Mass decomposition dynamics and soil microbial community changes during the photodegradation process of leaf litter from three plant species in hyper-arid deserts

The significance of photodegradation in litter decomposition has gained recognition in arid and semi-arid terrestrial ecosystems. However, few studies have directly examined the effects of photodegradation in hyper-arid regions (annual precipitation < 150 mm) and the role of microorganisms within this process. This study investigated how two different light conditions (full sun and shade) affected the one-year decomposition process of litter from three different species in a hyper-arid region. This study analyzed the impact of varying light conditions on litter mass loss and examined changes in the soil bacterial and fungal community composition during the decomposition process. This study found that litter exposed to environmental sunlight experienced a higher rate of mass loss compared to shade-exposed litter. Full sun conditions increased mass loss by 8.34% to 21.66%. During the litter decomposition process under full sun conditions, decomposition was not influenced by differences in initial litter composition, including variations in carbon, nitrogen, lignin, and cellulose contents. However, under shade conditions, Populus euphratica leaf litter, characterized by lower nitrogen and higher cellulose and C: N ratio, exhibited significantly lower mass loss compared to Alhagi sparsifolia and Karelinia caspia, indicating a slower decomposition of low-quality litter. Full sun conditions did not significantly change the number of bacterial and fungal ASVs in the hyper-arid desert soils during the litter decomposition period. During the litter decomposition process in the hyper-arid region, the dominant bacterial phyla were Proteobacteria, Firmicutes, Actinobacteria, and Bacteroidetes, while the dominant fungal phyla were Ascomycota and Basidiomycota. These results indicate that the higher mass loss under full sun was likely driven by the combined effects of photodegradation and microbial activity. Solar radiation plays a significant role in desert litter decomposition by accelerating mass loss, potentially through both direct photodegradation and indirect microbial facilitation, while microbial community structure remains resilient under high radiation.