Nitrogen (N) fixation by cyanobacterial associates in feather moss carpets is the primary source of N in northern boreal forests; however, there is little know regarding the influence of anthropogenic impacts on this process. Wet deposition of inorganic N on moss carpets has been found to reduce N fixation and reduce populations of cyanobacteria in the mosses. Automobile and truck traffic release nitrogen oxides within road corridors and a significant portion of the released N may be deposited in the immediate vicinity or transported offsite. Plant community studies conducted near highways may be directly influenced by traffic related N deposition, however, there is little data available with which to characterize the potential for such an impact. We investigated how distance from major highways in this region influenced N deposition rates and how these differences in turn influence N fixation. Four replicate 200 m transects were established running perpendicular to road segments along four major highways in northern
Results/Conclusions
Nitrate deposition was found to be elevated near major highways roads and decline with distance from the road corridor. No gradient in N deposition was observed in association with remote roads. Nitrogen fixation was below detection limit 0 – 10 m away from the highways and appeared to return to natural levels 100 m from the highway. There was no significant difference in N fixation rates in plots 0 – 200 m away from remote road corridors, demonstrating that this is not a gap phenomenon. Nitrogen fixation rates are highly likely to be artificially low in carpets that are within 50 m of busy road corridors. All biological studies conducted on lands in the immediate vicinity of busy roads may be influenced by automobile induced N deposition.