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- Title
Species Composition of Subalpine Grassland is Sensitive to Nitrogen Deposition, but Not to Ozone, After Seven Years of Treatment.
- Authors
Bassin, Seraina; Volk, Matthias; Fuhrer, Juerg
- Abstract
Reactive nitrogen (N) and ozone (O) are the most widespread atmospheric pollutants with significant implications for conservation of semi-natural vegetation; their combined effects have, however, not been tested in long-term field experiments. To investigate these effects on the species composition of a subalpine Geo-Montani-Nardetum pasture, 180 turf monoliths were exposed for seven years to five N loads (0, +5, +10, +25, +50 kg N ha y) in combination with three O levels (ambient, 1.2 or 1.6× ambient concentration) in a free-air fumigation experiment at 2000 m a.s.l. in the Central Alps. Aboveground biomass of grasses, forbs, sedges, and legumes, as well as individual species abundance was recorded annually. N addition caused strong changes in community composition and slightly reduced Shannon diversity: Sedges ( Carex sempervirens and Carex ornithopoda) tripled their fractional biomass at the expense of legumes ( Trifolium alpinum), grasses ( Agrostis capillaris, Briza media, Festuca spp.), and forbs, the latter of which responded inconsistently. Compositional changes were significant with +5 kg ha y; at all levels of N, however, changes ceased after 5 years. Elevated O and the combined O × N exposure had no effect on functional group productivity. Overall the results reveal high N sensitivity of the subalpine grassland, but low sensitivity to O singly or in combination with N. Thus, in the longer term any input of N above the current ambient deposition may cause a shift in the plant community composition of these ecosystems which are considered hotspots for biodiversity.
- Subjects
PLANT species; CHEMICAL composition of plants; SUBALPINE zone; GRASSLANDS; ATMOSPHERIC nitrogen; ATMOSPHERIC deposition; OZONE
- Publication
Ecosystems, 2013, Vol 16, Issue 6, p1105
- ISSN
1432-9840
- Publication type
Article
- DOI
10.1007/s10021-013-9670-3