Abstract
Nitrogen (N) pollution is a global threat to biodiversity. Moss biomonitoring is used to assess the levels of nitrogen pollution due to the high correlation between the nitrogen content in moss tissues (%N) and atmospheric N deposition. However, this relationship is controversial as %N can be affected by seasonal changes in climate and N depositions. This study aimed to investigate the effects of seasonal climate and N deposition patterns on %N in moss (Calohypnum plumiforme). Ten study sites in Japan were classified as “summer” and “winter” N deposition areas based on the season which received the highest N deposition (summer and winter, respectively). The %N showed a stronger positive correlation with N concentration than N amount in the wet deposition in both areas. These correlations exhibited seasonal differences and were not significant during the growing season with high precipitation and warm temperatures, or during the snowy season. Regression analyses revealed that winter and autumn N concentrations were the most important factors for determining the %N in the summer and winter N deposition areas, respectively. This may be due to: (1) the large contributions from high N concentrations in the initial rain on N uptake by mosses, (2) limitations in N uptake by mosses per rainfall event, (3) dilution of %N during growing seasons, and (4) low retention efficiency for snow N in mosses. The influence of the first and second factors on %N was noticeable in the summer group with large differences in seasonal precipitation, whereas the influence of the fourth factor was strongly reflected in the winter group with frequent snowfall. Based on these results, the %N can be determined not by the total N amount but by the N concentration in the wet deposition during the non-growing and snow-free seasons.
Published Version
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