Changes in precipitation mediate the inhibitory effects of reduced UV-B radiation on the litter decomposition of desert plants in arid regions

The decomposition of litter and nutrient cycling in terrestrial ecosystems are significantly influenced by ultraviolet-B (UV-B) radiation. The direction and magnitude of this effect are largely regulated by the dry and wet conditions of the environment. The impact of UV-B radiation on the decomposition process of different litter types in arid desert regions under future precipitation changes remains poorly understood.

A field experiment was conducted to investigate the impact of precipitation changes (natural precipitation, a 30% increase in precipitation, and a 30% reduction in precipitation) on the litter decomposition of Reaumuria soongarica and Salsola passerina under both natural and reduced UV-B radiation conditions.

The reduction in UV-B radiation significantly decreased mass loss and nutrient release. However, these adverse effects were counteracted by increased precipitation, with an average value of 4.17% for mass loss and 34.35% for nutrient release. Conversely, decreased precipitation intensified these negative effects. The ameliorating effects of increased precipitation were associated with improved soil properties, including higher soil moisture and lower soil temperature, as well as elevated soil enzyme activities such as higher CBH and POD. Moreover, these mitigating effects on mass loss and nutrient release were more pronounced in S. passerina litter than in R. soongarica. A structural equation model revealed that precipitation and UV-B radiation indirectly influenced mass loss by altering soil properties (ST and SM) and soil enzyme activities (CBH and POD).

Our results suggest that changes in precipitation will modify the effects of reduced UV-B radiation on litter decomposition and nutrient cycling of various plant litters, particularly in plants with lower initial nitrogen content, under climate change.