Decreased ultraviolet radiation and decomposer biodiversity inhibit litter decomposition under continuous nitrogen inputs

Atmospheric nitrogen (N) deposition has altered biogeochemical cycles and ecosystem functioning. As a key process involved in carbon and nutrient cycles in terrestrial ecosystems, litter decomposition is sensitive to external N inputs. However, it remains unclear how the interactions of ultraviolet (UV) radiation, soil biodiversity (bacteria, fungi and invertebrates) and conventional drivers (e.g., litter chemistry and microbial activities) regulate the responses of litter decomposition to continuous N inputs. Based on an N-addition experimental platform, we conducted a two-year litter decomposition experiment to examine the relative importance of N-induced changes in biotic and abiotic factors in mediating changes in the decomposition rates of four litter types (three representative species and their mixture) along an experimental N gradient in a Tibetan alpine steppe. Our results showed that litter decomposition rates exhibited a consistent decrease in response to N enrichment among a..., ,