Aim Seasonal snow cover may play an important role in litter decomposition in subalpine forest, but little information has been available on the effects of different snow depths on litter mass loss. Therefore, our objective was to characterize the rate of mass loss during litter decomposition under different snow cover conditions.
Methods A field litterbag experiment was conducted in an alpine fir forest of western Sichuan, China from October 2010 to October 2012. Samples of air-dried leaf litter of fir (Abies faxoniana), larch (Larix mastersiana), cypress (Sabina saltuaria) and birch (Betula albosinensi) were placed in nylon litterbags (20 cm × 20 cm, 10 g per bag), and the edges were sealed. Mass loss rates were investigated at different critical stages (onset of freezing period, deep freezing period, thawing stage and growing season) during two years of decomposition.
Important findings Two years of decomposition resulted in mass loss of 33.98%–39.55% for fir, 46.49%–48.22% for birch, 42.30%–44.93% for larch and 40.34%–43.84% for cypress. Compared with no snow cover, thick snow cover marginally increased mass loss by 1.73%–5.57%. The k values from the Olson decomposition constant for three coniferous litters (fir, larch and cypress) were highest under thick snow cover and lowest under no snow cover. However, the k value for birch, a broad-leaved species, showed the ranked order of no snow cover﹥thin snow cover﹥thicker snow cover﹥thick snow cover﹥medium snow cover. Although snow cover did not significantly promote decomposition of birch litter during growing season in the second year, snow cover significantly promoted decomposition of fir, larch and cypress litters at all investigated stages in two years. Additionally, mass loss during snow cover period in the first year accounted for 42.5%–65.5% of the entire first year decomposition, indicating that seasonal snow cover dramatically changed the decomposition of leaf litters in winter, especially at the deep frozen stage. In conclusion, litter decomposition in this alpine forest would be delayed by the decrease of winter snow cover predicted with climate change. Compared with broad-leaved litter, coniferous litter could display stronger responses to such changes of snow cover.