Litter decomposition is an important process involved in carbon (C) and nitrogen (N) cycling in ecosystems. Nitrogen input affects litter decomposition and nutrient dynamics, especially in N-limited ecosystems. To clarify the responses of litter decomposition to N input and identify potential enzymatic mechanisms, Dr. Song Yanyu and Prof. Song Changchun et al. from the Northeast Institute of Geography and Agroecology of Chinese Academy of Sciences evaluated the mass loss and enzymatic activity of Eriophorum vaginatum and Vaccinium uliginosum litter in peatland and Deyeuxia angustifolia litter in marshland during decomposition under N input.

Researchers found V. uliginosum litter decomposed faster than E. vaginatum litter in the peatland. N input increased the mass losses of V. uliginosum litter. No significant influence of N input was found on the decomposition of E. vaginatum litter. This result suggested that the decomposition of dwarf shrub litter with higher quality is more sensitive to N input than graminoid litter with lower quality. N and P content in E. vaginatum litter and V. uliginosum litter significantly increased with N input. Moreover, N input significantly promoted invertase and β-glucosidase activity in E. vaginatum and V. uliginosum litter. However, only in V. uliginosum litter was polyphenol oxidase activity significantly enhanced. These results showed that initial litter quality and polyphenol oxidase activity influence the response of plant litter to N input in peatland ecosystems. Increased N availability may change peatland soil N and P cycling by enhancing N and P immobilization during litter decomposition.

N input significantly accelerated D. angustifolia litter decomposition in marshland. N input increased D. angustifolia litter N concentration and decreased C/N ratio. Moreover, under N input, invertase, β-glucosidase, and acid phosphatase activities were stimulated during the D. angustifolia litter decomposition process, whereas urease and polyphenol oxidase activities were stimulated during the later stage of litter decomposition. Results suggested that N input promotes D. angustifolia litter decomposition by stimulating activities of enzymes related to C, N and P metabolism and N input profoundly changes C and N cycling in marshland ecosystems.

These findings provide mechanistic insights into the factors that control the litter decomposition and illustrate the important effect of N input on enzymatic activities. These results expand our understanding of the effect of N input on wetland ecosystem functions and will guide future work on decomposition dynamics in other ecosystems.

The research papers by Yanyu Song and Changchun Song et al. were published in the journal of Science of the Total Environment and the journal of Wetlands.

Yanyu Song, Changchun Song*, Jiusheng Ren, Wenwen Tan, Shaofei Jin, Lei Jiang. Influence of nitrogen additions on litter decomposition, nutrient dynamics, and enzymatic activity of two plant species in a peatland in Northeast China. Science of the Total Environment, 2018, 625, 640-646

Yanyu Song, Changchun Song*, Jiusheng Ren, Xinhou Zhang, Lei Jiang. Nitrogen input increases Deyeuxia angustifolia litter decomposition and enzyme activities in a marshland ecosystem in Sanjiang Plain, Northeast China. Wetlands, 2019, 39, 549–557