Effects of temperature increase and nitrogen addition on the early litter decomposition in permafrost peatlands

As one kind of the most important carbon (C) sink in the world, peatlands are sensitive to climate change. The decomposition of litter plays an important role in C fixation and nutrient utilization in peatlands. To reveal the mechanism of response of the litter decomposition to climate warming and the addition of nitrogen (N) in permafrost peatlands, we selected two typical plants, Eriophorum vaginatum and Sphagnum palustre, in the permafrost peatland of Da Xing' anling Mountains, China, as the research objects and conducted a 54-day litter decomposition experiment at 10 degrees C and 20 degrees C. Three N addition treatments (CK: 0 mg N g(-1), N1: 2.5 mg N g(-1) and N2: 5 mg N g(-1)) were established. Our results showed that the E. vaginatwn litter decomposed more quickly than that of Sphagnum, and an increase in temperature significantly promoted the litter decomposition and CO2 emission of E. vaginatwn and Sphagnum. The addition of N promoted the decomposition of E. vaginatum litter, whereas the decomposition of Sphagnum litter was promoted by the N1 treatment but was inhibited by the N2 treatment. The enzyme activity in both types of litter was inhibited with the increase in temperature. The abundances of bacteria and fungi positively correlated with the decomposition constant and mean CO2 release rate by E. vaginatwn and Sphagnum litter, indicating that the effects of temperature and N addition on the decomposition of plant litter were primarily regulated by microorganisms. This study provides a theoretical basis to understand and predict the effects of global climate change on the decomposition of plant litter in boreal peatlands.