Inter-species and intra-annual variations of moss nitrogen utilization: Implications for nitrogen deposition assessment

Moss nitrogen (N) concentrations and natural N-15 abundance (delta N-15 values) have been widely employed to evaluate annual levels and major sources of atmospheric N deposition. However, different moss species and one-off sampling were often used among extant studies, it remains unclear whether moss N parameters differ with species and different samplings, which prevented more accurate assessment of N deposition via moss survey. Here concentrations, isotopic ratios of bulk carbon (C) and bulk N in natural epilithic mosses (Bryum argenteum, Eurohypnum leptothallum, Haplocladium microphyllum and Hypnum plumaeforme) were measured monthly from August 2006 to August 2007 at Guiyang, SW China. The H. plumaeforme had significantly (P < 0.05) lower bulk N concentrations and higher delta C-13 values than other species. Moss N concentrations were significantly (P < 0.05) lower in warmer months than in cooler months, while moss delta C-13 values exhibited an opposite pattern. The variance component analyses showed that different species contributed more variations of moss N concentrations and delta C-13 values than different samplings. Differently, delta N-15 values did not differ significantly between moss species, and its variance mainly reflected variations of assimilated N sources, with ammonium as the dominant contributor. These results unambiguously reveal the influence of inter-species and intra-annual variations of moss N utilization on N deposition assessment. (C) 2017 Elsevier Ltd. All rights reserved.