Decline in carbon decomposition from litter after snow removal is driven by a delayed release of carbohydrates

Purpose Winter snow cover is a key control over soil biogeochemical cycles in cold biomes but has decreased with climate warming, particularly in high-latitude and high-altitude areas. Previous studies have found a decline in carbon (C) release from decomposing litter without snow cover, yet partitioning what C fractions respond to snow removal remains not fully understood. Methods Here we incubated fir and birch litter in microcosms over two years of decomposition in an alpine forest to assess the release of various C fractions with and without snow cover using C-13 nuclear magnetic resonance (NMR). Results We found that 51% and 61% of total organic C was lost from fir and birch litter, respectively, after two years of decomposition, and 59% and 60% of this C was decomposed during winter. More C was lost from both fir and birch litter under snow cover, and the decomposition rate of birch litter C was decreased by 50% after snow removal. However, only O-alkyl C (particularly carbohydrate C) release was reduced with snow removal, and the release of other C fractions (i.e., alkyl C, aromatic C and carbonyl C) did not change significantly after removing snow cover. Delayed O-alkyl C release from fir and birch litter was in accordance with the declines in soil dissolved organic C and microbial respiration rate under removed snow plots, but this delay induced by snow removal did not carry over to the following growing season. Conclusion We conclude that a reduction in winter snow cover regulates early decomposition of plant litter by controlling the rapid release of more labile C fractions (i.e., carbohydrates) in seasonally snow-covered ecosystems.

Automated summary

This study investigated the release of different carbon fractions during decomposition of fir and birch litter with and without snow cover. The results showed that a significant amount of organic carbon was lost from both types of litter, with a higher decomposition rate under snow cover. The release of O-alkyl C, particularly carbohydrate C, was reduced with snow removal, while the release of other carbon fractions remained unchanged.