Changes in snow cover caused by global climate change will profoundly affect the process of litter decomposition and soil nutrient cycling in terrestrial ecosystems. The presence of seasonal snow cover during the winter has a significant impact on forest ecosystems. The goals of this study were to explore how seasonal snow cover modulates litter decomposition dynamics and elemental cycling in forest ecosystems, and to characterize the ecological stoichiometry of nutrients in the leaf litter and soils over time. Seasonal snowfall leads to different snow depths on the ground, especially when comparing forest gaps to closed canopy. Snow cover in this study was categorized as absent, thin, intermediate, and thick according to depth (n = 4 treatments). Leaf litter and underlying soils were sampled in plots from each category of snow cover over the course of multiple seasons (i.e., the freeze–thaw period, deep‐freeze period, thaw period, pre‐growth season, and late growth season). The carbon, nitrogen, and phosphorus concentration of leaf litter and soils were determined at each stage. The litter decomposition rate and nutrient concentration were largely dependent on the thickness of the snowpack formed by seasonal snowfall. Overall, variability in the ecological stoichiometry of elements in the leaf litter and soils was small. However, in the leaf litter, carbon, nitrogen, and phosphorus concentrations and their stoichiometric ratios differed across the snow cover gradient during the winter when snow was present, but not when snow was absent in the warmer months. Thicker snowpacks better maintained litter decomposition and kept nutrient levels stable. Furthermore, correlations between leaf litter and soil ecological stoichiometry were affected by seasonal snow cover, with element concentration also varying over time.
Aims The effects of freeze-thaw cycles on seasonal snow thickness may play a significant role in the decomposition process of forest litter in arid areas, whereas the understanding on this issue remains poor. Therefore, our objective was to understand the effects of snow cover on the decomposition and the carbon, nitrogen and phosphorus release of Picea schrenkiana leaf litter, the representative species in arid areas in northwest China. Methods A field experiment was conducted in Mt. Tianshan of Xinjiang from October 2015 to October 2016 using litterbag method. Air-dried leaf litter of P. schrenkiana was put into nylon litterbags and the litterbags were placed on the forest floor along the gradient of snow cover depth from forest gap to full canopy. Mass loss rates and carbon, nitrogen and phosphorus release of P. schrenkiana leaf litter were measured at three critical stages (freeze-thaw period, deep-freeze period, thawing period) under snow cover and the growing seasons (early growing season and late growing season) during one year of decomposition. Important findings The results showed that (1) after one year's decomposition, the decomposition rates of the P. schrenkiana leaf litter under different snow depths were 24.6%-29.2%, and there were significant difference (p < 0.05) between the decomposition rates under different snow depths. The decomposition constant (k) was highest under thick snow cover and lowest under no snow cover. (2) The decomposition during the winter snow cover period contributed 46.0%-48.5% of total decomposition of P. schrenkiana leaf litter in the whole year, and the litter decomposition was the fastest during the freeze-thaw cycles. (3) With the decomposition of leaf litter, the nitrogen content of P. schrenkiana leaf litter increased while the content of carbon and C:N decreased roughly.
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