Nitrogen Input Increases Deyeuxia angustifolia Litter Decomposition and Enzyme Activities in a Marshland Ecosystem in Sanjiang Plain, Northeast China

Litter decomposition is an important process involved in carbon (C) and nitrogen (N) cycling in ecosystems. However, the biochemical mechanism underlying the response of litter decomposition to N input in marshland remains unclear. Mass loss, C and N dynamics, and enzymatic activity of Deyeuxia angustifolia litter during decomposition in a marshland were evaluated under different levels of N input (N0, control; N1, 12gNm(-2)year(-1); N2, 24gNm(-2)year(-1)). Results revealed that N input accelerated D. angustifolia litter decomposition. By the end of the experiment, mass loss increased by 5.0%, and 8.7% under N1 and N2 treatments, respectively. The half-lives of dry-matter decomposition under the N0, N1, and N2 treatment were 2.59, 2.27, and 1.77years, respectively. N input increased litter N concentration and decreased C/N ratio. Moreover, under N input, invertase, beta-glucosidase, and acid phosphatase activities were stimulated during the 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 phosphorus metabolism and N input profoundly changes C and N cycling in marshland ecosystems.