US EPA

2457340 

Journal Article 

The effects of adjacent land use on nitrogen dynamics at forest edges in northern idaho 

Pocewicz, Amy; Morgan, P; Kavanagh, K 

2007 

Yes 

Ecosystems
ISSN: 1432-9840
EISSN: 1435-0629 

10 

2 

226-238 

10.1007/s10021-007-9015-1 

WOS:000248135200004 

The effects of immediately adjacent agricultural fertilization on nitrogen (N) at upland forest edges have not been previously studied. Our objective was to determine whether N from fertilized agriculture enters northern Idaho forest edges and significantly impacts their N status. We stratified 27 forest edge sampling sites by the N fertilization history of the adjacent land: current, historical, and never. We measured N stable isotopes (delta N-15), N concentration (%N), and carbon-to-nitrogen (C/N) ratios of conifer tree and deciduous shrub foliage, shrub roots, and bulk soil, as well as soil available N. Conifer foliage delta N-15 and %N, shrub root delta N-15, and bulk soil N were greater and soil C/N ratios lower (P < 0.05) at forest edges than interiors, regardless of adjacent fertilization history. For shrub foliage and bulk soil delta N-15, shrub root %N and C/N ratios, and soil nitrate, significant edge-interior differences were limited to forests bordering lands that had been fertilized currently or historically. Foliage and soil delta N-15 were most enriched at forest edges bordering currently fertilized agriculture, suggesting that these forests are receiving N fertilizer inputs. Shrub root %N was greater at forest edges bordering currently fertilized agriculture than at those bordering grasslands that had never been fertilized (P = 0.01). Elevated N at forest edges may increase vegetation growth, as well as susceptibility to disease and insects. The higher N we found at forest edges bordering agriculture may also be found elsewhere, given similar agricultural practices in other regions and the prevalence of forest fragmentation.