Are tissue concentrations of Hylocomium splendens a good predictor of nitrogen deposition?

Emissions from fossil fuel combustion and intensive agriculture have led to a significant increase in global atmospheric concentrations of reactive nitrogen (Nr). Traditional monitoring networks do not capture the high spatial variability of Nr emissions sources; as such, pleurocarpous moss species have been used as a biomonitor for Nr deposition. Tissue concentrations of nitrogen (%N) in the moss species Hylocomium splendens at more than 100 locations in Ireland were used in conjunction with environmental variables (e.g., mean temperature (°C), sun hours, rain (mm), distance to coast) to determine predictive models of total nitrogen (N) deposition (kg N ha−1 yr−1) and atmospheric ammonia (NH3) concentrations (μg m−3). Tissue N concentrations ranged from 0.5 to 1.2%, with an average of 0.8%; concentrations showed a (low−high) gradient from the west (Atlantic) coast to the east coast. Univariate regression analysis showed that %N tissue concentrations and environmental variables had similar spatial trends and associations. Tissue N concentrations had a stronger relationship with total N deposition compared with atmospheric NH3 (R2 = 0.2, p