Effects of Long-Term Free-Air Ozone Fumigation on δ15N and Total N in Fagus sylvatica and Associated Mycorrhizal Fungi

Stuttgart

2007

S. 242-252

6 Abb., 3 Tab., zahlr. Lit. Ang.

Unselbständiges Werk

200144780

Patterns of nitrogen (N) isotope composition (δ15N) and total N contents were determined in leaves, fine roots, root-associated ectomycorrhizal fungi (ECM) of adult beech trees (Fagus sylvatica), and soil material under ambient (1 x O3) and double ambient (2 x O3) atmospheric ozone concentrations over a period of two years. From fine root to leaf material δ15N decreased consecutively. Under enhanced ozone concentrations total N was reduced in fine roots and δ15N showed a decrease in roots and leaves. In the soil and in most types of mycorrhizae, δ15N and total N were not altered due to ozone fumigation. The number of vital ectomycorrhizal root tips increased and the mycorrhizal community structure changed in 2 x O3. Simultaneously, the specific rate of inorganic N-uptake by the roots was reduced under the double ozone regime. From these results it is assumed that 2 x O3 changes N-nutrition of the trees at the level of N-acquisition, as indicated by enhanced mycorrhizal root tip density, altered mycorrhizal species composition, and reduced specific N-uptake rates.