Short- and Long-Term Effects of Snow-Depth on Korean Pine and Mongolian Oak Litter Decomposition in Northeastern China

Changes in snow-depth induced by climate change can affect litter decomposition, but it remains unclear whether the effects of snow-depth on litter decomposition vary among seasons. Our aim was to assess the possible short- and long-term effects of snow-depth on foliar litter decomposition for Korean pine (Pinus koraiensis) and Mongolian oak (Quercus mongolica). A snow-depth manipulation experiment that included snow-removal, control and snow-addition treatments was conducted in northeastern China. All the snowfall was intercepted by transparent plexiglass in the snow-removal treatment and then transferred to the snow-addition treatment. Three replicate litterbags per species were buried in each treatment and sampled in the freezing onset, deep freezing and thawing stages and in the early, middle and late snow-free seasons from November 2014 to October 2015. Our results showed that the oak litter decomposed faster than the pine litter, but the magnitude of the effect of snow-depth was greater for the latter because of differences in litter chemical traits. Litter mass loss decreased with decreasing snow-depth in the snow-covered season but increased in the following snow-free season. The short-term effect resulting from the changes in soil environments affected litter decomposition during the snow-covered season, while the long-term effect due to litter chemical traits and the microbial biomass carbon concentration controlled the decomposition in the snow-free season. These results indicated that snow-depth significantly influences the foliar litter decomposition of the two tree species with contrasting initial qualities, but the effects differed between the snow-covered and snow-free seasons. These results deepen our understanding of biogeochemical cycling in cold regions.