Soil organic carbon loss promoted by long-term warming and simulated chronic nitrogen enrichment in the Tibetan Plateau

Global air and soil temperature and nitrogen (N) enrichment are expected to increase in the future, which have the potential to change quantity and quality of soil organic carbon (SOC) pool and alter terrestrial C cycling. However, the underlying mechanism remain unclear especially in the alpine meadow ecosystem on the Tibetan Plateau, which is quite sensitive to global change and is of great importance in regulating future SOC emissions. Using a 9-year two-way factorial experiment involving warming and multilevel N enrichments in the Tibetan Plateau, we showed that both warming and N enrichment promotes soil and microbial C loss. We examined abundance of relative functional genes and found that N enrichment enhanced the ability of microorganisms to degrade labile SOC and reduced the ability to degrade less labile SOC. A long-term laboratory incubation combined with a two-pool model analysis and molecular component examination were conducted to examine potential mechanisms underlying the stabilization variations in different C pools. Diffuse reflectance infrared Fourier transform spectroscopy and biomarker analysis will be used to reveal SOC composition changes and underlying degradation mechanisms. This study highlights the crucial role of soil C stabilization mechanisms in regulating SOC – climate feedback when exposed to warming and chronic atmospheric N enrichment.