Nitrogen additions affect litter quality and soil biochemical properties in a peatland of Northeast China

Nitrogen (N) is a limiting nutrient in many peatland ecosystems. Enhanced N deposition, a major component of global climate change, affects ecosystem carbon (C) balance and alters soil C storage by changing plant and soil properties. However, the effects of enhanced N deposition on peatland ecosystems are poorly understood. We conducted a two-year N additions field experiment in a peatland dominated by Eriophorum vaginatum in the Da Xing'an Mountains, Northeast China. Four levels of N treatments were applied: (1) CK (no N added), (2) N1 (6 g N m(-2) yr(-1)), (3) N2 (12 g N m(-2) yr(-1)), and (4) N3 (24 gN m(-2) yr(-1)). Plant and soil material was harvested at the end of the Second growing season. N additions increased litter N and phosphorus (P) content, as well as S-glucosidase, invertase, and acid-phosphatase activity, but decreased litter C:N and C:P ratios. Litter carbon content remained unchanged. N additions increased available NH4+-N and NO3--N as well as total Gram-positive (Gram+), Gram-negative (Gram-), and total bacterial phospholipid fatty acids (PLFA) in shallow soil (0-15 cm depth). An increase in these PLFAs was accompanied by a decrease in soil labile organic C (microbial biomass carbon and dissolved organic carbon), and appeared to accelerate decomposition and reduce the stability of the soil C pool. Invertase and urease activity in shallow soils and acid-phosphatase activity in deep soils (15-30 cm depth) was inhibited by N additions. Together, these findings suggest that an increase in N deposition in peatlands could accelerate litter decomposition and the loss of labile C, as well as alter microbial biomass and function. (C) 2016 Elsevier B.V. All rights reserved.