Nitrogen deposition and forest expansion in the northern Great Plains

Citation
M. Kochy et Sd. Wilson, Nitrogen deposition and forest expansion in the northern Great Plains, J ECOLOGY, 89(5), 2001, pp. 807-817
Citations number
65
Language
INGLESE
art.tipo
Article
Categorie Soggetti
Environment/Ecology
Journal title
JOURNAL OF ECOLOGY
ISSN journal
0022-0477 → ACNP
Volume
89
Issue
5
Year of publication
2001
Pages
807 - 817
Database
ISI
SICI code
0022-0477(200110)89:5<807:NDAFEI>2.0.ZU;2-3
Abstract
1 Atmospheric nitrogen (N) deposition has become one of the most important agents of vegetation change in densely populated regions, It may also contr ibute to forest expansion into grasslands at the northern edge of the North American Great Plains. 2 We measured N deposition and available soil N with ion-exchange resin ove r 2 years in six national parks in areas varying in population density and industrialization. N deposition was significantly higher in four parks in d ensely populated regions than in two remote parks. 3 Available soil N increased significantly with N deposition across all par ks. 4 We measured N mass and N-15 abundance (delta N-15) in vegetation and soil in two parks: Elk Island, receiving 22 kg N ha(-1) year(-1), and Jasper, r eceiving 8 kg N ha(-1) year(-1). Differences between parks in tissue N conc entrations were small, but forest expansion over five decades resulted in t he mass of N in vegetation increasing by 74% in Elk Island but by only 26% in Jasper. delta N-15 in forest vegetation was significantly lower in Elk I sland than in Jasper, suggesting that anthropogenic sources contribute sign ificantly to the high rates of N entering that ecosystem. 5 We determined the rate of forest expansion within parks using six decades of aerial photographs, Parks in aspen parkland and boreal forest showed a strong positive relationship between forest expansion and N deposition. The relationships found between N deposition, available soil N and forest expa nsion suggest that even comparatively low rates of N deposition may acceler ate the expansion of forest into temperate grasslands.