Geoökologisches Kolloquium SS 2006

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Dr. Oleg Menyailo
Abteilung Biogeochemie, MPI für terrestrische Mikrobiologie (Marburg)
Monday, 15.05.2006 16:00 H7
Dr.-H.-Frisch-Str. 1-3

The Effect of Siberian Tree Species on N₂O and CH₄ Fluxes

The composition of tree species is changing world-wide as a result of natural changes, afforestation, and global climate change. Because tree species strongly alter soil biogeochemistry, to predict the future global N2O and CH₄ budgets the individual tree species effects on the fluxes and underlying mechanisms should be known.

I used a Siberian afforestation experiment to determine the tree species effects on the major N₂O proodcuing processes (denitrification and nitrification) and on activity and composition of soil methanotrophs. I showed that tree species differ 2-3 times by the potential rate of N₂O emission. Using ¹⁸O isotopes in NO₃^- it was determined that denitrification is the major N₂O producing process and the difference among tree species is mostly determined by the tree species effects on N2O reduction by soil.

Soil samples under different tree species were also very different in atmospheric CH₄ uptake rate. Incubation of soils with ¹³C-CH₄ and determining thereafter ¹³C incorporation into different PLFAs reveals similar pattern of labelling under all tree species. This means that tree species likely do not affect diversity of soil methanotrophs responsible for atmospheric CH₄ uptake. Other factors appear to be responsible for difference in CH₄ oxidation rate under different tree species.

Overall, tree species strongly affect N₂O and CH₄ fluxes. Therefore, future models of greenhouse gas fluxes should consider changes in tree species composition in the forests.


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