Abstract: Litters are exposed to intense sunlight for an extended period due to limited precipitation and prolonged sunshine duration in extremely arid regions. The influence of solar radiation on litter mass loss is predominant in extremely arid ecosystems. The litterbag method was employed to investigate litter decomposition of three dominant plant species under natural light exposure and shading from ultraviolet radiation in Cele Oasis desert area, the  southern edge of the Taklamakan Desert. The results showed that decomposition rate of all the three types of litter was significantly higher under natural light than under UV shading. The mass remaining rate of litter at the end of decomposition under UV shading was 79.97%, 77.79%, and 82.55% higher than that under natural light for Karelinia caspica, Alhagi sparsifolia, and Populus euphratica, respectively. The Pearson correlation coefficients between organic matter loss rate and mass loss rate under natural light were 0.975, 0.982, and 0.991 for Karelinia caspica, Alhagi sparsifolia, and Populus euphratica respectively, and 0.786, 0.906, and 0.800 correspondingly under UV shading, with a stronger association under natural light compared to UV shading. Additionally, UV shading significantly mitigated the loss of soluble salt, C, and N as well as altered the C∶N ratio in all three types of litter. Findings from this study contribute to enhance our understanding of the decomposition mechanism of litter in extremely arid regions, providing a fundamental basis for future investigations on litter decomposition in arid ecosystems.

Key words: litter decomposition, extreme drought region, photodegradation, nutrient release