulose:N, significantly affected soil C and N dynamics. Non-additive effects of litter mixture were predominant on soil C and N dynamics, while antagonistic effects were more frequent than synergistic effects. These results indicated that litter addition can significantly impact soil C and N dynamics through non-additive effects of litter mixture, and litter chemical structure is more important than species richness in affecting soil C and N dynamics of the alpine steppe in Northern Tibet.

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