Abstract

A study was undertaken to test the effects of molybdenum (Mo) and phosphorus (P) amendments on biological nitrogen (N) fixation (BNF) by boreal forest moss-associated cyanobacteria. Feather moss (Pleurozium schreben`) samples were collected on five sites, on two dates and at different roadside distances (0-100 m) corresponding to an assumed gradient of reactive N deposition. Potential BNF of Mo and P amended moss samples was measured using the acetylene reduction assay. Total N, P and heavy metal concentrations of mosses collected at 0 and 100 in from roadsides were also measured. Likewise, the needles from Norway spruce trees (Picea abies) at different roadside distances were collected in late summer and analyzed for total N, P and heavy metals. There was a significant increase in BM' with roadside distance on 7-of-10 individual Site x Date combinations. We found no clear evidence of an N gradient across roadside distances. Elemental analyses of feather moss and Norway spruce needle tissues suggested decreasing deposition of heavy metals (Mo-Co-Cr-Ni-V-Pb-Ag-Cu) as well as P with increasing distance from the roadside. The effects of Mo and P amendments on BM' were infrequent and inconsistent across roadside distances and across sites. One particular site, however, displayed greater concentrations of heavy metals near the roadside, as well as a steeper P fertility gradient with roadside distance, than the other sites. Here, BM' increased with roadside distance only when moss samples were amended with P. Also at this site, BM' across all roadside distances was higher when mosses were amended with both Mo and P, suggesting a co-limitation of these two nutrients in controlling BNF. In summary, our study showed a potential for car emissions to increase heavy metals and P along roadsides and underscored the putative roles of these anthropogenic pollutants on BNF in northern latitudes. (C) 2018 Elsevier B.V. All rights reserved.

Keywords

Boreal forest; Car emissions; N fixing cyanobacteria; Pleurozium schreberi; Picea abies

Published in

Science of the Total Environment
2018, Volume: 630, pages: 203-210
Publisher: ELSEVIER SCIENCE BV

SLU Authors

• Gundale, Michael

  • Department of Forest Ecology and Management, Swedish University of Agricultural Sciences
    

UKÄ Subject classification

Environmental Sciences


Publication identifier

DOI: https://doi.org/10.1016/j.scitotenv.2018.02.192

Permanent link to this page (URI)

https://res.slu.se/id/publ/95777