Snowfall Change Had Different Effects on Litter Decomposition for Two Typical Desert Species in Different Periods

In desert ecosystems, litter decomposition is the primary source of soil nutrients and is strongly affected by extreme climate events, which may influence desert plant survival and species diversity. To date, the effects of snowfall changes on litter decomposition in desert species remain poorly understood. Here, a snowfall manipulation experiment was conducted in Northwest China that included snowfall addition and removal treatments, as well as a natural snowfall control. Compared to the control, snowfall addition increased the amount of litter mass lost for Salsola passerina and Reaumuria soongarica during the snow-covered period by 21.54% and 21.8%, respectively. In contrast, snowfall addition effects differed between species during the snow-free period. More carbon was released from the S. passerina litter in the snowfall addition treatment during the snow-free period. Similarly, during the snow-covered period, more carbon and nitrogen were released from the R. soongorica litter in the snowfall addition treatment. Overall, the proportion of litter mass lost (from the annual total) increased with snowfall addition in the snow-covered period but was reduced with snowfall addition in the snow-free period. In the snow-covered period, the snowfall addition treatment affected litter mass loss to the same extent in both species but impacted S. passerina more strongly than R. soongorica in the snow-free period due to differences in soil urease activity. Changes in snowfall, therefore, significantly influenced litter decomposition in both desert species, but these effects differed between the snow-covered and snow-free period, particularly for litter with a higher C:N ratio.